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that there is still a remnant in these rep-tiles of the character which this gland socommonly presents in the class of fishes,where each simple division of the organopens, in the form of a separate csecum,into the intestine hv a distinct orifice.Even in birds, where the pancreas is large,from the imperfect salivation of the food,there are frequently several pancreaticducts arising from distinct lobes that open,alternately with the hepatic ducts, or abovethem, into the cavity of the duodenum. Inthe struthious birds, which come nearestto the mammalia, there is but one pan- creatic duct, as in the class of quadrupeds,and there are generally three in the rapa-cious birds. The division of the pancreasinto two lobes continues perceptiblethrough most of the mammalia, and theseare seen through the peritoneal coat to becomposed of smaller lobules, or groups ofminute ramified and convoluted caeca,which are the extreme terminations ofthe duct developed originally from theintestine

The salivary glands, so important in all masticating animals, commence their ca- Breer of development as simple undivided ‘minute caeca, or glandular tubes, deve-loped from the sides of the mouth or

œsophagus in the lowest tribes of animals;and as we advance to higher classes, wefind them gradually assuming a more Iramified and complicated structure, and greater dimensions, their forms and con- iditions still varying with the kinds of food, iand the living habits of the animals. Theyare already assigned by TIEDEMANN tothe holothuriae, by CHIAJE to the nereis, Iand by BRANDT to the leech, but they areoften obvious in insects as two lengthened iglandular tubes opening into the sides ofthe mouth, as shown by DUFOUR in thedipterous insects. They are almost en- Itirely deficient in the toothless acephalous ’mollusca, but are found of a simple formand structure in the brachiopodous con- Ichifera, as the lingula and terebratula.

They form large conglomerate and oftenlobed glands, with long ducts, in most ofthe gasteropods, and also in the cepha-lopods, while the pteropods and some ofthe inferior gasteropods have the salivaryglands in the form of simple lengthenedtubes, as they occur in insects. When intheir most conglomerate form, as in thegasteropods and the cephalopods, thereare generally distinct lobes which send outseparate ducts to terminate in the mouth,and sometimes they are unsymmetricallydeveloped on the two sides, or even entire-ly wanting. Fishes, which little requiresuch a fluid as saliva in the mouth, havethe place of the salivary glands suppliedby enlarged mucous glands, which pour

out a copious secretion into that cavity,and the same is the case with most of theamphibia and with many of saurian andchelonian reptiles, hut they are large andthe salivary secretion is copious in the

serpents. They are very rudimentary inthe aquatic birds, but we commonly findfour pairs of these glands in various condi-tions of development in the higher orders,and they present corresponding varietiesin the class mammalia, according to the

aquatic or terrestrial habits, or the kindof food of these animals.LECTURE LIII.

ON THE SECRETING AND LYMPHATICSYSTEMS OF ANIMALS.

’ THERE are numerous glands in animalsdestined to form important secretions fromthe blood, though not subservient to nutri-tion, or more remotely connected with theprocess of assimilation, than fhe great chy-lopoietic glands, the liver, the pancreas,and the salivary glands, we were examin-ing yesterday. They still present meremembranous sacs more or less divided,and more or less isolated from the surfaceon which they open. In each we observea peculiar mode of distribution in the

I bloodvessels which bring the materials of’, the secretion to the gland, and in thei nervous filaments, which, like electrical

wires, determine the affinities by whichthe secretion is produced, and also in

the mode and the extent of suhdivi- sion of the membranous csca, throughthe parietes of which the secretions

transude from the capillary bloodves-

sels. There are glands in every con-

dition of complexness or development,even in the highest animals, from the

simplest isolated mucous follicles to themost conglomerate form of the liver and’ the salivary glands; and we find already,in very low invertebrated animals, manyglands arrived at a most conglomerated’ structure, but the general plan of develop- ment is the same in every gland, tracedthrough all its varieties of form. The planof internal structure being thus so uniformthroughout the whole series of these se-

creting or glandular organs, we may con- sider their various forms and uses in svs-

tematic order, as they present themselvest in ascending through the different classes

, successively, from the polygastric animal-r cules to man.

y B We observe no distinct glandular organs in the polygastric animalcules, but theire outer surface, as well as the parietes ofi their internal canal, and the parietes ofr the various stomachs or cxca, which are

985

developed like biliary follicles from the the animals taken into that cavity to besides of that capacious internal canal, no consumed.doubt possess a power of secretion as well Many of the acalepha, especially of theas of absorption, like other membranous minuter forms, as equoreae and heroes, areparts. Distinct glandular organs, however, observed to emit a brilliant light, proba-adapted solely for some particular kind of bly the result of some secretion formedsecretion, have not been discovered either with a view to self-defence, but the par.in these polygastrica or in the poriferous ticular parts by which that luminosity isanimals. In both we perceive only an produced, and the nature even of thatextension of the general cutaneous and luminosity, are alike unknown. They areintestinal mucous and absorbent surfaces. considered bv CHIAJE as produced by aMany of the polygastrica, and of all the fluid secreted on the surface. The greaterother radiated classes, have been observed number of those soft gelatinous animalsto emit a bright luminous appearance when secrete a substance on the surface of theirirritated, which has been ascribed to the body, and which appears to be generallymucous secretion of their surface.

diffused over every part of the surface,

Among the polypiferous animals, we which is of a very poisonous and stinginghave seen that already the liver makes quality. This in all probability is like.its appearance in the jiustrse, as a small wise designed as a means of self-defence.appendix or single follicle extending from It is remarkable for its irritating eftectsthe alimentary cavity. We observe in on the human skin, often exciting in-those animals the power of secreting flamed spots or a diffused acute inflamma-from their surface, by their pouring forth tion over the more delicate parts of thelarge quantities of earthy matter, for the skin which have been touched. Some,most part of the carbonate of lime, with we have seen, secrete a firm cartilaginousa little of the phosphate, mixed with a internal axis, and many, as the physaliæ,coagulating muco-gelatinous substance ; secrete a gaseous fluid into a distinct sac,while others secrete upon their surface, or to enable them to float at the surface ofinto their interior, a soft homogeneous the water. Some secrete a bright blood-coagulable substance, which soon hardens red matter in their long tentacula, andto form a skeleton of a horny nature. We the velellæ are covered with a substance ofperceive, however, no distinct glandular a deep violet-blue colour. The marginal,apparatus for elaborating those materials cylindrical, opaque, granular bodies offrom the food which they take in. We many medusæ are regarded as the liver.observe that each species of those animals In the echinoderma we observe nume-

develops the gemmules always from a par- rous distinct matters to be separated fromticular point of the body, and that they the food by the vital processes of the ari-do not br:d out indiscriminately from every mals, but few secreting organs appropria-part of the fleshy substance. We may ted to their formation; the various colour-consider, therefore, that the ovarium or ing matters of the surface, the numerousthe gland for secreting ova, which is de- forms

of calcareous deposits, the secre-

veloped in higher classes of animals, pre- tions of the alimentary cavity, the copioussents itself here in a rudimentary state, as mucous secretions on the surface of thea gemmiparous point of the fleshy sub- Jaolntfizcrice and other naked species, thestance. Many secrete colouring matter of supposed calcifiant gland of the stellerida,various hues, sometimes along with the which is a small vascular sac containing aearthy matter, as corallium, tubipora, me- thick grurnous calcareous secretion.litcea, and sometimes without it, as actiniæ In the entozoa, besides the liver, theand zoanthi. Some of those animals, as the ovaries, and the testes, we scarcely ob-pennatulæ, have a power of producing, ap- serve traces of any distinct glands, eitherparently by means of secretion, very bril- connected with individual nutrition or

liant luminous appearances when they are with generation. In the rotiferous ani-excited or alarmed. They secrete upon their malcules we observe two oblong glandularsurface, as we see also detached in floc- sacs, which appear to open into the backculi from the surface and from the canals part of the mouth by short narrow ducts.of porifera, a thin mucous film, which is Those organs are regarded by some as thefrequently and periodically cast off. We pancreas, and from opening into this mus-may regard the glandular organs of these cular sac, like the stomach of a crusta-lowest classes as in their simplest condi- ceous animal, they might be the radimentstion of flat smooth secreting membranes, of a liver in this class of animals, not-which have not yet developed even cryptæ withstanding their elevated position to-or follicles for the different kinds of pro- wards the commencement of the digestiveducts. The surface of the stomach in canal; because we see, on passing down.the actiniæ. produces a copious secretion, wards from man, that the great secretingwhich appears to prove quickly fatal to chylopoietic organs, the liver and the pan-

986

creas, ascend in regard to the point of the and have seen the flashes of bluish-whitealimentary canal into which they pour light which they produce, extend alongtheir secretions. It is in the highest class their alimentary canal, as if covering in-of animals that we see those secretions stantaneously the whole of the straightpoured into the part of the alimentary and wide alimentary canal, from the headcanal most distant from the mouth and to the posterior part of the body, with afrom the stomach; but as we descend vivid and fluctuating light, which is keptfrom man, these secretions approach up for a longer or shorter time, and withnearer and nearer to the stomach, until in more or less intensity, according to thethe molluscous and the articulated classes irritation to which the worm has beenof animals they are actually poured into subjected.the stomach itself. Thus, passing wtill Besides the liver, consisting of twolower downwards in the scale, we should tubes and two salivary vessels, in the my-expect that those secretions formed by riapods, and the testes and the ovariescæca which compose the liver, should be placed on different individuals, we observepoured into a situation even higher than in the chilognatha, follicles opening bythe stomach itself. In those rotiferous ani- minute orifices along the sides near themals we also observe, besides the genera- haunches of the legs, which secrete an acidtive glands terminating in the cloaca, nu- and strongly odorous fluid. In the chilo-merous long and wide caecal appendices poda there are poison glands placed nearand tubular filaments extending from the the unciform palpi; many emit a shiningsides of the intestine. In the cirrhopods phosphorescent light, and they have seve-we observe, besides the liver already ral glandular follicles conneeted both withlargely developed, and two conglomerate the ovaries and the testes. The iltlus hassalivary glands, and the generative glands, distinct urinary long vessels, which enterthe secreting surface of the thin lining the lowcr part of their alimentary canal,mantle which forms the calcareous matter at the beginning of the wide intestine. Inof the external shells. A tough outer insects we observe many of the secretingdark epidermic layer is secreted from the glandular organs already advanced to asurface of the peduncle of anatifæ, and the considerable degree of development bywhole surface of the mantle pours out a their bulk, but not by their form. Themucous secretion. complicated and lengthened tubular form

In the annelides, besides the liver, in of the liver we have already examined, andthe form of biliary follicles, and the the more simple form of the pancreas andsalivary and generative glands, we ob- salivary glands in several of those animals.serve many of them to secrete a copious, We observe, besides these important chy-mucus, and often a colouring matter, lopoietic viscera, numerous other distinctwhich they throw out upon the surface of glands, and those are also generally, what-their body, as the yellow secretion, of an ever be their secretion, simple tubularacrid nature, from the skin of the areni- lengthened organs, sometimes convoluted,cola. The surface of their naked body is which pour their secretions into the in-lubricated often by a thick, viscid, mu- terior or upon the surface of the body. Thecous secretion of considerable abundance, testes and the ovaries are here remarkablethrown out from distinct orifices of their for their subdivisions and outward com-surface. We perceive numerous distinct plexness of structure. But besides thoseround muciparous follicles or glands, biliary vessels, there is often found anwhich pour out a copious secretion ge- inferior pair of vessels, opening likewisenerally near the orifice of the organs of into the intestine, and which have beengeneration, as in the common earthworm. found to secrete a suburate of potass andWe have seen that many annelides se- ammonia, from which they have beencrete calcareous or other matters to form considered as urinary organs, or kidneys.tubes for protection. Many of those red- We often observe a distinct series ofblooded worms exhibit a very brilliant gastric glands, like minute follicles, open-luminous appearance, extending along ing into the stomachs of insects. Manytheir body towards its centre when they coleopterous insects, especially the carni-are irritated. This we perceive in many vorous species, present glandular vessels,of the minute marine annelides; but the which pour a very acrid matter into thetrue nature of the luminosity here, as in rectum, and in the hymenoptera there is amany other classes of animals, is unknown; poison gland developed in the last seg-it is suddenly excited, and suddenly ex- ment in many species, which transmits itstinguished, and appears to be subjected to secretion through a perforated duct ofthe will of the animals. I have examined great density and sharpness, the stingalive some of the minute luminous nere- of these insects. We observe in the

ides, and excited them in the dark, and course of the oviduct, that there is alsoin sea-water, while under the microscope, generally a glandular organ of a kidney

987

form, which appears to secrete a fluid to the sting of insects. In the tarantulasenvelop the ovse, as they pass through and the spiders, as in the scolopendrae,the united oviducts. Many of these ani- the poison glands are situate at the sidesmals already distinctly present a rudiment- of the mouth, and pour their secretionsary state of the kidneys, consisting of a through the perforated, sharp, curved

lengthened, convoluted, undivided, glandu- rnaxillae. There are four subdividedlar tube, shut at its distal extremity, and glandular follicles in the lower and back

opening into the cloacal part of the intes- part of the abdomen of the spiders, whichtine. We find even in some of the species, open by four papillae in front of the anus,towards the lower termination of this and which secrete the glutinous threadsurinary tube, that there is a dilatation—a that compose the wehs. These glands cancsecal recess, forming a distinct urinary be suddenly compressed, so as to throNbladder. We observe the larvae of many out the threads to some distance whenof those animals, forming a secretion’ required.which (after being thrown out at first In the crustaceous animals we havein a liquid state, from two glands in the seen the great magnitude, the lobed form,silk-worm which open below the mouth, and the almost conglomerate structure, ofand in form of slender filaments) becomes the liver. The salivary glands, from theircondensed and hardened by exposure to liquid element and moist food, appear tothe air, and gives rise to those filamentous be seldom developed here even in thesubstances in various forms, so important highest of the decapods, and the pancreasin the living economy of many species of is ascribed to some of the entomostracousarticulated animals, to assist in their pro- crustacea,. The genital glandular organs,gressive motion, to suspend their ova, to the ovaria, and the testicles, are doubleentangle their prey, or to envelop and pro- and symmetrical, as in most of the ento-tect their own body while in the chrysalis moid articulated animals. Most of thestate. Many of those animals when ex- glands we have seen so numerously de-

cited, or when on the wing, spontaneously veloped in insects are incompatible withproduce brilliant flashes of light. Many the aquatic life of the crustacea, which haveof them which fly about in the evening, fewer secreting organs than any other en-in the twilight, are gifted, especially in the tomoid class. The glands of the air-breath-tropical climates, with the means of pro- ing entomoid classes are considered byducing this brilliant phosphoric light. SrRAus and others to be more simpleMany insects emit from cutaneous follicles and isolated in their form, on accountsecretions possessing every variety of of the limited development of their cir-odour, as a means of protection when ir- culating system, as in myriapods, insects,ritated, and often the odorous glands con- and arachnida, and they possess a moretained within the body near the anus, can conglomerate form in the annelides andbe protruded from the body and retracted the crustacea, where the sanguiferousat pleasure. Some have the odorous fol- system is more extensively distributed,licles near the head, on the back, oralong because the blood in them can be morethe joints of the trunk and legs. There easily sent to all their minute subdivi-are glandular follicles on the lower part of sions. The analogies of the chylopoieticthe abdomen of the bees, for the secretion and intestinal glands are determined,of the wax in which they envelop their under their simple forms in these classes,ova, and their honey is elaborated in the chiefly by the parts of the alimentarydigestive organs, from the juices they have canal into which they open, the salivarycollected from the flowers of plants. glands opening into the mouth or cesopha-

Distinct salivary, hepatic, and urinary gus, the hepatic, gastric, and pancreatic,vessels have been shown in the arachnida, opening into or near the stomach, and theand we observe, besides the chylopoietic urinary vessels near to the cloacal part ofglands and those connected with genera- the intestine.tion, that there are very often developed In the molluscous classes we have seenlarge distinct poison glands, accompanied the great development and the lengthenedby instruments to inflict wounds. Those subdivided and convoluted form of thepoison-glands are sometimes situated at alimentary canal, and the magnitude ofthe anterior and sometimes at the posterior the principal chylopoietic glands, but

extremity of the body. The last segment their liquid element and their slow move-of the body of the scorpion, as of many ments little require the development ofinsects, is formed into a sharp curved those numerous glands connected withsting, solid at the point, grooved at the the organs of relation which we find insides, and leading by two minute lateral the active articulated inhabitants of thecanals, continued from these grooves, to land or of the air. We find no glandulartwo poison glands situate above the broad organs developed in the tunicated anima.1base of the sting. It is not retractile like besides the most common chylopoietic and

988

genarative glands, the liver and ovaria lection to these defenceless animals, hasbut many of these animals secrete upoh been considered as analogous to the uri-their surface a glutinous substance, which nary excretion of the vertebrata. Thisserves to attach particles of gravel or shells gland has a cellular internal structure,to the parietes of their tunic, by which thick vascular parietes, and a wide duct,they are protected and concealed, and which opens into the anal portion of thewe observe a luminous secretion produced intestine. It is wanting in the nautilus,by the pyrosoma, salpa, and other genera, where the shell affords sufficient pratec-as by many inferior classes. Even in the tion to the animal. The surface of theconchifera the salivary glands scarcely skin is covered, in the naked cephalopods,make their appearance, excepting in the with coloured spots, resembling minutelirtgula, among the brachiopodous genera. vesicles of the matter of the ink gland,We observe the thick glandular appear- slightly diluted. These spots, situate be-ance cJ the striated oral appendices, the neath the epidermis, are constantly en-copious secretion of calcareous matter larging or diminishing their diameter, andfrom the outer surface of the mantle, and thus produce the undulating changes ofthe mucous secretion of its interior, in colour we observe taking place on themost of the bivalvia,and, in the more deli- skin of these animals. The great venouscate shelled genera, a glandular sac at the trunks, leading to the divided auricle, arebase of the foot, for the production of the covered, in these animals, with cellularfilaments of the byssus. Their pearly se- follicles, which some have compared tocretions are spherical concentric layers of urinary organs, others to a portal circula-nacreous matter, secreted around foreign tion. The ink of these animals is analo-

particles by the outer surface of the man- gous to many coloured secretions of gas-tie. In the naked and in the testaceous teropods. All the glandular organs con-gasteropods there are numerous mucous nected with digestion and with generationfollicles disposed on the surface of the are here presented in the most complexbody to lubricate and protect the skin ; and conglomerate forms met with in theand in the pectinibranchiate tribes, we invertebrated classes.

commonly see distinct muciparous glands In the class of fishes the spleen firstto moisten the interior of the respiratory makes its appearance-a gland apparentlysac. Many of these animals present also connected with the lymphatic system.at the bottom of this sac, or near its mar- The spleen exists here, for the most part,gin, soft follicular glands destined to afford as a single small vascular organ, appendedsecretions of various and often lively to the left side of the stomach; but in

colours, as the blue of the janthina, the many fisÌ1es it exists in a subdivided form,yellow of the bullse, the purple of the mu. as we see in the sturgeon. That subdi-rices. The jarathina derives the materials vided form of the spleen we perceive alsoof this deep blue secretion by feeding on among the cetacea, as in the porpcise.the velellip, which float like it upon the The exterior surface of fishes is lubricatedsurface of the sea. CHIAJE has shown the by a copious viscid mucous secretion,purple secretion of the mU1’ex tritonis to poured out off difi’erent parts of the body,be produced by the parietes of a glandular from long, ramified, muciparous, subcuta-sac situate at the bottom of the respira- neons glands. These are especially ob-tory cavity, and communicating with that vious and numerous on the head and sides

cavity by a small foramen. The float of of cartilaginous fishes. In many of the

the janthina is a secretion of a glutinous osseous fishes they are seen extending asmatter enclosing globules of air, and a continuous tube along each side of theformed also by the mantle. In the ptero- body, to the end of the nose, and sendingpods as in the gasteropods the secreting down branches along the operculum andorgans are still almost confined to the the lower jaw. These muciparous vesselsmost common glands connected with nu- .open from distance to distance along theirtrition and generation. JACOBSON and course; and they are often seen followingTREVIRANUs have found uric acid in the the course of the lateral line on both sides

supposed calcifiant gland of some gastero- of the body. The gaseous contents of theirpods and ccnchifera. Glands apparently air-bag are generally secreted by highlyanalogous to urinary organs are seen in vascular glandular parts of their parietes,many of the gasteropods, as the umbrella, which are obvious, generally, from theirpleurobranchu8, aplysia, dO1’is, and several vascularity and their glandular thickenedother gasteropods. appearance on opening the cavity of the

In the doris this gland opens close to air-sac. This rudiment of the pulmonarythe anus, by a distinct orifice on the snr- organ of higher animals we have seen,face of the body. The secretion formed however, to open, and to communicate

by the ink gland of the naked cephalo- more and more freely with the external at-

pods, and so important as a means of pro- mosphere, in more advaiiec-(l conditions

989

of its development in this class. Many variable in its form, and in its position, inosseous and cartilaginous fishes possess the reptiles, and appears to be wanting incomplicated electrical organs by which some of the serpents. The poison glandthey are able to communicate violent of the serpents occupies the situation oi’shocks to animals which touch or approach the parotid gland, below and behind thethem. In the gymnotu8 they occupy the eye on each side, and consists of nume-inferior part of the whole caudal region of rous lobules, each composed of manythe body, and are divided by numerous minute convoluted follicles, all of which

closely approximated transverse mem- lead to a common duct on each side of thebranous folds, like the plates of a galvanic upper jaw. Each of these ducts passespile, with a mucous secretion interposed forward to the base of the perforatedbetween the layers, and largely supplied poison-fang, where it forms a wide reser-with nerves, as we find all the electrical voir for the secretion, and is surroundedorgans of fishes. The two electrical or- with muscular fibres, to compress the ductgans on each side are separated from each when required, and force the poison intoother both by firm tendinous membranes, the tooth. The cutaneous follicles of theand by muscles, and extend tapering to the gecko of India secrete a fluid which is saidend of the tail. The transverse compart- to have the same acrid and poisonous pro-ments are further divided by crossing perties as that of the toad. 80m e reptiies,membranes, which convert them into as rattle-snakes and alligators, possesscells, the parietes of which are largely anal glands, like many carnivorous qua-supplied with bloodvessels. In the tor- drupeds, which secrete a strongly odorouspedo these organs are placed on each side substance, having the odour of musk, andof the head, and are supplied with large the same structure appears to belong tonerves from the fifth and from the eighth some chelonian reptiles and to many ser-pairs. These organs are possessed by pents, both poisonous and innoxious. Be-many fishes, both of fresh water and of sides these anal musk-glands, most of thethe sea. From Dr. DAVY’S observations crocodilian reptiles are known to possesson the torpedo, it appears that the fre- two glandular follicles under the lower jaw,quent excitement of this organ rapidly which secrete and pour out upon the sur-exhausts the influence of the ganglionic face of the skin a thick fluid with a similarnerves of digestion and secretion, and ar- odour. Insomelizards,theseodorousglandsrests those processes. The spleen appears open on each side of the anus externally,to be deficient in the lowest of the cartila- and in most of this order of reptiles, weginous fishes ; it has not been detected in observe numerous inguinal pores for thethe lampreys, and appears to be want- discharge of a similar strongly-odorousing also in the myxene and the gastro- secretion at the breeding season. Thebranchus. thymus gland, which first makes its ap-The muciparous glands, so largely de- pearance in reptiles, is there a permanent

veloped and extensively ramified on the organ, as it is also in some of the lower

body of the cartilaginous and osseous ! mammalia, the cetacea, and the rodentia.fishes immediately beneath the skin, we It is, however, a transitory organ in birds,find in a more divided form, pouring out as in most mammalia, where it makes itstheir secretion on all parts of the surface, appearance late in the progress of deve-in the naked amphibia. Their orifices are lopment, as it appears late in ascend-

large and conspicuous on the back of the ing through the animal kingdom. Theland salamander. These animals are al- spleen is sometimes divided in birds, asmost as deficient in salivary glands as we find it also in some fishes and cetacea.fishes and cetaceous animals ; but the In most birds we observe a short glandu-spleen constantly presents itself as a single lar ca’cum opening into the middle of thelengthened organ on the left side and posterior surface of the cloaca betweenbeneath the stomach. The thymus gland and behind the openings of the two ure-appears not to be developed in either of ters. This gland opening into the cloacathese two aquatic classes of vertebrata, is considered as the analogue of Cow-the fishes and the amphibia; and it is re- PER’s glands in mammalia. It was con-markable for its decidtioiis character in sidered by FABRICIUS to be a receptaclethe higher classes, where it appears as a for the male fluid, and is denominated thenormal part of the foetlis. The cutaneous bursa of FABRICLUS. It is sometimessecretion from the glandular follicles of divided so as to form the rudiments of twothe back of the toad is of an a,-iid and separate glands, as we find C’owpER’s

poisonous quality, and of an oily consist- ; glands in quadrupeds. Most of the fea-ence, and very bitter taste; the glands are tthered trihe, and especially the aquaticchiefly disposed on the back part of the birds, exhibit on the back part of theirand their secretion Í3 a meT.ns of body, over the region of the coccygealdefence. The spleen is still small and vertebrae two small glands, with their

990

ducts opening by tubular capilisp, whichsecrete an oily fluid, and this oily fluid isemployed by the aquatic birds to dress thesurface of the feathers, and render theplumage impermeable to the water inwhich they reside. All the ordinary se-

cretions of birds, from their high tempe-rature and their great muscular activity,are formed, expended, and reproduced withgreat rapidity,-the mucous secretions oftheir buccal, nasal, and intestinal cavities,the serous transudations into shut cavi-ties, as the abdomen and the pericardium,and especially the oily synovial secretions Iinto the capsules of their ever-movingjoints.The fluids of the eye, the ear, the lachry-mal, the Harderian, and the nasal glands,the oesophageal and gastric glands, andthe secretions of the oviducts, are all ra-pidly produced in this most hot-bloodedand most active of all the vertebratedclasses. This appears to depend, not onthe highly-developed or complicated struc-ture of the glands themselves, which arecomparatively simple, but on the rapidtransmission of highly arterialized andheated blood through their texture, andthe high development of the nervous sys-tem on which the secretions so imme-

diately depend.In the aquatic mammalia, especially in

the cetaceous animals, most of the secret-ing organs still preserve a very simple in-ternal structure, even in those first-de-

veloped, most important, and largestglands appropriated to the assimilationof the food; but it is in the higher terres-trial orders in this class that we find allthe more important glands arrived attheir most complicated and’ most con-glomerate forms, and numerous glands ofa simpler structure appropriated to specialpurposes, connected with their various

living habits. In the dolphins and nar-whals the salivary glands appear to bealtogether wanting, and the spleen inmost of these animals is divided into se-veral detached, small. round portions, con-nected only by sanguiferous and lymphaticvessels. The spleen is single and largein the ruminantia, of a lengthened equalform, and attached along the side of thepaunch. Between the hoofs of most ofthe ruminating quadrupeds there is a

tubular and slightly ramified glandularcavity, which pours out an oily secretionof a strong odour, to lubricate and protectthe hard hoofs, and by which the car-nivorous quadrupeds can trace the foot-steps of their prey, and some of theseanimals have also odorous inguinal glandsopening near the mammse. The musk so

extensively used as an aromatic is ob-tained from two glandular secreting sacsopening near the prepuce of the musk-

deer. The spur of the ornithorhyncus wasshown 1>y MECKEL and RUDOLPHJ, totransmit through its tubular canal the

poisonous secretion of a large gland placedin each thigh. In rodent quadrupedsthere are numerous glandular follicles,situate near the anus or near the prepuce,which secrete strongly odorous, sebaceous,or oily fluids. Two plicated glandularsacs are found on each side of the genitalsof the male and female beaver, whichpour out near the organ of excitement thewell-known fatty and resinous secietion,the castorenm of medicine. We have seenthe lobed gastric gland of this animal,embracing the cardiac orifice of the sto-mach ; and also in the wombat the samestructure is presented, which assists in thedigestion of their coarse food, and showsan analogy with the ventriculus succen.turiatus of birds. In many of the rodentiathe shut extremity of the long csecum-coliis covered with small glandular cryptt,which open into its cavity, and similarrudimentary glands occur in various partsof their alimentary canal. Anal glandssecreting odorous substances are also metwith in several of the marsupialia and

pachyderma, but they are most developedin the carnivorous quadrupeds, where theirsecretion is remarkable for the intensityof its odour in the civets, badgers, hyaenas,and some other genera. In the elephantsimilar glands are observed in the regionof the temples, opening on each side by asingle small round orifice, between the

eye and the ear. But notwithstanding theinfinite diversity of form, structure, andposition, which we observe in these se-

creting tubular membranes forming glandsthroughout the animal kingdom, and thevarious modes in which we perceive thebloodvessels and the nervous filamentsdistributed on their surface, we cannotat present discover how far these are

connected with the peculiar propertiesof the secretions they produce. Each ofthese complicated conglomerate forms ofglands may almost be viewed as a newvascular system, like the chyliferous andthe lymphatic, conveying fluids always inone direction, but that direction is from,and never to, the mass of the blood, beingthus contrary to these two systems. Mostof the products of these organs may, there-fore, be considered as excretions from theblood, but destined to serve some useful

purpose before they are discharged fromthe system.

On the Lymphatic System.In the lowest tribes of animals all the

assimilative functions are performed bythe same simple digestive sac, but as we

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ascend in the scale the functions become sively distributed over the body in themore complicated in their result, and spe- class of fishes, as has been long known,cial organs are appropriated to each por- still presents a very simple condition intion of the complex process of nutrition. its essential parts. Not only are theWhen the vascular system is first deve- glands still undeveloped on these vessels,loped in the radiated classes, the arteries but the valves scarcely yet make theirare scarcely distinguishable from the veins appearance, excepting at the openings ofin structure or in function, and to this the lymphatics into the veins, and the pa-simple plexus of ramified tubes, in which rietes of the vessels appear as a simple,the blood can often take a retrograde course, thin, and soft tunic. They have been seenare confided the functions of chylification, in almost every form of osseous and carti-

sanguification, circulation, and even ab- laginous fishes, excepting in the lowest cy-sorption. And, indeed, throughout the in- clostome species, as the myxine and thevertebrated classes the absorption of thenu- lampreys. Their functions, like those oftritious matter from the intestine, and the the lacteals, appear to be performed in theabsorption of the decayed materials from all invertebrated classes by the veins, or theyparts of the body, appear still to be func- have not been detected in them, from thetions confided to the ordinary sanguife- limpid colour of the sanguiferous fluid it-rous vessels. In the highest division of self in these inferior classes. Instead ofthe animal kingdom, however, we have the conglobate glands, which are seen onalready seen a distinct system of vessels the lymphatics in higher classes, we ob-and glands appropriated to the abburption serve in the fishes only groups of convo-of the nutritious part of the food, and to luted, or tortuous and anastomosing ves-its conversion into chyle, or almost into sels, which thus present us with a kind ofblood-the chyliferous system. Keeping analysis of these higher forms of lymphaticpace with the chylific system in the march glands. The few glands seen on the lym-of its development, we find a distinct vas- phatics in the neck of the roach are re-cularapparatus, withaccompanyingglands, garded by MECKEL as the rudiment of thein the vertebrated classes, destined to take thymus, which he considers, as well as theup from every point of the body the de- spleen, as merely a lymphatic gland.cayed materials, and to convey them to MoNRo considered the subcutaneousthe circulating fluid, to be discharged by muciparous vessels of fishes as lymphaticsthe excretions from the system. By this which opened by large orifices on the sur-means the parts are enabled to grow, and face of the body, but he observed that theto increase in all their proportions, and the ordinary lymphatic glands were still want-vascular apparatus appropriated to this ing in this class. Now you will observe,function of general absorption is termed the from these numerous plates of FOHMANN,lymphatic system, from the limpid fluid representing his injected preparations ofthese vessels convey. They have nearly the lymphatics of various fishes, how verythe same relation to the venous system as extensively these vessels are spread, boththe lacteals, and enter it at the same place, over the superficial and the deep-seatedthrough the medium of the thoracic ducts, parts of their body. From the thinness andwhich are common to both systems. They softness of their coats, these lymphaticsare more extensively distributed than the appear generally very wide and sacculated,lacteal vessels ; they appear with them and they present numerous constrictionsfirst in the class of fishes, and their glands of their parietes, as if from the develop-appear to be earlier developed than the ment of rudimentary valves. They al.mesenteric. The limpid contents of these ready cover, by their numerous plexuses,vessels are sometimes slightly yellowish, the whole surface of the larger veins, es-reddish, or whitish in their colour, and pecially when they are distended with in-are coagulable, and abundant in globules, jected matter; as we see also beautifullylike chyle, blood, or milk. The vessels I represented in these large plates of PA-conveying this fluid occur abundantly in NIZZA, representing the injected lympha-all the vertebrated classes, and are distri- tics and lacteals of various reptiles. The di-buted over every organ, following the rect communications of many of these lym-course chiefly of the large and deep-seated phatics with the branches of veins pointedarteries and veins, and occurring over all out by FOHMANN, are ascribed entirely, bythe subcutaneous parts, so that they ap- P ANIZZA, to rupture of the vessels andpear to confer the property of rapid ab- transudation, not only in fishes but in allsorption on all the mucous and serous other classes. The large sacs and recep-membranes, and on all the other tissues tacles which are commonly seen on theof the body, by their quickly conveying injected lymphatics of fishes, are, for thethe transuded matters to the circulating most part, produced by the pressure of theblood. injected matter on the thin and distensi-The lymphatic system, though exten- ble sides of these vessels. We commonly

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observe two great lateral plexuses of lym- compact layer of the lymphatics or ab-phatics passing forwards on the trunk of sorbents. . They are always wide vessels,

fishes, to terminate -with the anterior ven- and they present a knotted or beaded ap-tral plexus, in the thoracic duct behind pearance, from the constrictions causedthe heart. Those of the head and dorsal internally by the valves, and the dila-

parts enter it anterior to this point. tations of the vessels between these valves.The lymphatic vessels have been shown, PANizzA has detected a pulsating sac on

by the numerous careful injections of PA- the lymphatics of the posterior part of theNizzA, to be no less extensively distributed trunk in the coluber flavescens, like thosethrough every part of the body in the am- seen in several amphibia. The lymphaticspltibia, or the naked batrachian animals; are remarkably abundant on the spleen inand they appear to him to be here, and in the chelonian reptiles, and in the am-all the higher classes, a distinct system of phibia; and TIEDEMANN imagined thatvessels, from their origin to their termi- all the lacteals of the mesentery in thesenation by great trunks in the venous sys- cold-blooded classes passed through thetem. He considers these animals as inca.. spleen before entering the thoracic ducts.pable of respiring through their soft and We have already seen that the lactealsnaked skin; and he regards the skin as and the thoracic duct are very largelyaltogether different in its nature from mu- developed in the vegetable-eating che-cous membranes. In these large folio Ionian reptiles, and there are generallyplates he has represented their distribu- two or more ducts to convey the chyletion over the body and the interior vis- and lymph from the wide receptaculum tocera of frogs and salamanders, as well as the veins of the neck. The imperfect de-in serpents, lizards, crocodiles, and tor- velopment of the valves still allows thetoises. He discovered at Pavia, at the injections to pass from the larger trunkssame time with MuLLER at Berlin, two towards the branches and capillaries of

pairs of pulsating cavities on the lympha- the lymphatics in all the reptiles. In thetics of the trunk in these animals; and he class of birds the valves are more deve-has pointed out similar pulsating sacs on loped, the lymphatic vessels are more nu-the lymphatics in reptiles and in birds. merous,andare more firm in theirparietes,The pulsations of these sacs are not syti- and less wide and sacculated than in thechronous with those of the heart, nor chelonia. They are here, as in othereven with each other ; and they continue classes, seen clustered round the trunksafter the heart has been dissected from of the great vessels of the extremitiesthe body. In the frog they are seen pul- and of the trunk. Their course is now

sating through the skin, without dissec- more direct, and glands have been ob-tion, the anterior pair situate above the served on these vessels in the neck,broad transverse processes of the third though they are not yet developed on thecervical vertebra, and the posterior pair lacteals of the mesentery. The lympha-on each side of the free end of the long tics from the lower extremities and pos-coccygeal bone, near to the sides of the terior parts of the trunk, enter a largeanus. They propel the lymph into the plexus or receptacle at the origin of theneighbouring veins. casliac artery, along with the lacteals from

These splendid folio plates of BojANUs the lower portion of the intestine. Theand of PANizzA show the great extent and lymphatics from the head and anteriorthe plan of the distribution of the lym- parts of the body enter the two greatphatics in the chelonian reptiles. PA- trunks of the thoracic ducts, to be pouredrrzzzn has not been able, by all his injec- with the chyle into the angle between thetions, to discover a single direct entrance subclavian and jugular veins. As manyof a lymphatic vessel, or of a lacteal into as six lymphatic glands have been ob-a vein, even in the lymphatic and mesen- served on each side of the neck, in someteric glands, and he ascribes the commu- of the larger predaceous birds. It is innications pointed out by other observers, the class mammalia that we find all theto the rupture of vessels, and the extrava- parts of this absorbent or lymphatic sys-sation of the injected matters, especially tern the most developed, and in the con-in the glands, where the minute lymphatic dition the most isolated from the sangui-capillaries twine round and interlace with ferous and the lacteal systems. Thethe veins. These glands are not yet deve- lymphatics are here more numerous to-

loped in the reptiles, and their place is wards the superficial parts, and form

supplied by the tortuous windings and almost a stratum, distinct from the deeper-subdivisions of the vessels themselves, as seated plexuses which accompany thein the lower cold-blooded vertebrata. The great bloodvessels of the extremities andinjected preparations of these vessels in of the trunk. Their outer and inner coatsthe chelonia show almost every organ of are more distinct, their valves are moretheir body to be covered over with a numerous, more complete, and more effec-

993

tive in guiding the course of the contained Ilymph, and in preventing the flow of inject-ed fluids against their natural direction. IThe glands are large and numerous in thecourse of these vessels, especially in thegroin, in the axillae, and on the sides ofthe neck. We have seen that their con-tents are conveyed, with the white opaquelacteal fluid, by means of a single thoracicduct, into the left subclavian vein. Thereis a separate small lymphatic duct on theright side of the neck. Now the directcommunication of these lymphatic vessels,with veins in other parts of the body,observed by many anatomists, has beenalways observed by P ANIZZA to result fromrupture and extravasation. FonMANNimagined that in the seal all the fluidpoured from the small intestine into thepancreas Asellii was taken up only byveins, but it was shown, first by ROSEN-THAL, and then by RUDOLPHI, that thereare distinct lacteal vessels issuing fromthe group of glands which conveys thechyle to the thoracic duct, as in other ani-mals. Notwithstanding the fibrous coat ofthe lymphatic vessels in the mammalia,and the distinct pulsations in the lym-phatic sacs, seen in several of the lowervertebrated classes, no distinct contrac-tions or pulsations have been detected onany part of the lymphatic system in thehighest class of the animal kingdom.

LECTURE LIV.

ON THE EXCRETING AND TEGUMENTARYORGANS.

THE decayed materials of animal struc-ture taken up by the lymphatics from all Ipoints of the body, are conveyed by themto the circulating blood, to be removedfrom the system by distinct organs, or bythe general excreting surfaces of the body.But animals without lymphatics, and evenwithout bloodvessels, possess the means ofseparating from their economy the oldmaterials which for a limited time haveformed a part of their system ; and wherethose separated materials do not appearsubservient to some useful purpose in themaintenance of the individual or the

species, they are regarded as excretions.There can be little doubt that such ex-cretions are pouring incessantly, in a

gaseous or in a fluid state, from the ex-terior cutaneous surface of the body, orfrom the internal mucous surface of the

alimentary cavity, in all classes of animals,from the polygastrica to the mammalia,however inappreciable those products maybe. The naked surface of animalcules is

protected from the saline ingredients of

their aquatic medium by a cutaneous

exudation, as the naked surface of mol- lusca is by its copious mucous secretion.Flocculi are discharged from the canals ofporifera, along with the currents, whichappear to consist of particles of foreignmatter, mixed with the natural excretionfrom the parietes of these ramified in-ternal absorbent passages, and similarflocculi are observed periodically to detachthemselves, as a thin mucous or epidermicexcretion, from the fleshy surface of zoo -phytes, and of almost all the naked ani-mals higher than them in the scale. Theluminous, the electrical, and the stingingmaterials evolved by many of the inferiortribes arc so little connected with nutri-tion or with generation, that they are

nearly in the condition of excretions, asalso are the numerous poisonous fluidsand odorous materials formed by animalsfor self-defence, the gaseous materialsevolved in respiration, whether by cilia,by branchiæ, or by lungs, and the fluids

perspired by the skin. These excreted ma-terials, like the secretions of animals, arebut substances derived from the vital fluids,and modified by their transmission throughmembranes, follicles, or glands.

The most important and distinct emunc-tory organs, however, developed in animals,are the urinary apparatus, which exert themost immediate and the most extensiveinfluence over the condition of the vitalfluids, and which generally convey theirheterogeneous and copious products intothe cloacal or terminal part of the alimen-tary canal to be discharged directly fromthe system From the tubular, ramified,respiratory organs of the holothuriæ, open-ing into the cloacal part of the in-testine, and from the constant currents ofwater which thus pass to and fro throughthe anal aperture, these organs may ob-viously perform the functions of the twogreat emunctories of higher animals, therespiratory and the urinary organs. In

many insects and arachnida we observe,besides the ordinary biliary tubes, open-ing into the higher chylifiant portion ofthe alimentary cavity, distinct small se-creting tubes or follicles, which conveytheir products into the terminal or lower

excretory part of the intestine, and whichappear, therefore, to present a rudimentary

condition of the kidneys. These oftenL open near the anus, and they have beenfound by several chemists to contain intheir secretion distinct indications of uricacid, in the class of insects. They are de-, scribed by TREVIRANUS in the iulus

, among the myriapods. Similar urinaryor renal follicles are met with in some of; the crustaccous animals. In the coleop-f terous insects there is often a minute