No. 470.

LONDON, SATURDAY, SEPTEMBER 1. [1831-32.

LECTURES

ON

VETERINARY MEDICINE,DELIVERED IN THE

UNIVERSITY OF LONDON,BY

MR. YOUATT.

LECTURE XLII.

THE GASTRIC, HEPATIC, AND SPLENIC PLEX-USES OF THE TENTII PAIR OF NERVES.-

THE CEREBRO-VISCERAL, THE MOTOR

NERVE OF THE STOMACH.—THE STOMACH

OF THE HORSE AND THE RUMINANT.——

THE SPINAL ACCESSORY NERVE.—THE

PHRENIC NERVE.

WE had traced the cerebro-visceral nerveto the oesophagus, where it was about topierce the diaphragm and to enter the ab-domen. The right nerve was attached tothe under surface of the gullet inclining tothe right, and the other branch had foundits way to the upper surface inclining to theleft. The left branch is the larger of thetwo. Their fibres of intercommunicationhere increase in number. I cannot say thatthey form a plexus, although it has been sodescribed; but there are more frequent anas-tomoses between their branches, in order,it would seem, that the diffusion and con-nexion of their influence should be completebefore they leave the thoracic cavity. Icannot trace any branches to the diaphragm.The oesophagus passes obliquely throughthe grand scissure between the crura of thediaphragm, separated from, and not attach-ed to, that muscle by cellular substance, andthese nerves accompany it, clinging to itsexternal coat, and enveloped in the samesubstance.

Tiie Gastric Plexuses.-The oasopbagushas no sooner entered the abdomen, thanthese branches of inter-communication be-come more numerous, and a real plexus isformed about the base of the oesophagus,through which, however, the two nerves

can be traced distinctly. They graduallyseparate more from each other, and beforeit actually reaches the stomach the leftnerve divides into two branches.

The Ramifications of the Left Nerve.- Theone spreads over the upper part of the sto-mach, sending ramifications in every direc-tion ; several reach the cardiac orifice ;others pursue their radiating course overthe smaller curvature of the stomach; andthere they meet and anastomose freely withramifications from the right nerve, whichhad been distributed over the same portionof the viscus : so that there is communica-tion of the fibres and blending of the im8u*ence of both nerves for some important pur-pose. The other division of the left nervecrosses above the stomach towards theleft; itpursues the course of the gastric artery, andreaches and contributes to form the greatsemilunar ganglion. I have said that theleft nerve, even before its entrance into theabdomen, was larger than the right ; thedifference of size is more evident within theabdominal cavity; and the reason of thissuperiority of bulk in the left nerve is nowsufficiently plain, for it has an additional and.a most important duty to discharge.

. The Ramifications of the Right Nerve.-The right nerve runs on to the stomach,and distributes many filaments about thecardiac orifice, and then divides into seve-ral branches; some go to the smaller curva-ture, where, as I have said, they anastomosawith ramifications from the left nerve ;others supply the greater curvature ; theyspread over the under part of the stomach ;.they give branches which can be traced to.the spleen, and others which reach and en-twine round the pyloric orifice, and theyare not lost until they have travelled fatrdown the duodenum. A considerable branchhas previously been sent to the liver ; and.amidst all these ramifications the nerve ter-minates, and is seen no more. The French

might, therefore, with some propriety, callit the pneumo-gastric, for it is given te. thestomach and its dependencies as well as tothe lungs ; it is far more a gastric than a pul-monary nerve : but it is connected directlywith all the thoracic viscera, and with thoseof the abdomen, as far as the dUQdenum,

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and with all the rest by means of its commu-nication with the semilunar ganglion.

It is an Organic Nerve.-We do it injus-tice when we merely term it a respiratorynerve, or when we consider all its ramifica.tions, and all the viscera on which it be-stows its influence, as merely subsidiary tothe function of respiration. I have calledit the cerebro-visceral motor nerve, and wewill now inquire how far this title is appli-cable to it within the abdomen.

The Progress of Experiments on the Influ-ence of the Cerebro- Visceral Nerve.-The ear-liest experiments that were made on theinfluence of the cerebro-visceral nerve hadTeference to the function of respiration.Whether the mere branch of this nerve, therecurrent or the main trunk of the nerve

(and these were generally confounded), wasdivided, there resulted manifest disturbancein the respiratory function, and, sooner orlater, death. This, as the most evidentand palpable effect of the division of thenerve, engrossed almost the sole attentionof physiologists. Its influence on the ac-tion of the heart (circulation and respira-tion are functions nearly connected) wasnext inquired into; but this was an organsui generis; it was endowed with an intie-rent principle of contractility: if suppliedwith blood or even with warm fluid, itwould beat on, although this nerve was di-vided ; nay, although the organ itself was 1removed from the body. At length the in- t

ituence of this nerve on the process of diges- 1tion became the subject of inquiry. This ) is a slow process ; there is nothing about it ]that at once arrests the attention; it ismerely the gradual change of the food intoa uniform pulpy mass. I will not detain

you, Gentlemen, with a narration of thenumerous experiments instituted by phy-siologists with reference to this function,many of them ingenious ; others without

rhyme or reason : some apparently leading us on to a satisfactory conclusion ; andothers stranffelv inconclusive and contradic-tory : some conducted with a spirit of pbi- losophic humanity ; and others with a dis-graceful recklessness of animal suffering :but I will very briefly give you the ultimateresult. -

The Influence of the Cerebro Visceral, Nervein the Process of Digestion.-When the ce-rebro-visceral nerve is divided, and not onlyso, but a portion of it excised, so that thenervous influence shall be completely cutoff from the stomach, digestion, or the solu-tion or chymification of the food is not sus-pended but only delayed. Those portionswhich were in contact with the villous coatof the stomach become dissolved ; but thosethat are a little within the mass of ingesta,and out of the reach of the gastric juice,re unchanged. -1)1. Magendie divided the

cerebro-visceral nerves in the thorax andimmediately above the diaphragm. Alldisturbance in respiration which might pos.sibly produce derangement of digestion wasthus avoided, and the true influence of thenerve on the functions of the stomach wouldbe seen. He savs, that after having alloweda proper period to elapse, the substanceswere chynaified, and they furnished after.wards an abundance of chule.MM. Breschet and Edwards instituted

numerous experiments to ascertain thekind and degree of nervous influence in theprocess of digestion, and they arrived atthis conclusion, which may now, I believe,be taken as a physiological fact; that thegastric juice is the solvent principle or

agent, and that the function of digestion isperformed and completed by the differentportions of food being successively broughtinto contact with this fluid. We arenot

yet prepared for the inquiry into the poweror influence by means of which the gastricjuice is secreted,but we can no longer doubtthat it is by the stimulus of the par vagum

’ on the muscles of the stomach, that the ele.! mentary mass is brought into repeated andsufficient contact with this juice.

The Muscular Coat of the Stomach.—LL need not tell you that the second or centralt coat of the stomach is a muscular one, and

of singular construction, consisting of twolayers of fibres, intersecting each other;the one small and few in number, runninglongitudinally, and the other large and nit-numerous, running circularly. You mayplainly perceive how these fibres are multi-plied and strengthened around the cardiacorifice, so as to form not precisely a sphinc-ter muscle, nor a valve, but a strong, and,in the horse, an almost insuperable obstac!eto the regurgitation of the food. At thepyloric orifice they are also increased ia

number and strength, constituting to therequired extent, and, as it regards solidmatter, a true sphincter muscle. Thesemuscles effect some important purpose, orthey would not be placed around the sto.

mach and so curiously arranged there, andthey are supplied by the gastric portion ofthe cerebro-visceral nerve alone. Whilethe filaments from the semilunar ganglion,diffused likewise over the stomach, passwith the arteries through the coats of thisviscus, and are lost in its interior surface,the cerebro-visceral is seen pursuing itscourse between the peritoneal and muscularparietes, and evidently expending and los-ing itself in the muscular coat.

Illustrations of the Influence of the Cerebrn.Visceral Nerve on the Stomach. It preventsVomiting.-The oesophagus is not insertedinto the stomach of the horse vertically, nordoes it at once penetrate the parietes ; but

’ it runs obliquely between the muscular and

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cuticular coats for some distance, so thatthe contraction of the muscles at the baseof the œsophagus, or around the cardiacorifice, will obliterate, as it were, the canal,and render the regurgitation of the foodutmost impossible. Every contraction alsoof the circular fibres of the stomach gene-rally, aud particularly of those about thecardiac region, unite in producing the sameeffect, and preventing the act of vomiting,a liability to which would be inconvenientin a slave, the utmost exertion of whosepowers are required at every call of neces-sity, or freak of caprice, in sickness or inhealth, or whether the stomach is full orvoid.The difficulty of vomiting in the horse,

depends not upon any construction of thevelum palati, or posterior part of the mouth,but simple upon the ureter-like manner inwhich the œsophagus enters the stomach,and the power of the muscular fibres at thebase of the œsophagus, or in the parietes ofthe stomach, to diminish or obliterate thecanal.

It forces the Food from the Cuticitlai- Divi-sion of the Stomach.-The left portion of thestomach of the horse-the lesser curvature,is lined by a cuticular coat. No gastricjuice is secreted there ; but the food is de-tained as in a kind of reservoir, and under-goes a process of maceration, by which it isbetter prepared for the action of the truesolvent fluid. It is by the contraction ofthe circular and longitudinal fibres of themuscular coat of this part of the viscus, thatthe food, as soon as it is thus prepared, isforced out of the reservoir into the true di-

gestive stomach, and the cerfbro-visceralnerve is the agent ia producing this contraction.

lieepsit in Contaet with the Mucous Coat.-’When the food is brought into the largercurvature, be it in a greater or less quan-tity, all the muscular fibres contract, and

keep it in approximation with the mu-

cous coat, and consequently in contact with,and imbibing the gastric juice ; and that asperfectly when it is nearly empty, as whendistended to the utmost.

Exposes every Portinn of it to the Action ofthe (;a6t),ic Juice.-The separate parts ofthe muscular coat have the power of suc-

Mssively y cnn tracting- nnd relaxing, and thusin the language of Dr. Bostock, in his in-valuable " Systpmi of Physiology," andwhich should find a place in every veteri-nary, as well as medical student’s library." The successive contraction of each partof the stomach, by producing a series offolds and wrinkles, serves to agitate thealimentary mass, and by bringing everypart of it in its turn to the surface, to ex.pose it to the influence of the gastric juice ;

while, at the same time, the whole of thecontents are gradually propelled forwardsfrom the orifice which is connected withthe oesophagus, to that by which they aredischarged."

Office of the Pylorus.-Last of all, the food,more or less dissolved, reaches the pyloric.orifice, which is furnished not only with avalvular fold, hut with a sphincter muscle,in order to resist, when occasion requires,this onward pressure, and to return the ali-

mentary mass until the chymification iscomplete. The mechanism of this outlet isnot perfect, nor its function thoroughly per-formed in the horse ; for his stomach, com-pared with his size, is strangely small. Itwas designedly made so, that it might notpress too much on the diaphragm, or pain-fully or fatally interfere with the process ofrespiration, when his utmost energies wereoccasionally taxed immediately after he hadbeen fed. The food, therefore, remains in.his stomach but a little while ; and it passesthrough the pylorus very imperfectly di-gested ; while liquids flow through it as soonas they are drunk.

’

The Fu7ictioit of the Duodenum.-This,however, is fully counterbalanced by theincreased size, and muscular and villouscoats of the duodenum. In other animals,this portion of intestine has been consider.ed as devoted entirely to chylification ; butthe previous process-the conversion of thefood into chyme-has been very imper-fectly performed in the stomach of thehorse ; and therefore we want, in the upperpart of the duodenum, a kind of second 8to-mach,—a similar muscular apparatus to

compress and to mix up and dissolve thefood. That apparatus is evident enough,and also the branches of this nerve, ramify-ing over the duodenum, and ceasing beforewe arrive at the pancreatic and biliaryorifices. Its mucous coat also is far morevascular than that of any of the other in-testines. I might go further than this, andassert with Magendie, that the phenomenaof digestion may be observed in the wholeintestinal canal, and even in the great in.testine of the horse ; but this belongs to the

digestive system, and will afford a beauti.ful illustration of the adaptation of the ani-mal to the purposes for which he wasdestined.

The Fonctiun of the Ceuebro-Irisceral Nerveas it regards the Stomach,-Then, observationof the course of this nerve, and the mecha-nism of digestion, unite with the result ofexperiment in determining its proper func-tion. It is the motor nerve ; it has to dowith the mechanical part of the affair ; ithas to keep the parietes of the stomach incontact with the food, and the food in con-tact ifvith the gastric juice; it has to bring

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the different parts of the food in successivecontact with the food, and to propel thefood through this portion of the alimentarycanal, in 0’ del’ that it may be diseliar--(,dinto the duodenum. The other part of thebusiness,-the production of the solventmenstruum, is referable to another in-fluence.

The Influence of the Cerebro- Visceral Nerveon the Stomachs of Ruminants.-Let us turnto another of otir patients, and the case is

yet stronger. The food hastily gatheredbv the OT. Dosses into the rumen, and thereit is retained in an immense reservoir,macerating in the mucous fluid secretedfrom the cuticular coat of the paunch, anda little liquid which occasionally breaksthrough the floor of this œsophagean canal.Soon after this viscus is filled, the processof rumination commences. The food is re-turned to undergo a second mastication.But, how returned ? Why, in the preciseorder in which itwasswallowed, and has beenprepared by this maceration for its return.This is effected by a slow revolution of thefood through the various compa! tments ofthe rumen, and that is accomplished bv the Ialternate contraction- of the longitudinal, IIhand circular, and oblique muscles, for theyare not only strong, but they run in everydirection. Here too the successive con-

traction of the different parts of the sto-mach agitates the alimentary mass, and

brings every portion of it, m its turn, intocontact with the mucous secretion ; and allthis is effected by no spinal motor nerve,for no one can be traced to the stomach,but by this cerebro-visceral one, which isseen ramifying in every direction under theneritoneal coat.- A portion of the food which was first re-ceived is now, by some voluntary effort(the will is not excluded from every partof the process), brought over the valve-like projection which separates the rumenfrom the reticulum-the first stomach fromthe second. This pellet being received intothe honeycomb, all voluntary influence andpower for a while cease, and the cerebro-visceral takes up the work; and it com-presses the pellet, and forms it into the

proper shape to reascend the gullet; and itsqueezes from is beautifully arranged cellsa viscid fluid with which the pellet is en-

veloped; and then by an act partly volun-tary or in which, and that is the essenceof our system, many voluntary muscles arebrought to lend their aid to the involun-tary, or organic ones-the pellet breaksthrough the floor of the canal, and by thesame mingled influence reascends the cesoph-ngus, and is subjected to a second mastication, and is once more swallowed; and,being reduced to a semifluid form, has nolonger sufficient momentum to breakthrough

the cesopbagean canal, but passes on to thethird stomach.There again the cerebro-viscera.lacts, and

acts exclusively. The food has been twicemasticated, but there may remain some

hard fibres which would resist the solvent

power of the gastric juice. These al taken

up by the leaves of the manyplus, and anew action commences-a triturating rind-ing motion ; the animal is not conscious ofit ; it is a purely organic ailair ; and thesefibres are mechanically rubbed down be-tween the roughened papIllated leaves ofthe manyplus. In accordance with this,there are here, compared with the size ofthe stomach, muscular fibres ten times

stronger than in the paunch, and there arefar more abundant ramifications from thecerehro-visccral nerve.The food is at length prepared for diges.

tion, and enters the fourth or true stomach;and there is the muscular action of the pa.rietes of the stomach, and all its effects, as1 have just described in the horse. I havedwelled at considerable, I trust not tpdi-ous, length on this part of my subject, forthe’ stomachs of the ruminant aR’ord themost varied and satisfactory illustration ofthe function of the cerebro-visceral nerve,and

prove it to be an organic motor nerve.The Sensitiie Infiuence of the Nerve.-Ihave not forgotten the ganglion curiouslybelonging to this motor nerve, nor the pos·sible or probable sensitive influence whichit bestows-namely, that kind of sensationwhich belongs to organic life-a conscious.ness of healthy, or of deranged action; norhave I forgotten the wide and perfect sym.

, pathy which must exist between the vari-ous parts of so complicated a machine, that

it mav act orderlv and beueficialiv : and Ican conceive, that by auastomoses withother parts of this nerve, and more particu-larly with the great organic nerve withwhich it is already so closely united, andwith which, by-and-by, it becomes inter-mingled—I say that I can readily conceivehow, b anastomoses between these and

fibres from the sensitive nerves of the

spinal column, an indescribable but real

feeling of pleasure should accompany thedischarge of many of the organic functions,and pain, and sometimes to an acute da-gree, should mark the departure from

healthy action.The Hepatic and Splenal P2exnses.-As to

the fibres, which can be plainly traced to

the liver and spleen, we know little of the, minute structure of either; and the func.tion of the latter is not yet determined:. but there are nutritive vessels in both;

there are vessels conveying the fluid, fromwhich the biliary secretion is formed, or

) which is to be retained in the reservoirs ofthe spleen; there are vessels to carry away

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the secretion or the residuum ; there areimportant ’functions to be performed; andtherefore I can easily conceive of the

agency both of the motor and sensitivefibrils of this organic nerve: the motorones concerned with the mechanism of the Ipart, and the sensitive ones with peculiaror sympathetic organic feeling and co-ope-ration. But it is time to return to the me-dulla oblongata and its lateral column.

The Eleventh or Spinal Accessory Nerve.-There is another nerve, not interminglingwith the glosso-pharyngeus or the cerebro-visceral, which, within the cranium, isincluded in the same sheath with thelatter, and passes with it through the fora-men lacerum. The origin of this nerve is

very singular. As low down as the fifthcervical nerve we observe some minute

threads; they are smaller than the fibriculiwhich go to form any of the other spinalmotor nerves ; and they arise evidentlyfrom the centre of the lateral column. 1 hey Bunite and they form a larger thread, whichtakes a direction up the neck. It passesbetween the motor and sensitive roots of thenerves above it-lying under or penetratingthrough the ligamentum denticulatum ; and ias it climbs it is augmented by fresh threads.It reaches the foramen magnum-it entersit-it continues to climb until it has reachedthe ninth and tenth nerves, and then itturns round and escapes again from the cra-nium, as I have described, through the sameforamen with them. It has scarcely quittedthe cranium when it separates from thesenerves, and, after that, its own trunk divides.Although separated from the sheath of thecerebro-visceral, it sends a branch to unitewith the main trunk of that nerve, and alsowith the glosso-pharyngeus ; it sends many branches to blend with the guttural plexus,and thus to form anastomosis with all the

neighbouring nerves ; a large and mainbranch, proceeding anteriorly, reaches thesterno-maxillaris, and afterwards buriesand loses itself in that muscle ; another

large division winds round the transverse

process of the atlas, proceeds between thelevator humeri and the splenius, and, be-coming superficial, reaches so far as the topof the shoulder, and then ramifies on therhomboideus brevis, and vanishes in thesubstance of that muscle.

An organic Motor Nerve.-The minute fi.briculi from which it rises would create a sus-picion that it is a motor nerve ; the musclesun which it expends itself prove that it isso ; and the lateral column whence it springswould indicate that it is employed in theperformance of some organic function. Themuscles to which it is directed are voluntarymuscles ; they are concerned in the motionsof the head, the neck, and the fore extre-

mities ; they are supplied with nerves fromthe spinal chord, and which excite them tosufficiently powerful action, for the pur-poses which they are to accomplish. Theyare voluntary muscles, but they are also con-cerned, some of them at all times, and thatinvoluntarily and unconsciously, in assistingin the function of respiration, and, when thebreathing is hurried, they are all called intoaction consciously, yet, in a great measure,involuntarily. This is plainly a respiratorynerve, it is concerned with the function ofrespiration alone, but respiration is one ofthe organic functions. I class it with theothers as an organic motor nerve.

The Twelfth or Phrenic Nerve.- We Dowleave the cranium and the spinal chord,and, observing the numerous ramificationsand anastomoses of the cervical nerves, we

find a very small one from the fifth (fourth)’ which takes its course down the neck,seemingly unconnected with any othernerve ; we follow it, and it is joined by abranch from the sixth (fifth) cervical, andthese, united, pursue the course whichthe first little filament had taken; and,by-and.by, these are associated with a

branch from the seventh (according to tlic-

common nomenclature, the sixth) cervicalnerve ; and I have met with a filament fromthe lowest cervical nerve. The nerve thusformed, pursues its singular and solitarycourse down the remainder of the neck, andpenetrates into the thorax, above the rootof the axillary artery ; it enters the me-diastinum, and proceeds on, attached to theouter side of the pericardium, a beautifulobject to the young and even the ex-

perienced anatomist ; and it continues its

lonely path until it reaches the diaphragm,which is its ultimate destination. It pe-netrates the pleura-its branches beauti-fully radiate for some distance over the

diaphragm, and are then lost in the sub-stance of that muscle. One branch, how.ever, goes on from the right nerve,-theramus anastomoticus-and contributes toform the semilunar panglion.

An orgaaaic Alotor Nerve.-This is evi-

dently an organic nerve, for it supplies themuscle mainly concerned in respiration.In its natural or relaxed state, the dia.

phragm bellies into the thorax. It is stimu-lated by nervous influence derived from thephrenic nerve, and it contracts. In the act ofcontraction it is flattened, and the cavity ofthe thorax is enlarged, and the air rushesin through the nostrils and mouth, and theact of inspiration is performed. The ner-vous influence is then withdrawn, and th9muscle relaxes, and once more bellies intothe thorax ; and the cavitv is diminished and

the air is expelled, or, in other words, theact of expiration its performed, There are

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other auxiliaries of which I have spokenwhen treating of the function of respiration,but this is the main agent. The divisionof the phrenic nerve will not at once sus-pend respiration, for that will be carried on,painfully and laboriously, by the othermuscles, which assist ill’ raisma and de-

pressing the ribs; but, by degrees, theyand the animal generally will be exhaustedby their unaccustomed and violent action,and death will ensue. lf the spinalchord is divided above the origin of thephrenic nerve respiration immediatelyceases, for all the nerves concerned in thedilatation and contraction of the chest are

cut off. The cerebro-visceral mav continueta influence the glottis and the-lung, butthat will be of little service when the

parietes of the chest are fixed.Whether a puoe Oroanic Nerve.-It has I

been taken for granted by physiologists ge- Bnerally that the phrenic nerve is one ofvoluntary motion, and that the diaphragm is under the control of the will. In its usualaction the phrenic is a pure organic nerve, and uninfluenced by the will. The func- tion of respiration,---the arterialization of the blood,-is necessary to the animal fromthe moment of his birth ; it is identified with the continuance of life ; and the continuedcontraction and relaxation of the diaphragm,the main agent in the discharge of thisfunction, is co-existent with the commence-ment of life, and ceases ouly when the vitalment of life, and ceases only when the vitalprinciple is extinct. In its natural actionthen it is perfectly independent of the will.But is not the diaphragm occasionally a voluntary muscle 1 Can we not increase or

suspendits action when and how we please ?Indirectly we can ; we can call in othermuscles to the aid of the diaphragm ; wecan give to them a certain velocity andpower of action, with which the diaphragmfrom its relative situation must correspond.We can more fully and rapidly than usualexpand the chest by the action of the in-tercostals, and also by that of the spinalaccessory; we can rapidly and violentlycontract it by the power of the abdominalmuscles, or we can give fixidity to thechest ; we can excite that kind of opposedor antagonist action between the muscles ofinspiration and expiration, which the powerof the diaphragm shall be insufficient to

destroy, and between which it is in a man-ner paralyzed. We simplify the matter byconsidering the phrenic nerve as one of in-voluntary action,-a pure orgunic one;-and a diligent observation of the mechanismof respiration, will render it highly pro-bable that it is so.-

Difficulty as to its Origin.-How thenshall we account for its origin as a true spinall1erre, curiously made up of fibrils from

different nerves, but all to be traced to thecolumns of animal sensation and voluntarymotion ’! This is a difficulty which no ana-tomical fact will enable me to surmount;and to relieve myself from it, I am obligedto have rt-course to that which is unphilo-sophical, and rarely, indeed, admissible,-the supposition of that which 1 cannot

prove, that when from a better process ofmaceration or hardening, we are enabled

to unravel the complicated fibres of thespinal chord, it may hereafter appear thatcertain portions of the fifth, the sixth, andthe seventh cervical nerve are derived fromthe lateral column, or that which is con.nected with the functions of organic life.Until then we must rest content with theundeniable fact, that the phrenic nerve is, inthe ordinary distribution of its influence, annrelv organic rme ’ and the strong inclina.tion of my belief is, that it is on’yindirectlythat it can be ever brought under the powerof the will. It acted before a volition couldbe formed ; it continues to act when themind is passive ; and it is only by opposinga superior power, by the combination ofmany a muscle, that the will has any con.trol over it. There are stages, and states,

and modifications of the respiratory functionwhich are necessarily to a great degreesubjected to the influence of the will. If Iwere to select alone the faculty whichevery animal possesses of communicatinghis ideas, or expressing the pieasure or thepain which he feels through the medium ofthe voice, I should have a sufficient il!us-tration of the association of voluntnrsy powerwith the organic principle, in away whichneither the function of circulation, or diges-tion. and, in fact, which no otherfunctien canrequire. Hence arises the diihculty, but adifficulty which is resolved bv the ohserra-tion, that the discharge of the function, so

far as essential to life, depends on theorganic principle ; and that the interven-tion of the will is permitted only when ouroccasional , comfort or accommodation"

requires. But, Gentlemen, I am here againtheorizing somewhat too much. We haveone more nerve, and that a most importantone to describe, and then neither you nor Ishall be sorry to return to that which oughtto be the main object of our anatomical andphysiological researches, and which givesthem their highest, and, comparativelyspeaking;, their only value, a considerationof the uuture and treatment of disease.