No. 2958

MAY 8, 1880.THE

Lumleian LecturesON

THE DIGESTIVE FERMENTS, AND THE PRE-PARATION AND USE OF ARTIFICIALLY

DIGESTED FOOD.Delivered before the Royal College of Physicians,

BY WM. ROBERTS, M.D., F.R.C.P., F.R.S.,PHYSICIAN TO THE MANCHESTER ROYAL INFIRMARY; PROFESSOR OF

CLINICAL MEDICINE TO THE OWENS COLLEGE.

LECTURE III.-PART II.

Modified Casein or Metacasein.-The conversion of caseininto peptone does not take place by a direct transformationof, the one body into the other. You all know that milkdoes not curdle or coagulate in the least degree on beingboiled, but when milk is subjected to the action of pan-creatic extract (provided no alkali is added) it speedily losesthis negative property and curdles abundantly on boiling.This coagulation on boiling is most intense a few minutesafter the addition of the extract, and it very gradually dimi-nishes in intensity as the action goes on, and ceases alto-gether at the same tim that acetic acid ceases to cause aprecipitate. It was moreover found that if the milk wasboiled at the period of the greatest intensity of this reaction,and thrown on a filter, the whole of the albuminoid matterof the milk was caught on the filter in the form of curds,and the filtrate sboyed not the slightest reaction of casein.These reactions revealed the interesting fact that in thetransformation of casein into peptone by pancreatic extract,the first step in the process is the conversion of casein intoan intermediate body, and that it is this intermediate bodywhich is subsequently gradually changed into peptone. Thisbody may provisionally be called "metacasein," signifyingthereby that it is still casein, but in a modified condition.Metacasein is characterised by two reactions, which, takentogether, serve to distinguish it from other proteid bodies;it is coagulated by boiling in neutral media, and it is pre-cipitated in the cold by acetic acid. The conversion of caseininto metacasein in pancreatic digestion takes place almostsuddenly, as is shown by the following experiment, per-formed on the 3rd December :-Five cubic centimetres ofpancreatic extract were added to 100 cubic centimetres ofmilk, diluted with one-fourth of its bulk of water, and main-tained at blood-heat. The first slight, almost doubtful,evidence of coagulation on boiling was perceived in threeminutes; in five minutes coagulation on boiling was pro-nounced ; and in nine minutes it had reached its maximum.From this point coagulation on boiling, and precipitation onthe addition of acetic acid, diminished in intensity pari passuvery gradually for a period of two hours, when both reactionsfinally ceased.Taking these observations and reactions together, it is

evident that the conversion of casein into metacasin con-stitutes a first and distinct step in the transformation ofcasein by trypsin, and that this step is antecedent to thefurther and slower changes by which metacasein is trans-muted into peptone. It is impossible not to see in this astriking analogy with the sudden transformation of gelati-nous starch into soluble starch under the action of diastase,as described in a previous lecture.When milk is rendered slightly alkaline by the previous

addition of a little bicarbonate of soda, no precipitation onboiling occurs during its digestion by pancreatic extract.But the metacasein is nevertheless produced, and its presencemay be detected by carefully saturating the alkali, andthen boiling. For although metacasein is precipitated onboiling when the solution is neutral, it is not precipitatedwhen the solution is even slightly alkaline. This is thereason why, in preparing peptonised milk for the sick, it; desirable to add to it a small quantity of bicarbonate ofada.The foregoing account of the behaviour of milk with pan-

clatic extract will greatly facilitate the comprehension of

the practical rules which must be followed in preparingpeptonised dishes for invalids. I confine myself for thepresent to articles of which the basis is milk, or farinaceousgruel, or both together.

Peptonised Milk. -A pint of milk is diluted with aquarter of a pint of water, and heated to a temperature ofabout 140° F. (60° C.). Two or three teaspoonfuls of liquorpancreaticus, together with ten or twenty grains of bicar-bonate of soda, are then mixed therewith. The mixture isthen poured into a covered jug, and the jug is placed in awarm situation under a "cosey," in order to keep up theheat. At the end of an hour or hour and a half the productis boiled for two or three minutes. It can then be used likeordinary milk.The object of diluting the milk is to prevent the curdling

which would otherwise occur and greatly delay the pep-tonising process. The addition of bicarbonate of soda pre-vents coagulation during the final boiling, and also hastensthe process. The purpose of the final boiling is to put a stopto the ferment action when this has reached the desired de-gree, and thereby to prevent certain ulterior changes whichwould render the product less palatable. The degree towhich the peptonising change has advanced is best judgedof by the development of the bitter flavour. The pointaimed at is to carry the change so far that the bitter tasteis distinctly perceived, but is not unpleasantly pronounced.As it is impossible to obtain pancreatic extract of absolutelyconstant strength, the directions as to the quantity to beadded must be understood with a certain latitude. The

extent of the peptonising action can be regulated either byincreasing or diminishing the dose of the liquor pancreaticus,or by increasing or diminishing the time during which it isallowed to operate. By skimming the milk beforehand, andrestoring the cream after the final boiling, the product isrendered more palatable and more milk-like in appearance.

Peptonised Gruel. - Gruel may be prepared from any ofthe numerous farinaceous articles which are in common use- wheaten flour, oatmeal, arrowroot, sago, pearl barley, peaor lentil flour. The gruel should be very well boiled, andmade thick and strong. It is then poured into a coveredjug, and allowed to cool to a temperature of about 140° F.Liquor pancreaticus is then added in the proportion of atablespoonful to the pint of gruel, and the jug is kept warmunder a " cosey" as before. At the end of a couple of hoursthe product is boiled, and finally strained. The action ofpancreatic extract on gruel is twofold-the starch of themeal is converted into sugar, and the albuminoid mattersare peptonised. The conversion of the starch causes thegruel, however thick it may have been at starting, to becomequite thin and watery. The bitter flavour does not appearto be developed in the pancreatic digestion of vegetableproteids, and peptonised gruels are quite devoid of any un-pleasant taste. It is difficult to say to what extent theproteids are peptonised in the process of digestion by pan-creatic extract. The product, when filtered, gives an abun-dant reaction of peptone ; but there is a considerable amountleft of undissolved material. Most of this, no doubt, con-sists of insoluble vegetable tissue, but it also contains someunliberated amylaceous and albuminous matter. Peptonisedgruel is not generally, by itself, an acceptable food for in-valids, but in conjunction with peptonised milk (peptonisedmilk-gruel), or as a basis for peptonised soups, jellies, andblanc-manges it is likely to prove valuable.Peptonised Milk-G3°uel.-This is the preparation of which

I have had the most experience in the treatment of the sick,and with which I have obtained the most satisfactory re-sults. It may be regarded as an artificially-digested bread-and-milk, and as forming by itself a complete and highly-nutritious food for weak digestions. It is very readily made,and does not require the thermometer. First, a good thickgruel is prepared from any of the farinaceous articles abovementioned. The gruel, while still boiling hot, is added toan equal quantity of cold milk. The mixture will have atemperature of about 125° F. (52° C.). To each pint (550 cc.)of this mixture, two or three teaspoonfuls of liquor pan-creaticus, and twenty grains of bicarbonate of soda, areadded. It is kept warm in a covered jug under a

14 cosy for a couple of hours, and then boiled for a fewminutes, and strained. The bitterness of the digested milkis almost completely covered in the peptonised milk-gruel ;and invalids take this compound, if not with relish, withoutthe least objection.

Peptonised Soups, Jellies, and l3lane-nanges. - havesought to give variety to peptonised dishes by preparing

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soups, jellies, and blanc-manges containing peptonised ali-ments. In this endeavour I have been assisted by a memberof my family, who has succeeded beyond my expectations.She has been able to place on my table soups, jellies, andblanc-manges containing a large amount of digested starchand digested proteids, possessing excellent flavour, andwhich the most delicate palate could not accuse of havingbeen tampered with. Soups were prepared in two ways.The first way was to add what cooks call " stock " to anequal quantity of peptonised gruel, or peptonised milk-gruel. A second and better way was to use peptonised gruel,which is quite thin and watery, instead of simple water, forthe purpose of extracting shins of beef and other materialsemployed for the preparation of soup. Jellies were preparedsimply by adding the due quantity of gelatin or isinglassto hot peptonised gruel, and flavouring the mixture accord-

ing to taste. Blanc-manges were made by treating pep-tonised milk in the same way, and then adding cream. In

preparing all these dishes it is absolutely necessary to com-plete the operation of peptonising the gruel or the milk, evento the final boiling, before adding the stiffening ingredient.For if pancreatic extract be allowed to act on the gelatin,the gelatin itself undergoes a process of digestion, and itspower of setting on cooling is utterly abolished.Peptonised Beef-tea.-Hali a pound of finely-minced lean

beef is mixed with a pint of water and twenty grains ofbicarbonate of soda. This is simmered for an hour and a half.When it has cooled down to about 140° Fahr. (60° C.) atablespoonful of the liquor pancreaticus is added. Thismixture is then kept warm under a "cosey" for two hours,and occasionally shaken. At the end of this time the

liquid portions are decanted and boiled for five minutes.Beef-tea prepared in this way is rich in peptone. It containsabout 4’5 per cent. of organic residue, of which more thanthree-fourths consist of peptone, so that its nutritive valuein regard to nitrogenised materials is about equivalent tothat of milk. When seasoned with salt it is scarcely distin-guishable in taste from ordinary beef-tea.The extreme solubility of digested products-whether of

starch or of proteids-detracts from their acceptability to thehealthy. To them they appear thin and watery-they missthe sense of substance and solidity which is characteristic oftheir ordinary food. But to the weak invalid without appe-tite this sense of substance or thickening is generally anobjection, and they take with more ease an aliment whichthey can drink like water. The jellies and blanc-manges,on the other hand, give to invalids of more power that senseof resistance and solidity which is desired by those of strongerappetite.

Clinical RemarksON

STRICTURE OF THE URETHRA.BY EBEN. WATSON, M.A., M.D.,

SENIOR SURGEON TO THE GLASGOW ROYAL INFIRMARY.

WE have at present three cases of stricture of the urethrain Ward No. 17, and these seem to me so typical of the greatbulk of such cases that I wish to call your attention tothem. I shall first notice a few points in their history andtreatment, and then make a few remarks on the generalsubject.The first case we come to is that of an old soldier, who

has served both in Africa and India, and who has for manyyears been the subject of stricture. Some years ago he wasunder my treatment, and was dismissed cured for the time ;but having neglected to have a catheter passed after leavingthe hospital he has now returned worse than ever. Hiswater comes in a very small stream after great pressure andstraining. I began the treatment by passing a silver catheter(No. 7 Eng.) down to the stricture, and found that its pro-gress was arrested in the spongy portion at the posteriorpart of the scrotum. From that point along the wholemedian line of the perineum a hard and somewhat bulkytumour was felt. He was then put under the influence ofchloroform, and after trying various sizes I introduced No. 2

Eng. silver catheter, which was retained in his bladder tillthe evening, when it was withdrawn on account of the painit caused. This was done on the 18th December last.Next day the stream of water had improved, but he still

felt pain referred to the left groin. Fomentations wereassiduously applied to the side and to the perineum, hisbowels were opened with castor oil, and he had a hot sitz.bath, followed by a laudanum injection each night.

After a few days’ rest (24th December), and withoutchloroform, No. 2 was again introduced with great difficulty,and retained for a few hours. I then employed the bougiesolivaires and silver catheters of gradually enlarging sizesuntil he could bear them to be retained for several days andnights continuously. Finally, a full-sized catheter (No. 10)was introduced, when the patient left with instructions tohave the catheter passed twice a week.

In this case the deposit of lymph causing the stricture wasvery thoroughly organised, and therefore it was hard andcartilaginous to the feeling. For the same reason it yieldedslowly to the plan of somewhat interrupted dilatation whichI was obliged to adopt. Some patients bear continuousdilatation very well, and are quickly cured; others do notbear it so well, and it is a great mistake-a mistake whichhas brought this plan of treating strictures into some dis.credit-to insist on the retention of the catheter when itcauses pain or severe rigors. A more gradual dilatation israther to be recommended in such cases, until the strictureis able to receive a No. 5 catheter, after which the patientcan generally bear it longer in the bladder, and the furtherdilatation proceeds more rapidly. In this cautious way Ihave treated a great many cases of stricture, both in publicand private practice, without any death, and with no

bad effects whatever.I put all such cases under full doses of the iodide of

potassium, and I believe that by its action, and by the pressureof the catheter, as well as by the diminution or absoluteremoval of straining in micturition, which is the fertilecause of renewed congestion of the parts, I obtain in manycases the absorption of the lymph-deposit, and somethingvery like a cure of the complaint. Instead of the so-calledrapid divulsion of a stricture leaving the urethra in a betterstate than dilatation by catheters, I think it really leaves itin a worse state, because the rupture caused by it in theurethra or in the surrounding areolar tissue must be filledup with new lymph, and thus the morbid mass is increasedinstead of being diminished ; and, although a full-sizedcatheter may be sooner introduced with ease than it can bein the method of dilatation, still, the new material in theruptured tissue being even more contractile than the old,the calibre of the urethra must be maintained for some timeby catheterism. Hence the one method is about as long asthe other for the patient; and I have seen bad resultsoccur after Holt’s operation, while dilatation has beenfree from any such in my experience. The question ofinternal urethrotomy did not arise in this case, becauseof the success which attended the use of the catheter, yet Ibelieve it was just such a case as would have appeared tosome surgeons a suitable one for that operation. From theamount and hardness of the mass of lymph surrounding thestricture, urethrotomy was certainly more reasonable thanHolt’s operation; but, though that operation would havefacilitated the early introduction of the catheter, I do notsee that it would have yielded a better result ; in fact, Ithink the objection to both operations is the same-viz., thata fresh deposit of lymph is rendered necessary by eithercutting or tearing the urethra at the stricture, and thus anaddition is really made to the morbid condition. Hence thefull relief-for we cannot call it cure-in such cases is notobtained at an earlier date than by dilatation, which, as Ipreviously said, leaves the urethra in a healthier state thaneither of the other operations.The next case to which I call your attention is also one of

old stricture. It was at one time cured by the late Mr. Symein the Edinburgh Infirmary, and has been sent to my wardsas an impassable stricture. I, however, managed to pass afine catheter, and succeeded in treating the case to a favour.able termination just as the previous case was treated. Thepatient was always very nervous and had several severe

rigors, for which he seemed to get advantage by using ten.grain doses of quinine, as well as from hot sitz-baths andmorphia suppositories.Many writers on stricture place great importance on thr

kind of instrument used for passing the stricture. I believthat experience in the use of an instrument is of more ir