and Laboratory Methods. 1217 



only to urge a more general co-operation between the medical scientist and the 

 medical practitioner, in attacking the many problems that lie before us, the solu- 

 tion of which will make medicine more and more an applied science, as well as 

 an art. 



One of the difficulties in the way of careful analysis of chyme is the small 

 amount obtainable — not usually over eighty and often less than thirty cubic 

 centimeters, after the ordinary test meals. Free HCl and total acidity can be 

 estimated at one titration, if we are careful and meet with no mishap. Com- 

 bined acidity requires another titration, proteids another, and at least a small 

 quantity must be reserved for various qualitative tests. While the tests for 

 acidity are best applied to unfiltered chyme, proteolysis requires a clear filtrate, 

 and a considerable loss occurs on account of the mass left on the filter. As a 

 matter of practical experience, I have found that the tests for proteids must be made 

 with ten or sometimes only five cubic centimeters. Filtration, especially if much 

 mucus is present in the stomach contents, is a tedious process. I have tried all 

 sorts of expedients, such as the use of absorbent cotton, separation by a colan- 

 der, etc., but have not succeeded as yet in obtaining rapid filtration. By centri- 

 fugalizing the stomach contents, they can readily be separated into three layers, 

 the lower one consisting of undigested food, the upper one of butter and mucus, 

 the middle one of comparatively clear liquid. By removing the upper layer, the 

 middle one can be decanted and filtered in the usual way, without the delay 

 required if the stomach contents are simply poured into the filter. 



There is no natural separation of the various steps of the peptonizing pro- 

 cess, but, by common consent, chemists consider that every proteid not precipi- 

 tated by ammonium sulphate in saturated solution is a peptone, and that every- 

 thing between albumin and peptone may be called albumose. Of course, the 

 process of peptonization could be further subdivided by using different reagents. 

 To precipitate albumose — or rather albumoses — I add one gram of ammonium 

 sulphate to ten cubic centimeters of decantate, dissolve the salt by heat, and 

 cool. As the mixture cools, a turbidity forms, due to albumose. This is very 

 light and is precipitated only with the greatest difficulty; in fact, I do not usually 

 try to clear it absolutely by the centrifuge, but simply estimate what is thrown 

 down by 10,000 revolutions ; ] per cent, may be taken as the normal maximum. 



To precipitate peptones, I employ phospho-molybidic acid, which makes a 

 very bulky precipitate. I should prefer tannic acid, the precipitate from which 

 is only about a sixth as bulky, and tannic acid is the reagent usually recom- 

 mended by chemists, even in experimenting with stomach contents ; but they 

 forget that tannic acid also precipitates starch, which is almost invariably present 

 in chyme. This little oversight alone cost me several months' time, as it neces- 

 sitated throwing out quite a series of observations. Normally, the precipitate 

 with phospho-molybdic acid is from ten to nearly thirty per cent, of the filtrated 

 chyme. This relatively enormous bulk suggests that something else than pep- 

 tones is precipitated, and it was only after careful search of chemic literature and 

 consultation with chemists that I became convinced that we could rely on this 

 reagent. Phospho-molybdic acid precipitates alkaloids and certain biliary con- 

 stituents, but it is impossible that there should be anything of a non-proteid 



