ALIMENTARY TRACT A3 AN EXCRETORY SYSTEM. 31$ 



digestion has gone on for two or three hours. The yellowish- 

 brown contents of the small intestine assume a somewhat 

 darker color when the ileocsecal valve is passed, and from 

 here down to the anus the alimentary contents lose water, 

 and in consequence increase in consistency very rapidly. 

 Semisolid scybala begin to appear in the transverse and 

 descending portions of the large intestine, and in the lower- 

 most portions of the large bowel the faeces proper are formed. 

 Throughout the small intestine the alimentary contents have 

 no faBcal odor under ordinary circumstances. This is de- 

 veloped after the ileoca?cal valve is passed. 



The question of the reaction of the gastro-intestinal contents 

 has within the last few years come up again for discussion. 

 In consequence of more careful analyses, made possible through 

 advances in our knowledge of indicators, some of our older 

 ideas regarding the reaction of the intestinal contents will 

 have to be set aside and newer ones adopted. The reaction 

 of the gastric contents after these have remained in the stomach 

 for some time is, under normal circumstances, acid, and this 

 fact has never been disputed since the middle of the last cen- 

 tury. Broadly speaking, the contents of the small intestine 

 have always been considered alkaline. Except for the first 

 few inches of duodenum in which the fresh acid gastric con- 

 tents may be found, the contents of the remaining portion of 

 the alimentary tract were considered alkaline in reaction, 

 because they had poured out upon them the u pronouncedly 

 alkaline" secretions of the pancreas, liver, and intestine 

 itself. Neglecting for the time being the reaction of these 

 juices, let Us ask what means were employed to ascertain the 

 reaction of the gastro-intestinal contents? For the most 

 part only one indicator was used to determine their acidity 

 or alkalinity, litmus, and this in its poorest form, as litmus 

 paper. Litmus in any form, however, is an exceedingly 

 fallacious indicator, at times even useless, in solutions in 

 which carbonates are present, for litmus is not sufficiently 

 sensitive toward carbonates. For this reason litmus may 



