DIGESTION IN THE SMALL INTESTINE. 411 



the acid constituents alone of the gastric secretion, which, as has been 

 already mentioned, has but slight degree of acidity, and does not inter- 

 fere with pancreatic digestion. 



The bile, on the other hand, while disturbing gastric digestion, con- 

 siderably assists the action of the pancreas, not only in facilitating the 

 emulsification of fats, but apparently also in some wa}' aiding the solvent 

 action of the pancreas on proteids. The pancreas, in addition to the 

 three ferments already described, is also said to contain a ferment which 

 coagulates milk, which ma}' be extracted from the gland by means of a 

 concentrated solution of common salt, the ordinary solvent used in 

 making rennet from the calf's stomach, and which in general is claimed 

 to behave like the milk-curdling ferment of the gastric juice. 



This ferment has been found in the pancreas of the pig, the sheep, 

 the calf, the ox, and the fowl. The principal difference between the 

 action of the milk-curdling ferment of the pancreas and that of the 

 gastric juice lies in the fact that even 1 per cent, of sodium bicarbonate 

 does not prevent coagulation in the former case, while one-fourth of 

 1 per cent, in the latter case does. The pancreatic rennet is also quite 

 active in a neutral or even faintly acid medium. Boiling, as with other 

 soluble ferments, destroys its power. It may likewise be precipitated by 

 alcohol and again dissolved in water without losing its activity. 



When a pancreatic digestive mixture is allowed to remain in contact 

 with food-stuffs, it rapidly acquires a putrefactive odor, and swarms with 

 microscopic organisms. Usually in eight hours a high degree of putre- 

 faction has taken place. It is to be supposed that a similar state of 

 affairs occurs in the small intestine, since the conditions are there favor- 

 able for the reproduction of bacteria ; for it is scarcely possible to assume 

 that the acidity of the gastric juice is sufficient to destroy the germs 

 which we must suppose are constantly taken into the alimentaiy tract. 

 A characteristic result of the putrefaction and decomposition of proteids 

 is indol, to which the ftecal odor of putrefying pancreatic secretion is due. 

 When salicylic acid is added to pancreatic digestive mixtures, they remain 

 free from odor, and the presence of indol cannot be detected. It there- 

 fore seems clear that indol is a result of putrefaction of the results of 

 pancreatic digestion, and is not normally a digestive product. Never- 

 theless, the constant presence of indol in the small intestine would show 

 that in this portion of the alimentary canal such putrefactive changes 

 almost invariably result. 



In addition to indol, putrefying pancreatic solutions will develop 

 ammonia, carbonic acid, butyric acid, valerianic acid, acetic acid, phenol, 

 sulphuretted Irvdrogen, carburetted hydrogen, and hydrogen, gases 

 which are also found in the alimentary canal. 



While such putrefactive changes undoubtedly occur in the alimentary 



