DIGESTION IN THE SMALL INTESTINE. 421 



very complete the contents of the small intestine amount to only one- 

 tenth or one-twentieth of the gastric contents. Aliments more or less 

 liquefied, according to the quantity of fluid contained in the alimentarj' 

 tract, present a different character in each portion of the intestinal tube. 

 In solipedes, for example, in the small intestine they are mixed with a 

 thick, yellowish, viscid fluid; in the csecum they are suspended in a large 

 amount of fluid not deprived of viscidity ; in the great fixed colon they 

 are still soft, but as the floating colon is approached they acquire pro- 

 gressive dryness and are moulded into balls, which stick to the valvulee 

 conniventes. 



The bile of the hog, as has been mentioned, contains no amylolytic 

 ferment, but is capable of emulsifying rancid fats. The intestinal juice, 

 according to Ellenberger and Hofmeister, contains a diastatic but no other 

 ferment, a statement which, in view of the general presence of the invert 

 ferment in the secretion, needs confirmation. The pancreatic juice con- 

 tains three ferments, and is, therefore, possessed of the same properties 

 as in other mammals. Consequently, in the intestinal canal of the hog, 

 albuminoids are peptonized, starch converted into sugar, and fats 

 digested and emulsified. Absorption in these animals is exceptionally 

 rapid, so that examination of the intestinal contents will reveal but 

 small amounts of digestive products. Peptone, especially, seems to be 

 absorbed as rapidly as it is formed, while 69 to 75 per cent, of the 

 albuminous food-stuffs and 65 to 72 per cent, of the carbohydrates found 

 in the small intestine has been digested. 



The reaction of the small intestine of the hog is usually acid through- 

 out half its extent, the acidity sometimes extending through five-sixths 

 its length. 



After feeding, the first portions of the meal appear in the small intes- 

 tine in from three to four hours, while three hours later a portion of the 

 intestinal contents has already reached the caecum. Intestinal diges- 

 tion, therefore, in the hog is of but short duration. 



One is accustomed to speak of the reaction of the small intestine as 

 self-evidently alkaline, and it is almost universally taught that as soon 

 as the acid chyme enters the duodenum its acid reaction, through 

 the influence of the bile and pancreatic juice and intestinal secretion, 

 at once passes into an alkaline reaction. This, however, is an error. As 

 a rule, an alkaline reaction is rarely met with until the very lowest por- 

 tion of the ileum is reached. It has been already mentioned that the 

 acid chyme produces precipitation in the bile, the glycocholate of sodium, 

 glycocholic acid, and mucin being carried clown, while the acid reaction 

 is still maintained, and that this precipitate carries the pepsin mechan- 

 ically down with it. The importance of this is seen when it is remem- 

 bered that in acid solutions pepsin will destroy the pancreatic ferments. 



