CHAP. XXV.] INTESTINAL DIGESTION. 243 



starchy substances undergo in the stomach and intestines in dogs. 

 Man and carnivora are unable to digest raw starch in the stomach 

 or intestines. Raw potato-starch introduced in a muslin bag into 

 the stomach through a fistulous opening in the walls of the stomach, 

 and withdrawn after a sojourn of twenty-four hours in that viscus, 

 showed no sign of any change, nor did the gastric juice out of the 

 body, the mixture having been kept at a high temperature for 

 the same time, exert any influence upon the starch grains. When 

 dogs were made to swallow raw starch, the grains were afterwards 

 found intact in every part of the intestinal canal. Rabbits and 

 granivorous birds, however, were found to possess the power of 

 digesting raw starch, although more slowly than that which had 

 been cooked. But this power was found to reside mainly in the 

 upper part of the small intestine, and as the grains of starch be- 

 came gradually fewer as the food descended in the intestinal canal, 

 it seems reasonable to believe that each succeeding portion exercises 

 a certain digestive power over them. In birds, the digestive power 

 of the small intestine was greater than in rabbits, the lower part of 

 the intestine in the forager exhibiting no traces of the starch 

 grains. In the upper part of the small intestine, sugar and dex- 

 trine were found, and the lower the contents had passed down, 

 the more did all traces of starch disappear. 



Boiled starch is more readily digested by all animals than raw ; 

 to the carnivora and to man, cooking is essential to its perfect 

 digestion. The same changes take place in it as in the raw starch, 

 i. e., it seems to undergo conversion into sugar, dextrine, and 

 lactic acid. This change, however, is very slow and gradual, and 

 although it occurs chiefly in the upper portion of the intestine, it is 

 found taking place throughout the whole canal. The rapid forma- 

 tion of sugar in the intestinal canal leads to a proportionally rapid 

 absorption of it, and to the elimination of it by the kidneys. It is 

 apparently to guard against this, to protect the kidneys against the 

 irritating influence of this substance, that the change of the starch 

 into sugar and dextrine goes on with great slowness throughout the 

 whole intestinal canal. 



Our own experiments have yielded results similar to those of 

 Bouchardat and Sandras, and confirm their conclusion, that neither 

 azotised matters nor amylaceous substances contribute to form the 

 true white chyle. At least it may be affirmed, that when animals 

 are fed on such food, carefully freed from all oily or fatty matters, 

 the fluid which is found in the lacteal vessels is perfectly trans- 

 parent, and in all respects identical with that which is found in 



