354 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



same products as albuminoids of animal origin. On carbohydrates the 

 ferment of gastric juice is without effect, the cases reported in which 

 starch has promptly been converted into sugar in the stomach being 

 attributable to the action of saliva which had been swallowed. The sali- 

 vary ferment is not destroyed in the stomach, since saliva may be kept 

 for days together in contact with gastric juice, and if the acid be then 

 neutralized the diastatic power of the saliva may still be exerted. The 

 change of starch into sugar in the stomach will vary in intensity 

 according as the animal is carnivorous or herbivorous. In the former 

 case the saliva possesses but little diastatic power, and the food being 

 swallowed without mastication no conversion of starch into sugar may 

 be said to occur in the mouth, while the high degree of acidity of the 

 gastric juice will almost entirely prevent the action of saliva in the 

 stomach. Carbohydrates, therefore, when given to carnivora, pass 

 through the stomach almost unchanged, and are only converted into 

 sugar when brought into contact with the pancreatic and intestinal secre- 

 tions. In the case of ruminant herbivora the food and saliva are carried 

 together to the rumen, where the high temperature and alkaline reaction 

 favor the conversion of starch into sugar. In the non-ruminant her- 

 bivora, as in the horse and rabbit, the sojourn of the food in the mouth 

 is much more prolonged than in other animals, and time is given for the 

 partial conversion of starch into sugar to take place. When the uncon- 

 verted starch and saliva reach the stomach the process ma}^ still go on, 

 for, in the first place, the acidity of the gastric juice is much less in 

 these animals than in carnivora, and, in the second place, as will be shown 

 directly, the acid of the gastric secretion in these animals in the first 

 stage of digestion is lactic and not hydrochloric acid, and the action of 

 ptyalin may still take place in a fluid containing 2 per cent, of the former 

 acid, while it ceases in 0.5 per cent, of the latter. By the time, there- 

 fore, that hydrochloric acid has been substituted for lactic acid, it may 

 be concluded that the starch has been mainly converted into sugar. 



Again, cane-sugar is slowly converted in the stomach into invert- 

 sugar, apparently through the influence of hydrochloric acid. Fats are 

 but slightly digested by gastric juice, it appearing that a small part of 

 the fat is broken up into glycerin and fatty acids. When adipose tissue 

 is subjected to the action of gastric juice, the albuminous cell-envelopes 

 are dissolved and the fat liberated in the form of free oil-globules, only 

 a small portion of which is broken up into fatty acids and glycerin, while 

 the remainder escapes into the small intestines to be acted upon by the 

 pancreatic secretion. When milk is introduced into the stomach, the 

 casein, through the action of the milk-curdling ferment, together with 

 the acid of the gastric juice, is coagulated and forms the curd, in which 

 the oil-globules are held. In a subsequent stage of digestion, the casein 



