The Digestive System. 47 



later. In the true stomach of the ruminant, albumen 

 is converted into peptone, milk is coagulated and its 

 casein peptonized, gelatin is converted into an available 

 form, some of the fats are split up, cane sugar being but 

 slightly acted upon. 



Gastric digestion takes place in the stomach, is the 

 most complete in the ruminant, in which intestinal diges- 

 tion is simple. In birds the food is macerated (softened) 

 in the crop and mixed with an acid fluid, the crushing 

 or grinding being done in the gizzard; the digestive pro- 

 cess is very active and thorough in birds. The food 

 having undergone the action of the stomach juices is 

 then passed to the small intestines, where it meets the 

 bile, pancreatic and intestinal juice. The small intes- 

 tines are tube-like in form and of a musculo-membranous 

 character, in the horse measuring over one hundred feet 

 in length. They are divided into three portions, named 

 respectively, the Duodenum, one foot in length, Ileum 

 and Jejunum. The first section is fixed and has an 

 opening into it the ductus communis, which conveys the 

 secretions of the liver and pancreas. The other portions 

 are hanging free in the mesentery (a double fold of the 

 peritoneum"). The small intestines are lined with mucous 

 membrane, which contains glands and lacteals. These 

 lacteals originate in finger-like projections of the mucous 

 membrane, known as villi. Those glands which have 

 to do with secretion, with which we are now concerned, 

 are the liver, spleen and pancreas. The thyroids, little 

 reddish round bodies on the sides of the windpipe just 

 below the jaws, are of interest, owing to the scientific 

 curiosity as to their functions, which up to the present 



