180 PHYSIOLOGY AT THE FARM. 



behind the stomach, between the spleen and the duodenum. It 

 is in the dog, as in other animals, of a structure closely resem- 

 bling the salivary glands. For the most part the pancreatic ducts 

 and the common bile-duct have a separate insertion into the 

 duodenum, the pancreatic duct being the most distant from 

 the pylorus. There are, however, sometimes two pancreatic 

 ducts, one of which unites with the common bile-duct, while 

 the other is inserted into the intestine at the distance of a 

 few lines. This latter arrangement exists when there is one 

 pancreatic duct for the principal gland, and another separate 

 duct for the accessory or duodenal gland. 



Spleen. The spleen is closely connected with the left side of 

 the stomach. The omentum, between the layers of which the 

 stomach is contained, passes thence to the spleen, which thus 

 receives for its outer covering a part of the shut sac of the 

 abdominal peritoneum. The spleen is of a deeper colour than 

 in man. Its shape is long, flat, and prismatical. It is a very 

 vascular organ. The splenic artery is a branch of the cseliac 

 axis on the inferior aspect of the abdominal aorta. The 

 splenic vein is the most direct part of the portal vein with 

 which the veins of the rest of the chylopoetic and assistant 

 chylopoetic viscera successively unite. The nerves are from 

 the splanchnic nerve of the sympathetic system of nerves. 

 The peculiar structure of the spleen has been already described 

 under the head of the horse (p. 65). 



The digestive tract in the dog may be minutely traced in 

 fig. 16. 



ORGANS OF NUTRITION IN POULTRY. 



Bill, Mouth. The part which supplies the place of the 

 teeth in birds is the bill. This is formed of a horny sub- 

 stance of the same nature as the claws and spurs, and is 



