194 PHYSIOLOGY AT THE FARM. 



pancreatic juice in animals generally has the power of convert- 

 ing starch into sugar, as is the case .with the secretion of the 

 salivary glands. And it has been alleged, on the evidence of 

 direct experiment, that the pancreatic juice of fowls and geese 

 possesses this property. 



Spleen. There is generally one spleen only in birds, very 

 variable in figure, being in different species round, oval, or 

 reniform. It lies between the left lobe of the liver and the 

 stomach, and is retained in its place by folds of the peritoneum, 

 as in mammals. It has no excretory duct ; its venous blood is 

 sent, as in mammals, to the portal vein. 



SUPPLEMENT TO THE ACCOUNT OF THE ACTS SUBSERVIENT 

 TO NUTRITION IN DOMESTICATED ANIMALS. 



The prehension of the food exhibits some remarkable dif- 

 ferences in different animals. The assistance which man and 

 many other animals derive from the thoracic extremities in the 

 prehension of the food shows how far from absolute is the 

 distinction between the functions of relation and the func- 

 tions of assimilation. The horse, the ox, and the sheep make 

 no use whatever of the thoracic extremities in the prehension 

 of food. The dog holds his prey with his fore feet while he 

 tears it with his teeth. The pig plants at least one foot on any 

 large piece of aliment while he detaches a portion of it with 

 his teeth. These are but trivial effects compared with the 

 aid obtained from the thoracic extremities in the prehension 

 of food by man, the monkey tribe, the rodent animals, and 

 other animals possessed of a clavicle or collar-bone. When 

 the fore legs no longer supply assistance in this act the lips 

 come to take an important share in this office, as in the horse, 

 the ox, and the sheep. The incisor teeth and the tongue are 



