36S 



THE FROG. PHYLUM CHORDATA 



and consists of an anterior and a posterior lobe, of different 

 tunction ihe anterior lobe arises solely from an ingrowth, 

 known as the hypophysis, from the roof of the mouth. The 

 posterior lobe is i)arth- hypophyseal, partly a yentral appendage 

 of the brain (the infundibulum). Its secretion is the means of 

 dilating the pigment cells in the frog's skin (p. 348), and has 

 yarions other effects (Fig. 285). 



The spleen is a small, round, dark red body, lying m the 



Fig. 265. — Two trogs nineteen days after operation. From that on the left only 

 the anterior lobe of the pituitary body has been removed ; from that on the 

 right both anterior and posterior lobes. Lack of the hormone from the posterior 

 lobe has caused in the right-hand frog pallor due to non-expansion of the 

 pigment in the pigment cells. — From Hogben. 



mesentery opposite to the beginning of the rectum. Its cells 

 remove and destroy effete red corpuscles or cells of the blood 

 (p. 375), and certain minute parasites. In some animals at least, 

 including man, it acts as a reservoir of blood. Its removal is not 

 fatal. 



The fat ])odies are two orange-coloured tufts of flattened 

 processes, attached in front of the ovary or testis to the dorsal 

 wall of the body cavity. They consist of fatty tissue (see p. 516) 

 which, like the reserves in the liver, increases during the summer 

 and decreases during the winter sleep, when it is being drawn 

 upon for nourishment, particularly in the preparation of germ 

 cells for breeding in the spriner^ 



