286 



AMPHIBIA 



Urinogenital Organs. — Every cell excretes as well as secretes, 

 part of the waste passing off as CO2, while solids are discharged by- 

 special organs. The skin is an organ of excretion in the frog. In 

 higher vertebrates the sweat glands excrete. The liver is an im- 



Suprarenal qlond 

 Kidney 



Lcydic^s duct 

 S&rninal vesir.l& 

 Rectum 



Open'inq of Leydiqs duct 



—Urinary bladder 

 (pulled bock) 



Fig. 153. Urinogenital system of male bull-frog. (Drawn by W. J. Moore.) 



portant excretory organ, through bile and the formation of urea. 

 The walls of the intestines are important in excretion. The kidneys 

 are the most important. The kidneys of the frog are oval, flattened, 

 dark red bodies in the posterior part of the body cavity. The duct 

 of the kidneys (ureter) is at the outer margin of the kidneys. The 



