182 VEKTEBRATE& 



the contents of the gall bladder out into ito The pale 

 or whitish compact mass lying between the stomach, in- 

 testine, and liver, is the pancreas. What is the relation 

 between this organ and the duct of the gall bladder ? 



IL Reproductive Organs. A pair of digitate, yellow 

 fatty bodies are attached to the dorsal wall of the body 

 cavity, behind the stomach, and close beside the median 

 line. The paired reproductive organs lie just poste- 

 rior to these, rounded yellow testes in the male ; and 

 folded or lobed, lighter colored ovaries in the female. 

 In the breeding season, the ovaries may be found so 

 distended with eggs as to fill out most of the body cavity. 

 The oviducts, which convey the eggs to the cloaca, are 

 very long and much convoluted tubes, having no connec- 

 tion with the ovary, but opening by a funnel-shaped 

 orifice into the body cavity near the esophagus. 



III. Renal Excretory Organs. A pair of reddish brown 

 kidneys lie on the dorsal side of the body cavity, near the 

 cloaca; and ducts from these pass to the large, white, 

 bilobed urinary bladder, which occupies the extreme pos- 

 terior end of the body cavity, and which, when found 

 empty, presents a crumpled appearance = 



The small, roundish red body, dorsal to the cloaca, arid 

 near the anterior end of the kidneys, is the spleen. 



IV. Circulatory Organs. The central organ of circu- 

 lation in the frog is the heart. In it find three divisions, 

 a firm muscular, conical posterior division, the ventricle; 

 and two anterior, thin-walled divisions, auricles. A cylin- 

 drical arterial trunk arises from the anterior end of the 

 ventricle, and passes obliquely forward across the upper- 

 most ventricle, and soon divides into two principal 

 branches. 



Now trace the principal arteries and veins. If the 

 arterial system has been injected, there will be no diffi- 

 culty in distinguishing between arteries and veins ; if not, 



