236 THE BIOLOGY OF THE ANIMAL 



its various coils and attachments. Endeavor to 

 make out the following parts : a posterior, thin- 

 walled portion, the uterine segment, near the 

 Iddney ; a middle portion, or glandular seg- 

 ment, which is very much coiled; and an ante- 

 rior, thin-walled portion, which passes back of the 

 lung and opens into the pleuro-peritoneal cavity 

 just behind the root of the lung. How long is 

 the oviduct ? Does it in any part of its course 

 unite directly with the ovary? Look for the 

 opening of the oviduct into the cloaca. 

 Make a diagram of the arrangement of the various 

 parts of the urino-genital system. 



F. — The Circulatory System. 



Kill with chloroform the largest obtainable 

 frog, fasten it down on its back in a dissecting- 

 pan, and open the skin by incisions extending, one 

 along the entire length of the median ventral line, 

 one along the middle line of each limb, one from 

 the pubis around the top of each thigh, in the 

 angle between the thigh and the body, and an- 

 other following the lower jaw-bone on each side. 

 Carefully turn back the flaps thus formed, pay- 

 ing particular attention to the points where blood- 

 vessels issue from the underlying parts to ramify 

 on the skin. Cut through the abdominal muscles 

 a little to one side of the median line ; cut through 

 the sternum, being careful not to injure the under- 

 lying blood-vessels ; and pin back the flaps. In 

 frogs dissected immediately after being chloro- 

 formed the heart will be found beating. 



If desired, the vascular system may be injected 

 from the heart; but this is not necessary, as the 



