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TEXTBOOK OF ZOOLOGY 



body, Bidder's organ, Avhich is thought to represent a rudimentary 

 ovary. Some experiments on the toad in which the testes were 

 removed have indicated that this body may develop into a func- 

 tional ovary. In male toads there also may be found alongside the 

 mesonephric duct a coiled tube which is the remains of a rudi- 

 mentary oviduct that is nonfunctional. This rudimentary structure 

 is not found in the male bullfrog, although it is encountered in the 

 male leopard frog. 



Blood Vascular System 



For studying the blood vascular system, as well as some other 

 systems, the toad is quite superior to the leopard frog. The vessels 

 are of larger caliber, and the broad interior of the body makes the 

 dissection more easily examined. The bullfrog, of course, is superior 

 to either of these. 



Scapu la 



Coracoid 



Epicoracoid 

 Mesosterrium 



rnuTTi 



Fig. 293. — Diagram of ventral view of tlie arciferal, pectoral girdle of toad. 

 (Modified from Kellog, Mex. Tailless Amphibia. U. S. National Museum Bulletin 

 No. 160.) 



Arterial System. — The subclavian artery is larger in proportion 

 to the size of the animal than in the bullfrog. It sends large 

 branches to muscles of the pectoral girdle, forelimb, and to the 

 upper portion of the bulky side muscles. Two or three conspicuous 

 branches of the vertebral artery run diagonally across the dorsal 

 wall of the body cavity to the lateral muscles of the body which 

 they enter. One large femoral branch, instead of two small ones, as 

 in the bullfrog, is given off from the sciatic artery in the upper leg 

 and runs ventrally, branching into the surrounding muscles. 



Venous System. — The parietal branches of the ventral abdominal 

 vein are relatively larger in the toad and may extend horizontally 

 across the ventral body wall to the large side muscles, The dorso- 



