ANATOMY AND PHYSIOLOGY 



13 



Difficulty in locating and tracing the ureter arises from the fact that 

 it is attached to the dorsal surface of the expanded portion of the 

 rudimentary oviduct. The ureter is, however, entirely distinct from 

 the oviduct ; each oviduct and each ureter opens separately on the dor- 

 sal wall of the cloaca. Each testis discharges its seminal fluid, con- 

 taining the male germ cells, through the ductus efferentes (vasa effer- 

 entia), several very slender ducts which can perhaps be seen running 

 through the mesorchium from testis to kidney. Inside the kidney 

 these ducts connect with the ureter, which functions as a ductus def- 

 erens (vas deferens) through which the seminal fluid reaches the 

 cloaca. Make a drawing ( X 3 or 4) of the male urino-genital organs, 

 including the cloaca and the bladder, as seen from the ventral aspect. 

 Be very careful to show accurately the relationship of ureters, ovi- 

 ducts, bladder, and cloaca. Examine a dissection of the urino-genital 

 system of a female frog. 



E. The Circulatory System 

 Exercise 13. — The Heart and Larger Arteries, 

 (a) Remove the large intestine, cloaca, bladder, oviducts, gonads, 

 and fat-bodies, but be careful not to injure the kidneys, blood vessels, 



ccrx)fkf cr/ery 

 Si/sfc/n/c arfery 

 po/mo-catc7neoui> 



f^/ff^f oor/c/e ■ 



semi-fahar va/^e 



trurycas 

 onrer/o5(y5 



ope^'ncjr of 

 pu/monary ve/n 



openjnof of 

 sinus i/enosus 



■/eff- ac/r/c/e 

 aan/ca/o -i^nfr/cufar 



ventn/c/Q 



Fig. 15. — Heart of the frog, with the ventral walls of the ventricle and 



auricles removed. 



and nerves. Cut away any remaining portions of the pericardium, the 

 thin membrane surrounding the cavity in which the heart lies. The 

 heart consists of three chambers: the ventricle, a thick- walled, conical 

 portion, and in front of this the right and left auricles which are thin- 

 walled and lie on each side of a single large vessel, the truncus arteri- 

 osus, which passes diagonally forward from the ventricle (Fig. 15). 



