THE FROG, OR THE TOAD. 113 



yellowish tissue in the back part of the abdominal cavity constitute 

 the corpus adiposum or fat body. 



i) The reproductive organs lie to the right and left of the median line, 

 the ovaries of the female probably more or less distended with 

 very many small, dark eggs or ova. The long, coiled oviducts 

 open at one end into the cloaca. Find the other end of the ducts 

 by careful searching. How might the ova get from the ovaries 

 into the oviducts? The two whitish, oval testes of the male 

 discharge their products into the kidneys. From there they pass 

 into the cloaca through the urino-genital ducts. 



j) The elongated, dark colored kidneys are located above the repro- 

 ductive organs. Trace their connection by means of the ureters 

 (female) or urino-genital ducts (male) with the cloaca. It will be 

 observed that the urinary bladder is not, as in the catfish, an 

 enlargement of the ureter, but a pocket from the cloaca filling by 

 gravitation. 



Technical Note. Remove the remaining internal organs and rinse the 

 body cavity. Make out such portions of the bony skeleton as can be 

 determined without further dissection. 



k) Note the several vertebrae forming the backbone. Determine the 

 number if possible. Are there any ribs ? The last vertebra, 

 sacral, is followed by a long, slender bone, the urostyle. On 

 each side of the urostyle is a part of the pelvic girdle called the 

 ilium. The two ilia unite posteriorly, thus forming an arch 

 shaped very much like the wish-bone of a bird. The anterior ex- 

 tremities of the arch articulate with lateral projections of the sacral 

 vertebra. At these articulations we have the two humps so 

 noticeable on the frog's back when sitting at rest. All these struc- 

 tures and arrangements can be made out, without dissection, by 

 the sense of touch. Relate them to the animal's movements in 

 jumping. 



THE NERVOUS SYSTEM. In a specimen that has been preserved in 

 alcohol, or one that has been macerated for a day or so in 20 per cent 

 nitric acid, dissect away carefully the roof of the skull and the top of 



