26 THE FROG 



(nr), by which the urine, formed in the kidneys, is 

 carried to the cloaca (Fig. 7). 



It has been pointed out that the abdomen is lined 

 by peritoneum, and that the various organs are sus- 

 pended by folds of the same membrane, called, in the 

 case of the enteric canal, the mesentery. The relations 

 of this membrane are best seen in a diagrammatic 

 transverse section of the body (Fig. 5), though many 



S CU.ll/.S 



' v.per- 



z&ct.v 



FIG. 5. Diagrammatic transverse section through the trunk of a Frog, to show the 



relations of the peritoneum, (x 2\.) 



abd. t. abdonr'nal vein ; d. ao. dorsal aorta ; i/. ilium : int. intestine ; kd. kidney ; 

 m. muscles of back ; m'. muscles of abdomen ; mes. mesentery ; p. per. parietal 

 layer of peritoneum ; p. per', the same, turning down to cover the kidney ; 

 pt. cv. postcaval vein ; sk. skin ; s. cu. ly. s. sub-cutaneous lymph-sinuses ; 

 spy. spermary ; s. t;. ly. s. sub-vertebral lymph-sinus ; u.st. urostyle (part of the 

 vertebral column); v. per. visceral layer of peritoneum, investing intestine; 

 v. per", the same, investing spermary. 



points can be perfectly well made out from the actual 

 specimen. The body-cavity is lined by what is called 

 the parietal layer of the peritoneum (p. per], which ad- 

 heres closely to the body-wall except in the middle 

 dorsal region, where it becomes closely applied to the 

 ventral surface of the kidneys and reproductive organs. 

 Leaving these, the peritoneum of the right side 



