26 



THE FROG 



These arc the kidneys. With the outer edge of each is 

 connected a tube, the ureter [iir), by which the urine, 

 formed in the kidneys, is carried to tlie cloaca (Fig. 7). 



It has been pointed out that the aladomen is lined 

 by peritoneum, and that the various organs are suspended 

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

 enteric canal, the mesentery. 'I'he relations of this mem- 

 brane are best seen in a diagrammatic transverse section of 



p.per 



C'.Jtjir ' 



ppe 



s cujys 



v. per 



Fig, 5. — Diagrammatic trans\'ci'se section tltrough llie trunk of a frog, to show the 

 relations of the peritoneum. 

 al'd. V. abdominal vein; tL ao. dorsal aorta: //. ilium; int. intestine: kd. 

 kidney ; m. muscles of back ; in', muscles of abdomen ; ntcs. mesentery ; p. per. 

 parietal layer of peritoneum ; p. /itr . the same, turning dottn to cover the 

 kidney: pt. a', postcaval vein; sk. skin; s.cn.ly.s. sub-cutaneous lymph- 

 sinuses ; spy. spermary ; s. v. ly. s. sub-vertebral lymph sinus ; u. St. urostylc 

 (part of the vertebral column); 7'. per. visceral layer of peritoneum, investing in- 

 testine ; -'. pii\ the same, Investing spermarj', 



the body (I'ig. 5). tlioiigh many points can be perfectly 

 well made out from tlie actual specimen. 'I'he body-cavity 

 is lined l.iy wliat is called the parietal layer of the 

 peritoneum (/. per), which adheres closely except in the 

 middle dorsal region, where it lea\es the body-wall and 

 becomes closely applied to the ventral surface of the 



