IX KIDNEYS 145 



into either a parallel or a divergent position. When they 

 are parallel the air, passing to and from the lungs, sets their 

 edges in vibration and gives rise to the characteristic croak, 

 the pitch of which can be slightly altered by stretching or 

 relaxing the cords. 



Structure of the Kidneys.— The form and situation of 

 the kidneys (Figs. 3, -4, and 7, ki) have already been referred 

 to. Each is a flattened organ of a deep reddish-brown 

 colour, its inner edge nearly straight but for one or two 

 notches, its outer edge curved. Its ventral face is covered 



urtu 



per 



per' 



nat 



ffl 9^ fJ-st 



Fig. 46. — Transverse section of frog's kidney. 

 gl. glomerulus ; m. cp. Malpighian capsule ; nsi. nephrostome ; per. peritoneum 

 covering ventral face of kidney ; per' . fold of peritoneum supporting its outer 

 border ; per^'. fold supporting its inner border ; UR. ureter ; ur. iu. urinary 

 tubules, (After Marshall and Bles.) 



by peritoneum (Fig. 46, per), continued on the one hand 

 into the parietal layer (Fig. 5, /. per), of that membrane, on 

 the other into the mesentery {mes^ ; its dorsal face is bathed 

 by the lymph of the subvertebral sinus {sv. ly. s.) From the 

 posterior end of its outer edge a delicate tube, the ureter 

 (Figs. 3, 4, and 7, ur), passes backwards and opens into the 

 dorsal wall of the cloaca. On its ventral face is a singular 

 yellowish-white stripe, the adrenal ox supra-renal body, an 

 organ of unknown function (Fig. 7, between the lines from 

 kd and ts). 



PRACT. ZOOL. L 



