78 ALLEN 



renal arteries and finally breaks up on the posterior end of the 

 air-bladder. The single sperinatic artery (PL IV, fig. 31 ; Sper.- 

 A.), which performs part of the function of the urinary bladder 

 artery of Op/iiodon is given off from the aorta immediateh' in 

 front of the point where the caudal vein penetrates the kidney. 

 Near its source it sends off an intercostal arter}' (see fig. 31). 

 It then follows along the posterior margin of the kidney, to the 

 right of the caudal vein, and passing between the suprarenal 

 bodies,^ supplies each with a branch. The spermatic artery 

 then continues ventrad between the kidney and the reproduc- 

 tive organs, gives off caudad the tirinary bladder artery (fig. 

 31, Ur.Bl.A.), which is the only artery observed for the bladder. 

 When the genital organs are reached, the spermatic artery 

 anastomoses with the 2 anterior spermatic arteries already de- 

 scribed under the head of the mesenteric artery. 



VII. PERIPHERAL DISTRIBUTION OF THE VEINS. 



The veins in general follow their corresponding arterial 

 trunks, but not so closely as they do the nerves. There is 

 much less literature on the veins than on the arteries. In Se- 

 lachians where it is so much more difficult to inject the veins 

 this is not strange, but with the Teleosts no more difi^iculty is 

 experienced in injecting the veins. Generally the whole venous 

 system can be satisfactorily injected from one point. (See 

 under paragraph on technique). 



I. Jugular Veins. 

 These large sinus-like vessels (Pis. I and II, figs. 1,5, 15 

 and 16; J. v.), which are much longer than the corresponding 

 common carotid arteries, arise in front of the prootic process 

 from 3 principal trunks (see fig. 15). The external jugulars, 

 coming from the facial region ; the internal jugulars, coming 

 from the eye, eye-muscles, and brain ; and the orbito-nasal 

 vein. Each jugular immediately enters the foramen formed 

 by the prootic process and in its course through this foramen it 

 is a rather small vessel lying directly above the external carotid 



'The suprarenal l)odies are situated further caudad on the kidney than in 

 Op/it'odon. 



