234 ELEMENTARY BIOLOGY. [CHAP. 



/3. Towards the bottom of the leg it comes to 

 the front of the ankle-joint, and divides into 

 branches which are distributed on the dorsum 

 of the foot. 



[F. DISSECTION OF THE VASCULAR SYSTEM. 



The dissection of the blood-vessels is much facilitated by 

 previous injection: this maybe done as follows: Dissolve 

 some gelatine, with the aid of heat, in a coloured fluid 

 (solution of carmine or of Berlin blue) ; the gelatine ought 

 to be added in such quantity that the fluid just sets when 

 cold : kill a frog with chloroform ; lay bare its heart, taking 

 care not to injure the anterior abdominal vein ; prick a 

 small hole in the venous sinus and sop up any blood that 

 flows out; pass a ligature round the trunctts arteriosus; 

 make a small aperture in the ventricle and pass a glass 

 tube, drawn out to a fine point, through the ventricle into 

 the arterial bulb, and tie it in ; fill this tube with normal 

 salt solution and connect it, by a bit of gutta percha tubing, 

 with a syringe filled with the injecting fluid, which should 

 not be warmer than 35 C. ; inject very slowly and with 

 slight pressure. The venous system may also be readily 

 injected by dividing the anterior abdominal vein and 

 passing the syringe into its posterior end. When the in- 

 jection is finished, put the animal in alcohol for some 

 hours.] . ; 



i. The anterior abdominal vein. 



a. Carefully dissect the belly-walls away from the 

 anterior abdominal vein : at its posterior end 

 this vessel will be found to get a small branch 

 from the front of each thigh and then to divide 

 into two large trunks (pelvic veins) which nin, 

 , . c one on each side, towards the back of the thigh. 



