XIII.] THE FEOa 225 



/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 may be 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 hgature round the truncus 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 pos- 

 terior end. When the injection is finished put the animal in 

 alcohol for some hours.] 



1. 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 run, one 

 on each side, towards the back of the thigh. 

 M, 15 



