274 



THE BIOLOGY OF THE FROG 



from the tongue, hyoid, thyroid, and pseudo-thyroid glands 

 and floor of the mouth. 



The innominate vein, or second branch of the anterior 

 vena cava, passes laterally and divides into the internal 

 jugular, which receives blood from the brain and various 

 parts of the head, and the subseapular, which runs along the 

 outer side of the fore limb and receives branches from the 

 shoulder. 



The subclavian, or posterior branch of the anterior vena 

 cava, is formed by the confluence of the braehial, which is 

 distributed to the fore limb, and the large eutaneous vein, 

 which is extensively distributed over the side of the body 

 and head. The latter returns most of the blood carried by 

 the cutaneous artery. 



The XdiXgQ posterior vena cava arises between the kidneys, 

 and runs forward ventral to the dorsal aorta to the tapering 

 posterior end of the sinus venosus. Near the latter it 

 receives the large but very short hepatic veins from the 

 liver. 



The renal veins, four to six in number on each side, lead 

 from the kidneys into the posterior vena cava ; the veins 

 from the reproductive organs {spermatic or ovarian, accord- 

 ing to the sex of the' animal) lead either directly into the 

 vena cava or first into the renal veins. The vena cava also 

 receives one or two branches oft either side from the fot 

 bodies. 



The blood from the hind limbs does not empty directly 

 into the posterior vena cava as in the higher vertebrates, but 

 it is forced to pass through a second system of capillaries 

 before reaching that vessel. Two large veins convey the blood 

 from the hind legs, the sciatic, which runs along the post- 

 axial side of the thigh, and \.\\q femoral, which courses along 

 the dorsal and anterior side of the thigh and passes under 



