VEKTEBRATA. 59 



Class II. AMPHIBIA. 

 Order BATRACIHA. 



93. A Common Frog (Rana temporaries), dissected and in- 

 jected to shew the reni-portal system, and the chief trunks of the 

 arterial and venous systems. 



A white bristle has been placed beneath the crural vein ; 

 if this vein be traced upwards from the leg it will be seen that 

 in the groin it divides into two branches, and that one of them, 

 the outer one, passes upwards to the kidney, along the outer 

 side of which it runs, and ultimately breaks up into capillaries 

 in that organ. This is the reni-portal vein. The second 

 branch of the crural curves round the front of the groin, 

 towards the medio-ventral line, where it unites with the cor- 

 responding branch of the crural vein of the other leg to form 

 the epigastric or umbilical vein. The latter vein, after receiving 

 one or two small twigs from the large and persistent allantois, 

 passes up the median line of the abdomen till it reaches the 

 liver, where it joins the portal vein, and subsequently ramifies 

 through that organ. It will thus be observed that the whole of 

 the blood in the hinder extremities of the body, after passing 

 through the capillaries proper to these parts, traverses in addi- 

 tion one of two sets of capillaries, either going by the reni-portal 

 vein to those of the kidney, or by the epigastric to those of the 

 liver. The hepatico-portal system is also shewn. A loop of 

 intestine has been pulled out and fastened to the right side of 

 the animal. The veins of the intestine are seen to unite and 

 re-unite, and by successive unions to form the portal vein which 

 passes upwards to the liver. The left superior vena cava is, 

 as usual, formed by the union of the jugular and subclavian 

 veins. A black bristle has been placed beneath it, just before 

 it curves round the base of the heart to reach the right auricle. 

 The large inferior vena cava is formed by the confluence of 

 the veins from the two kidneys, between which it is to be 

 seen. It passes forwards in relation with the posterior surface 

 of the liver, and, after receiving the hepatic veins, enters the 

 right auricle, (The liver has been displaced to the right so 

 that the posterior surface has, in this specimen, become the 

 anterior.) 



