J 



PLATE III. 



Common Frog [Rana Temporaria), 



Injected and dissected so as to show its circulatory organs, and especially its two 

 systems of veins supplying the liver and the kidney, and known as the 'portal' 

 and the ' renal portal ' systems. 



The ramifications of a subcutaneous veinj which must, like 

 the renal and hepatic systems, have a dej^uratory action on 

 the blood in these animals with transpirable skin; the renal, 

 reproductive, and parts of the muscular, lymphatic, and other 

 glandular systems of the creature are also shown in the figure. 

 An injection having been thrown into the ' renal portaF or renal 

 afferent vein of the left side, in a direction the reverse of that 

 which the blood took in it during life, that is to say, towards and 

 not away from the lower extremities, the figure shows that by this 

 means .the greater part or the whole of the main venous system 

 can be injected. And it shows, secondly, that a very free anasto- 

 mosis exists, not only between the two renal inferent veins of the 

 two sides of the body, but also between each renal inferent vein 

 and the epigastric, one of the main factors of the hepatic inferent, 

 or true portal system in all cold-blooded air-breathing vertebrata. 

 Hence the blood from the deeply-placed parts, muscular and other, 

 whence the radicles of these vessels arise, can return to the heart 

 through the venous system of either liver or kidney, as circum- 

 stances may require ; whilst the blood of the more superficially- 

 placed organs, glandular, cutaneous, and other, is aerated to a con- 

 sideral)le extent in the vascular network of the musculo-cutanoous 

 vein seen at d in the figure. By these arrangements the functions 

 of the lungs, which are lowly developed, and, in correlation with 

 the periodically recurring vast turgcseence of the generative organs, 

 of small size in the Amphibia, are efficiently supplomcntcd. 



