.142 I'HOK. W. N, F. WOODLAND O.N LIGATURING TUli 



contivactioiKS to propel the ciuTent of blood along the systemic 

 arteries, and the pulmonary vessels require the greatest possible 

 supply of blood to serve the heart with the due quantity of 

 arterialized fluid : the digestive system, on the other hand, is in 

 a state of repose, and we may conceive the portal circulation to 

 be at its lowest ebb. Suppose the Eagle to be glutted witli his 

 quarry and reduced to a state of torpor ; the anima,! functions 

 are now at rest, but the organic powers concerned in the assimi- 

 lation of the food are in full play, and the portal or hepatic 

 circulation is as active as was the pulmonary a short time before.'' 

 And Owen further adds that "the anastomosis of the pelvic veins, 

 in beino- the means of conveying common venous blood into the 

 liver goes to prove that the blood of the venae portre does not 

 require any peculiar preparation l)y circulation in the spleen or 

 otiier viscera to fit it for the secretion of bile.' This explanaticui 

 seems plausible, especially when we reflect that tlie common 

 assumption made in nearly all modern text-books to the eftect that 

 the blood always flows anterm^l]/ in the so-called hypogastric veins 

 (also sometimes called the " renal portal " veins) of the l.tird 

 is almost certainly wrong, it being, on the contrary, more than 

 probable that the blood in these veins always flow^s posteriorly *, 

 as conjectured long ago by Jacobson (1817), Jourdainf, and other 

 authors. But this explanation evidently does not apply to animals 

 like Amphibia and Reptilia, which are notoriously sluggish and 

 yet pour into their livers a much greater proportion ot non-gut 

 venous blood than birds. Also in Mammals, which mo.st resend)le 

 Birds in the alternating activity of the respii'atory and portal 

 systems, a communication between the post-renal and portal veins 

 does not exist. 



Now a supply of ordinary non-gut venous Idood to tlie liver 

 may signify (1) that the venous blood is to enable the liver to 

 obtain a o-veater supply of water than it would otherwise receive, 

 or (2) that the liver is, in part, in these forms, an organ of 

 excretion and supplementary to the kidneys. The first supposition 

 naturally occurs to one when Amphibia are in question, since a. 

 toad or frog certainly never drinks water by mouth, but always 

 absorbs it by the belly and thigh skin, and this water pre- 

 sumably is taken to the liver by the anterior abdominal vein 

 (and to the kidneys by the renal afferent veins), and this is 

 probably the case in all Amphibia. Though in Pishes, Reptdia, 

 and Birds there is no certain evidence of cutaneous absorption 

 of water, yet it is well known that Snakes and Lizards frequently 

 evince a desire to lie in water, and Fishes, Crocodiles, and Turtles 

 of coui'se habitually live in it. It may also be remarked that the 

 anterior abdominal vein, or its equivalent, usually has factors from 



* This is a subject I hope to investigate in the near future. It is ahnost certain 

 that these so-called hypogastric veins of birds are the homologues of the " pelvic " 

 veins of Amphibia and Reptiles and not of the "renal portal " veins, and if this be 

 so, the blood must flow posteriorly in them. 



t M. S. Jourdain, " Rechevches sur la Veine Porte Renale." Annales dos Sciences 

 JIa!}urelles, 4 ser., Zoologie, Tome xii, 1859, p. 134. 



