-142 



PROF. W. N. F, WOODLAND ON LIGATURING THE 



contract] OIKS to propel the current of blood along tlie systemic 

 arteries, and the pulmonary vessels leqnire 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 coiiceive the portal circulation to 

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

 quarry and reduced to a state of torpor ; the animal functions 

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

 lation of the food are in full pla}-, 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 being the meaiis of conveying common venous blood into the 

 liver, goes to prove that the blood of the venae portae does not 

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

 other viscera to flt it for the secretion of bile."' This explanation 

 seems plausible, especially when we reflect that the commori 

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

 the blood always flows anteriorly in the so-called hypogastric veins 

 (also sometimes called the " renal portal " veins) of the bird 

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

 prol)able that the blood in these veins always flows posteriorly *, 

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

 authors. But this explanation evidentlydoes not apply to animals 

 like Amphibia and lleptilia, wdiich are notoriously sluggish and 

 yet })Our into their livers a much greater proportion of non-gut 

 venous blood than birds. Also in Mammals, which njost resemble 

 Birds in the alternating activity of the respiratory and portal 

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

 does not exist. 



Now a supply of ordinary non-gut venous blood to the liver 

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

 obtain a greater 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 alw\ays 

 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 Fishes, Reptilia, 

 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 course 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 almost certain 

 that these so-called hypogastric veins of birds are the lionioh)g-ues of the " pelvic " 

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

 so, the blood must tiow posteriorly in them. 



f M. S. Jourdain, " Recherches sur la Veine Porte Renale." Annales des Sciences 

 Na'^urelles, 4 ser., Zoologie, Tome xii. 1859, p. 134. 



