STOMACHIC ABSORPTION. 97 
be the result of digestion or of venesection, the course of the 
blood to the heart becomes quickly re-established. 
The intimate relation existing between the vena portae and 
the kidneys, as shown by comparative anatomy, informs us 
that, in reptiles, the trunk of the vena portae receives the 
veins from the posterior extremities, and often from the kid- 
neys as well, prior to the vena furnishing the ramifications 
which run directly into the uriniferous tubes, to constitute a 
renal vein, whose divisions receiving those of the emulgent 
artery, the blood of the first mixes with the arterial before 
the capillary network envelops the uriniferous conduits. From 
this anatomical arrangement, results a fresh approximation of 
structure and function between the liver and kidneys. 
We may generally call to our aid, according to the theory 
of M. Bernard, the muscular structure of the posterior vena 
cava, indicated by most writers on anthropotomy and 
veterinary anatomy ; though nobody has studied this with 
more care, or described it with more exactitude, as the fol- 
lowing passage will convince us : 
“ The vena cava of the horse, at the moment of its passage 
through the liver, as well as the sub-hepatic veins, present a 
muscular structure developed to a degree which I have no- 
where seen described. In every part connected with the 
liver, the posterior vena cava presents a larger calibre, and its 
parietes acquire increased thickness, owing to the existence 
of a strong muscular tunic. The fleshy fibres, for the most 
part, run longitudinally, forming red bundles lying parallel 
to one another. Before entering the liver, and after quitting 
it, the walls of the vena cava are much mOre attenuated, and 
present a structure altogether different. 
“ The muscular system I have just described in the vena 
cava, is equally. demonstrable in the sub- hepatic veins. There, 
as in the cava, the fibres run longitudinally, and form the 
same sort of fasciculi. 
“ Examined through a microscope, the said muscular layer 
surrounding the cava and hepatic veins, appears composed of 
smooth, not striated, fibres. 
“ The parietes of the hepatic vena portse presents no such 
muscular arrangement. And, for the rest, are surrounded by 
the capsule of Glisson, which allows of their dilatation or 
contraction independently of the substance of the liver; 
while the parietes of the sub-hepatic veins, being intimately 
adherent to the tissue of the liver, are to shorten themselves 
without causing a sort of compression or contraction of the 
hepatic tissue. 
“ Man, the sheep, the dog, rabbit, &c., have the same 
xxvii. 13 
