STOMACHIC ABSORPTION. 
99 
of the blood of the vena portae is able to pass into the general 
venous system, without traversing the capillary tissue of the 
liver.” * 
This fact, plainly demonstrated by anatomical researches, 
as well as the preceding one, explains the rapid passage of 
the blood from the vena portae into the vena cava ; and in- 
deed the latter has, under certain circumstances, been of 
aid in the progression of the two currents of fluid poured 
into it; but they establish no evident proof of the retro- 
gradation of the same fluid to the kidneys. 
A grave argument, and a serious one, against the theory in 
question, is deduced from the opposition met with by two 
currents of blood into the vena cava; of which one is di- 
rected from the liver to the kidneys, while the other tends to 
conduct venous blood from the hind quarters to the heart. 
Though the remark made on this subject by M. Bernard and 
the more celebrated modern physiologists, that the sangui- 
neous reflux in the vena cava is carried on by jets or waves, 
while the thoracic abdominal one, which is continually 
flowing through the collateral channel of the vena azygos, is 
of great assistance in explaining the mechanism of the hepato- 
renal circulation. 
We put the same faith in the w^ords of an author, the 
latest writer on veterinary anatomy, who, w hile describing 
the azygos of the horse, expresses himself thus : “ Its origin 
takes place along the inferior surface of the loins, on a level 
with two of the lumbar vertebrae, through deep-seated radi- 
cal muscular branches, having no communication with the 
posterior vena cava. At this point it receives two or three 
lumbar branches, coming from the superior muscles and the 
rachidian sinuses.” 
Arriving in this manner at the physiological consequences 
deducible from this disposition of the great venous trunk 
serving the office of posterior cava, he adds, — 
“The great vena azygos represents a canal for supply- 
ing the place of the posterior vena cava, too distant from 
the vertebral column in its thoracic portion to receive the 
vertebro-costal venous branches; wdiile, at the same time, it 
constitutes a collateral channel, in connection w ith the ra- 
chidian sinuses, to establish a readier communication between 
the posterior and anterior vena cavae. In this last respect, 
the function of the vena azygos becomes still more evident in 
certain animals, particularly in the ox, in which we find this 
* Notice sur les Travail x d’Anatomie et de Physiologie de M. Claude 
Bernard. — Comptes-rendus a 1’ Academic des Sciences, 3 Juin, 1850. 
