THE HEPATIC AFFERENT VESSEL. 
609 
like the pulmonary or the aorta, the vessel which takes the blood 
to and propels it through the capillaries of the liver would be as 
well understood as the vessel which takes the blood to and propels 
it through the capillaries of the lungs, or as the vessel which 
takes the blood to and propels it through the capillaries of the 
general system. Physiologists understand the pulmonic and sys- 
temic afferent vessels, which consist each of a heart and artery, 
but not the hepatic afferent vessel, which consists of a spleen and 
vein. They perceive that the pulmonic and systemic afferent 
vessels produce a constant and rapid motion of the blood through 
the pulmonic and systemic capillaries; and if the hepatic afferent 
vessel had consisted, like them, of a heart and artery, they 
would have perceived that it also produced a constant and rapid 
motion of the blood through the hepatic capillaries; but, con- 
sisting as it does of a spleen and vein, they do not perceive 
that it produces an intermittent and slow motion of the blood 
through those capillaries. Heart and spleen, and artery and vein, 
are anatomical antitheses, and produce opposite physiological 
effects : — 
Heart -f artery = constant and rapid motion of blood. 
Spleen -f vein = intermittent and slow motion of blood. 
If the right auricle and ventricle were a spleen, and the pul- 
monary artery and its branches a vein in the middle of which the 
anterior and posterior venae cavse terminated, there would be an 
intermittent and slow motion of the blood through the pulmonic 
capillaries; and if the left auricle and ventricle we're a spleen, and 
the aorta and its ramifications a vein in the middle of which the 
pulmonary veins terminated, there would be an intermittent and 
slow motion of the blood through the general and systemic capil- 
laries ; and if the spleen were a heart in the auricle of which the 
mesenteric veins terminated, and the splenic and portal vein and its 
ramifications an artery, there would be a constant and rapid motion 
of the blood through the hepatic capillaries. 
Oct. 11, 1847. 
4 M 
VOL. XX. 
