THE VASCULAR SYSTEM. 87 
THE VASCULAR SYSTEM. 
In the rabbit, as in all vertebrates, the vascular system 
(Fig. 46) embraces a central, muscular organ of propulsion, the 
PLAN OF THE heart, and a series of branched tubes, the blood- 
CIRCULATION. Vessels, the latter being of three different kinds: 
(a) thick-walled, elastic, distributing vessels — 
arteries ; (b) microscopic terminal canals in the peripheral organs— 
capillaries ; and (c) thin-walled collecting vessels—veins. 
The chief mammalian feature in this system consists in the 
division of the heart into two portions, 
each consisting of a receiving chamber, or 
atrium, and a driving chamber, or 
ventricle, and the arrangement of their 
vascular connections in such a way that 
two complete circulations are established. 
One of these is the long, or systemic 
circulation. It is concerned with the 
distribution of blood to the various parts 
of the body, with the exception of the lungs. """~ 
It is established by the left ventricle, the 
aorta, the carotid and subclavian branches 
of its arch, and the parietal and visceral 
branches of its thoracic and abdominal 
portions. The blood is collected from the body wal post limbs 
anterior portions of the body through ee AG. NES AAI 
. . irculation. rv, lv, right and 
paired internal and external jugular and {eft ventricles; ra, la, right and 
. . . . . left tri SCH SD FEES il 
subclavian veins, communicating with the  atves of gorta and pulmonary 
right atrium of the heart through paired  Sioventricular ehh are 
superior cavals; from the posterior portions 
of the body through the unpaired and also asymmetrical inferior 
caval vein, the latter passing forward on the right of the median 
plane and entering the posterior end of the right atrium. The 
second, short, or pulmonary circulation, is concerned with 
the distribution of the blood to the lungs for purposes of aeration. 
It is established by the right ventricle, the pulmonary artery and 
its paired branches, and by the capillaries of the lungs. The blood 
is delivered to the left atrium through several pulmonary veins. 
head, ant.limbs 


-precardial sustemic’ 
lungs 
precaval 
vein---- 
