malf, this organ consists of two hearts, called the fleshy columns of the ventricle, 
closely and intimately connected. One of The structure of the ventricle is very dif- 
these is concerned with the circulation ferent from that of the auricle. It is a strong 
through the body, or the greater circula- muscular cavity, adapted to the office of 
tion ; the other with the circulation through forcibly projecting the blood through the 
the lungs, or the minor circulation. These arterial ramifications ; whereas the auricle 
might perform their offices if separate and is a mere reservoir, holding the blood until 
even distant from each other. Each of the ventricle has emptied itself by its con- 
these hearts consists of two cavities ; an au- traction. 
ricle, or membranous bag, placed at the The pulmonary artery, which arises from 
mouths of the veins ; a ventricle, or strong the upper and anterior part of this ventricle 
muscular organ, placed at the orifice of the conveys the blood into the lungs. The open- 
artery, and constructed for the purpose of ing of this artery, which is called the arte- 
driving the blood into that vessel and its rial orifice of the ventricle* is furnished with 
branches. three valves, called sigmoid or semilunar. 
The two auricles are placed at the basis which prevent any retrograde motion of the 
or broadest part of the heart ; and the two blood from the artery towards the heart, 
ventricles composing the chief bulk of the The venous blood, by being exposed to 
organ, are found in front of the former ca- the atmospheric air in the lungs, is altered 
In the following description of the struc- in which state it is returned to the left auri- 
ture of the heart, we shall trace the parts in cle of the heart by four pulmonary veins, 
the same order in which the blood passes two of which belong to each lung. This 
through them. This fluid, then, after cir- left or posterior auricle consists of a large 
culating through the blood-vessels of the cavity, called the sinus of the pulmonary 
body, after serving the various purposes of veins ; and of a smaller process or auricula, 
nutrition, secretion, &c. is returned into the Jt ; s situated quite at the upper and back 
right auricle of the heart by three large part of the heart, and transmits the blood 
veins, viz. the superior and inferior vena through the auricular orifice of the left ven- 
cava, and the great coronaiy vein. The tricle into that cavity. This opening is per- 
properties of this blood have been so alter- fectly similar in all essential circumstances 
its anterior part; the rest ot the cavity is a ] mgs t like a solid mass of flesh ; while the 1 
called the sinus of the vena; cavae. The right is comparatively thin and flabby. The 
lining of this bag, as indeed that ot all the reason of this difference is obvious. The 
other parts of the heart, consists of a smooth ] e ft ventricle has to drive the blood to the 
and Dolished surface. Hie muscular fioics nans nf ihp r < w . .1 . n. 
the right, anterior, or pulmonary ventricle, structure of the arteries. 
through a large circular orifice, called the 
annulus venosus, or the auricular orifice of Those vessels, through which the blood 
the ventricle. When this latter cavity con- flows from the heart into every part of the 
tracts, the blood would be driven back to- body, are called arteries. The term, which 
wards the auricle, were not this prevented is derived from «>ip, air, and t-nfau, I hold, 
chine. This valve is formed by a produc- Alexandrian school, in consequence of the 
tion of the lining of the heart, divided erroneous opinion which they entertained, 
' into three pointed portions. These are that these vessels were designed for the 
tied by tendinous strings to certain pro- distribution of air throughout the body, 
jecting packets of the muscular fibres, The larger arteries have thick and elastic 
