OP ANIMAL BODIES. 
95 
distributed anew into the system. This assigns to the 
heart a double office. The pulmonary circulation is a 
system within a system; and one action of the heart is the 
origin of both. 
For this complicated function, four cavities become ne¬ 
cessary; and four are accordingly provided: two, call¬ 
ed ventricles, which send out the blood, viz. one into the 
lungs, in the first instance; the other into the mass, after 
it has returned from the lungs: two others also, called 
auricles, which receive the blood from the veins; viz. one, 
as it comes immediately from the body; the other, as the 
same blood comes a second time after its circulation 
through the lungs. So that there are two receiving cavi¬ 
ties, and two forcing cavities. The structure of the heart 
has reference to the lungs; for without the lungs, one of 
each would have been sufficient. The translation of the 
blood in the heart itself is after this manner. The receiv¬ 
ing cavities respectively communicate with the forcing 
cavities, and, by their contraction, unload the received 
blood into them. The forcing cavities, when it is their 
turn to contract, compel the same blood into the mouths of 
the arteries. 
The account here given will not convey to a reader, ig¬ 
norant of anatomy, anything like an accurate notion of the 
form, action, or use of the parts, (nor can any short and 
popular account do this;) but it is abundantly sufficient to 
testify contrivance; and although imperfect, being true as 
far as it goes, may be relied upon for the only purpose for 
which we offer it, the purpose of this conclusion. 
“ The wisdom of the Creator,” saith Hamburgher, “is 
in nothing seen more gloriously than in the heart.” And 
how well doth it execute its office! An anatomist, who 
understood the structure of the heart, might say before¬ 
hand that it would play; but he would expect, I think, 
from the complexity of its mechanism, and the delicacy 
of many of its parts, that it should always be liable to de¬ 
rangement, or that it would soon work itself out. Yet 
shall this wonderful machine go, night and day, for eighty 
years together, at the rate of a hundred thousand strokes 
every twenty-four hours, having, at every stroke, a great 
resistance to overcome; and shall continue this action for 
this length of time, without disorder and without weari¬ 
ness. 
But farther: from the account which has been given of 
the mechanism of the heart, it is evident that it must re¬ 
quire the interposition of valves; that the success indeed 
