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wards divides into tliree cavities, which, contract in succession ; 
one of these is an auricle, another is a ventricle, and the third 
is a large bulb, which receives the blood as it leaves the heart. 
The heart has thus assumed the condition in which it exists 
permanently in fish, namely, a two-chambered cavity ; for the 
bulb must be regarded as a vessel, and indeed soon splits up 
into a number of arches, which remain permanent in fish, and 
carry the blood first to the branchial or gills, and afterwards 
round the body ; but in higher animals these arches become 
closed after a time, with the exception of three, one of which 
remains persistent, and forms the arch of the aorta ; a second 
is the vessel which we mentioned above as connecting the 
right ventricle with the arch of the aorta before birth, and 
becoming closed in one part soon afterbirth; and the third is a 
similar vessel on the right side, which, however, becomes closed 
before birth. The part of the second one which remains open, 
gives off the artery to the lungs, which, of course, remains 
persistent ; and some parts of the other closed arches still 
remain open, and become the arteries for the head and arms. 
Next in order, in the development of the heart itself, comes 
the separation of the auricle into two chambers, thus giving 
us the heart of the Batrachians and lower reptiles (an opening, 
however, still remaining until birth, as is mentioned above) ; and 
then a division is formed in the ventriele also, which is com- 
pleted before birth, and is found in the crocodiles, birds, and 
mammalia, including man himself. The bulb mentioned above 
becomes swallowed up in the ventricles, and the partition, after 
separating the ventricle into two, goes on, and separates the 
base of the bulb into two, thus separating the roots of the 
pulmonary artery and aorta. 
We have thus given a brief outline of the structure, functions, 
and development of the heart, that beautiful machine by which 
circulation is kept up and nutriment supplied to all parts of the 
body. Who can witness such contrivance, such resource and 
ingenuity, without feeling himself compelled to acknowledge the 
existence of an Almighty and benevolent Designer ? If it be 
true that “ the undevout astronomer is mad,” much more, we 
think, is the undevout anatomist, and they most unjustly libel 
the science, who say that the study of it has a tendency to foster 
atheistic sentiments. 
We have seen this machine, the heart, at rest, as it is pre- 
sented to the view of the anatomist, both at various stages of 
its development, and in its perfect state. It is possible even to 
witness it in motion discharging - its functions, as it is presented to 
the view of the physiologist, yet even then we should have seen 
but the commencement of the wonders that exist there ; for 
what those mysterious forces are which first develope its struc* 
