THE CIRCULATION OF THE BLOOD. 919 
‘in no other way. By a little manipulation the heart may be so 
held that water may be poured into the orifices, prepared by a 
removal of a portion of the blood-vessels or the auricles, when 
the valves may be seen closing together, and thus revealing 
their action in a way which no verbal or pictorial representa- 
tions can do at all adequately. 
Fie. 197.—View of the orifices of the heart from below, the whole of the ventricles having 
been cut away (after Huxley). RAV, right auriculo-ventricular orifice, surrounded by 
the three flaps, ¢. v.1, ¢.v. 2, t. v. 3, of the tricuspid valve, which are stretched by weights 
Stith Mulucnary ariery, Wie aetitiniek valved Menreeeniad ae HAVRE Wel ald elosedl 
together. .AO, orifice of the aorta. 
A heart thoroughly boiled and allowed to get cold shows, 
on being pulled somewhat apart, the course, attachment, and 
other features of the fibers very well, as also the skeleton of 
the organ, which may be readily separated. 
When this has all been done, the half is not yet accom- 
plished. A visit to an abattoir will now repay amply for the 
time spent. Animals are there killed and eviscerated so rapidly 
that an observer may not only gain a good practical acquaint- 
ance with the relations of the heart to other parts, but may 
often see the organ still living and exemplifying that action 
peculiar to it as it gradually approaches quiescence and death 
—a matter of the utmost importance. 
If the student will then compare what he has learned of the 
mammalian heart in this way with the behavior of the heart 
of a frog, snake, fish, turtle, or other animal that may be killed 
after brief ether narcosis, without cessation of the heart’s ac- 
