218 ANIMAL PHYSIOLOGY. 
and the working of its various parts, we recommend him to 
pursue some such course as the following: 
1. To consult a number of plates, such as are usually fur- 
nished in works on anatomy, in order to ascertain in a general 
way the relations of the heart to other organs, and to the chest 
wall, as well as to become familiar with its own structure. 
2. To supplement this with reading the anatomical descrip- 
tions, without too great attention to details at first, but with 
the object of getting his ideas clear so far as they go. 
3. Then, with plates and descriptions before him, to examine 
several dead specimens of the heart of the sheep, ox, pig, or 
other mammal, first somewhat generally, then systematically, 
with the purpose of getting a more exact knowledge of the 
a various structures and 
; their anatomical as well 
as physiological relations. 
We would not have 
the student confine his 
attention to any single 
form of heart, for each 
shows some one structure 
better than the others; 
and the additional advan- 
tages of comparison are 
very great. The heart of 
the ox, from its size, is 
excellent for the study of 
valvular action, and the 
framework with which 
the muscles, valves, and 
vessels are connected; 
while the heart of the pig 
(and dog) resemble the 
human organ more close- 
ly than most others that 
can be obtained. 
It will be found very 
helpful to perform some 
of the dissections under 
Fra. 196.—The left auricle and ventricle opened and iad 
nts of their walls removed to show their cavities water, and by the use of 
Allen Thomson). 1, right pulmonary vein cut g . 
short: 1’, cavity of left auricle ; 8, thick wall of this or some other fluid 
left ventricle; 4, portion of the same with papillary q 
muscle attached ; 5, 5’, the other papillary mus- the action of the valves 
cles; 6, one segment of the mitral valve; 7, in : 
aorta is placed over the semilunar valves. may be learned as it can 
