Nor do we need to seek any
other reason for the number of these pellicles beyond this that the
orifice of the venous artery being of an oval shape from the nature of its
situation, can be adequately closed with two, whereas the others being
round are more conveniently closed with three. Besides, I wish such
persons to observe that the grand artery and the arterial vein are of much
harder and firmer texture than the venous artery and the hollow vein; and
that the two last expand before entering the heart, and there form, as it
were, two pouches denominated the auricles of the heart, which are
composed of a substance similar to that of the heart itself; and that
there is always more warmth in the heart than in any other part of the
body- and finally, that this heat is capable of causing any drop of blood
that passes into the cavities rapidly to expand and dilate, just as all
liquors do when allowed to fall drop by drop into a highly heated vessel.
For, after these things, it is not necessary for me to say anything more
with a view to explain the motion of the heart, except that when its
cavities are not full of blood, into these the blood of necessity flows, -
- from the hollow vein into the right, and from the venous artery into the
left; because these two vessels are always full of blood, and their
orifices, which are turned towards the heart, cannot then be closed. But
as soon as two drops of blood have thus passed, one into each of the
cavities, these drops which cannot but be very large, because the orifices
through which they pass are wide, and the vessels from which they come
full of blood, are immediately rarefied, and dilated by the heat they meet
with.
Pages:
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58