436 | [ NovEMBER, 
During prolonged inspiration, therefore, the left heart receives but little blood. 
In the state of expiration, on the contrary, it receives a larger share. But the 
heart’s movements are to some extent regulated by the amount of blood which 
enters its cavities, and hence we have in inspiratory movements a slow pulse, and 
in expiratory action a quick pulse. Such are, to acertain extent, the explanations 
of Dr. J. Reid, who noticed the phenomena in question, during his vivisections. 
I have found no occasion to contradict his conclusions, and my own explanations 
go to prove what that great physiologist merely inferred. I have also made cer- 
tain novel applications of this knowledge, such as will be found in my paper, de- 
tailed at some length. 
i have observed the above mentioned phenomena on animals, and even in the 
unusually prolonged respiratory movements of a few human subjects. 
During fixed inspiration the pulse lowers, in a large proportion of men. In 
fixed expiration, on the contrary, the pulse rises. Thus,an average of 40 cases 
gave the following results :-— 
Normal pulse 80, inspiratory pulse 70, difference 10 ; expiratory pulse 93; ex- 
cess over normal pulse, 13 beats ; extreme of numeral difference between the in- 
duced pulses, 23. 
Of the 40 pulses thus recorded, during fixed inspiration, 6 fell, over 20 beats, 
8 fell, over 12 and 18, 5 or over 5 beats, per minute. 
Some of the most extreme cases are yet more remarkable. Thus pulses of 
108, 96 and 92, fell respectively, 49, 28 and 26, per minute. The largest rise in 
fixed expiration was 36 pulsations per minute; the normal pulse being 83. Ina 
case of hypertrophy of the heart, with a pulse of 80, it fell so much in fixed in- 
spiration and rose so much in a like expiratory condition, as to make a total dif- 
ference of fifty pulsations between the two states. 
For more minute information, I refer to the paper above mentioned. 
I offer the following explanation of the facts thus recorded. 
It is possible that nerve power may in some way assist in producing the re- 
sults: of this, I have no direct evidence. Jn asphyxia, the heart beats rapidly at 
first, becoming slow, as the circulation is checked in the capillaries of the lungs. 
In this stage of asphyxia, the right heart is congested and the left heart has too 
little blood. That slow pulsation of the heart which then ensues has usually 
been ascribed by physiologists, th part at least, to this double irregularity in the 
distribution of the blood. 
During profound and retained inspiration, we dilate the air cells at the expense 
of the neighboring capillaries. As a consequence their circulation is somewhat 
impeded, blood accumulates in the right heart, is deficient in the left heart, and 
the whole organ beats slowly. Dilation of the pulmonary vesicles may be pro- 
duced by direct distension, as when we blow into the trachea, or by forces acting 
from without, as occurs during life, in the thoracic movements. In the first case, 
we have the additional element of pressure, which, however, does not very ma- 
terially alter the conditions, as | have shown elsewhere. The following experi- 
ments illustrate the propositions above stated. 
Owing to difficulties almost insurmountable, the dilatation of the air cells was 
made by insufflation, and not by expansible forces acting from without. A tube 
was placed in the trachea of a pair of dead lungs taken from a sheep, a glass tube 
+ inch in diameter and three feet long, was tied in the mouth of the pulmonary 
artery. A similar tube was in like manner adjusted to the left auricle, so as to 
receive all fluids coming from the lungs. A column of fluid was placed in the 
tube of the pulmonary artery. It ran into the lungs, and at last rose slowly in 
the tube which I had tied in the mouth of the left auricle. The lung was now 
filled with air by gently inflating through the tracheal tube. As the lung ex- 
panded, the fluid usually fell a little in both tubes, and most in that of the pulmo- 
nary artery. ‘The water still passed through the vessels until a state of extreme 
tension was attained, when the tide was checked. To do this completely, re- 
quired a fuller inflation than could occur in health. In fact, I have sometimes 
been able to force both columns of liquid in a reverse direction, 2 or 3 inches up 
the tubes. As the lung was allowed to contract in expiration, the fluid ran 
through the vessels with a facility which seemed greatest during complete ex- 
piration. When the bloody fluid stood at a level in both tubes, inspiratory 
