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 niovements are to some extent regulated by the annoutit 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 a certain 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 SO, 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. 



Soma of the most extreme rases are yet more remarkable. Thus pulses of 

 108, 9G 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. In a 

 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. In asphyxia, the heart beats rapidly at 

 first, becomip.ii: slow, as the circulation is checked in (he 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 w^hich then ensues has usually 

 been ascribed by physiologists, in 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 I 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 

 i 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 

 receiv<i 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 



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