RESPIRATION, 209 



threatening in the chest equally during expiration and inspiration, 

 the shrinking of the lungs should occasion the blood to stream 

 towards the heart as much during the one as the other, to fill up 

 the vacuum. But this is not the fact, any more than, as we saw, 

 that air rushes into the wounded pleura during expiration. The 

 coincidence of the effect of inspiration on the venous blood, and, 

 when the pleura is wounded, on the air, prevents us from sup- 

 posing that inspiration affects the circulation merely by giving a 

 free passage of blood through the lungs. " The great venous 

 trunks of the head, neck, chest, abdomen, fore-extremities," 

 says Haller, " swell during expiration, from the blood either being 

 obstructed or retrograding, and at inspiration are emptied of 

 it from its flowing freely to the heart." n Or, in the words of 

 Magendie, " when the chest contracts, the blood is driven back 

 into the cavae by the pressure experienced by all the organs of 

 the chest." That the blood does really retrograde during ex- 

 piration, appears by an experiment of Magendie's, in which a hol- 

 low bougie was passed into the great veins as far as the cava, or 

 auricle itself, and the blood flowed from its extremity .during ex- 

 piration. This fact seems to show compression of the thoracic 

 organs during expiration, and therefore is an additional argument 

 that ordinary expiration is not the effect solely of the elastic and 

 muscular shrinking of the lungs. Such, indeed, is the pressure 

 of expiration, that the heart during it propels the blood more vio- 

 lently into the arteries, and even into the veins; and, on the other 

 hand, less forcibly during inspiration. P A continuance in refrain- 



n 1. c. ibid. Journal de Physiologie, t. i. p. 186. Paris, 1820. 



P Bordeu, Du Fouls, p. 324. quoted by Haller; and Bichat, Eecherches Physiol. 

 p. 223. See Magendie for the veins, Journal de Physiol. t. i. p. 138., and Tul- 

 pius, Obs. Med. ii. 3. p. 106. In violent efforts the chest is still more com- 

 pressed, whence the blood accumulates without the heart in the veins, and is 

 driven more forcibly from the heart to all parts. These may be made after ex- 

 piration or inspiration ; but for a very violent effort we usually inspire first, to 

 afford a better fixed point, and to continue the effort longer than would be pos- 

 sible after expiration. Respiration is generally suspended and the glottis closed ; 

 but if the effort is made after an inspiration, the glottis need not be closed, pro- 

 vided the air is allowed to leave the chest very slowly. 



In myself, a deep inspiration, not followed in due time by an expiration, causes 

 the pulse in a few seconds to become suddenly slow for a few seconds, falling as 

 much as five and twenty beats per minute, and even double this, if it has just be- 

 come rapid by a deep and prolonged expiration : but, as the breath continues to 

 be held, which may be done much longer than inspiration can be refrained from 



p 3 



