RESPIRATION. 205 



the second, there is no proof of the agency of the abdominal 

 muscles in expiration ; it proceeds equally well in cases of ina- 

 nition, when their contraction would rather enlarge than diminish 

 the abdominal cavity, and in experiments when they are entirely 

 removed from animals, a child was born without them, and had 

 lived eighteen months at the time of the publication of its case, 

 and was very well a : and I may add, thirdly, that, although the 

 elasticity of the cartilages of the ribs must conspire with that of 

 the lungs, numerous cases are recorded of immobility of the ribs, 

 by ossification of their connections, where respiration was not 

 materially impeded. 5 These cases are adduced to show that the 

 diaphragm is the chief instrument of respiration ; but, as its 

 elasticity cannot produce expiration, they show that this was 

 accomplished entirely, or in a great measure, by the lungs them- 

 selves. Even where there is no ossification, the motion of the ribs 

 has very little share in respiration; and Dr. Bostock considers the 

 chief use of the intercostals to be that of giving a fixed point for 

 the action of the diaphragm, and the operation of the abdominal 

 muscles in expiration to be nearly passive. It is commonly 

 known, however, that, if the pleura is wounded, air rushes into 

 the chest during inspiration only, and is in some measure ex- 

 pelled again during expiration. Galen showed this, notwithstand- 

 ing his object was different, by wounding the chest and fixing 

 a bladder upon the wound. The bladder shrunk at inspiration, 

 and became distended at expiration. d Were the ascent of the 

 diaphragm and descent of the ribs in expiration the effect of 

 solely the contraction of the lungs of a tendency to vacuum 

 occasioned by their shrinking, air and fluids should stream to 

 the chest as much during expiration as inspiration should rush 

 to fill up the vacuum as much as the diaphragm should ascend and 

 the ribs descend for that purpose: nor should air be expelled 

 from the wounded pleura ; for we may regard the thoracic cavity 



a Gazette de Sante, Dec. 5. 1826. A child of seven years is said in Lieutaud 

 to have had no diaphragm. 



b Dr. Bostock, An Elementary System of Physiology, vol. ii. p. 15. 



c 1. c. vol. ii. pp. 7. 15. 



d Administ. Anat. lib. viii. c. ult. 



If, instead of a bladder, a tube immersed in a coloured fluid is employed, this 

 will of course rise in inspiration, and remain stationary or fall in expiration. See 

 Experimental Researches on the Influence exercised by Atmospheric Pressure upon 

 the Progression of the Blood in the Veins, $c. By Edward Barry, M. D. Lon- 

 don, 1826. 



P 



