194 THE MECHANISM OF 



in a position of ultra -expiration after death, and we infer that if 

 the elasticity of the thorax is in antagonism to the elasticity of 

 the lungs at the end of expiration, then the elastic recoil of the 

 thorax in the dead is an exaggeration of that in the living. Sir 

 Douglas Powell made observations on ten subjects ; he noted the 

 expansion of the thorax when the pleural cavity was punctured 

 and the lungs allowed to collapse. In six of these there was no 

 expansion of the thorax ; in four the average expansion forwards 

 of the chest wall was 2'3 mm. When it is remembered that the 

 lateral or antero -posterior thoracic expansion varies from 1 to 2 

 mm. in normal respiration, even in men with the thoracic type of 

 breathing, it is evident that the elasticity of the thorax can play 

 but a slight part in normal expiration. Any observation made on 

 the dead body is vitiated by the rigor mortis and post-mortem 

 changes of the muscles. I observed that when the muscles are 

 removed from the thorax that the weight of the ribs and sternum 

 was enough to cause the thorax to assume an expiratory position 

 when the body was turned in the feet-down position, and to pass 

 into the inspiratory position when the body was inverted. One 

 must conclude from a study of the thorax of the dead that the rib 

 movements are so free that elastic recoil of the thorax comes to 

 be a factor in expiration and inspiration only towards the extreme 

 limits of respiratory movements. 



Recently the writer had reason to compare the elasticity and col- 

 lapsibility of the thorax in living subjects with that of dead subjects. 

 The matter has some importance in determining the best method 

 for performing artificial respiration on the apparently drowned, 

 and also in selecting the position of patients in performing intra- 

 thoracic operations. Elsberg, for instance, asserts that the pleura 

 may be opened without collapse of the lung if the patient be 

 placed in the prone position ; it is certainly possible to reduce the 

 capacity of the thorax in adult human beings to a point when it 

 is too small to contain the collapsed lungs, and hence a part is 

 extruded as a hernia. The writer's investigations show that the 

 living and dead thorax react quite differently when compressed, 

 the difference being due, in his opinion, to the reflex action of the 

 respiratory musculature. The following table gives the results of 

 his experiments ; the measurements for the living are the average 

 for ten students varying from eighteen to twenty-four years 

 of age ; those given for the dead are the averages from five 



