206 RESPIRATION. 



resisting such a force, must not be confounded with, a former 

 statement of ' two-thirds being lifted by the inspiratory 

 muscles, and one-third left dormant,' under a force equal 

 to 301 Ibs. In this case the 301 Ibs. are lifted; in the 

 other, nine-tenths of 1046 Ibs. are said to be resisted. 



" The glass receiver of an air-pump may resist 15 Ibs. on 

 the square inch, yet it may be said to lift nothing. This 

 question of the thoracic muscular force and resistance, and 

 muscular distribution, is rendered complicate by the pre- 

 sence of so much osseous matter entering into the composi- 

 tion of the chest, which can scarcely be considered to act 

 the same as muscle." 



The great force of the inspiratory efforts during apncea 

 was well shown in some of the experiments performed by 

 the Medico- Chirurgical Society's Committee on Suspended 

 Animation. On inserting a glass tube into the trachea of 

 a dog, and immersing the other end of the tube in a vessel 

 of mercury, the respiratory efforts during apnosa were so 

 great as to draw the mercury four inches up the tube. 

 The influence of the same force was shown in other expe- 

 riments, in which the heads of animals were immersed 

 both in mercury and in liquid plaster of Paris. In both 

 cases the material was found, after death, to have been 

 drawn up into all the bronchial tubes, filling the tissue of 

 the lungs. 



Much of the force exerted in inspiration is employed in 

 overcoming the resistance offered by the elasticity of the 

 walls of the chest and of the lungs. Mr. Hutchinson esti- 

 mated the amount of this elastic resistance, by observing 

 the elevation of a column of mercury raised by the return 

 of air forced, after death, into the lungs, in quantity equal 

 to the known capacity of respiration during life ; and he 

 calculated that, in a man capable of breathing 200 cubic 

 inches of air, the muscular power expended upon the elas- 

 ticity of the walls of the chest, in making the deepest 

 inspiration, would be equal to the raising of at least 



