216 RESPIRATION. 



11 In round numbers it may be said, that the parietes 

 of the thorax resisted 1000 Ibs. of atmospheric pressure, 

 and that not counterbalanced, to say nothing of the 

 elastic power of the lungs, which co-operated with this 

 pressure. 



' ' I would not venture at present to state exactly the 

 distribution of muscular fibre over the thorax, which is 

 called into action when resisting this 1046 Ibs., but I think 

 I am safe in stating that nine-tenths of the thoracic sur- 

 face conspire to this act. 



" What is here said of the muscular part of the chest re- 

 sisting 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 pres- 

 ence 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 apnoea 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. 



