QUANTITY OF AIR RESPIRED. 2O$ 



so the power exerted, when we recollect that hydrostatic- 

 law, which Mr. Bramah adopted to the construction of a 

 very convenient press. To apply this law here, the 

 diaphragm alone must act under such an effort, with a 

 force equal to the weight of a column of mercury 3 inches 

 in height, and whose base is commensurate to the area of 

 the diaphragm. The area of the base of one of the chests 

 now before the Society, is 57 square inches; therefore, had 

 this man raised 3 inches of mercury by his inspiratory 

 muscles, his diaphragm alone in this act must have 

 opposed a resistance equal to more than 23 oz. on every 

 inch of that muscle, and a total weight of more than 83 Ibs. 

 Moreover, the sides of his chest would resist a pressure from 

 the atmosphere equal to the weight of a covering of mer- 

 cury three inches in thickness, or more than 23 oz. on every 

 inch surface, which, if we take at 318 square inches, the 

 chest will be found resisting a pressure of 73 1 Ibs. ; and i 

 allowing the elastic resistance of the ribs as i^ inch of 

 mercury, this will bring the weight resisted by the chest 

 as follows : 



Diaphragm . . . . . 83 Ibs. 

 Walls of the chest . . ..731,, 

 Elastic force . . . . . 232 ,, 



Total .... 1046 



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

 of the thorax resisted rooolbs, of atmospheric pressure, 

 and tliat not counterbalanced, to say nothing of the J , . 

 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 



