POWER OF RESPIRATORY MUSCLES. 



215 



Power of 



Inspiratory Muscles. 

 1.5 in. . 



2.0 



2-5 

 3-5 

 4-5 

 5-5 

 6.0 

 7.0 



Power of 

 Expiratory Muscles. 



"Weak 2.0 in. 



Ordinary 2.5 





. Strong 3.5 



. . . Very strong .... 4.5 



, . . Remarkable .... 5.8 



, . . Very remarkable . . 7.0 



, . . Extraordinary . . . 8.5 



, . . Very extraordinary . . 10.0 



Mr. Hutchinson remarks : " Suppose a man to lift by 

 his inspiratory muscles three inches of mercury, what 

 muscular effort has he used ? The mere quantity of fluid 

 lifted may be very inconsiderable (and as such I have 

 found men wonder they could not elevate more), but not 

 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 3 1 8 square inches, the 

 chest will be found resisting a pressure of 731 Ibs. ; and 

 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 



