204 RESPI1UTIOX. 



inspiratory muscles are capable of acting, is greatest in 

 individuals of the height of from five feet seven inches to 

 five feet eight inches, and will elevate a column of three 

 inches of mercury. Above this height, the force decreases 

 as the stature increases ; so that the average of men of six 

 feet can elevate only about two and a half inches of mer- 

 cmy. The force manifested in the strongest expiratory 

 acts is, on the average, one-third greater than that exer- 

 cised in inspiration. But this difference is in great 

 measure due to the power exerted by the elastic reaction of 

 the walls of the chest ; and it is also much influenced by 

 the disproportionate strength which the expiratory muscles 

 attain, from their being called into use for other purposes 

 than that of simple expiration. The force of the inspira- 

 tory act is, therefore, better adapted than that of the 

 expiratory for testing the muscular strength of the body. 



The following table expresses the result of numerous 

 experiments by Mr. Hutchinson on this subject, the instru- 

 ment used to gauge the inspiratory and expiratory power 

 being a hcomadynaniometer (see p. Nfc$/)> to which was 

 attached a tube fitting the nostrils, and through which the 

 inspiratory or expiratory effort was made : 



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 



