1078 



The Effect of Age on the Vital Capacity. 



30 years, and from 30 to 60 it decreases 

 43 cubic inches, or 1'43 (nearly 1-J- cubic 

 inches) per year, or 7 cubic inches in 5 

 years, or 14^ cubic inches in 10 years. Al- 

 though this appears by calculation, yet we do 

 not strictly follow this ratio, as we find by 

 experience that the effect of age may be more 

 diminished, as follows : 



TABLE D D. Vital Capacity at three Periods of 

 Life, from 4800 cases (males). 



From 55 to 65 we have deducted 5 cubic 

 inches per cent, and from 65 to 75 years of 



age 8 cubic inches per cent. We have not 

 brought in the effect of time before the age of 

 55 years. This is supposed to be at the mean 

 weight. The first column is derived from 

 observation, the two second are derived from 

 calculation. 



6th. Of the effect of disease upon the vital 

 capacity. The effect of disease upon re- 

 spiration was well known to Boerhaave and 

 Morgagni, they considered that the disturb- 

 ance of any organ in the body would dis- 

 order the whole function of respiration. 

 Morgagni devotes more than one-sixth of his 

 celebrated work, the " Seats and Causes of 

 Disease," " to diseases which affect respiration." 

 We may safely say all thoracic and abdominal 

 diseases, as tumours, abscesses, and acute in- 

 flammations, will affect the respiration. Of the 

 different respiratory volumes, we select that 

 one which requires the most extended mo- 

 bility, viz. the vital capacity, which becomes 

 altered to an extent commensurate with 

 that of any disease physically affecting our 

 respiration, it is therefore a test of the pre- 

 sence and extent of such diseases. Such 

 movements as command this volume, extend 

 from the neck to the plantar muscles of the 

 feet. 



One condition which we have been accus- 

 tomed to look upon as affecting our breathing, 

 does not affect it, viz. old pleuritic adhesions. 



Fig. 710. 



Heights. [ Sfl 



ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in. ft. in ft. in. !t. in. !t. in. ft. in. ft. in 



50 51 52 53 54 55 .56 57 5 8 5 9 5 II) 5 1160 



51 5 ii 53 54 55 56 57 58 595 10 5 11 606 + 



Healthy- 



Diseased. 



Vital Capacity of the healthy and diseased Cases compared. 



