820 SPECIAL PHYSIOLOGY. 



mean height, 5 feet 6J inches, would be about 20 cubic inches, for the 

 average of the day and night respirations. The vital capacity in an 

 adult male, of the stature of 5 feet 7 inches is, on an average, about 

 230 cubic inches, the air being supposed to be at a temperature of 60. 

 The complemental air would therefore be 120 cubic inches. 



The following are the estimated quantities, in cubic inches, calcu- 

 lated for the daily and nightly average, in a man of the stature of 5 

 feet 6J inches : 



Cubic Inches. 



Residual Air, ... . . 90 



Reserve Air, 90 ) Total displaceable Air, 



Breathing Air, 20 V or Vital Capacity = 



Complemental Air, . . . 120 ) 230 cubic inches. 



Total Air after deepest Inspiration, 320 



These numbers cannot be regarded as absolutely accurate, but they 

 illustrate the general proportions. The depth of an ordinary inspira- 

 tion, as measured by the breathing air, and the total displacement of 

 air in forced respirations, indicating the vital capacity, differ much, 

 according to the size of the body, but even in persons of the same 

 age, height, and weight, they are liable to variation ; for they do not 

 merely depend on the size of the thorax, but necessarily on the mo- 

 bility of its walls, and on the extent to which they are actually moved 

 in the several inspiratory and expiratory acts. This may partly ac- 

 count for the great diversity in the estimates of the breathing air. 

 The vital capacity has been shown to differ according to the stature ; 

 the variation in persons between the heights of 5 and 6 feet, follows a 

 sort of law, every additional inch of height being accompanied by an 

 average increase of 8 cubic inches in the vital capacity. Thus the 

 capacity at 5 feet 6J inches being 230 cubic inches, that at 5 feet 

 would be about 174, whilst that at 6 feet would be about 270 cubic 

 inches. The vital capacity in women is much smaller than in men, 

 the proportion being almost as 1 to 2. It increases, in both sexes, 

 from 15 to 35 years of age, at the rate of about 5 cubic inches per 

 annum ; whilst from 35 to 65, it diminishes by 1 J cubic inch in a like 

 period. The greatest capacity met with by Hutchinson, was in a 

 giant 7 feet high, who weighed 308 Ibs. ; his capacity was 464 cubic 

 inches. The minimum was 46 cubic inches, and occurred in a dwarf 

 measuring 29 inches in height, and weighing only 40 Ibs. Modern 

 dress impedes respiration, for a man who could only expire 130 cubic 

 inches when his clothes were on, accomplished 190 cubic inches when 

 unclothed. The posture of the body modifies the vital capacity ; for 

 if, in the attitude of standing, it be 260 cubic inches, in the sitting 

 posture it is 235, in the recumbent position 230, and in lying on the 

 face 220. The degree of distension of the stomach, likewise influences 

 the vital capacity of the chest. Corpulency, in persons weighing 

 more than 160 Ibs., diminishes the vital capacity at the rate of 1 cubic 

 inch for every additional pound up to 196 Ibs., or 14 stone weight. 

 Practice with the spirometer increases the power of forcing up the 

 inner cylinder, whilst nervousness and awkwardness operate the other 





