366 THE HUMAN BODY. 



tidal and complemental air together, is known as the vital" 

 capacity. For a healthy man 1.7 meters (5 feet 8 inches) 

 high it is about 3700 cub. cent. (225 cub. inches) 

 and increases 60 cub. cent, for each additional centime- 

 ter of stature; or about 9 cubic inches for each inch of 

 height. 



The Quantity of Air Breathed Daily. Knowing the 

 quantity of air taken in at each breath and expelled again 

 (after more or less thorough mixture with the stationary 

 air) we have only to know, in addition, the rate at which the. 

 breathing movements occur, to be able to calculate how 

 much air passes through the lungs in twenty-four hours. 

 The average number of respirations in a minute is found 

 by counting on persons sitting quietly, and not knowing, 

 that their breathing rate is under observation, to be fifteen 

 in a minute. In eacli respiration half a liter (30 cubic inches) 

 of air is concerned; therefore 0.5 X 15 x GO x 24 = 10,800 

 liters (374 cubic feet) is the quantity of air breathed under- 

 ordinary circumstances by each person in a day. 



Hygienic Remarks. Since the diaphragm when it con- 

 tracts pushes down the abdominal viscera beneath it, these 

 have to make room for themselves by pushing out the soft 

 front of the abdomen which, accordingly, protrudes when 

 the diaphragm descends. Hence breathing by the dia- 

 phragm, being indicated on the exterior by movements of 

 the abdomen, is often called "abdominal respiration," as 

 distinguished from breathing by the ribs, called "costal" 

 or "chest breathing." In both sexes the diaphragmatic 

 breathing is the most important, but, as a rule, men and 

 children use the ribs less than adult women. Since both 

 abdomen and chest alternately expand and contract in 

 healthy breathing anything which impedes their free move- 

 ment is to be avoided; and the tight lacing which used to 

 be thought elegant a few years back, and is still indulged 

 in by some who think a distorted form beautiful, seriously 

 impedes one of the most important functions of the Body, 

 leading, if nothing worse, to shortness of breath and an in- 

 capacity for muscular exertion. In extreme cases of tight 

 lacing some organs are often directly injured, weals of; 



