404 RESPIRATION. [CHAP. XXIX. 



conditions under which the organs are placed do not allow of their 

 expelling this remnant. If now the deepest possible inspiration be 

 taken, it is found that they are capable of inhaling a further quan- 

 tity, varying much in different persons, but on an average about 

 240 cubic inches.; which, with the former residual quantity, make a 

 sum of 280 cubic inches as the full capacity of the lungs of a person 

 of good height (5 feet 8 inches) . But in ordinary breathing, the 

 lungs are neither very empty nor very full they maintain a 

 middle condition ; and their range of movement, in natural or ordi- 

 nary respiration, is only sufficient to pump in and out a quantity of 

 air equal to about 30 cubic inches. From the best observations, it 

 may be concluded, that a person whose full capacity is 280 cubic 

 inches, contains in his lungs, after an ordinary expiration, about 

 110 cubic inches; and after an ordinary inspiration, about 140 

 cubic inches ; a quantity which he is enabled to double by a full 

 inspiration. Thus rather more than one-fifth of the ordinary con- 

 tents of the lungs are expelled at each expiration, and again renewed 

 by inspiration. 



Dr. Hutchinson, by means of a gasometer, which he terms a 

 spirometer, has examined a large number of persons with reference 

 to their power of taking air into the lungs. The person first in- 

 spires to the full extent, and then breathes into the instrument as 

 much air as he can ; and it results that the height of the individuals 

 has much to do with their respiratory range. Thus, while on an 

 average a person of 5 feet breathes 174 cubic inches, one of 5 feet 

 1 inch will breathe 182 cubic inches; and for every inch of height, 

 up to 6 feet, will breathe about 8 cubic inches additional. Weight has 

 much less influence than height, but tends to diminish the respira- 

 tory power, when beyond a certain limit. In males of the same 

 height, the respiratory range (vital capacity of Hutchinson) in- 

 creases from 15 to 35 years of age ; but from 35 to 65 it decreases 

 nearly 1J cubic inches per year. Bourgery agrees nearly with 

 this : he states, that more air can be inspired at thirty than at any 

 other age, and that in old persons the range is very limited. Bour- 

 gery calculates, that a child of ten years of age, with a weight three 

 times less than that of a man of eighty, has a respiratory power 

 eight times greater. This is due to the great difference there is in 

 the range of the respiratory movements. The old man being able 

 to increase the amount breathed by less than a half; while the child 

 may increase it nearly fourteenfold. Herbst has shown that the capa- 

 city of the lungs is much smaller in the female than in the male. 



Having now considered the anatomy of the respiratory organs, 



