THORAX. 



1077 



the Ib. will correspond to the inch, for that 

 is accidental, merely depending upon the 

 units employed, but that the increase of each 

 will be found in an arithmetical progression, 

 and hence, probably, the reason why tall men 

 breathe more than short men. 



But the weight can never be the sure guide 

 that the height is, because the former varies 

 at any time in life, even in a few days ; where- 

 as the latter varies only at the extremes of life. 



4th. Relation of vital capacity to the circum- 

 ference of the thorax. We notice this here, 

 because the question is so natural, " Has 

 the size of the chest no relation to the 

 vital capacity?" We do not find that there 

 exists any direct relation between the cir- 

 cumference of the chest and the vital capa- 

 city. We have found 



Height. Circura. Vital 



Men. ft. in. in. capacity. 



11 58 35 235 



10 58 38 226 



Therefore, the men with chests 3 inches 

 larger, breathed 9 cubic inches less, or 21 men 

 of the same height, but of different-sized chests, 

 breathed a mean vital capacity of 230 (the 

 due quantity according to TABLE T). We 

 have consolidated the following result upon 

 994 cases, the height is kept in view, calcu- 

 lated at 5 feet 6i inches. 



TABLE B B. Circumference of the Chest,'in Re- 

 lation to the Vital Capacity Volume, in 99-t 

 cases (Males). 



There is nothing in this table to confirm 

 that which we had thought would be the main 

 guide to the vital capacity volume ; thus, 

 compare together the first and last 14 men 

 whose chests differ 10 inches, and their vital 

 capacity only 17 inches ; or compare together 

 the first and last columns, the one is perfectly 

 regular and the other most irregular. There 

 is a certain rude relation between the thoracic 



dimensions and the vital capacity ; if, for in- 

 stance, one man has a chest 35 inches in cir- 

 cumference, and 3 inches mobility, and another 

 man has a chest 40 inches in circumference, and 

 4 inches mobility, then the latter will surely 

 displace a larger volume of air than the former, 

 but omitting this, we expect as large a vital 

 capacity from a man with a thin and narrow 

 thorax, as from a man with a broad and deep 

 thorax. In fact, aeration need have no re- 

 lation to the thoracic dimension ; and, for the 

 same reason, the size of the chest no relation 

 to the vigour of the whole man. Indeed we 

 incline to the contrary, viz. that it is most 

 likely the respiration is most vigorous in the 

 narrow-chested man, when the mobility is 

 greatest. The vigour of the lungs, like every 

 other organ in the body, we believe, has no 

 relation to the dimensions. One person may 

 have a brain 1 Ib. lighter, or 1 less than an- 

 other person, and yet their capacity and men- 

 tal qualities shall not appear different. 



5th. Vital capacity affected by age. Age 

 affects the breathing movements, but less re- 

 markably than the height and weight. Indeed 

 the influence of age was not apparent in the 

 first calculation upon 1012 cases, nor until we 

 took a basis of 19^3 cases. Time affects life 

 in two ways, first bringing it to perfection, 

 and then determining that perfection. 



TABLE C C. Effect of Age, from Observations 

 on 1775 healthy Men. the Height being kept 

 in View. 



The column of "difference" exhibits the 

 effect of time upon the breathing volumes. 



From 15 to 35 years of age the vital ca- 

 pacity is increased, and from 35 to 65 years 

 of age it is decreased in the progression of 

 19, 11, and 13 cubic inches. We illustrate 

 this by a curve mfig. 709. The curve of the 

 vital capacity will be seen to rise slightly as 

 it passes the perpendicular lines of years until 

 it conies to 35 years of age, after which it 

 keeps declining as it cuts all the succeeding 

 lines of quinquennial periods down to 65 

 years. We may say, therefore, that the 

 vital capacity increases with the age up to 



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