386 OF RESPIRATION. 



as Dr. C. R. Hall has justly remarked, this measure indicates, not what a 

 person does breathe, but what he can breathe. The maximum " vital ca- 

 pacity" met with by Dr. Hutchinsou in his entire series of observations, was 

 464 cub. in.; this was in a man 7 feet high, whose weight was 308 Ibs. The 

 'minimum was no more than 46 cub. in. ; this was in a dwarf (Don Francisco), 

 whose height was only 29 inches, and weight 40 Ibs. 



307. But however constant the above averages may prove to be, when 

 tested by a still larger number of observations, it yet remains to be deter- 

 mined within what limits individual variation may range, without departure 

 from the standard of health. It is considered by Dr. Hutchinson 1 that a 

 deficiency of 16 per cent, (unless the individual should be very corpulent) 

 should excite suspicion of disease ; but the observations of Dr. C. R. Hall 

 (loc. cit.) seem to show that the range is considerably wider, especially in 

 females. They also indicate that even a marked deficiency in vital capacity 

 must not be regarded as indicative of pulmonary disease ; for it may be de- 

 pendent upon disorder of the abdominal viscera, especially upon congested 

 liver. 



308. In estimating, however, the effects of the Respiratory function upon 

 the air which passes through the lungs, we are not so much concerned with 

 the quantity w r hich may be drawn in and forced out, as with that actually 

 exchanged at each movement. The estimates of the earlier observers, Herbst, 

 Valentin, 2 etc., which ranged from 10 to 92 cub. in., are in general imper- 

 fect, having been based upon comparatively few respirations, and without 

 taking into consideration the many circumstances we now know to exercise 

 an influence upon the depth and frequency of the respiratory acts. Dr. Ed. 

 Smith 3 has arranged a spirometer, by which the quantity of air inspired may 

 be registered from 1 to 1,000,000 cub. in., and therefore for any period. He 

 has used it for 24 hours without intermission, except for meals, and ascer- 

 tained the quantity of air inspired during sleep, and in almost every condi- 

 tion met with during the day. From numerous experiments upon several 

 persons, each extending over a whole day, he found that the average depth 

 of inspiration was 33.6 cub. in. when at rest, and when walking at 1, 2, 3, 

 and 4 miles per hour, 52, 60, 75, and 91 cub. in., and even 107 cub. in. 

 when working the treadmill. If we take 30 or 40 cubic inches as the aver- 

 age quantity exchanged at each inspiration, we cannot but observe how small 

 a proportion it bears to the entire amount which the lungs usually contain : 

 for the " residual air," which cannot be expelled, is estimated by Dr. Hutch- 

 inson at from 75 to 100 cubic inches, and the "supplemental air," which 

 can only be expelled by a forced expiration, is about as much more; the 

 sum of the two being from 150 to 200 cub. in., or from 5 to 7 times the " breath- 

 ing volume." Now it is obvious that if no provision existed for mingling 

 the air inspired with the air already occupying the lungs, the former would 

 penetrate no further than the larger air-passages ; and as this would be again 

 thrown out at the next expiration, the bulk of the air contained in the lungs 



1 Op. cit, p. 1079. 



2 Tin' following are some of the amounts assigned by different observers: 



Herbst, .... . 20 30 cubic inches. 



Valentin, . 

 Vierordt, . 



Cotithupe, 



f average. 

 Hutchinson, ! t 



Grehant, . 

 (GreMmnt, Robin's Journal do 1'Anatomie, t 



i, p. 523.) 



3 Many of the following statements respecting Dr. Edward Smith's experiments 

 were kindly communicated by himself. 



1492 " 



104:2 " 



16 " 



1620 " 



777 

 0.510 of a litre. 



