518 Dr. Rattray on the effects of Change of Climate [June 



or 270 cubic inches, he might be supposed to have contracted incipient 

 phthisis on reaching England in winter labouring under catarrh, with the 

 pneumatic capacity of his chest reduced by from 25 to 35 cubic inches. 

 On the other hand, a patient actually in incipient phthisis might be erro- 

 neously considered to have permanently recovered by a trip to the tropics 

 having raised the capacity of his lungs for air by a similar amount, i. e. al- 

 most or actually up to the normal standard for his age and height in a 

 temperate climate. A similar mistake might be made, especially if the 

 instrument is carelessly used, in the same climate, e. g. that of England, at 

 different seasons of the year, such as the height of summer and depth of 

 winter, when a considerable difference in the capacity of the lungs for air 

 must not be taken as an index of disease *. The greater the range between 

 the summer and winter temperatures, the more marked will be the differ- 

 ence in the spirometric indications. 



But it is not by deep inspirations like these that ordinary respiration is 

 carried on ; and it is important to ascertain whether the air inspired 

 in each ordinary breath undergoes a similar increase and decrease according 

 to climate. The difficulty in limiting and measuring the small quantity 

 of air expired during our usual faint breathings makes this a far more 

 delicate and difficult experiment than the preceding. From analogy, 

 however, we may infer that it does vary ; and the following will go far to 

 prove it. My ordinary respirations ranged from 4 to 8, and averaged 6 

 cubic inches in a temperature of 44° F. (shade) during the winter of 

 England. At Lisbon, during an average temperature of 65° F. (shade), 

 they ranged from 5 to 13, and averaged 9 cubic inches j\ .Unfortunately 

 while in the tropics I had not the proper apparatus to ascertain how much 

 they increase during the far greater temperature of equatorial regions. As 

 these results therefore only prove the existence of an increase, and do not 

 show its extent, it will be necessary, as it is doubtless correct, to calculate 

 the minor from the major increase. 



The following Table will show the negative effect of period of the day 

 on the capacity of the chest for air in the tropics. 



Table IV. — The capacity of the chest for air, as influenced by period of 

 the day in the tropics. 





In the Tropics, as a whole, 

 51 days. 



Doldrums, or warmest part 

 of the Tropics ; average 

 temperature 781° F. 



9 A.M 



cubic inches. 

 244-3 



244- 42 



245- 06 



cubic inches. 

 243 

 242-57 

 243 





9 P.M 





* Table I. cols. 4 & 5. 



t These amounts are all small, because those taken were the short ones which imme- 

 diately follow the deep inspiration in which ordinary breathing usually culminates 

 trery twentieth ©r thirtieth inspiration. 



