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Dr. Rattray on the effects of Change of Climate [June 16, 



induced in the human economy in passing from cold to warm regions, or 

 the reverse, is derived from experiments carried out in artificially made or 

 seldom encountered climates. By hot-air chambers we illustrate the effects 

 of augmented temperature on the respiration, pulse, &c, and by the 

 rarefied atmosphere of mountain-tops show how diminished density acts. 

 Neither of these, however, are fair examples of natural climates. Thus the 

 former, dry and warm, is unlike the tropics, with its triple combination of 

 increased heat, rarefied air, and excessive moisture ; as the latter, dry and 

 chilly, is dissimilar from the usual surface-climates of extra-tropical latitudes, 

 which conjoin cold, condensation, and moisture. The dry and warm, or 

 dry and cold, climates which occur in nature are usually local and limited. 

 Nor do such abrupt and temporary exposures to heat and cold have any 

 parallel in ordinary life, or are they likely to induce results similar to the 

 comparatively slow transition involved in an ordinary change of climate ; 

 and though the rarefied air of heated chambers will decrease, while that of 

 great altitudes will accelerate respiration, the former will do so less, and the 

 latter more, than they otherwise would, from the skin, and especially the 

 more slowly acting liver and kidneys, being unable at once to increase their 

 action so as to aid the lungs in eliminating carbon. The functional changes 

 so induced cannot therefore be taken as a fair criterion of what occurs in 

 nature ; and as mere approximates to truth, such observations, though in- 

 teresting, are evidently wanting in practical importance. 



I. The Influence of Tropical Climates on the Respiration, 



It has been ascertained, by the experiments already alluded to, that the 

 respirations are diminished in frequency in warm and increased in cold air ; 

 but we do not yet know what happens in the tropics, where great heat, 

 rarity of air, and moisture are conjoined. Nor has it yet been shown 

 whether the quantity of air respired is greater in the tropics or less. It is 

 obviously necessary to ascertain both before we can decide whether the total 

 quantity of air and oxygen respired, and the amount of carbonic acid and 

 watery vapour exhaled, be different or not. 



The following experiment will show that the capacity of the chest for 

 air is materially affected by tropical climates : — 



