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Dr. A. Rattray on Change of Climate. [Feb. 16, 



VI. Conclusion. 



The ultimate object of these varied functional and organic changes 

 induced in the human frame by change of climate, is to accommodate it to 

 altered meteorological and other conditions, and assimilate it to those of 

 native races. It is the ease or difficulty with which different varieties of 

 mankind, ages, sexes, and idiosyncrasies become accustomed to this that 

 indicates their capability for what we term acclimatization. [Would not a 

 more intimate acquaintance than we yet possess with the differences 

 in the minute anatomy and functions of the various tissues and organs 

 of these different races and families, and also their correlation and capability 

 or not of assimilation under change of climate, go far to decide the long- 

 vexed questions as to the unity or plurality of species and of creative centres 1 

 — Feb. 27.] In these important changes, moreover, especially that in the 

 current of the blood from the interior to the surface of the body on proceeding 

 to the tropics, there is an evident analogy with certain great operations which 

 take place under similar circumstances in the inorganic world. The air and 

 ocean likewise heat as they proceed towards the equator, and finally overflow 

 to form those beneficent winds and sea-currents which play so important a 

 part in the economy of the globe, and influence its hygiene, therapeutics, and 

 etiology, not less than its commerce. And although in these it acts on what 

 may be termed the centre of their circulation, whereas in the human frame it 

 operates on its periphery, the agent in all three is the same, viz. the sun's 

 heat, as is the primary effect, viz. a change in the direction of original 

 currents, as well as the final results, viz. purification and modification of 

 temperature. The general physical and general hygienic and curative 

 schemes of nature are thus evidently connected. "Without these pheno- 

 mena the heat of tropical lands and seas, and cold of other regions, would be 

 intolerable, and that of the skin and body too high or too low for the main- 

 tenance of their vitality ; while both the air, ocean, and blood would rapidly 

 become impure and unfit to sustain life. 



Deriving its first and chief impulse from the heart, the blood merely 

 undergoes redistribution — the current in cold and temperate climates being 

 directed towards internal, and in the tropics towards external organs, espe- 

 cially the skin. In either case it flows from cooler towards more highly 

 heated regions. Is not this vital process, therefore, in this respect also, at 

 least partly akin to the allied phenomena in the air and ocean, and physical 

 as well as physiological ? The blood generally being probably somewhat 

 warmer in the tropics than elsewhere, does not the heating of the surface 

 and contents of the turgid cutaneous capillaries act as a vis a fronte in in- 

 ducing it to flow towards and accumulate here, as the warm interior does 

 in cold regions ? 



