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Dr. A. Rattray on the Effects of 



[Feb. 16, 



safety-valve for the kidneys in warm, as the latter do for the former in 

 colder ones. While the perspiration depends much on the temperature, 

 the urine is most influenced by the drink. Although heat, or its absence 

 (cold), is thus the chief agent in causing these fluctuations, the humidity, 

 velocity, &c. of the air are not altogether negative. The first acts by sti- 

 mulating or checking the sudatory glands, and all three by favouring or 

 opposing evaporation. Frequent change of climate tends to develope the 

 ordinary and safety-valve range of action in both organs. In these facts 

 lie several important hygienic and therapeutic indications for the tropics, 

 with a view to prevent or lessen distressing hyperemia of the skin and 

 excessive perspiration, both the result of undue imbibition, and the latter 

 highly dangerous when suddenly checked, and a frequent cause of disease. 

 By them the reason of the efficacy of tropical, and especially subtropical 

 climates in the prevention when imminent, and cure or relief when actually 

 present, of many diseases of internal organs, not of the abdomen alone, but 

 of thoracic ones, is explained. The sanatory haematic and secretive de- 

 rivative action of natural (tropical) and artificial heat has been already 

 pointed out with regard to the lungs*. Might not the practical phy- 

 sician more frequently act on this hint as to the means and extent by 

 which both the circulation and the function of diseased or over-taxed in- 

 ternal organs may be relieved by thus transferring their blood-current and 

 secretion to sounder ones ? Is not this great and general law of a deriva- 

 tion of blood from internal to external organs under heat, and the reverse 

 under cold, the soundest and most philosophical basis on which to erect a 

 new, safe, satisfactory, and permanent system of therapeutics and hy- 

 gienics 1 



V. The Influence of Tropical Climates on the Weight and Strength. 



Besides the already discussed functional, vascular, and other changes in 

 the lungs, skin, kidneys, and other organs of vegetable life, which follow 

 a transition from temperate to tropical climates, various phenomena affecting 

 those of animal life are also common — e.g. languor of body and brain, and 

 generally a loss of weight. More tardy and less evident, but equally worth 

 study, these are not due, like the former, to the general diversioivin the 

 blood-current from internal to external parts, but to changes in the blood 

 itself and the tissues which it nourishes, to be hereafter investigated. 



Occasionally an individual fattens oh going to the tropics, and, instead of 

 losing, gains health and strength. Again, a corpulent person may decrease 

 considerably in weight, while his health, so far from impairing, actually 

 improves. But such cases are exceptional, and, doubtless, consist merely 

 in vitally unimportant fluctuations in the adipose tissue ; and as a rule the 

 issue includes a loss in both respects, which, if not disease, is closely allied 

 to it. An opposite result usually follows a contrary change of climate. 



* Proc, R, S, 1870, vol. xviii. p. 520. 



