30 Influence of Atmospheric Temperature 



membranes, of the lungs, of the alimentary canal, and other 

 viscera, depend more certainly on changes in the distribution 

 of blood thus made ; either suddenly, or by continuance and 

 repetition. And these also are among the changes which have 

 direct influence on the brain ; the result of various averages 

 shewing that apoplectic seizures are most frequent when either 

 heat or cold are severe in degree ; — the mode of action doubt- 

 less different in the two cases ; yet in each depending princi- 

 pally on disturbance excited in the movements of the blood.* 



The influence of external temperature on the functions of 

 the skin, whether those of transudation or simple evaporation, 

 is scarcely yet fully estimated ; though the researches of Dr 

 Edwards and others have done much to extend our knowledge 

 on the subject. The changes so made, either in augmentation 

 or diminution of the natural discharge, are obvious and often 

 very great. Without reciting the observations directed espe- 

 cially to these points, it may be remarked that a natural pro- 

 vision against injury exists here, as in the case of the tempe- 

 rature of the body, in the diminution of other excretions, and 

 in the relation of absorption to the matters perspired ; — a re- 

 medy inadequate, indeed, to repair extreme or continued losses, 

 but sufficient for all the ordinary occasions of life. This sub- 

 ject belongs, subordinately with that of heat, to the general 

 doctrine of climates ; the influence of which on the animal eco- 

 nomy is regulated, in part, by the provisions just named ; in 

 part, by actual changes in the state and texture of the integu- 

 ments of the body ; exclusively of those modifications which 

 depend on the usages of life in each country or community. 



The effects of perspiration suddenly checked by external 

 cold, are the subject of general apprehension, and influence 

 many of the details of medical practice. Though in some in- 

 stances mischief may arise from this source, I believe the alarm 

 to be unwarranted in degree ; and many of the effects, so at- 



* Regarding the Coup de soleil, usually cited as one of the most striking 

 examples of the effects of heat on the brain, we have some recent evidence 

 (though hardly decisive), to show that the change, thus suddenly induced, 

 belongs rather to the pulmonary circulation, than directly to the head. This 

 is contained in a paper by Mr Russell, surgeon of the 68 th Regiment, at 

 Madras ; read before the College of Physicians two years ago* 



