SUN-STROKE. 349 



tected my head, and have avoided rash experiments. 

 Of the reddening and bhstering of the skin I have 

 had very frequent experience in Europe, upon the 

 Alps and other mountains ; but I observed none but 

 very sHght effects of this kind in the tropics, even 

 with a nearly vertical sun, either on land or while at 

 sea. Dr. Hann * cites many statements on the 

 subject. In the West Indies cases of sun-stroke are 

 rare, and the inhabitants expose themselves without 

 danger. In nearly all parts of British India, as is too 

 well known, the danger of exposing the head to the 

 sun is notorious, and the same is certainly true of 

 most parts of tropical Africa. 



The most obvious suggestion is that, inasmuch as 

 dry air absorbs less of the solar heat than air 

 charged with aqueous vapour, the injurious effects 

 should be more felt in dry climates than in damp 

 ones. But, so far as what is called sun-stroke is con- 

 cerned, the balance of evidence is opposed to this 

 conclusion. Sir Joseph Fayrer, who has had wide 

 experience in India, expressly asserts that the hot 

 dry winds in Upper India induce less cases of sun- 

 stroke than the moist though cooler climate of Bengal 

 and Southern India. Dr. Hann quotes Borius for a 

 statement that in Senegambia the rainy season is that 

 in which sun-stroke commonly occurs, while he further 

 asserts that on the Loango coast, in very similar 

 climatal conditions, the affection is almost unknown, 

 and that Europeans even expose the head to the sun 

 with impunity. 



My own conclusion, fortified by that of eminent 



* " Klimatologie," p, 382. 



