TEMPERATURE AND HUMIDITY 



75 



He gives the following conclusions: — 



1. The average pulse is lower by 2*5 beats in the Tropics than in the Tem- 

 perate Zone. 



2. This change holds good for the average morning and evening pulse. 



3. The average afternoon pulse is higher in the Tropics than in the Tem- 

 perate Zone, probably because the solar heat is greatest then. 



4. The morning pulse has the greatest and the evening the lowest range. 

 He considers that this reduction in the pulse-rate is related to the diminished 



respiratory function. Parkes, Jousset, Crevaux, Feris, and Plehn, according 

 to Huggard, maintain, on the contrary, that the pulse is increased by ten beats 

 per minute. Plehn says, however, that on acclimatization the pulse-rate 

 sinks to normal. 



There is said to be a lowering of tension (associated, according to Huggard, 

 with the dilatation of the peripheral vessels), as well as increased elasticity 

 and dicrotism, all of which probably pass away on acclimatization. 



Chamberlain in the Philippine Islands concludes that the average blood- 

 pressure, measured by a Cook's modification of a Riva-Rocci's apparatus 

 and a I2'5 centimetre armlet, in Filipinos and Americans of the same age dwell- 

 ing in those islands, does not appreciably differ from one another, nor from 

 that of similar Americans in the Temperate Zone, but that the pulse-rate of 

 active Filipinos and Americans is a few beats above the usual standard of 

 72 per minute. 



In our experience, in Europeans coming to the Tropics, the pulse-rate is 

 occasionally slightly increased. This disappears after acclimatization, and 

 the pulse-rate becomes the same as in Temperate Zones. We have never 

 noticed dicrotism of the pulse in normal individuals. 



As regards natives of the Tropics, it is stated by some authorities that their 

 pulse is quicker than in the inhabitants of Temperate Zones, but we are unable 

 to confirm this, and find it to be the same as in Europeans. 



Effect on the Blood. — Mitchell, as the result of his work in the 

 Persian Gulf, considers that damp heat of itself frequently produces 

 anaemia, but gives no details of the blood examinations. In 1916 

 W. M. Strong, noting that persons who had lived for long in the 

 Tropics became ansemic -looking, investigated this point, and con- 

 cluded that the pallor was not due to deficiency in haemoglobin nor to 

 ischaemia of the cutaneous capillaries, but to pigment deposited in the 

 epidermis, which becomes partially opaque to red light, which is 

 important because the colour of the skin depends upon the relative 

 amount of each spectral tint which is reflected back to the eye. 

 Further, he considers that when more pigment is deposited the skin 

 becomes yellow-brown. 



The ' Arneth count' (see p. 1898) in healthy native children has been 

 investigated by Breinl and Priestley; taking the figure for normal Europeans 

 as 40, native children varied from 71-6 to 83-86, while in adult natives it 

 stood at 74*04. They are of the opinion that the alteration of the blood 

 picture is the outcome of climatic influences, and not, as suggested by Scott 

 Macfie, as the outcome of abortive inoculation with malarial parasites, 

 though they think that the higher figure — viz., 83-86 — may be accounted for 

 by infection. 



Sweet agrees that high ' Arneth index ' is very regularly present in healthy 

 children over the whole coastal area of Eastern Australia ; he maintains that 

 no factor apart from disease is found definitely to influence this index, but 

 he says that external temperatures do apparently influence the index in 

 animals, and that further research is required with reference to this in man. 



We are disinclined to believe in a marked anaemia purely and solely due to 

 climatic influences without any other causal factor, but diminished resistance 

 against disease is certainly produced by long residence in the tropics, and is 



