76 



TROPICAL CLIMATOLOGY 



probably largely climatic in its cause, though food may also be a causal factor 

 therein; but the chemical factors of resistance to disease still require investiga- 

 tion. 



With regard to the sugar content in the blood, McCay finds that for Euro- 

 peans it is 0'o8 per cent., while for Bengalis it is 0-13 per cent., and the increase 

 appears to be entirely due to the excessive amount of the carbohydrate in 

 their diet. In the fatlndolent classes it is o - 1 50 per cent., while in the poorest 

 classes it is only 0*125 per cent., and he points out that there is a very close 

 relationship, other things being equal, between the sugar content in the blood 

 and the amount of fat deposited in the tissues, which again is a dietetic and 

 not a climatic effect. 



Effect on Digestion.— With regard to the alimentary canal there 

 is often less appetite and less desire for animal food, and greater 

 demand for spiced articles of diet, all of which show a tendency to 

 lower power of digestion; but we are convinced that the tropical 

 hypersemia, other than alcoholic, is a myth, and we base this state- 

 ment on a large number of clinical and pathological observations 

 spread over a period of some twenty-one years. 



There is, however, one point to which special attention should be 

 drawn, and this is to the danger of constipation in tropical climates 

 with low humidity, and to the necessity of imbibing daily a suffi- 

 ciency of water to combat the loss of moisture from the skin. This 

 tendency to constipation in healthy people in very hot dry climates 

 is usually aggravated by the difficulty in obtaining fresh vegetables 

 and fruits in those regions during the driest times of the year. 

 Constipation, if allowed to become chronic, may cause passive 

 hypersemia, but this is pathological, and due to the lack of free 

 evacuation of the bowels and not due directly to the climate. 



Effect on the Nervous System. — It appears that the cells of the 

 nervous system obey the general law that vital activity is increased 

 with a higher temperature, but only up to a certain point, after 

 which their functional activity becomes markedly depressed. This 

 is the case in most Europeans, though a great deal of mental and 

 physical work can be done in the tropics if the bodily health is 

 maintained. Natives naturally are less prone to feel the depressing 

 effects of continuous high temperature. 



It is possible that this condition, together with the effect of the 

 actinic rays of the sun, may result in weakening the control of the 

 higher centres over the lower, and thus inducing outbursts of what 

 Plehn calls * tropical fury ' [Tropenkohler), by which he means fits 

 of passion caused by trivial incidents. This is seen not only in 

 Europeans, but in natives, who are apt to do violent deeds under 

 the impulse of unreasoning anger. It appears to be one of the 

 causes of assaults and violent crime in certain parts of the Tropics. 



Effect upon the Urinary System. — Urine is diminished in quantity 

 in the tropics, and this is said to be due not merely to diminution 

 of water, but also of solids, among which urea and chlorides may 

 be noticeably mentioned. Lawson says that the pigments are 

 increased. 



The diminution of the urine is very markedly noticed in hot dry 



