CHAP. XX.] INSECTS AND DISEASE. 179 



large extent in the interna] organs. The number ol days between 

 attacks of " fever " depends, of course, upon the fact of whether the 

 inf< one time or on successive days; in a 



imple infection by quartan malaria, tor example, tin- attacks 

 recur after everj seventy-two hours (the period ol time which the 

 parasite takes to complete its life-cycle in the human body), but if 

 infection on two successive nights the patient develops 



■ on two mii cessive days, because the parasites are of different 

 - and each lot lakes seventj -two hours to complete its life-cycle, 

 and remains fret- from lever on the third day of each period of 

 three days Lertian malaria, characterized in simple cases by a 

 recurrence of the attack ever} forty-eight hours, is the commonest 

 and nio^t widely-distributed form ; the interval without feverish 

 symptoms is about thirty-six hours. Subtertian malaria is usually 

 very prolonged and severe ; the incubation period. /.<■„ the interval 

 between first infection and first attack of fever, is 9 10 days; the 

 duration of each attack is twenty-four hours or more, the inter- 

 val between attacks twenty-four hours or K-s S according to the 

 prolongation of the attack. Chronic malaria is usually caused 

 by infection with the subtertian parasite ami is accompanied by 

 repeated slight attacks of fever, enlargement of the spleen and liver 

 and pigmentation of the skin and mucous membranes. 



treatment of malaria cannot be entered into here but. on 

 the principle of prevention being better than cure, we may note 

 briefly that the lessening of (I) the Anophelinc mosquitos and (2) 

 their capacity to bite man in any locality must help to reduce the 

 total number 'if cases mfected or reinfected. Draining and oiling 

 "i 1 Is and the introduction of larvivorous fish into them, the 



ning of wells, the prevention of standing water near houses 

 and various other methods, will all help to prevent the mosquitos 

 from breeding, whilst the use of mosquito-proof houses or rooms 

 and nets and the application ol repellents will considerably reduce 

 the chance of being bitten and infected even when malaria-carry- 

 ing mosquitos are prevalent. Tin- use of quinine as a preventive. 

 to kill off any malarial parasites which may obtain access into the 

 body in spite of other precautions, is also an obvious measun 

 take as a matter of routine when in a " feverish " locality. 



umber of deaths due to malaria every year is officially 

 estimated atom- mil lion for the whole of India. I have no infor- 

 mation regarding the annual mortality from this cause in Southern 

 India but it may be placed at 100,000 on a conservative estimate. 

 The mere money loss to the State may be imagined rather than 

 calculated when it is remembered that, in addition to the actual 

 mortality, the productive capacity of millions of the populatioi 

 1 -• \ 



