ENDEMIC INDEX IN MALARIA 83 



is to determine the proportion of children aged 10 years 

 or less in whose blood evidence of malaria is found. 

 This age is rather high, and the results differ if a large 

 proportion are over or under 5 years of age. In the 

 same country the results would therefore appear to vary 

 greatly according to the ages of the children examined 

 (fig- 25). 



The best method would be to determine the age at 

 which the largest proportion of children are found to be 

 infected. Thus, if the largest proportion of infected chil- 

 dren were under 2 years old, it would indicate a higher 



FIG. 26. Negroes (native Africans), in a most malarial district in 



Central Africa. Residence required for probable infection with malaria, 

 under six weeks. (1899.) 



Native African, in less malarial district. Residence for one 



year by a European does not render infection certain. 



endemic index than if the maximum proportion was at 

 5, and still more if the maximum was in children aged 10* 

 A low rate in persons over 10 years of age in a place 

 where malaria is known to occur suggests a high endemic 

 index. 



(B) Prevalence of enlarged spleen. This test has fallen 

 undeservedly into disuse on account of the manner in 

 which it was at one time abused in India by the laity as 

 well as by medical men. With limitations it is of con- 

 siderable value. The limitations are : (i) That other 



