212 
THOMPSON YATES LABORATORIES REPORT 
fever is the discovery, first by Professor Koch, the director of the German Malaria 
Expedition, that the native children of tropical towns and villages are infected to an 
enormous extent with the parasites of malarial fever, and that they probably constitute 
the only source from which the disease is conveyed, by the agency of mosquitoes of 
the genus Anopheles, to Europeans. This has been corroborated by the members of 
the Royal Society's Commission in West Africa, and also by us. Professor Koch's 
reports 1 show that he found malarial parasites in the blood of a proportion of the 
native children under two years of age, to the extent, in some places, of 100 per cent.; 
of children between two and five, up to 46* i per cent. ; and between five and ten, 
up to 2 2' 5 per cent, were infected ; while in natives over ten, none were found to 
contain parasites. The proportions obtained by the Royal Society's Commission in 
West Africa, who also discovered the infection of native children independently, are 
somewhat higher than these; at Accra", from 23 to 90 per cent, of 'babies'; 
from 20 to 57 per cent, of children up to eight years ; from 28 to 30 per cent, up 
to twelve years ; and over that age infection was rare ; while at Lagos, of children 
under two years, from 50 to 100 per cent.; between two and five years, 40 to 75 per 
cent. ; and between five and ten years, 25 per cent, showed either parasites or pig- 
mented leucocytes in their blood, the percentage varying according to the locality. 
We were able at almost every town we visited to obtain a number of children 
for examination. The following tables show our results : — Our method of examina- 
tion consisted in making a blood smear of about two inches in length and half an 
inch in breadth. After drying and fixing in absolute alcohol, the preparation was 
stained by a modification of Romanowsky's method for 'chromatin' staining, and 
the whole smear carefully examined with a one-twelfth oil immersion objective (Zeiss). 
The presence of pigmented leucocytes was not specially recorded in the results, the 
presence of parasites alone serving as the index of infection. The number of para- 
sites found varied from two or three per whole smear up to a large number in every 
field of the microscope. The ages of the children are given as nearly as could be 
judged from a general glance. It is possible that in some cases they may be one or 
two years out. Of those over ten years the majority were from ten to fourteen ; 
only very few between fourteen and eighteen were examined. The different places 
at which examinations were possible are as follows : — 
(A) Bonny Town. — The native town is close to the Government Vice- 
consulate and European factories. Many of the specimens 
were obtained by a house to house visitation indiscriminately, 
others by visits to huts belonging to one or two Bonny chiefs. 
(B) Herbert Jumbo's Plantation. — This is some five miles up the river 
from Bonny Town. Here lives the chief, Herbert Jumbo, in 
the midst of his men and boys and their families, previously 
' slaves.' 
