126 Dr Stephens , The Prevention of Malaria. 
breeding grounds occur in the greatest profusion and in the huts 
adult Anopheles are to be caught in myriads. 
But a more important side of this question still remains for 
consideration, viz. where do we find infected Anopheles and by what 
means do they become infected, for it is not so much the existence 
or absence of Anopheles that is the vital question as whether or 
no the mosquitoes contain sporozoites in their salivary glands ? 
We found that an examination of the salivary glands of 
Anopheles caught in native huts always gave a certain proportion 
of infected ones. This proportion was generally about 1 0 — 20 °/ 0 5 
in some cases as high as 50 °/ 0 and in others again as low as 2 °/ 0 . 
The highest percentages we unexpectedly found in those 
places where Anopheles were at first sight scanty and where there 
might be a complete absence of breeding grounds for at least 
some months, whereas our lowest value 2 °/ 0 was found in Lagos 
island where there were innumerable breeding grounds ; and it 
may be that the difference was dependent solely on the fact that 
in the latter case the large number of insects always present was 
sufficient to reduce the percentage of infected ones. 
All native huts examined by us contained infected Anopheles 
in variable proportion. 
Source of infection of Anopheles. The source of this uni- 
versal condition of infection was moreover made clear when 
systematic blood examinations of the inmates of the huts were 
made. For it appeared that we had in the huts a universal 
condition of infection with malarial parasites and that this in- 
fection was confined almost entirely to the youngest children, 
especially those of 1 to 5 years old. It is not that these children 
were suffering from attacks of “ fever ” in the ordinary acceptance 
of the term, but that they, although to all intents and purposes 
quite healthy, almost all contained parasites in their blood. Here 
then was revealed a complete explanation of the mode of infection 
of the Anopheles. Prof. Koch working at the same time in the 
East Indies found an exactly parallel condition. 
Since these results were published some authors have at- 
tempted to claim that this had been previously recognized. It is 
not denied that the existence of malaria in children has long been 
known, but it would appear that these authors have not realized 
the actual condition that exists among native children which is, 
that in children apparently perfectly healthy there exists an 
almost universal condition of infection with malaria parasites; 
this, it will be recognized, is quite a different state of things to the 
existence of cases of malaria among children : just as in small birds 
in Africa there exists a very large infection (about 50 °/ 0 ) °f Halteri- 
dium , so in native children below a certain age, who are apparently 
quite well, as many as 100 °/ 0 ma y contain parasites in their blood. 
