PROPHYLAXIS OF MALARIA. 
97 
the blood will prevent their being discharged from hospital before the 
gametes , if present, are reduced to a noninfectious minimum, but 
there are many individuals in malarial regions who are gamete car¬ 
riers and who have never suffered from marked symptoms of malarial 
disease. Therefore it is necessary not only to control the treatment 
of acute infections by blood examinations, but to examine the blood 
of the apparently healthy if we wish to discover all gamete carriers 
and render them harmless. 
The time of occurrence of gametes. —It is universally admitted 
that gametes do not develop in patients who have been properly 
treated with quinine, and that in untreated cases they do not develop 
until the infection has presisted for several days. The length of 
time required for the development of the gametes of the estivo- 
autumnal plasmodia varies from 8 to 15 days, the usual period being 
about 12 davs. In other words, an estivo-autumnal infection must 
have persisted for nearly two weeks before we can expect to find the 
crescents, or gametes , in the peripheral blood. The gametes of the 
tertian and quartan plasmodia appear in the peripheral blood of 
man in from 7 to 10 days after the onset of definite symptoms of 
infection. j 
Although the time given is based upon the appearance of the' 
gametes after symptoms are noted, it should be remembered that 
these forms are often found in individuals who have never shown 
marked symptoms of infection, and we may find these forms pres¬ 
ent on what appears to be the very first day of an obvious infection. 
However, in the vast majority of patients, gametes do not appear 
in the blood until several days after the appearance of definite 
symptoms of malaria, and this fact is of great importance in the 
prophylaxis of the disease, for proper treatment will prevent their 
development and thus prevent the infection of the mosquito. The 
fact is also of significance in explaining the origin of these forms, 
and would appear to indicate that gametes are not introduced into 
man by the mosquito, but that, as Schaudinn believed, they are dif¬ 
ferentiated during the human life cycle of the plasmodia as the 
result of the reaction of the human organism to the parasites, and 
certainly all the evidence we possess points to this conclusion. 
The percentage of individuals showing gametes .—As only those 
individuals in whom the sexual forms, or gametes , occur are capable 
of infecting the mosquito, and thus, indirectly, of infecting man, 
it is of interest to know how large a percentage of our malarial 
patients become “ carriers." It may be stated at once, that unless 
properly treated, practically 80 per cent will probably become capa¬ 
ble of infecting the mosquito, but the statistics here given are based 
upon actual observations. 
58000°—14-7 
