94 
PROPHYLAXIS OF MALARIA. 
Methods of recognizing latent infections .—We have two methods 
of recognizing latent malarial infections—the examination of the 
blood and the palpation of the spleen, which is generally enlarged. 
Of these methods the examination of the blood is altogether the 
most accurate, although it involves considerable labor, and for this 
reason is often neglected. The splenic index, as it is called, is often 
a valuable guide as to the prevalence of malaria in a locality, but this 
organ is enlarged from other causes than malaria, and this fact often 
renders the splenic index misleading. In addition, the enlargement 
of the spleen may simply mean past infection and does not always 
indicate that treatment is needed at the time of examination. Where 
blood examinations can not be made, the splenic index must be 
relied upon, but in the military service, when it is desired to ascer¬ 
tain the actual amount of malaria present, blood examinations of 
the natives should always be depended upon, and in the prophylaxis 
of the disease among the troops a blood examination should always 
be made before patients are returned to duty after an attack of 
malaria and in any effort to discover latent infections among the 
men. Every medical officer should be familiar with the appearance 
of the various species of malaria plasmodia in both fresh and stained 
preparations of blood, and for this reason the detailed description of 
these organisms and the methods of demonstrating them have been 
given in the opening chapter of this contribution. It is true that 
much time and patience is required in making an estimate of latent 
infection in a native population and in discovering these infections 
in the men of a command, but the importance of the procedure is so 
great that it is time well expended, and the labor involved is no ex¬ 
cuse for the neglect of this very valuable prophylactic measure. 
The treatment of latent infections. —Immediately upon the dis¬ 
covery of latent infections treatment should be commenced, and the 
treatment will vary with the particular species of plasmodium pres¬ 
ent, and whether gametes have developed. The treatment of the lat¬ 
ter class of cases will be considered in the following section dealing 
with “ carriers ” of malaria, as it differs widely from that necessary 
in those individuals in whom only the forms of plasmodia concerned 
in the human cycle of development are present, comprising approxi¬ 
mately 50 per cent of all latent infections. 
The proper treatment of the class of cases just referred to is im¬ 
perative if one wishes to prevent the development of gametes , for in 
the vast majority of such cases it is only a question of time before 
they will become u carriers ” of the disease, for while gamete forma¬ 
tion may be delayed it undoubtedly occurs at some time in the vast 
majority of latent infections, as has been repeatedly shown by blood 
examinations in individual cases. Fortunatelv, these infections, be- 
fore the formation of gametes , are even more amenable to treatment 
