xiii, b, 6 Haughwout : Endemic Malaria 297 



examination of such preparations with the expectation of dis- 

 covering even a fair proportion of carriers amounts to a waste 

 of time, pure and simple, unless the general blood picture, in 

 the absence of parasites, yields the evidence of latent malaria. 



The Ross thick-film method may be employed. This, in all 

 probability, will yield a higher proportion of positives than the 

 thin smears; still, many will be missed. Reliance must not be 

 placed on this method, if it is desired to secure accurate results. 



The differential leucocyte count may, in itself, be sufficient to 

 place a man under suspicion as being a latent malarious subject. 

 Fever and parasites may be absent ; but if the blood shows a high 

 percentage of mononuclear leucocytes or if there is occasionally 

 a transient leucocytosis unaccompanied by fever, one may sus- 

 pect malaria and place the subject under observation. 



2. CONCENTRATION AND CULTURAL METHODS 



There are several of these, all based in principle on the scheme 

 underlying Bass's method of cultivating Plasmodium. The or- 

 iginal procedure was devised by Bass and Johns (l) and involves 

 a careful technic which, however, is not beyond the resources 

 of the advanced student of medicine. Modifications have been 

 devised by Row(27) and by J. G. and D. Thomson. (33) All of 

 them are practical. In selected cases one may use the technic 

 of Dudgeon and Clark, (9) although these authors point out that 

 they have failed to secure results in infections with Plasmodium 

 vivax of benign tertian fever. The method of Bass and Johns 

 may probably be considered as the best for precise work. 



3. PROVOCATIVE METHODS 



By these are meant the employment of certain drugs, biological 

 products, or the quartz lamp. Such measures have a tendency 

 to force the parasites out of the spleen, bone marrow, and else- 

 where, into the peripheral circulation, where they can be detected 

 on the ordinary blood films and then be dealt with by the regular 

 specific treatment. 



James, (15) in an able paper, has reviewed the etiology of 

 malarial relapses. Relapses, he says, almost invariably follow 

 the so-called spontaneous cure of primary cases of malaria ; that 

 is, the cessation of symptoms without treatment. This is just 

 the class of cases for which we must be very watchful in a body 

 of men drawn from malarious tropical regions, for it is ex- 

 tremely likely that a large proportion of such men never received 

 treatment for the malaria from which they have suffered. In- 

 fections insufficiently treated with small doses of quinine will, 



