xui. b, 6 Haughwout: Endemic Malaria 299 



But for a broad general rule we may, I think, accept the principle 

 (pending more exact researches) that if we cannot find the parasites 

 after careful search their number is not usually sufficient to produce 

 fever. 



This statement of Ross's, made in 1911, with the reserve 

 characteristic of the careful scientist, will certainly not be safe 

 to follow to-day in the handling of carriers, and it is questionable 

 if it is to be strictly followed in the case of active malaria. 

 The theoretical cases mentioned by Ross and Thomson, where 

 malignant parasites mature simultaneously, are sufficiently com- 

 mon occasionally to trouble a microscopist who tries to find the 

 trophozoites of Plasmodium falciparum during a febrile attack. 

 In this connection it will be interesting to recall the statements 

 of Garin and of Kaminer and Zondek I have already given. 

 James, (15) too, has pointed out the difficulty of attacking the 

 parasites in the parenchyma of the spleen and in the bone mar- 

 row with quinine. In this connection he cites cases in which 

 patients dying from malaria showed no parasites in the periph- 

 eral blood, but did show a few in splenic smears, where of course 

 the erythrocytes were much less abundant. He also noted that, 

 in cases where the patient died after three to five days' treat- 

 ment with quinine, the parasites were more frequently seen in 

 the spleen and bone marrow when the quinine had been admin- 

 istered orally, less frequently when it had been administered 

 by hypodermic injection, and least frequently when the quinine 

 had been given in three to four doses of 22.5 grains intraven- 

 ously. His explanation was that the parasites in the spleen 

 and marrow escape the full effects of the quinine, so that when 

 those in the peripheral circulation are killed some still remain 

 in the spleen and marrow. When these multiply above a certain 

 number, they appear in the peripheral circulation, and further 

 multiplication there brings about a febrile relapse. While much 

 of this does not have a direct bearing on the question of hand- 

 ling carriers, the general point might well be borne in mind. 



As to concentration and cultural methods I can do little more 

 than refer the reader to the original papers of the authors to 

 whom I have already alluded. The methods in every case are 

 too detailed and technical to make their presentation here prac- 

 ticable; but many of them are of great and undoubted aid in 

 the detection of parasites in the blood when these are present 

 in numbers too few to admit of discovery on the ordinary .blood 

 film except after long and painstaking search. 



Some two years ago at a meeting of this society, I ventured 

 to suggest to my medical colleagues the advisability of resorting 



