298 The Philippine Journal of Science 1918 



James goes on to say, in all probability relapse. If prompt and 

 vigorous treatment is instituted after the onset of an attack of 

 malaria, relapses are less likely to occur; and, conversely, the 

 later the primary attack is treated (even though the doses of 

 quinine given were large and treatment continued for a long 

 time), the more certainly will the symptoms recur. 



James says, further, that occasionally relapses will occur when 

 parasites are present in the blood and the patient has not stopped 

 taking quinine. He also believes that the infection will, in 

 time, die out, if reinfection is excluded and death does not take 

 place. This, he adds, applies in the last analysis even to persons 

 who are carriers, but who manifest no febrile symptoms though 

 parasites may be found in the peripheral blood. 



Under the first heading, the detection of carriers through 

 the medium of blood films, but little need be added to what has 

 already been said. The difficulties are pretty well understood 

 by all laboratory workers. Macfie and Ingram (18) have called 

 attention to a condition they encountered in West Africa that 

 adds to the difficulty of identifying species of the parasite in 

 blood films. These workers noted the rarity of crescents in the 

 blood of peripheral subtertian infections they encountered in 

 that field. This made necessary the identification of the para- 

 site from the character of the trophozoites, a task that offers 

 some difficulty to the inexperienced microscopist. 



Of interest in connection with the examination of blood for 

 malarial parasites is the question as to the number of parasites 

 that are necessary to produce fever. Ross and Thomson (26) 

 have made some studies on sporulating forms in the peripheral 

 blood and give the following figures: 



In benign tertian fever 100 adults per cubic millimeter of 

 blood are necessary to produce a fever of 99° F., and 300 adults 

 or more per cubic millimeter are necessary to produce a fever 

 of 100° F., or over. 



In malignant tertian fever 3,000 young rings per cubic milli- 

 meter of blood are necessary to cause a fever of 99° F., while 

 from 5,000 to 300,000 young rings per cubic millimeter will 

 give a fever ranging from 99° to 106° F. 



This has led these authors to state that in a case of true 

 malaria the microscopist is certain to find parasites if the blood 

 is taken at the time of the paroxysm, except in those theoretical 

 cases of malignant tertian fever when all the parasites are 

 sporulating simultaneously. This is in line with the statement 

 attributed to Ronald Ross by Dudgeon and Clark (9) as follows: 



