646 MALARIA. 



man, except in so fur as they serve as breediiju- places for inos(|uitoe8 

 of the genus Anophelei<. The green scum is made up of harmless algai, 

 such as Spirogyra, Zygnema, Protococcus, Euglena, etc.; and the gas 

 which is given otl' from the uuid at the l)ottoni of such stagnant pools is 

 for the most part a well-known and comparative!}'^ harmless compound 

 of hydrogen and carbon — methane or ""marsh gas." In short, we now 

 know tliat the air in the vicinity of marshes is not deleterious because of 

 any special kind of bad air present in such localities, l)ut because it 

 contains mosipiitoes infected with a ])arasite known to ))e the specific 

 cause of theso-calU'd malarial fevers. This parasite was discovered in 

 the blood of patients suHVring from intermittent fevers by Laveran, a 

 surgeon in the French army, whose investigations wei'c conducted in 

 Algiers. This famous discovery was made toward the end of the year 

 188<>. luit it was several years later before tlie profession generally 

 began to attach nuich importance to th(^ alleged discovery. It was 

 lirst confirmed by Richard in IS.Si'; then l)y the Italian investigators, 

 Marchiafava, Celli. (xolgi, and Bignaini; by Councilman, Osier, and 

 Tha3'er, in this country, and by many othei- com})etent observei's in 

 various parts of the world. The Italian investigators named not only 

 confirmed the presence of the parasite discovered b}'^ Laveran in the 

 blood of those suffering from malarial fevers, l)ut they demonstrated 

 its etiological role by inoculation experiments and added greatly to 

 our knowledge of its life history (1883-189S). The fact that the life 

 history of the parasite includes a period of existence in the bod}' of 

 the mosquito as an intermediate host has recently been demonstrated 

 by the English army surgeons Manson and Ross, and confirmed ])y 

 numerous observers, including the famous (TCi-man bacteriologist, 

 Koch. 



The discoveries referred to, as is usual, have had to withstand the 

 criticism of conservative physicians, who, having atlopted the prevailing 

 theories with reference to the etiology of periodic fevers, were naturally 

 skeptical as to the reliability of the o})servations made by Laveran and 

 those who claimed to have confirmed his discovery. The first conten- 

 tion was that the bodies described as present in the blood were not para- 

 sites, but deformed blood corpuscles. This objection was soon set at 

 rest by the demonstration, repeatedly made, that the intra-corpuscular 

 forms underwent distinct auKeboid movements. No one witnessing 

 these movements could doubt that he was observing a living micro- 

 organism. The same was true of the extra-corpuscidar flagellate bodies, 

 which may be seen to undergo very active movements, as a result of 

 which the red blood corpuscles are violently displaced and the flagellate 

 bod}^ itself dashes about in the field of view. 



The first confirmation in this country of Laveran's discovery of 

 amceboid parasites in the blood of malarial-fever patients was made by 

 myself in the pathological laboratory of the Johns Hopkins University 



