As numerous and different as the attempts to culture malarial parasites have been, all have resulted negatively. Moreover, not only the media used in bacteriology have been employed, but also other substances, which, a priori, seemed to offer the parasites the most favorable conditions, yet no medium and no method have proved successful. Coronado's statement that he succeeded in culturing malarial parasites from the air of swamps, water, etc., is not of the kind to awaken confidence.
* In general I can confirm this rule of Golgi's, yet it must be added that the individual constitution, perhaps, too, the virulence of the parasites, may influence considerably the severity of an attack.
The most that has been done so far was the preservation of parasites for one or two days.
The attempts to keep them parasitic or capable of reproduction by introducing them into the peritoneal cavities of animals met with not much better success.
Rosenbach observed in leeches which he had applied to a fever patient tertian parasites still living after forty eight hours; at least they showed pigment movement. Sakharoff placed the filled leeches on ice; four days later he inoculated himself with the blood of one and was attacked by a fever which showed corresponding parasites (parasites of the second group).
These experiments were repeated by Blumer, Hamburger, and Mitchell. Hamburger asserted that the parasites, which were of the second group and non pigmented, increased somewhat in size in the body of the leech and showed pigment formation. Mitchell found that tertian parasites were still evident in the leech after ten days, though from the beginning they manifested no ameboid movement. Crescents did not change their form. Ziemann examined the malarial blood in leeches after varying intervals, and found that the chromatin, as a rule, held its color for several days.
I repeatedly fed flies with malarial blood rich in sporulation forms or crescents. The parasites were preserved only a short time and did not increase.
At Manson's suggestion Ross had mosquitos suck blood rich in crescents. He found that a very large number of the crescents became flagellate within a few minutes. Manson, who at that time regarded flagella as spores, maintained that mosquitos constituted the hosts of the malarial parasites (as they do of the filaria) outside the human body. He contended that the mosquitos "rescue" the parasites from the human blood vessels by sucking them out, and offer them an opportunity for further development within their body. How this view, it is true, in a different form, has eventually been established is discussed in the appendix.