Cultivation of the Parasites 511 



tubes of the same kind. The method of transplantation recommended is 

 very simple: a drop of the culture is drawn into a fine (not capillary) glass 

 pipet and then followed by about five times the volume of the fresh corpuscle 

 suspension. These are mixed in the pipet, care being ta,ken not to mix air 

 with the blood, and are then transferred to the new media in the same manner 

 as in making the original inoculation. The transplantation should be done within 

 five hours of the time of maximum segmentation, and therefore every forty- 

 eight hours for the tertian and aestivo-autumnal parasites. AU species of the 

 Plasmodia have been successfully cultivated by these means. The parasites 

 have also been grown in red blood-cells in Lock's solution, free of calcium chlorid 

 and in the presence of ascitic fluid. 



According to Bass and Johns, the parasites grow in the corpuscles, 

 not upon them as believed by Koch. They are destroyed in a few 

 minutes in vitro by normal human serum or by all the modifications 

 of it that they have tested. This fact, together with numerous ob- 

 servations of parasites in all stages of development apparently 

 within the corpuscles render untenable the idea of extra-corpuscular 

 development. Leukocytes phagocytize and destroy malarial para- 

 sites growing in vitro only when they escape from their red-corpuscle 

 capsule or when the latter is perforated or becomes permeable. 



The substance of the malarial plasmodium is very different in con- 

 sistency from that of the blood-cells, and therefore they cannot pass 

 through the smallest capillaries like the more yielding fluid-like red 

 blood-cells. That the consistency of the protoplasm of the parasite 

 is less yielding than that of the red blood-cell is shown by the fact 

 that when a small quantity of a culture containing large parasites 

 is spread over a slide with the end of another slide, the parasites are 

 dragged to the end of the spread though the red blood-cells are left 

 behind. Large cestivo-autumnal plasmodia are round or oval; the 

 tertian variety are more or less flattened. As a result of their un- 

 yielding consistency, malarial parasites lodge in the capillaries of 

 the body, especially where the current is weakest, and remain and 

 segment. In the meantime other red corpuscles are forced against 

 them and if in a favorable situation, one or more merozoites pass 

 directly into the other cells. AVhen the segmented parasite has be- 

 come sufficiently broken up it can pass through the capillary into 

 the circulating blood where the remaining merozoites are almost 

 instantly destroyed. 



They further observed that .calcium salts added to cultures of 

 aestivo-autumnal parasites caused hemolysis of the infected, possibly 

 also of non-infected red blood-ceUs. Such salts have no effect on 

 the corpuscles of normal blood, possibly because of the precipitation 

 of other substances from the serum. The amount of calcium neces- 

 sary to cause hemolysis of malarial blood is only slightly in excess 

 of the quantity present in normal blood and possibly might be 

 reached by the ingestion of considerable quantities of calcium in 

 drinking water or food. They speculate that malarial hemoglobi- 

 nuria may be the result of the presence of an excess of calcium in 

 drinking water. 



