6. _Cultivation of parasite._—As to cultivation of malarial parasites. Bass takes from 10 to 20 cc. of blood from the malarial patient’s vein in a centrifuge tube which contains 1/10 cc. of 50% glucose solution. A glass rod, or a piece of tubing extending to the bottom of the centrifuge tube is used to defibrinate the blood. After centrifugalizing there should be at least one inch of serum above the cell sediment. The parasites develop in the upper cell layer, about 1/50 to 1/20 inch from the top. All of the parasites contained in the deeper-lying red cells die. To observe the development, red cells from this upper 1/20 inch portion are drawn up with a capillary bulb pipette. Should the cultivation of more than one generation be desired, the leucocyte upper layer must be carefully pipetted off, as the leucocytes immediately destroy the merozoites. Only the parasites within red cells escape phagocytosis. Sexual parasites are much more resistant. Bass thinks he observed parthenogenesis. The temperature should be from 40° to 41°C. and strict anaerobic conditions observed. Aestivo-autumnal organisms are more resistant than benign tertian ones. Dextrose seems to be an essential for the development of the parasites. Bass considers that _P. vivax_ has a disc-like structure which enables it to squeeze through the brain capillaries while adult schizonts of _P. falciparum_ have a solid oval form which causes them to be caught in the capillaries. The Thompsons have rather simplified the method of Bass. They draw 10 cc. of blood into a test tube containing the usual amount of glucose solution. They then defibrinate the blood by stirring with a thick wire for about five minutes and remove the wire with the adhering clot. They then pour this defibrinated blood into several small sterile test tubes, which should contain at least a one-inch column. Rubber caps are adjusted over the cotton plugs and the tubes placed in the incubator. They note the tendency of cultures of _P. falciparum_ to agglutinate which is not true of _P. vivax_. They think this agglutination the great cause of the plugging of capillaries in pernicious malaria. They note 32 merozoites as maximum number in sporulation of _P. falciparum_ while _P. vivax_ has usually 16 or more, but never as many as 32. This would explain the shorter incubation period of malignant tertian. The pigment of _P. falciparum_ clumps much earlier in the developing schizont than that of _P. vivax_ and is much coarser and more discrete. While Bass thought he noted parthenogenesis in cultures others have failed to observe any evidence of it. 7. _Immunity._—As to immunity. There is no real immunity to malaria, it is a continuance of the infection, but the parasites are not in sufficient numbers to give rise to fever. If, however, the patient becomes chilled or fatigued or otherwise depressed, fever results.