A large number of attempts have been made to cultivate the avian malaria parasites, using, in most cases, Plasmodium praecox (relictum). The results may be briefly outlined as follows:
1.Of the various methods employed so far incubation at 25°C. of capillary tubes drawn out and sealed after the blood has been drawn into them has proved the most satisfactory. Bacterial contamination is easier to avoid with such tubes and smaller amounts of blood can be used.
2.Cultures of Plasmodium praecox incubated in this way retain a fairly normal appearance for some time, but the viability of the parasites diminishes. It has been found possible however to produce infection in a fresh bird after as long as five days of cultivation, although the incubation period is greatly prolonged.
3.The addition of dextrose does not seem to be essential. Amounts have been added sufficient to bring the percentage to three per cent without any apparent effect.
4.Heparin has been found to be the best anti-coagulant, and apparently does not affect the parasites in any way. It makes it possible to dispense with any diluting agent.
5.Although parasites of this species appear to reproduce normally for at least one, and probably for several generations, and remain capable of producing an infection for at least five days in some cultures, yet it is apparent that much more study will have to be done before a really practicable method of cultivation is developed. Whenever such a method is devised it will probably work, with modifications, on the human and other malaria plasmodia as well as on the avian types.