481
May
The
be
showing cloudiness after incubation, at once discarded as useless. By following the directions, given under the heading of Haemosporidia, however, this technical error will, in the majority of cases, be found easy to avoid. The amount of blood transferred to each tube of broth or Novy-McNeal media, ought to be at least 5 c.c.; more than this is an advantage rather than a drawback. These amounts are necessary as it often happens that the trypanosomes in the frog's blood are few in numbers.
The incubation temperature is found to be 20-25°C in order to obtain the best results. High temperatures, e.g., 37°C or over, arrest the development of the trypanosomes almost at once, and kill them completely in 48-72 hours. Similarly, low temperatures arrest their development.
At temperatures obtained by ice, the trypanosomes may be kept alive for a considerable period of time - especially on culture media like that of Novy and McNeal. In citrated broth, they live for 1 period...