A simple device for counting Jerne's plates to detect haemolytic antibody-forming cells.

heater. This system is adequate for rooms with a capacity of up to about 16 m3 and for temperatures of up to 40°C. Temperature recording is by a Cambridge recorder which is mounted externally and, over a period of over one year since the installation of the hot room, the internal temperature has remained constantly at the set temperature (37°C). Local temperature variations within the hot room have been observed but they are small (about ± 1°C) and individual areas maintain a constant temperature. Frequent and prolonged opening of the door does not result in more than minor variations in temperature and a very rapid return takes place.