1 . The test for the detection of pyrogen by the thermometer method was examined and found to be unreliable although the results obtained were within the limits of the test as described in the United States Pharmacopoeia, thirteenth revision, and the British Pharmacopoeia, 1948. 2. A thermocouple circuit was constructed which could accommodate ten rabbits and a test for detection using this apparatus devised. The sensitivity of the test was such that an average maximum rise in rectal temperature of 0.3
