During the period of fever produced by physical means, it is essential that the systemic temperature be known at all times. This is best determined by observation of the temperature in the rectum. The most commonly used technic is the insertion of a clinical thermometer at short intervals. This procedure disturbs the patient and is tiresome to the attendant.
The use of a continuous recording device such as a resistance thermometer is of great value. It allows of continuous observation—which is very important in that it permits the careful modulation of the thermal energies applied so as to maintain the desired temperature. Resistance thermometers have a time lag, require careful adjustment, are expensive, and occasionally get out of order. Thermocouple devices have similar objections.
A continuous indicating mercury thermometer permits visualization of the rectal temperature at all times. I employ a specially designed instrument 13½ inches in length and three-eighths