18 



TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY. 



insulation. The wires are then twisted and soldered together in the usual 

 way, tied with silk, and finally covered with thin pure gum tubing. Before 

 insulating the bare copper wire, however, the precaution is taken to protect 

 it from the corrosive action of the sulphur in the rubber by "tinning" it 

 or covering it with solder. It was found that the lag of the thermometer, 

 due to the rubber tubing, was about 2.5 minutes; 1 this was regarded as being 

 not too great. 



For taking temperatures in the axilla a thermometer of the type illustrated 

 under B, fig. 3, recommends itself. Here the joint is made by twisting and 

 soldering two wires which approach each other from opposite directions, the 

 inclosure in tubing being the same as before. 



Another type of thermometer is shown in C, fig. 3. Here one of the metals 

 of the junction touches the body without the intervention of any isolating 

 material, so that the conditions for the taking up of the temperature by the 

 thermometer are ideal. The copper element is made in the form of a very 



Fig. 3. Types of thermal-junction thermometers used. A, junction inclosed in rubber tube, used 

 principally for internal measurements; B, same, arranged for use in axilla; C, junction in 

 which one metal touches body, for taking internal temperatures; D, modification of this 

 type for surface measurements. 



thin hollow thimble, to the inside of which, at the end, is soldered the con- 

 stantan wire, properly insulated. A copper wire soldered to the thimble 

 completes the circuit. The connecting wires and the open end of the cap are 

 covered by rubber tubing, and tied with silk, after which the copper is silver- 

 plated. This arrangement fulfils the theoretical condition that both elements 

 should not touch the skin, and at the same time provides an excellent thermal 

 relation between the thermometer and the body whose temperature is being 

 measured. 



Thermometers for surface temperature. The attempts made to obtain accu- 

 rate measurements of the surface temperature were not successful, but a brief 

 description of the thermometers used may be of interest. Several types of 

 skin thermometers were constructed. At first the ordinary rubber-covered 



'The method of testing the thermal -junction thermometers for lag was as follows: The 

 thermometer being tested was connected to the measuring circuit and suddenly thrust 

 into a flask of water at about body temperature. This caused a galvanometer deflection 

 which at first changed rapidly but gradually became more nearly constant and finally 

 could not be observed to change at all, the change in deflection corresponding to the 

 change in temperature of the junction. The length of time noted above (2.5 minutes) 

 is the interval elapsing from the instant when the thermometer was immersed until the 

 deflection had become constant. 



