20 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY. 



press into the flesh and take up the deeper temperature. The thermometer is 

 held in place by a cloth strap. The junction itself must be shielded so that it 

 may take up the body-temperature, and yet this must not interfere with the 

 natural liberation of heat. These two conditions are incompatible, but the 

 shape of thermometer chosen seems to fulfil both as well as possible. 



Thermal junctions used in the constant-temperature bath. The thermal 

 j unctions used in the constant-temperature bath are all made in the same way. 

 The two small wires are slipped into separate capillary rubber tubes and a 

 soldered joint made exactly as in type A (fig. 3) previously described. The 

 different junctions are then supported in the following manner: A piece of 

 glass tubing (A, fig. 4) is used, about 15 centimeters long and having a 16 

 millimeter bore. The upper end of this tube is passed through a block of 

 wood B and secured with silk and shellac. Along the outside walls of the 

 tube the thermal-junction wires C are laid, and firmly tied with silk in such a 

 way as to leave the junctions protruding 1 or 2 centimeters from the bottom 

 of the tube. The ends of the junctions are carefully separated, and the 

 whole arrangement dipped in paraffin. The paraffined junctions, together 

 with the glass tube, are then immersed in water contained in a large spherical 

 Dewar vacuum flask D with silvered-glass, double walls. This flask has an 

 outside diameter of about 15 centimeters, the distance between the walls being 

 8 millimeters, the length of the neck approximately 10 centimeters, and the 

 capacity 1100 cubic centimeters. 



A mercury thermometer, E, which indicates the temperature of the bath, 

 passes through the tube A to such a depth that its bulb lies very near the 

 thermal junctions and at the same level. This construction allows the ther- 

 mometer to take up the temperature of the junctions very closely. The 

 mercury thermometer is of the Beckmann type, having a range of 5 C, is 

 graduated in hundredths of a degree, and calibrated by the Physikalisch- 

 Technische Reichsanstalt. The true temperature, as obtained from the read- 

 ing of such a thermometer, would be expressed by the formula T = A-\-KR, 

 where T is the temperature desired, A being the zero reading of the thermome- 

 ter, K a calibration constant which equals the true value of a scale division 

 for the particular conditions of use, and R the reading. 



CONSTANT-TEMPERATURE OVEN. 



The flask D is placed in an oven, F (see fig. 5), in which the air is maintained 

 at a constant temperature by the use of a mercury thermostat G which auto- 

 matically supplies the proper amount of gas to a small burner H located 

 beneath the oven. This oven, which is of sheet metal and about 33X40X50 

 centimeters, is inclosed in a slightly larger asbestos case with a sheet-metal 

 bottom, the air space between the oven and the outside case being about 25 

 millimeters. The fronts of both are hinged; in the top are three holes, one for 

 the insertion of the thermostat, one for the mercury thermometer E, and one 

 for the insertion of the wires of the thermal-junction system. Through the 

 last opening is also inserted a mercury thermometer for indicating roughly the 



