V. TEMPERATURE DETERMINATIONS 



151 



covered in the extremities of resting man — ^particularly in the regions 

 of large blood vessels (9). Hill and co-workers {10-12) have used 

 thermopiles for measuring the heat of nerve conduction and of 

 muscular contraction and have studied the effects of many variables 

 upon this heat. Extreme sensitivity is required for these measure- 

 ments since the temperature changes are of the order of 0.0001 °C. 



THERMOCOUPLES 



Duco cement 



#40 gage wire - 

 copper-constantan 



":zr 



-p"^ 



-ZL 



#28 gage wire - copper-constantan 



(bare} 

 Flattened solder 



^ ■T^mum ^— bead 



IP' 



#40 gage wire — copper-constantan 

 (bare) 



#28 gage wire — 

 copper-constantan 



SURFACE PYROMETER 



Bimetallic strip 

 thermocouple 



Flattened bead 



V pRmiT^ ' •"~^-'- Plastic tiolder 



DERMALOR 



Millivoltmeter 

 calibrated in 



Resistance wire 

 applicator 



Fig. 7. Surface temperature measuring devices. Methods of mounting 

 thermocouples shown in upper portion of figure, surface pj'rometers in lower 

 portion. After Stoll and Hardy {IS). See text page 152. 



The small dimensions of the thermocouple permit very rapid record- 

 ing. Response times as short as one millisecond can be obtained 

 with fine ■udre thermocouples. Using thermocouples of this type 

 Adrian {IS) and Bronk illi) have been able to record the rise in tem- 

 perature due to the passage of an impulse down a nerve fiber. 



For studies of the tj'pe just mentioned, no other thermometer has 

 the flexibility, sensitivity, and accuracy that is necessary. Thus 

 wherever such temperature measurements are anticipated, the ability 

 to mak^ thermocouples in the laboratory is desirable. For precision 



