RESEARCH TO MEDICAL PROBLEMS. 239 



couple circuit of an electromotive force corresponding to a tempera- 

 ture difference of 4° C, so that continuous temperature readings 

 could be made over a range of 14° C. 



One junction of each thermocouple was inserted in a constant 

 temperature bath, constant to within one one-hundredth of a degree 

 Centigrade, the other junction being inserted in the organ under 

 investigation. In most measurements one thermocouple was in- 

 serted in the brain and one in some other organ or tissue. In some 

 cases, however, three thermocouples were employed. 



In order to avoid the influence of bioelectric, or galvanic forces, 

 it is necessary to insulate thoroughly the wires that are inserted in 

 an organ. This was done by enameling the wires and coating them 

 with de Khotinsky cement. 



A special metal holder was constructed for the thermocouple that 

 was inserted in the brain. The wires, constantan No. 35 and copper, 

 No. 40, were passed through a hard rubber cylinder, the thermo- 

 j unction extending about one centimeter beyond the end of the rub- 

 ber, the exposed portion being covered with de Khotinsky cement 

 which served also to cement the thermoj unction in place. 



The skull of the rabbit was trephined to make an opening 6 mm. 

 In diameter and the holder clamped in place, the hard rubber rod with 

 the thermocouple junction being then inserted. The depth of pene- 

 tration of the brain varied in different experiments from 2 mm. to 

 about 8 mm. The trephined opening was made to the right of the 

 mid-line on a level with the posterior superciliary ridge. 



The thermocouples inserted in other organs also were constructed 

 of No. 35 constantan and No. 40 copper wire. The wires were 

 soldered together, the constantan wire extending about three inches 

 beyond the junction. By passing this free end through a needle the 

 junction could be readily drawn into the desired position within the 

 tissue. 



We wish to express our appreciation of the cooperation of Mr. 

 Seitz of the Electromechanical Engineering Department of the 

 Cleveland Clinic in the construction of the apparatus described above. 



The accompanying group of curves shows the effects of various 

 drugs upon the temperature of certain tissues of rabbits, especially 

 of the brain. In a later paper we propose to discuss the relative 



