Heat by Conduction in Bone, Brain-tissue, and Skin. 195 



rises of temperature of o, 2 C, and even o, 3 C. may not occur in the 

 brain of man, and perhaps in the brains of other of the higher animals, 

 during intellectual and emotional activity, with, consequently, de- 

 cidedly greater external manifestations than those given in our calcu- 

 lations. 



Table IX. — Permanent 'thermal condition effected by 0°*1 C. through 

 7'5 millims. of sheep's skull and 3 millims. of sheep's scalp, taken 

 together. 1° of galvanometer is equal to C '0006742 C. ; and o, l 

 is equal to 148° '316 of galvanometer. 





Degrees of 

 galvanometer. 



Thermometric 

 values. 



Percentages of 

 heat transmitted. 



86-038° 

 119572 

 58-010 



0-058006° C. 



0-073877 



0039112 



58-006 per cent. 



73-877 



39-112 



With regard to the effect of the blood circulating between the 

 surface of the brain and the outer surface of the skin, the only way in 

 which this liquid could check the outward thermal propagation would 

 be by virtue of its specific heat. The writer has considered this 

 question at some length in the work already cited,* and he sees no 

 reason now to depart from the line of argument there followed. If, 

 as was there done, we allow a loss of 50 per cent, of the initial rise of 

 temperature to satisfy the capacity for heat of the blood (and we are 

 really not warranted in granting such a loss) our o, l C. — now 

 reduced to o, 05 C. — would still show itself at the outer surface, at 

 the end of the second minute, by a galvanometric deflection of 5 o, 704, 

 equal to 0°'003846 C. 



We have next to see how far the good conductivity of brain-tissue 

 would act to prevent localisation at the outer surface of the scalp of 

 changes of temperature in a narrowly circumscribed area of the 

 cerebral surface. 



Imagine, as before, a point of the cerebral surface to have its tem- 

 perature raised 0°'l C. Now, setting out from this point, the excess 

 of heat would be transmitted to points in the surrounding cerebral 

 mass situated at a distance of 7*5 millims., in the proportions shown in 

 Tables III and IV. What the transmission to a point of the external 

 surface situated directly over the focus of heat would be we have just 

 seen. We have, then, merely to take the temperatures contained in 

 Tables III and IY, and using the percentages of transmission through 



* Op. cit., pp. 115, 118. 



o 2 



