1881.] Heat by Conduction in Bone, Brain-tissue, and Skin. 13 



Average effects of o, l C. 



Time from the 



moment of 

 contact of free 

 surface of bone 

 or copper plate 

 of paraffine box 

 with the water. 



Skull. 

 7"5 millims. thick. 



Brain. 

 7'5 millims. thick. 



Scalp. 

 3 millims. thick. 



Degrees 



of 

 galvano- 

 meter. 



Thermo- 

 metric 

 values. 



Degrees 

 of 



galvano- 

 meter. 



Thermo- 

 metric 

 values. 



Degrees 

 of 



galvano- 

 meter. 



Thermo- 

 metric 

 values. 



At the end of — 



1 min. 15 sec. 



2 „ „ 

 4 „ „ 

 6 „ „ 



23-864° 

 54-170 

 88-804 

 116-476 



0-01609° C. 

 03652 

 0-05987 

 0-07853 



21-036° 

 42721 

 74-840 

 99-075 



001418° C. 

 0-02880 

 0-05045 

 0-06679 



17191° 

 31-241 

 59-208 

 80-766 



001159° C. 

 0-02106 

 003992 

 005445 



It will be seen that at the above periods the bone is the best con- 

 ductor, the brain coming next, and the skin last, although the latter 

 is 2*5 times thinner than the two former. 



We have, in the third place, to see what is the transmission of heat 

 through the three tissues, when the permanent thermal condition is 

 reached. The following figures show the amounts of this transmission 

 at the period in question. 



Average effects of o- l C. at permanent thermal period, through 7*5 

 millims. of skull, 7'5 millims. of cerebrum, and 3 millims. of scalp, 

 respectively. 





Degrees of 

 galvanometer. 



Thermometric 

 values. 



Percentages of 

 heat transmitted. 



127 -431° 

 113 -029 

 100 155 



-08591° C. 

 -07620 

 06751 



85-918 per cent. 

 76 -208 

 67 -514 



Here again the bone shows the highest, and the skin the lowest, con- 

 ductivity. 



Suppose, now, that we have a change of temperature of o, l 0. at 

 the surface of the brain of a sheep. As a matter of simple conduction, 

 what would be the change of temperature at the outer surface, after 

 the passage through the thicknesses of skull and scalp given ? We 

 will give the averages for two minutes and for the permanent thermal 

 state only. 



