174 Dr. J. S. Lombard. On the Propagation of 



Many years ago the writer made a few (not, however, very exact) 

 experiments on the conductibility of bone, which did not lead him to 

 anticipate any serions obstacle in the sknll to the outward transmission 

 of heat from the brain. Moreover, the experiments of Professor 

 Tyndall on conduction in elephant's tusk, whalebone, cow's horn, &c, 

 pointed to tissues of this nature as being better conductors than 

 sealing-wax and bees'-wax, on both of which substances the writer 

 had made many experiments, and which he knew would conduct suffi- 

 ciently well to enable one, with delicate apparatus, to appreciate a 

 slight change of temperature through a thickness of them greater than 

 the average thickness of the skull. 



In order to make tbe theoretical conditions of transmission to the 

 outer surface as unfavourable as could, with any justice, be warranted, 

 the writer selected the conductivity of parafnne as the representative of 

 the conductivity of bone and skin combined, and founded on this basis 

 his line of reasoning respecting the effect of slight variations of the 

 temperature of the surface of the brain on the temperature of the 

 exterior of the skin. But in June, 1880, M. Francois Franck, in a 

 communication made to the Societe de Biologie, gave the results of 

 experiments made by him on the conductivity of bone, skin, and 

 brain-tissue, which placed the whole subject in a new light.* M. Franck 

 stated that a difference of temperature of 1° C. failed to make itself 

 felt at the end of fifteen minutes through 3 millims. of bone, using a 

 thermometer detecting o, 05 C. With 2° C. difference of temperature 

 a doubtful change of o, 05 C. was obtained ; indeed, it required a 

 difference of 4° C. to effect a change of 0"2°. Using thermo-electric 

 apparatus detecting 0° "01333 C. (yV)? Franck failed to find any 

 indication of a transmission of heat with a difference of temperature 

 of 1° C. Skin he found to conduct about the same as bone, while on 

 the contrary, through 30 millims. of brain- tissue transmission readily 

 took place. 



As it is difficult to conceive of rises of temperature in the brain, 

 due to changes of mental activity, measured by whole degrees Centi- 

 grade, M. Franck's experiments on bone and skin, if correct, would 

 peremptorily end all question of the possibility of changes of tempera- 

 ture in the superficial layers of the brain, arising from psychical pro- 

 cesses, affecting directly the outer surface of the scalp. 



So able an experimenter as M. Franck making the above statements, 

 the writer felt himself obliged to go over the whole ground thoroughly, 

 although convinced at the outset that, as regards bone at least, 

 M. Franck was in error. Accordingly, the writer devoted himself for 

 the space of nearly six months entirely to the experimental examination 

 of the conduction of heat in tbe tissues in question, drawing his 



* " Gazette Medicale," July 3, 1880. 



