DR. TYNDALL ON MOLECULAR INFLUENCES. 
231 
those which are best calculated to avert such changes. It is yet to be estimated 
what influence the extreme non-conductibility of muscular tissue exerts in producing 
the remarkable constancy of temperature observed in the human body in different 
climates. The cuticle is an exceedingly bad conductor, and this explains the insen- 
sibility to heat of hands on which the skin has been thickened by exposure. Probably 
many escapes from the fiery ordeal, which have been hitherto referred to collusion, 
might be scientifically explained by reference to this fact. While studying at Mar- 
burg, I have sometimes heard Professor Bunsen make a good-humoured remark on 
the tenderness of his pupils’ fingers. Accustomed as he was to the manipulation of 
the glass used in his admirable eudiometrical researches, his fingers had acquired an 
insensibility to heat sufficient to carry him safely through an ordeal which, in other 
cases, would undoubtedly invoke the judicial condemnation of the middle ages. The 
experiments of Chantrey and Blagden are often referred to as illustrations of the 
surprisingly high temperature to which the human body may for a short time be 
exposed without injury. These experimenters owed their safety to two things, — to the 
non-conductibility of their tissues, and the non-conductibility of the air in contact 
with them. Were either of these materials changed, the experiments could not have 
been made. If air were a good conductor, and parted with its heat readily, their 
hands and faces would have shared the fate of the beefsteak and eggs which were 
cooked in contact with tin in the same oven. Were their bodies good conductors, 
they would have become heated like the tin, the heat would have been transferred to 
the deeper tissues and organs, to the probable destruction of the latter. As it was, 
however, both the causes mentioned contributed to the success of the experiment, and 
a mere surface irritation was the only inconvenience felt. 
