437 
Sir E. Home's microscopical observations^ &c. 
on the other parts of the body ; and had we been able to 
produce the necessary degree of cold, he certainly would 
have tried the experiment. 
From the time of Mr. Hunter's death to that of the ex- 
pedition to the polar circle being fitted out, the subject had 
never recurred to my mind ; it was then revived ; and I had 
no doubt of being fully informed upon its return, whether 
animals after being frozen could be revived ; but in this I 
was disappointed. 
In the winter before last an experiment was made in the 
presence of several Members of this Society, of freezing a 
frog, inclosed in tin foil, in a mixture cooled to zero. The 
frog recovered ; but there was reason to doubt of the brain 
having been frozen ; and this experiment was repeated by 
Mr. Faraday, in the laboratory of the Royal Institution, 
in the presence of Sir H. Davy, Professor Brands, and 
myself, in the following manner. 
Two healthy frogs, nearly of the same size, were sepa- 
rately wrapped up in tin foil, and immersed in a cooling 
mixture at zero. At the end of four hours one of them was 
examined ; the brain and heart were found completely frozen ; 
the other was allowed to thaw gradually, but had no remains 
of life. Upon opening the skull the brain was dissolved, 
and the cavity contained nothing but a watery fluid, with 
some gelatinous matter. 
By this experiment it is decided that an animal whose brain 
has been frozen can never be restored to life. 
Having, in the Croonian Lecture for 1823, illustrated the 
more minute structure of the human brain by three drawings, 
magnified in different degrees by Mr. Bauer, made from a 
