438 Sir E. Home’s microscopical observations on the 
healthy brain very recently after death, I became desirous of 
decomposing a similar portion of brain by the act of freezing, 
and then having drawings similar to the others made, to 
show the contrast between the two. 
For this purpose I got Mr. Faraday to inclose in tin foil 
a thin slice of human brain soon after death, then weigh the 
tin foil in which it was enveloped in the balance belonging to 
the Royal Institution. After being thus accurately weighed, 
it was immersed in a cooling mixture as low as zero. When 
it had remained there for four hours it was taken out, and the 
tin foil unfolded that it might thaw gradually ; a quantity of 
watery fluid had separated in the act of thawing from the por- 
tion of brain : this was allowed to drain off, and the tin foil 
with its contents was re-weighed, and had lost 20 per cent^ 
from its decomposition. Mr. Bauer’s drawings of it in this 
state, magnified in three different degrees, to correspond with 
the others, are annexed. 
These two sets of drawings establish the real appearance 
of the more minute structure of the brain, and the changes 
that structure undergoes when exposed to the effects of 
having been frozen, and led me on to ascertain the effects of 
freezing upon the molecule of the pullet’s egg after it has 
been impregnated, that I might ascertain whether the opinion 
I had formed, of its more minute parts corresponding with 
those of the brain, was correct ; and as I have given draw- 
ings of the molecules highly magnified, similar drawings 
made after it had been frozen, would enable me to preserve 
the difference in appearance between the two. 
To freeze the egg without disturbing the molecule, I en- 
closed it in a leaden case, with a cover exactly fitted to it ; 
