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XIX. Microscopical observations on the Materials of the Brain, 
and of the Ova of Animals, to show the analogy that exists 
between them. By *S/rEvERARD Home, Bart. V. P. R. S. Read 
at the Society for promoting Animal Chemistry, April 12, 
1825. • 
Read at the Royal Society June s, 1825. 
Half a century ago, when I began my professional educa- 
cation under Mr. Hunter, he was deeply engaged in investi- 
gating the properties of the blood, and ascertaining the 
changes it underwent in different circumstances. His ob- 
ject in this inquiry was to prove that the blood possessed 
within itself a principle of life, by which all these changes 
were regulated. 
By his direction I made the following experiment, which 
proved that when frozen and thawed it had undergone no 
change. 
Two inches in length of the jugular vein distended with 
blood and secured at each end by a ligature, when immersed 
in a cooling mixture and frozen, was found after it was 
thawed to remain fluid, and to coagulate on exposure like 
recently drawn blood. From this fact, which is published 
in his work on the blood, corroborated by many others, he 
concluded that as the principle of life resided in the blood, 
and no change was produced in that fluid by the act of 
freezing, none were to be expected to arise from its action 
! 
