4S9 
materials of the hrain and ova of animals. 
then exposed the molecule, put on the cover, and immersed 
the whole into a cold mixture, and carried it to Kew, that 
Mr. Bauer might represent the appearance. 
EXPLANATION OF PLATE XXVII. 
Fig. 1. A small portion of the cortical and medullary sub- 
stance of the human brain that had been frozen and thawed, 
magnified 5 times. 
Fig. 2. A part of the above, magnified 25 times. 
Fig. 3. A still smaller part of the above, magnified 200 
times. 
These three drawings correspond with three that have a 
a place in the Philosophical Transactions : taken from the 
human brain recently after death, in a natural state. 
Fig. 4. The molecule of the pulleFs egg after impregna- 
tion, that had been frozen and thawed, magnified 10 times, 
to correspond with a similar drawing of the molecule in a 
natural state. 
