Dr Brewster and Dr Gordon on the Human Eye. 45 
tlie crystalline after death to that of water, as 21 to 20, which- 
gives 1.4025 for the index of refraction, differing only 0.0035 
from our measure, and 0.0175 from that of M. Chossat. It 
is by no means improbable, however, that the crystalline em- 
ployed by M. Chossat had actually a greater refractive density 
than ours. The one which we used was that of a female above 
fifty years of age. 
In the preceding observations I have limited myself to a 
general notice of tlie polarising structure of the crystalline lens ; 
but, in the course of an extensive series of experiments upon the 
anatomical conformation of this part of the eye in animals 
of all kinds, I have ascertained the precise manner in which its 
fibres are arranged, from the examination of a great variety of 
crystalline lenses, and by the use of new methods of observa- 
tion. This series of experiments, which is now nearly ready for 
publication, was undertaken at the particular request of Dr 
Gordon, for the purpose of ascertaining if the polarising struc- 
tures exhibited in the crystalline lens, had any connection with 
that singular arrangement of its fibres, which had been remark- 
ed by Leuenhoek, Sattig and Dr Young. In the results which 
I obtained, after a very few experiments, no such connection 
appeared; but the anatomical structure of the lens presented 
several curious phenomena, which, with the aid and encourage- 
ment of Dr Gordon, I was induced to investigate. The pre- 
mature loss of this distinguished individual put a temporary 
stop to pursuits, which owed their origin and continuance to his 
wishes ; but though the inquiry was in some degree foreign to 
mv own studies, and by no means inviting to one unaccustom- 
ed to anatomical operations, I have resumed and completed it 
from the same motives which induced me to undertake it. 
Whatever importance may be attached to it by physiologists, 
it will always have to me the higher value, of being the only 
memorial I can leave of a friendship which I deeply valued, and 
the best tribute I can pay to the memory of distinguished 
talents and exalted worth. 
