25 
for the Croon i an Lecture. 
whale tribe, the sclerotic coat being above half an inch thick, 
and composed of a strong tendinous substance. In many fish 
this coat is composed of cartilage ; and in all birds the anterior 
part of it is (I believe) composed of bone. From all these 
considerations, I saw no power that could adapt the eye to the 
various distances of which we find it capable in the human 
body, unless we suppose the crystalline humour to be varied 
in figure, which can only he effected by a muscular action 
within itself. With this idea strongly impressed upon my 
mind, and finding that in many animals, when the crystalline 
humour was coagulated, it had a fibrous structure like muscles, 
I confess it seemed to me to confirm it ; but as this might to 
others appear only conjecture, requiring some proof, I set 
about such experiments as were best adapted for that purpose. 
Knowing that in all violent deaths the muscles contract, I 
supposed the crystalline humour, if muscular, would show 
signs of this effect ; for which purpose I got the eyes of bul- 
locks when removed from the sockets, the moment the animal 
was knocked down, and while the eyes were warm the humours 
were removed.” 
Mr. Hunter had proceeded thus far in the account of his 
experiments, when he was suddenly, and very unexpectedly, 
carried off; and as he has left no notes upon this subject, I am 
unable to make any addition to the account I have already 
given. 
Mr. Hunter’s laying claim to the discovery of a fibrous 
structure in the crystalline humour, which had been observed 
long before, and described by the accurate Leuwenhoek, may 
appear to require some explanation. The discovery of a fibrous 
MDCCXCI V. E 
