on Muscular Motion. 
23 
account for the alteration we find in the focus of the eyes of 
old people. 
There are many other circumstances respecting vision, and 
many which occur in disease, that may be explained by a 
knowledge of these facts ; but as this lecture is only intended 
to establish the facts themselves, in doing which I have already 
taken up too much of the time of this learned Society, I shall 
at some future period consider their application to the phe- 
nomena of vision in health, and disease. 
EXPLANATION OF THE PLATE. (Tab. I.) 
Portions of the four straight muscles of the eye, with their 
tendons insensibly lost in the external lamina of the cornea, 
stretched out and dried. The tendons become broader as 
they approach the cornea, and form a circle of which the cor- 
nea appears to be a continuation. 
