2 
Mr. Home’s Lecture 
not confined to the separate, or combined actions of the 
muscles, but also vary according to the degrees of their con- 
traction. 
The first and most simple of these effects is that of moving 
the eyeballs in different directions. 
The second is that of making the motions of the two eyes 
correspond with such a degree of accuracy, that when an ob- 
ject is viewed with both eyes, the impressions from the object 
shall be made on corresponding parts of the retina of each 
eye. 
The third is that of compressing the eyeballs laterally, which 
renders the cornea more convex, and pushes forwards the 
crystalline lens, to adjust the eye to near distances. 
Distinct vision with two eyes depends upon these different 
actions of the straight muscles ; an imperfection in any one of 
them, as it renders the organ unfit to perform its functions, 
must be considered as a disease. 
Three different diseases occur in practice, which appear to 
arise from morbid actions of the straight muscles. These are, 
an inability to see near objects distinctly ; double vision ; and 
squinting. 
I shall consider each of these separately. 
Of the inability to see near Objects distinctly. 
As that action of the muscles which produces the adjustment 
of the eye to near objects, consists of the greatest degree of 
contraction usually exerted by them, it puts the fibres into a 
very uneasy state ; which while in health they support with the 
utmost difficulty, and when affected by disease are unable to 
