130 VETEEINAEY OPHTHALMOLOGY. 



slide your head, (and with it your eye) with the scope 

 in position, to the right and left, upward and down- 

 ward. There are two methods of examining the 

 fundus — direct and indirect. In the direct method, 

 the image (that which we see and appreciate, at the 

 bottom or fundus of the eye, is the image), will be 

 erect, i. e., it will have suffered no inversion, as is 

 the case when the indirect method is employed, 

 for there we interpose a biconvex lens between the 

 eye examined and our own, thus 'inverting the image 

 This I demonstrated early in the session upon the 

 blackboai-ddiagra'mmatically. Now, if you, for experi- 

 ment, will take a piece of card- board and drive a pencil 

 through it, you will lind on looking through the result- 

 ing hole that the nearer your own eye you bring the 

 card the larger will be the field of vision. Yes? So 

 with the eye of the subject, for the pupil represents 

 the hole in the cardboard. J3ut there is a bar here 

 ■which can be overcome only by experienced pilots. 

 The observer must put his own eye in a condition 

 equivalent to his looking at an object in the distance 

 ■ — twenty feet — i.e., his eye, to see the fundus (the ac- 

 commodation of the observed eye being suspended, at 

 rest) must be in a condition to receive parallel rays. 

 Fortunately, the horse under examination being in a 

 semi-darkened room, relaxes his accommodation, and 

 thus one factor is overcome. This is to be accom- 

 plished only by practice, and' like all good things is 



