i68 THE HORSE OF MR. VON OSTEN 



meager on this point. In order to make a few tests at 

 least, I undertook to examine nine horses with the aid of 

 Dr. R. Simon, oculist, to whom I am greatly beholden 

 for the assistance given in these and other tests to be 

 mentioned presently. In not one of the nine cases did 

 we discover anything like the curved deflection which is 

 supposed to be the sign of the form of astigmatism in 

 question. But in order to test objectively whether Ber- 

 lin's assumption were justified, we examined in the 

 laboratory fresh specimens taken from two horses. The 

 eyes were fastened in a frame in what corresponded to 

 their normal position. Their posterior spherical wall 

 (i. e., their respective retinal surface) was replaced by a 

 piece of ground glass. On a spherical surface linear 

 movements of a point of light are always imaged as 

 curves, no matter what the shape of the lens forming 

 the image may be. (For a more detailed statement see 

 page 170, at close of note.) Since, however, our inves- 

 tigation had to do only with those curves which were 

 due to the qualities peculiar to the lens, we had to replace 

 the spherical by a plane projection surface. In front of 

 the eye thus modified a strong light was placed at such 

 a distance that the image of it, produced on the im- 

 provised back of the eye by the cornea and the lens, 

 was a sharply defined point of light. Now, when the 

 source of light was moved, the point of light would also 

 move on the glass plate. Sitting at some distance behind 

 the eye, we observed the movements of this point through 

 a telescope. Thus we became witnesses of what happens 

 upon the horse's retina when a moving object passes in 



a tendency to shy easily. Be this as it may, for little could be concluded 

 from it, since in many extremely shy horses, no kind of visual imper- 

 fection can be discovered. 



