174 THE HORSE OF MR. VON OSTEN 



some unknown power in the eye of the horse,* or else 

 seek a cause in the animal's brain. Further experiments 

 on other horses would be necessary in order to discover 

 whether the species as a whole possesses this ability or 

 whether only certain ones are thus endowed. The 

 former is of course more probable. In this particular 

 case conditions were unusually favorable for the develop- 



* Konigshofer, who as we have already said, seconds the explanation 

 given by the ophthalmologist Berlin (and who confounds " Butzen- 

 scheiben " astigmatism with the common, so-called regular form), be- 

 lieves " that not only astigmatism but also the shape of the blind-spot of 

 the eye must be taken into consideration. This portion of the retina, 

 where the fibres of the optic nerve enter the eye (and called " blind-spot " 

 because there are no cells there that are sensitive to light) is very nearly 

 circular in man, but differs in shape in the different species of animals. 

 Konigshofer thought he had discovered that a relatively elongated blind 

 spot was favorable to keenness of vision. If we place the mammalia 

 in series on the basis of their relative keenness of vision, he says, we 

 would find that this series is identical with the one in which they are 

 grouped with reference to the form of the blind-spot from the circular 

 up to the most elongated. (In such a series the marmot takes the place 

 of honor.) > 



This exposition is not very satisfactury, however. We cannot be sure 

 what he means by " keenness of vision " (" scharfaugigkeit "). Is it 

 visual acuity in the usual sense of the term (as is said in one of his pas- 

 sages), or keenness in the perception of the movements of objects, (this 

 would appear to be his real meaning), or both at the same time. But 

 whatever the significance he may put into the term, any such attempt 

 at grouping the lower forms must prove unsatisfactory from the very 

 start on account of the scant data which we possess on visual perception 

 in animals. The experiences of the hunt upon which Konigshofer 

 partly bases his view, are entirely inadequate for such a purpose. This 

 much is certain, that the Osten horse, in spite of a blind-spot which, 

 thought somewhat oval, is by no means very elongated, possesses an 

 extraordinary acuity in the perception of movements. Even if the par- 

 allelism' mentioned by Konigshofer were really shown to exist, it would 

 not explain the matter until it were also shown in what way keenness of 

 vision is dependent upon the shape of the blind-spot, — a portion of the 

 eye which is not immediately operative in the visual sensation at all. 



