EXPLANATION OF OBSERVATIONS 173 



merits °^ have shown that the rods and cones of the horse's 

 eye are more minute than ours. Assuming that, in the 

 case of the horse, as is presumably the case in human 

 vision, the transition of a stimulus from one retinal cell 

 to the next already in itself induces a sensation of move- 

 ment, then the horse ought indeed be extraordinarily keen 

 in the perception of moving objects (provided that the 

 horse's more minute cells are packed just as closely as in 

 the human retina). And besides, there are two specially 

 adapted areas within the retina of the horse. The 

 "band" (streifenformige Area") which was discovered 

 fifteen years ago by Chievitz,^'' is a strip of i to 1J/2 mil- 

 limeters in width, traversing the entire retina horizontally, 

 and is noteworthy on account of its structure and prob- 

 ably, too, on account of its greater efficiency. It may 

 have something to do with the accomplishments of the 

 Osten horse; but in how far it would be hard to say. 

 The other noteworthy portion of the horse's retina is the 

 "round area " discovered some four years ago, located 

 at the rear outer end of the " band ", and it is the best- 

 equipped part of the horse's retina and corresponds to the 

 area of clearest vision, the yellow spot, in the human eye. 

 But this round area need not come in for consideration 

 by us, for its location would indicate that it is used in 

 binocular vision, that is, seeing with both eyes.°^ But in 

 all our experiments the Osten horse observed only with 

 one eye. That does not mean, however, that under other 

 circumstances the round area may not be of very great 

 importance. 



In the present state of our knowledge, all attempts at 

 explanation are, of course, of the nature of hypotheses. 

 If further investigations should disclose this explanation 

 to be untenable, then we would either have to suppose 



