EXPLANATION OF OBSERVATIONS 171 



But to come now to the most pertinent objection. We 

 saw that Berlin's whole train of thought rested upon the 



where as a personal observation. In Berlin's calculation ♦' of the in- 

 crease in the extent of the retinal pathway an ambiguity has crept in. 

 He says that " in the astigmatic eye there are stimulated 207 times as 

 many nervous elements as would be stimulated in the ideally normal 

 eye." It ought to read " 207 more " instead of " 207 times as many." 

 And this number holds only for the one case computed by Berlin, and 

 under the specific assumption that exactly ^ times the normal number 

 of elements were stimulated (571 instead of 364). Therefore the gen- 

 eral statement which Bayer ^^ makes in his text-book, that according to 

 Berlin's evaluation " 207 times more nervous elements " are stimulated 

 in the astigmatic eye than in the non-astigmatic one, does not hold true. 

 Closing this note, a few remarks concerning the experiments made 

 by Dr. Simon and myself. AU of the nine horses were tested for the 

 vertical image by means of the ophthalmoscope. In most cases Wolff's 



electric speculum was used. Atropine was not employed. For the 



laboratory tests the adipose and the muscular tissues were removed 

 from the eye-ball and the rear part of the bulb cut away. The front 

 part, containing the cornea and the lens, was fastened over one opening 

 of a metal cylinder which was closed at the other end by means of a 

 disc of ground glass. The whole, approximately as long as a horse's 

 eye, was filled with a normal salt solution whose refractive index (1.336) 

 corresponds quite closely with that of the vitreous humor of the horse's 

 eye. The pressure from within was regulated so that on the one hand 

 it was not dimmed and yet on the other there were no wrinkles in the 



cornea. The source of light the filament of a Nernst lamp was 



moved about in a plane 120 cm. distant from the eye and perpendicular 

 to the optic axis. It was moved through the point of intersection as 

 well as at various distances from it. Movement in horizontal and verti- 

 cal directions was in each case along lines 150 centimeters in length, 

 which would correspond to an angle of vision of not less than 64°. The 

 pathway of the imaged point was controlled by means of the cross-hairs 

 of the telescope. If in the same way we observe through the sclerotic 

 of an intact eye-bulb a point of light falling upon the retina and shining 

 through the sclerotic and choroid (which is not difficult when we use an 

 intense light), then to the observer its pathway will, of course, appear to be 

 deflected convexly toward the periphery, — and the deflection will appear 

 the greater, the farther the point of light is removed from the optic axis. 



