xHv Journal of Comparative Neurology. 



mysterious power of projecting the perceived object in the direction 

 from which the incident rays come. It is noticed by Dr. Hyslop that 

 this statement is too simple, the rays do not reach the retina in paral- 

 lel lines but in converging cones so that he finds it necessary to so 

 modify the theory as expressed by LeConte as to take the axial direc- 

 tion of each pencil the direction in which the outward projection is 

 performed and this becomes practically a perpendicular to the surface. 

 (The reviewer is unable to see how this assumption of perpendicular- 

 ity assists, by analogy with the process of outward projection in the 

 skin, as Hyslop seems to hold.) 



In the first of the above theories it appears that the muscle con- 

 tractions mysteriously afford a knowledge of direction which the pure- 

 ly visual process is incompetent to produce. We have, in fact, even 

 in this case, to find the origin of the sense of position m the assimilat- 

 ing of various experiences from diverse senses and it is not apparent 

 why the reverse notions of the muscles would not serve the purpose 

 in hand as well. In the second theory the power of outward projec- 

 tion is the very thing to be explained and it does not appear that the 

 analogy from the tactile sphere really explains anything, as the eccent- 

 ric projection is there a result of experience and if the organs were 

 differently constructed it is reasonable to suppose that essentially the 

 same tactile impressions would be formed by a different process. It 

 is plain that if one could subject himseh'" for a sufficiently long time to 

 an experience in which all images are caused to fall upon the retina m 

 the upright position the result would be to permanently invert the per- 

 cepts if either of the theories mentioned were true, while if our ideas 

 of position and direction are formed as a product of experience, it 

 might be possible to readjust the percepts so that the new position 

 would cease to appear abnormal or inverted. To determine which of 

 these suppositions would prove correct was the purpose of Dr. Strat- 

 ton's painstaking experiments. This was done by binding upon the 

 eye an erecting system of lenses which caused the retinal image to be 

 upright. At all times when not wearing the apparatus the eyes were 

 carefully blindfolded. The compass of the field of vision was 45 de- 

 grees. Objects at first, of course, all seemed inverted but they were 

 lacking in the predicates of reality for which memory images from pre- 

 vious experience continued to be the criterion. Things were seen 

 in one way and thought of in a different way. Soon the vivid con- 

 nection of tactual and visual perceptions began to overcome the effect 

 of previous visual vestiges and hands and feet began to seem to be in 

 the place where vision reported them, but objects out of the field of 



