XX Journal of Comparative Neurology. 



natural reactions of the system. Great stress is laid upon action as a 

 means of character building. 



The importance of the subject is obvious from the great demand 

 for the various patent remedies for drunkenness and we are glad to 

 commend a temperate and scientific treatment of inebriety. 



c. L. H. 



The Physiology of Visual Sensation.^ 



Under the above heading a series of papers, originally published 

 in the Zeitschrift f. Psychologie, are in convenient form for reference. 



The first paper, by the editor, concerns the function of the reti- 

 nal rods. 



It is found that when the eye has been adjusted to the darkness 

 of a poorly lighted room all parts of the retina except the macula 

 function in a peculiar way characterized by the absence of color, by a 

 greatly increased sensitiveness to feeble light and especially to the 

 colors with short waves in so far that it does not discern the red at all. 

 Now if the anatomical fact that the rods are absent from the macula 

 be coordinated with the above it is but reasonable to conclude that the 

 peculiarities described belong to the rods of the retina. 



It may then be concluded that the rods are color blind, adapted 

 to short wave-lengths and are exceedingly adaptable. Per contra, the 

 cones may be regarded as trichromatic organs demanding greater in- 

 tensity of light. According to this theory the perception of white 

 may be reached either by any sort of stimulation of the rods or by a 

 definite composition of light waves affecting the cones. 



The existence of these two method of producing white sensations, 

 the author claims, affords an explanation of several vexed questions. 

 He sums up the variations from Newton's law of color mixtures as 

 follows : 



The comparisons serving for high intensities become erroneous 

 as the light is diminished according to the rule that the mixture which 

 has the greater rod-valence contains a superfluity of colorless light. 



Persons completely color blind may be supposed to lack the cones 

 or the pigment appropriate to them. 



In a second paper the variations due to modifications of intensity 

 in the case of the green-blind are discussed by Kries and Nagel. 



Very interesting results bearing upon the same problem were ob- 

 tained by Dr. Kries in a study of the effect of brief light stimuli on the 



* Abhandlungen zur Physiologic der Gesichtsempfindungen aus dem physi- 

 ologischen Institut zu Freiburg. Edited by J. von Kries. Part I. 1897. 



