KANSAS ACADEMY OF SCIENCE. 31 



blindness in producing accidents on railways and at sea; and so thoroughly 

 did he discuss this subject, that the Great Northern Railway compelled its em- 

 ployes to furnish satisfactory evidence of the perfection of their color sense. 

 The wide-spread interest on this subject, and its agitation at the present time, 

 are due mainly to the efforts of Prof F. Holmgren, teacher of physiology 

 in the University of Upsala, Sweden. He treats this subject from all stand- 

 points — historical, theoretical and practical, and gives specific instructions for 

 using colored worsteds for testing the color sense, which is everywhere known 

 as the Holmgren method. The Professor has tested by his method great 

 numbers of students, soldiers and railroad employes, and gives statistical re- 

 sults. In his native country, such has been the interest which his labors 

 have awakened, that the Swedish Government has caused to be discharged 

 from the railway service all persons found with impaired color sense. His 

 book was quickly translated into the leading tongues of Europe, and into 

 English by the Smithsonian Institution. The number of foreign scientists 

 engaged in the study of this subject are too numerous to be mentioned, and 

 I only insert here the names of Professors Bonders, Mauthner, Hering and 

 Helmholtz. This historical outline would be imperfect if I were not to add 

 the name of Prof. B. Joy Jeffries, of Boston, who has written, in addition 

 to numerous essays and reports on this subject, a work entitled "Color- 

 Blindness: Its Dangers and Detection." This is the most exhaustive trea- 

 tise on this visual irregularity in our language; and, besides the experiments 

 and original researches of the author, contains a compilation of most of our 

 knowledge on the subject up to the time of its publication, in the early part 

 of the present year (1880). 



What then is color-blindness? Is it the absence of the perception of light? 

 Is it a disease, congenital or acquired? Is it an objective or subjective de- 

 fect? — an imperfection of the mind, or of its visual apparatus? Color- 

 blindness is not blindness in the ordinary sense of the word. The visual 

 apparatus is perfect as an optical instrument, and the person has a natural 

 perception of light, and of the form and outline of objects. It is inability 

 to perceive certain colors, usually red and green, and tints of the same; so 

 that the individual cannot distinguish the difference between the color of the 

 leaves of a tree and its fruit. "The color-blind, however, see white and 

 black, and their intermediate and compound, gray, provided they are free 

 from alloy with other colors, precisely as others do." 



Again, there are two colors properly so called which they see, namely, 

 yellow and blue, which also if unalloyed they see in the normal manner. 

 But these are the only colors of which they have any sensation, and hence 

 their defect has been called by Sir John Herschel dichromic vision. ("Color- 

 Blindness, Its Dangers and Detection," by B. Joy Jeffries, page 42.) 



Here we digress for a moment to state that the evolutionists claim to find 

 in the existence of this defect evidence of their favorite doctrine. Accord- 

 ing to Geiger and others, what would now be color-blindness was the normal 



