378 KANSAS CITY REVIEW OF SCIENCE. 



made in Europe show that a similar law as to the relative proportion of color- 

 blindness between the sexes prevails there. The subject has been over-looked 

 until within a few years, but the value of the knowledge of it that has been gained 

 cannot be disputed. This knowledge can be applied practically on a scale of 

 considerable extent in determining the vocation to which boys should be trained. 

 A person who is color-blind is obviously unfit for any business in which he must 

 know how to distingush colors. Yet the person himself and those who are around 

 him are seldom aware of his defect. 



If examinations are regularly made in the schools and records kept of them, 

 as has been done by Professor Jeffries, a sure practical test may be found which 

 can be applied directly to each person, so as to guide him aright on this point. 

 The inquiries of Dr. Jeffries have disclosed a great lack of knowledge of colors, 

 aside from. color-blindness, among adults as well as among the boys in the schools. 

 But very few boys of the grammar or higher schools, he says, are familiar with 

 the color-names of even the primary colors, and still less can they correctly apply 

 those names they do remembe, when shown colored objects. " I have received 

 letters from adults, not color-blind, whose lack of color-names had been a serious 

 drawback to them in their occupations in every-day life ; and they have besought 

 me to urge the teaching of color-names and the education of the color-sense in 

 our public schools." The teaching of colors and color-names has been partly in- 

 troduced into our primary schools, but without any system ; it has been begun in 

 Europe, especially in Germany, in the lowest schools, in a systematic manner. 



The exemption of women from color-blindness has been attributed to their 

 familiarity with color objects and materials ; but this holds only of the sex as a 

 whole, not with reference to individuals, for the color-sense cannot be changed 

 with practice in colors. The question arises whether generations of color-educa- 

 tion have caused this sexual difference, and is important; for, if answered in 

 the affirmative, it proves that we may begin to eliminate color-blindness from fu- 

 ture generations of boys by teaching and exercising the present generation in the 

 perception and distinctness of colors. 



DIAGNOSIS OF BLOOD-STAINS. 



Dr. J. G. Richardson, of Philadelphia, gives the following summary of the 

 results of his measurements of blood-corpuscles : 



First — That in unaltered blood-stains, as ordinarily produced by the sprink- 

 ling of drops of blood upon clothing, leather, wood, metal, etc., we can, by tint- 

 ing with aniline or iodine, distinguish human blood-corpuscles from those of the 

 ox, pig, horse, sheep and goat, whenever the question is narrowed down by the 

 circumstances of the case to these limits. 



Second — By tlie method I have devised we can measure the size of the cor- 

 puscles, and apply the two corroborative tests of tincture of guaiacum with ozon- 

 ized ether and of spectrum analysis, to a single particle of blood-clot weighing 



