In an examination which was carried on some years ago under the supervision of Dr. Jeffries, among the pupils of the Boston schools, in which were 14,469 boys and young men, and 13,458 girls and young women, it was found that about one male in every twenty-five was colour-blind, while the same defect among the girls and young women was extremely rare, only 0.066 per cent. of them being thus affected.[37] [37] _Pop. Science Monthly_, vol. xix., p. 567. At a convention held in the city of Chicago for the purpose of organizing an association for educational reform, the teacher of drawing in the St. Paul schools made a statement that “four per cent. of all male pupils were colour-blind, while only one-tenth of one per cent. of female pupils were so affected.” No explanation was offered for this strange fact; indeed, it was pronounced a mystery, “even oculists and surgeons having given it up as impenetrable.” That defective vision is beginning to interfere with the activities of men, is shown by the fact that in many instances, in later times, colour tests have been required to determine fitness of applicants for positions in various departments of commercial enterprise. In this country, during the last fifty years, much attention has been given to the subject of visual defects in seamen, railroadmen, and other persons occupying positions of responsibility in which unimpaired vision is an important qualification. In response to a request sent by the German Government through its minister to the Surgeon-General of the United States Army, for statistical and other information on the subject of colour-blindness, Mr. Charles E. Pugh, General Manager of the Pennsylvania Railroad, in September, 1884, sent to William Thomson, M.D., surgical expert for the same company, the following statement: Total number examined on lines east of Erie 25,158 Colour-blind 481 Defective vision 661 Of this report Dr. Thomson says: The apparently small percentage of colour-blind in this table may be ascribed to the non-application of men who knew their deficiency, and to the fact that men in the service, knowing their defect, would leave the road before examination, and thus escape detection, and be enabled to gain employment on other roads where no examinations are required.[38] [38] _Pop. Science Monthly_, vol. xxxi., p. 796.