Today, color-blindness is a serious difficulty in the way of a person earning a living. A generation or so ago, it was considered a matter of small importance. Many persons, suffering from the disease, went through life without knowing they were afflicted. The only persons, as a class, who were greatly affected by the problem were railroad men, who had to take tests for the distinction of colors.

Today, with the common use of automobiles and the rapidly growing use of colored lights for signs and signals, color-blindness becomes an important matter.

The defect is hereditary and much more common in men than in women. A woman may have normal eyesight herself and yet transmit the color-blindness to her children. This is because it is what the geneticist calls a recessive character. A man may have a color-blind father and still not transmit the defect. But a color-blind woman, married to a color-blinded man, transmits the defect to all off-springs, both sons and daughters.