ARE YOU COLOURBLIND?

Dominion, Volume 15, Issue 159, 31 March 1922, Page 6

ARE YOU COLOURBLIND?

PECULIAR NATURAL DEFECT A COMPARATIVELY MODERN DISCOVERY SCEPTICAL RAILWAY AUTHORITIES (No. I.) A New Zealand authority on colour-blindness, who has made a life-long study of this deficiency In so many people, has recently been to the pains of jotting down some of his ideas, which doubtless will prove to be a valuable contribution to tho literature of the subject when he finds time to complete his work. The authority in question has been good enough to hand to us one section of his notes to make such extracts from as are likely to interest our readers. In the course of this paper the writes states “The term .colour-blindness is misleading -and frequently leads to misunderstandings. Total colour-blind-ness, in the sense that no colours are perceived, is a rare affection. The majority of so-called colour-blind people are only partially colour-blind; that is, they can distinguish some colours, but not others. Colour-blind people can see differences in spectral colour-mix-tures that are not perceptible to the normal-sighted person. No reference to colour-blindness ia to be found in literature previous to the year 1684. In that year Dr. Tuberville described one of his patients. This was a young woman, 22 years of age, who told the doctor that although her eyesight was very good she could not see any colours, everything appearing her either black or white. At night she saw tigers and other wild animals, and was very much frightened. Usher has suggested that this was not col-our-blindness, but of some nerve lesion, probably hysteria. The first authenticated case was reported by D. Huddart, in 1777. This was the case of a Cumberland shoemaker named Harris. This man was naturally col-our-blind. He could see no colours. Every bright colour ho called white, and every dark colour black. He detected his defect at the age of five years. One day he picked a stocking up in the etreet, ana on taking it to a neighbour’s house to find tho owner was struck by the people calling it red, whereas he considered it a black stocking. He also noticed that his child mates spoke of cherries as red in colour, and the leaves as green, but he saw no difference excepting in the shape, size, etc. Harris had two col-our-blind brothers. ,• “DALTONISM.” “John Dalton, the eminent scientist, was colour-blind, and to him we owe the first accurate description of a Case of colour-blindness. Dalton was twenty-seven years of age before he discovered his defect. He had noticed that at times he made mistakes about colours, but attributed those mistakes' to colour ignorance:—that is, that he was ignorant of colour names. He was led ,to investigate his colour vision by noticing that a pink geranium, which to him appeared sky blue, had changed to red without a trace of blue, when seen by candlelight. His household, with the exception of one brother —this is worthy of note — assured him that the change to artificial light made no material difference in the colour. In ono of the Manchester philosophical journals he published a description of his case, explaining that he only saw two colours in the rainbow—yellow and blue—and that he could not see any difference in colour between a stick of red sealing wax and the leaves of a laurel tree. Two brothers were also colour-blind. This accounts for the one agreeing with him in regard to the change of colour of the geranium. Dalton took considerable interest in his defect, and in 1798 published the facts of twenty cases of people who suffered from a similar defect. At this time Dalton had become famous as a scientist, and largely for this reason, chiefly because he was the first to write an accurate description of colour-blindness, the defect was for a long time called Daltonism. ... In 1837 Seebeck devised a test for colour-blindness. No special test had hitherto been used. Any cases that had been found had been discovered accidentally. His test consisted of three hundred pieces of coloured paper, each having a different hue and tint, and a few coloured glasses and wools. His method of testing was to ask the examinee to classify the-papers in accordance with their resemblance of colours. In his researches, which were chiefly among schoolboys, he found twelve colourblind cases. He was also able to prove that there are two distinct classes of colour-blindness, as well as a third, though the persons in the third class had a colour perception very little apart from the normal.

PERCENTAGE OF COLOUR-BLIND.

“Professor Gep. Wilson, of Edinburgh, published many papers on the subject during the years 185255. He had been led to investigate tho subject by noticing that some of his students, many of them brilliant, were unable to recognise tho colour of chemical precipitates. He devised a test somewhat similar to that of Seebeck, and proceeded to examine tho students. Much to his surprise, ho found a number of them to be colour-blind. In all he tested 1154 persons, and 1 found 65 to be colour-blind—that is a percentage of 5.6. In several of his papers he pointed out the danger of engaging colourblind people in various occupations. He did his best to interest the railway authorities in the matter, but his efforts met with no success.

“Professor Holgren, of Upsala University, Sweden, had read Wilson’s and Seebeck’s papers, and at once recognised their importance. At the same time he recognised that a test must be devised which was at once efficient, inexpensive, and capable of being conducted rapidly. Adopting the YotihgHolmholtz theory, he planned his famous wool test (in which the examinee is asked to distinguish the tints and colours of dyed wools, and to match them as best he can). He thou did his best to interest the railway authorities, pointing out the great danger the travelling public were subjected to by the employment by the railway • companies of colour-blind engineers, drivers, and others. At first, as with Wilson, his efforts were futile. The railway people argued that if such a thing as colour-blindness did exist it could not be found among their men, manv of whom had been years in the service and had never made a mistake. But in 1875 a railway accident occurred in Sweden, one express running into another. Nine people were killed and many injured. At tho inquest it was proved that the accident was caused through colour-blindness. As this was the first railway accident known to have been caused in this manner public interest was aroused, and the Swedish Parliament, in the following year, passed an Act making it compulsory

on all railway employees to be examined for colour-blindness. THE EVOLUTION OF COLOUR SENSE. In 1858, Gladstone, in his studies on “Homer and the Homeric Age,” pointed out the vagueness of colour names used by Homer and other ancient Greek writers, and concluded that the people who Jived in those days had not the colour perceptions similar to ours of the present day. In 1868, Goiter came to tho same conclusion. He stated that in the ancient Chinese, Semitic literature, the Vedi hymns, the Norse Eddes, and Greek literature, there is not only t. vagueness in the colour names, but an absence of such colour names as green and blue. . . . Hirschberg argued that he had seen a cave maussoleum opened in Egypt containing gorgeous colourings, dating from a period at least 1400 years before Homer and anyone who had seen the statues and the gorgeous heiroglyphs contained must have concluded that the people who lived in those days had as good a colour perception as our own. BLUE COWS AND HORSES. On the other hand there are to be seen in other caves statues of men with blue hair, and in the Acropolis there are statues of men with blue hair and blue beards. There are also blue horses and cows. Edridge Green says: “There is no doubt that an evolution of the colour sense has taken place. The only point is how and when did this occur?” Also, “It is obvious that light must have been discovered first, and then tho sense of colour.” He believes that in the earliest stages of evolution of the colour sense the colours of the extreme end of the spectrum were the first to ba seen — that is, red and violet. In a further stage, green appeared midway between red and violet, and as the evolutionary process proceeded, the colours appeared in the following order: Yellow, blue, orange, indigo. In his book on “Colour Vision” he remarks that ho had met only two cases of people who had seen the seven colours. He himself had only seen six. It mav be said, therefore, that the evolutionary process is still going on. n.nd in tho future wo may expect an eighth colour to appear in the spectrum.” (To be Continued.)