NA TURE 



477 



THURSDAY, SEPTEMBER i8, 1879 



COLOUR-BUNDNESS 



Colour-Blindness, its Dangers, and its Detection. By 

 B. Joy Jeffries, A.M., M.D., Ophthalmic Surgeon. 

 (Boston, America : 1879.) 



SOME months ago the subject of colour-blindness was 

 introduced into the columns of this periodical as 

 bearing on a question of colour nomenclature. Little 

 was then said on the subject itself beyond what was 

 necessary to illustrate the point in dispute, but it may 

 now be added that the general features of this remarkable 

 defect of vision have lately been exciting much attention, 

 and have given rise within the last few years to a some- 

 what extensive literature, involving points on which there 

 has been much difference of opinion and some energetic 

 controversy. 



It is just a century since the first public announcement 

 was made, through Dr. Priestley, of a case of defective 

 vision, which, by the account left on record, we can easily 

 recognise as being of the kind subsequently found so 

 common. About twenty years later we come on the well 

 known and often-quoted description of his own case, 

 given by John Dalton, which, after another lapse of thirty 

 years, was commented on by Sir John Herschel in a 

 very lucid and instructive manner. This celebrated case 

 has given rise to the name " Daltonism," by which the 

 complaint is most generally designated by Continental 

 writers, but which has been objected to by the English, 

 on the ground that it is no compliment to their great 

 chemist to associate his name with an unfortunate natural 

 defect in his optical apparatus. Many other words, 

 chiefly derived from the Greek, have been from time 

 to time proposed, but the simple term colour-blindness, 

 adopted generally by English writers, and its equivalent, 

 Farbenblittdheit, used by the Germans, appear to answer 

 every purpose, and to be unobjectionable. For, whatever 

 may be the special characteristics of the defect (and on 

 this point there are differences of opinion), it is admitted 

 on all hands that an inability to appreciate the sensation 

 conveyed by some particular colour or colours to the 

 normal eye must be its most distinguishing feature. 



In 1840 appeared an essay by Prof. Elie Wartmann, of 

 Lausanne ; but the first complete work on the subject was 

 the "Researches on Colour-Blindness," by Dr. George 

 Wilson, of Edinburgh, published in 1855. After this 

 several memoirs are to be found, chiefly in transac- 

 tions or journals ; but the subject attracted little notice 

 beyond mere curiosity, till a few years ago, when oculists 

 and physiologists suddenly woke up to a conviction that 

 it had a real importance, both theoretical and practical, 

 and therefore deserved more careful study than it had 

 yet received. This movement appears to have originated 

 in a more vivid appreciation of certain dangers that were 

 considered likely to arise from the employment, in railway 

 and marine service, of persons who were colour-blind, and 

 were consequently liable to mistake coloured signals. 

 This danger had been clearly pointed out by Prof. Wilson, 

 but it had required many years for its importance to 

 become recognised. When, however, attention was 

 roused, there was no lack of persons ready to undertake 

 Vol. XX. — No. 516 



the investigation of the subject, and a host of works have 

 appeared by many men of eminence proposing means 

 of providing against the evil; and although the in- 

 quiries have been instituted at first with chiefly a prac 

 tical bearing, they have naturally, in the hands of scien- 

 tific men, been mixed up with a good deal of speculation 

 of a more theoretical kind. Among the workers who 

 hive busied themselves with the subject may be men- 

 tioned Prof. Holmgren, of Upsala, in Sweden ; Dr. 

 Stilling, oculist at Cassel ; Dr. Magnus and Prof. Cohn, 

 of Breslau ; Prof. Donders, of Utrecht ; Prof. Ewald 

 Hering, of Prague ; Dr. Daae, of Norway ; Drs. de Wecker 

 and Landolt, of Paris ; and Professors Delbceuf and 

 Spring, of Liege. Unfortunately, although we know that 

 some of our most eminent oculists in England have also 

 lately had the subject under their consideration, their 

 researches have not yet been made public, and it is, 

 therefore, opportune that we are able to announce the 

 appearance of a work which, although not by an English- 

 man, is in our language, and will, therefore, make the 

 English reading public acquainted with what has been 

 done. 



The author is ophthalmic surgeon to several hospitals ; 

 he is otherwise much connected with ophthalmological 

 matters, and has had large experience in regard to colour- 

 blindness. He gives a good and full account of the 

 general nature and statistics of the defect, and the means 

 he considers best calculated for its detection ; enlarging 

 on the necessity for a systematic testing of the vision of 

 servants on railways and sea-going vessels, and recom- 

 mending the rigid exclusion of those who have imperfect 

 colour-vision. He further devotes some attention to 

 matters of theory, adopting and advocating the views 

 most generally entertained. 



It is impossible, in the short space of such a notice as 

 the present, to give any extended analysis of the recent 

 comprehensive investigations ; it must suffice to make a 

 few remarks on some of the more prominent points of 

 interest ; and first as to the statistics. Dr. Jeffries 

 has some interesting chapters on this head, and states 

 that variable statistics have been given by different ob- 

 servers, depending largely on the mode of testing. 



In regard to males, he gives a tabic of the results 

 obtained by eleven different observers, who had examined 

 on the aggregate about 50,000 persons, chiefly pupils in 

 schools, employes on railways, soldiers, or sailors. The 

 proportion of colour-blind persons was given variously 

 from 3 to 6 per cent., the average being about 4. Assuming, 

 therefore, the examinees to represent fairly the general 

 population, we may take it for granted that one out of 

 every twenty-five men we meet is deficient of any true 

 ideas respecting the colours of objects he sees around 

 him. 



With females, the case is very different, the defect in 

 that sex being exceedingly rare. Out of nearly 20,ocx> 

 women and girls examined, there were only registered 

 forty cases of colour-blindness, or o'2 per cent. ; and some 

 of these are of doubtful accuracy. This is a very singular 

 fact, for which no sufficient explanation has ever been 

 suggested ; it has indeed been remarked that women 

 devote much more attention than men to colours in 

 general, but this has no bearing on the question, inas- 

 much as the evil is not a functional derangement, which 



