838 REPORT— 1888. 



land. Weaving and embroidery, which are the chief occupations about Appenzell^ 

 St. Gall, &c., may be blamed as productive of degeneration, but watchmaking, in 

 the Jura, does not seem to be so ; and the low position of the Oberland, whach 

 extends to other points besides stature, is difficult to explain. Goitre seems to have 

 a geological distribution ; myopia belongs to the towns, to the highly-educated, to 

 the Germans (readers of German type), to the lacemakers and embroiderers. On 

 the whole, the physical development is healthiest in Nidwalden and Tessin, and it 

 ia suggested by the Swiss officials that the diet in these two cantons consists largely 

 of cheese. 



5. On Oolour-hlindness. By Kael Geossmann, M.D. 



The question of colour-blindness, which, when first described 90 years ago, had 

 only the interest of a scientific curiosum, has become one of very great importance- 

 in our age of ocean- and railroad-racing. 



Still, although everyone, with the exception perhaps of the official authorities, will 

 be of the same opinion as to the danger of employing colour-blind people in posts 

 where coloured signals are to be distinguished, not the same unity exists as to the 

 theories concerning colour-blindness and colour-perception. The old theory of 

 Thomas Young (1802) obtained a new lease by the support of no less a name than 

 Helmholtz ; but this theory is fast losing ground against the theory of Hering, who 

 admits two pairs of simple or fundamental colours. A third theory, that of the 

 evolution of the colour-sense, has, as one of its supporters, Mr. W. E. Gladstone. 

 But it has not been considered anything else than a misunderstood Darwinistic 

 deduction, carried out with a great amount of philological knowledge. 



Colour-blindness in its typical form is congenital, and, with the vei-y rarest excep- 

 tion, is double-sided : it is either red-green-blindness or blue-yellow-blindness, or 

 total colour-blindness. As red-green-blindness is the usual and most important 

 form, we will consider it exclusively here for simplicity's sake. 



The colour-blind individual ' makes mistakes' in distingmshing certain colours. 

 To him the ripe strawberry and its leaves, the blossom of the pomesrranate-tree and 

 its foliage, the blush on a rosy cheek and the sky, are three pairs of equal colours. 

 The names given to certain colours by the sufierer may be right or wrong ; they do 

 not convey to them the correct notions. A keen perception of dark and light shades 

 exists and often leads to the correct naming of colours. Still, naming is utterly 

 misleading as a rule. Holmgren has therefore modified Seebeck's mode of testing 

 by placing a bundle of coloured skeins before the colour-blind, who has to select to 

 a given shade all those which match. If there be two different colours which 

 appear absolutely alike to the colour-blind, a pattern made of these two colours 

 will appear as of one colour only. On this principle Stilling based his plates, 

 an excellent idea, which, however, fails very often ; the reasons will be .seen 

 soon. 



The author calls two such apparently identical but different fundamental colours 

 ' twin-colours.' Such colours are, for instance, a certain yellow and green. To these 

 two we may find a third fundamental colour, equally identical to the colour-blind, 

 a certain red, thus forming with the two others a set of ' triplet-colours.' He now 

 found that while a certain green and yellow were twin-colours for all his colour- 

 blind patients, the corresponding red was right for some, too dark for others, too 

 light for others again. This he found was due to the way in which the different 

 eyes perceived the spectrum. If the red end of the spectrum was shortened, cer- 

 taiu reds appeared darker than to eyes with a normal extension of the spectrum. 

 Dr. Grossmann utilised this by embroidering letters of three colours so as to form 

 on a brownish ground a red letter, say an F, completing it by green in such a 

 manner as to form a B. A red-green-blind eye with normal spectrum will then 

 see a blank ground ; while one with a shortened spectrum sees the letter F dark ou 

 a lighter ground. 



Another difficulty is the variability of the daylight, which affects the different 

 colours in twin combinations to a diflerent degree. Both these reasons explain 

 why Stilling's plates so often fail. 



