Hal 



VISION. 



vision is perfect in regard to colour. In the 

 sixth, four brothers and five sisters, of whom 

 two of each sex have the defect. In the 

 seventh, two brothers and three sisters, both 

 of the former having the defect. In the 

 eighth, there was no issue, and in the ninth 

 there a e two sisters, both of them capable of 

 appreciating colours." Of the fifth genera- 

 tion " the defective perception has hitherto 

 been detected in but two of the families. In 

 one of them, consisting of three brothers and 

 three sisters, one of the brothers has the 

 defect, and in the other, a male, an only child, 

 is similarly affected." 



Sex exercises a considerable influence on 

 the occurrence of achromatopsy ; of the 

 thirty-one cases mentioned by Dr. Earle. 

 twenty-seven were males and four females, 

 and the result of upwards of two hundred 

 cases shows that as a general rule the propor- 

 tion of males is nine tenths of the whole. A 

 very remarkable instance has however been 

 published by M. Cunier*, where achroma- 

 topsy occurred in five generations of one 

 family, there being thirteen cases, and all 

 females ; but this stands alone as a notable 

 exception to the general rule. If it be true 

 that the works of the needle are the means 

 of perfecting a delicacy in the judgment of 

 tints, and in women the organ of colour is 

 more developed than in men (as asserted by 

 Gall), these very works ought to lead daily to 

 the detection of achromatopsy if it existed ; 

 and we may reasonably conclude that as cases 

 are not discovered they do not exist. 



According to the observations of Szokal.ski, 

 this defect of vision especially obtains among 

 nations having a Germanic origin, as the 

 Germans, English, Swiss and Belgians; the 

 French, Italians, and Spaniards being com- 

 paratively free : it seems to be common in 

 the United States, but this does not militate 

 against the proposition, the Americans being 

 descendants of the old British stock. How 

 far this peculiarity may be attributable to 

 the greater sensibility of the inhabitants of 

 southern climes, where the more brilliant sun- 

 shine develops colours in a degree unknown 

 in the northern latitudes, is a question which 

 cannot be decided in the present state of 

 our knowledge: nor can we affirm with con- 

 fidence, as stated by the same writer, that 

 achromatopsy occurs most frequently in ro- 

 bust constitutions, combined with a bilious 

 and melancholic temperament. A difference 

 of opinion exists as to whether achromatopsy 

 is indicated by any visible signs ; Szokalski, 

 Ruete, and Himly affirm that there is no 

 diagnostic mark, and Rau considers that a 

 yellowish tinge of the iris, which has been 

 considered by some to be indicative of it, is 

 far too common to be so regarded. Professor 

 Wartmann has in his first memoir drawn 

 attention to a peculiar golden lustre of the 

 eyes, which presents itself in cases of achro- 

 matopsy, where the iris is hazel. Miss Sedg- 

 wick f says of the historian Sismondi, that he 



* Op. cit. 



t Letters from Abroad, vol. i. p. ?50. 



had brilliant hazel eyes ; he was a Daltonian. 

 At least five other cases are known to have 

 presented the same peculiarity, but the num- 

 ber is yet too small to admit of this being 

 regarded otherwise than as a coincidence, for 

 in truth there appears to be as many Dalto- 

 nians with blue, black, and grey eyes, as with 

 hazel, and as many eyes without a yellow 

 pupillary margin as with it. 



There is sufficient evidence before us to 

 warrant our considering achromatopsy under 

 two distinct forms : congenital and non-con- 

 genital. The former is always persistent: the 

 latter may be divided into permanent and tem- 

 porary. 



Writers have classified the defect according 

 to degree; but the simplest and most practical 

 arrangement is that of Wartmann, who recog- 

 nises two classes only : the Dichromatic and the 

 Polychromatic. This we think advantageous, 

 as avoiding unnecessary sub-classification, the 

 varieties of the defect being endless. 



Congenital Achromatopsy. This form is 

 most common, and the majority of recorded 

 cases of insensibility of the eye to colour 

 are examples of it. It presents the best 

 marked illustrations of both varieties, which 

 we shall proceed to consider. 



Class I. (Dichromatic Daltonism of Wart- 

 mann). Black, white, and the intermediate 

 shades of grey are the only tints recognized by 

 patients of this class. Such persons dis- 

 tinguish with facility the forms of objects and 

 the gradations of light and shade, but to them 

 all the charms of nature and of art, as ex- 

 pressed by colour, are unknown ; their retinae 

 are rather sensitive than otherwise, and they 

 not only sec objects at a great distance, but 

 can read with facility in an obscurity amount- 

 ing to darkness. 



The first of these cases on record was pub- 

 lished by Dr. Dawbeny Tubervile, an oculist of 

 Salisbury,* being that of a young woman who 

 consulted him about her sight, which, though 

 excellent in every other respect, incapacitated 

 her from distinguishing any other hues than 

 black and white ; it is especially mentioned 

 that she could read " for nearly a quarter of 

 an hour in the greatest darkness." The next, 

 best marked case has been recorded by M. D. 



Hombres Firmas.-)- M. , of Anduze, of a 



bilious and melancholic temperament, but lead- 

 ing a very active life, had arrived at an ad- 

 vanced age without its being known, except 

 to a very few individuals, that there was any- 

 thing uncommon in his sight ; but all colours 

 appeared to him as tints of grey, between black 

 and white. Like several others having this 

 infirmity, he was fond of painting, and had 

 painted in his apartment two friezes and a 

 pannel between the windows: of these he was 

 proud ; but some of his visitors inquired why 

 he had represented the ground, the trees, 

 houses, and persons all blue ? He replied that 

 he wished them to match the furniture, he 



* Phil. Trans. No. 164. p. 73G. and Lowthorp's 

 Abridgement, vol. iii. part i. p. 40. 

 t Ann. d'Oculistique, torn. xxii. p. 72. 



