VISION. 



being quite unconscious that this was red. 

 He had a collection of engravings, some 

 coloured and others plain, but the only dif- 

 ference he could perceive was, that some 

 were clearer than others. When criticising a 

 picture he would discuss the composition of 

 the design, the light, shade, and perspective ; 

 but, as to the colours, he was silent. When 

 walking with others in a garden, he affected to 

 speak of the beauty and size of the flowers, 

 their regularity and perfume, but to his eyes 

 they, like the pictures, were all grey. The case 

 of a shoemaker named Harris, described in 

 the Philosophical Transactions,* has been ge- 

 nerally quoted as a well-marked example of 

 this form of achromatopsy, but on carefully 

 considering the remarks made upon it by Dr. 

 Dalton -f-, we are doubtful whether it really 

 was as supposed, and are inclined rather to 

 refer it to the second class. 



The case of M. Collardeau J has been 

 described as of this nature. This gentleman 

 was an amateur artist, but the imperfection 

 of his vision gave rise to the strangest pro- 

 ductions. So long as he confined himself 

 to the pencil, or to sketching in one colour, 

 he designed with much skill, but his paintings 

 in colours were the reverse of happy. For in- 

 nce, wishing to work up a scene in which 

 had drawn a dog, he unfortunately mistook 



e colour, and painted red all those parts 



hich should have been deep blue. He has 

 een known to confound on the canvass yel- 

 low with blue, and red with green, regarding 

 his work with the complaisance of a man who 

 felt that he had achieved success. 



The following interesting cases are of a 

 character forming a connecting link between 

 the two classes of achromatopsy. The first 

 is related by D'Hombres Firmas. Count 

 - of Alais, aged thirty -eight, married, 

 and the father of a family, possessed excellent 

 vision in every repect, except the perception 

 of colours ; but yellow, and the shades be- 

 tween black and white, were the only tints 

 he could recognise. On a number of dif- 

 ferent roses being placed in his hands, he 

 merely saw that white flowers were brighter 

 than purple ; yellow flowers he distinguished, 

 but red, blue, violet, and white blossoms all 

 appeared more or less dark though he dis- 

 tinguished the yellow centres. This gen- 

 tleman was fond of geology, but found it im- 

 possible to judge of the colours which marked 

 various formations in the map of M. Dumas. 

 Lacustrine formations and the lias were the 

 only ones which he distinguished, all the 

 others appearing to him tinted in grey; and 

 he would have confounded them together, 

 if his excellent sight had not enabled him to 

 follow the dotted lines and letters by which 

 they were indicated. He drew with taste in 

 crayon, Indian ink, and sepia ; but only on 



* Phil. Trans, vol. Ixvii. p. 260. 



t Memoirs of the Literary and Philosophical So- 

 ciety of Manchester, vol. v. part i. p. 38. 



|" Observations sur la Physique et 1'Histoire Na- 

 turelle, vol. xiii. p. 87. 



Op. cit. p. 73. 



one occasion attempted a scene in colours, of 

 a peasant and a bouquet of flowers. The re- 

 sult was so very unsatisfactory to ordinary 

 eyes, that he was not tempted to repeat the 

 experiment. 



The second case has been recorded by Dr. 

 Deconde.* A soldier applying for his discharge 

 on the ground of the formation of cataract, 

 attracted particular attention on account of 

 the cyanic colour of his sclerotica ; and on 

 investigating his power of distinguishing co- 

 lours, it was found that all those of the spec- 

 trum were confounded in two fundamental 

 hues, yellow and blue. Dark red, bright 

 red, rose, orange, yellow, green in which yel- 

 low predominated, and grey white, all ap- 

 peared as different shades of yellow : whilst 

 blue, green, and white with a blueish shade, 

 were perceived as blue. All the very deep 

 colours were regarded as black, and all the 

 very light ones had a whitish appearance, 

 though the man did not seem to have cogni- 

 zance of white, properly so called. Light, de- 

 composed by a prism, appeared to him of uni- 

 form blue. His sight was feeble and easily 

 fatigued. Numerous trials always led to the 

 above results. 



Class II. (Polychromatic Daltonism of 

 Wartmann.) This form includes the vast ma- 

 jority of cases of insensibility to colours, and 

 presents a very remarkable diversity of phe- 

 nomena. The colour, which, of all others, is 

 the stumbling-block, is lilac, and next to it 

 rose, indigo, and violet; on the othei hand, 

 yellow and blue are most commonh recog- 

 nised. A very general form is that first de- 

 scribed by the illustrious Dalton "j", who has 

 given his name to the affection ; and the 

 following are the chief features of his case. 

 He was not conscious of any peculiarity of 

 vision until the age of twenty-six, when, a dis- 

 cussion arising as to the colour of the flower 

 of Geranium zonale, it was discovered that he 

 and his brother differed materially from other 

 people in their ideas upon the point. About 

 two years afterwards he entered upon an in- 

 vestigation of the subject, and the following 

 are the principal results at which he arrived. 

 The solar spectrum appeared composed of 

 three colours, yellow, blue, and purple, the 

 red being little more than a shade or defect 

 of light. Orange, yellow, and green were 

 shades of yellow, whilst green and blue were 

 strongly contrasted. Of ordinary colours, 

 crimson and dark blue were identical ; the 

 colour of a florid complexion being a dull 

 opaque blackish blue, upon a white ground ; 

 blood seemed bottle green ; the face of a 

 laurel leaf was a good match for a stick of 

 sealing wax ; and the back of the leaf an- 

 swered to the lighter red of wafers. Green 

 baize appeared a dark brownish red : and a 

 liiiht drab was not to be distinguished from 

 a light green ; browns were very diversified, 

 some having a great affinity for green, others 



* Annales d'Oculistique, torn. xx. p. 52. 

 % Mem. of the Lit. and PhiL Society of Man- 

 chester, vol. v. part i. 



