VISION. 



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place easily, hence achromatopsy results 

 from a certain state of torpor and indolence 

 of the retina and motor muscles of the eye ! 



Professor Wartmann, the most recent au- 

 thority upon this subject, stated in his first 

 Memoir that achromatopsy (or Daltonism) 

 has its origin in a defect of the sensorium. 

 In his second Memoir he enters at length 

 into a somewhat different explanation of the 

 phenomena. " I admit (says he) with Harvey, 

 Young, Jiingken, Miiller, and others that its 

 seat is in the retina, and I think that it is 

 produced by an abnormal state of the nervous 

 expansion, in such sort that it reacts equally 

 under two or more differently coloured vi- 

 brations. If the vibration caused by a ray of 

 red is identical with that engendered by a 

 green ray, there will be confusion of these 

 colours. This theory is independent of all 

 systems destined to explain light. * * * The 

 theory which explains Daltonism by an ab- 

 normal elasticity of the retina has the ad- 

 vantage of substituting a reasonable physical 

 condition for a vague notion of the sensorium : 

 besides, it is supported by facts, because the 

 injuries which alter the ordinary constitution 

 of the visual organ are capable of exciting, 

 permanently or temporarily, a false perception 

 of colours. Lastly it appears to be confirmed 

 by the circumstance that with many Daltonians 

 the eye sees less distinctly the red rays than 

 those of which the refrangibility is greater. * 



The actual seat of the phenomena of achro- 

 matopsy must, after all, remain matter of 

 speculation, as it is one of those things in- 

 capable of demonstration. D'Alembert says: 

 " It is very plain that the word colour does 

 not designate any property of body, but 

 merely a modification of our mind : that, for 

 instance, whiteness and redness exist only 

 in us, and by no means in the bodies to which 

 we refer them by a habit in force from in- 

 fancy." The knowledge that we possess of 

 the existence of colours is derived from the 

 evidence afforded by the thousands of persons 

 endowed with the power of distinguishing 

 them, and therefore we conclude that they 

 do exist. But supposing we were all like 

 Dalton and many others whose visual organs 

 never appreciate red any more than the gene- 

 rality of eyes distinguish the calorific or ac- 

 tinic rays, we should then not be aware 

 of the existence of the colour called red, which 

 plays so conspicuous a part in the adornment 

 of the universe ; or if some few eyes gifted 

 with superior powers discerned it, the majority 

 would have to admit its existence on the 

 evidence of others, not from knowludge de- 

 rived from their own eyes 



As regards remedial measures, Wartmann 

 and Seebeck recommend the employment 

 of coloured glasses of a certain known tint ; 

 suppose this tint red, the impression of a 

 green body and of a red body at first the 



same to the naked eye will be distinguished 

 by the use of the transparent screen. 

 Wartmann, however, admits that this me- 

 thod only remedies mistakes in the specific 

 nature of colours, and not those which apply 

 to the shades of one and the same tint. 

 Jiingken and Chelius have recommended the 

 use of coloured bands, bearing the name of 

 their colour, and Szokalski has suggested that 

 sensations of the various shades may be ex- 

 cited by fixing the eyes on different coloured 

 patterns, and then on a black or white 

 surface. But this proceeding is scarcely 

 so likely to be productive of benefit as that 

 recommended by Professor Wartmann. 



Should the achromatopsy result from con- 

 gestion, such means should be adopted as 

 are best calculated to subdue it; as depletion, 

 purgatives, and low diet. If it arises from 

 menstrual suppression, it will be proper to pre- 

 scribe emmenagogues, with mustard pediluvia, 

 hip baths, and such other means as are likely 

 to restore the catamenia. Should derange- 

 ment of the hepatic s_ystem be the exciting 

 cause, a dose of calomel, followed by a black 

 draught-, will often be sufficient to remove it ; 

 but it will be proper to follow such a pre- 

 scription with alterative doses of mercurials 

 and saline aperients, of which the Pullua and 

 Marienbad waters are very serviceable : ta- 

 raxacum with or without the nitro-muriatic 

 acid may also be advisaMe. 



Dyspepsia is too protean a disorder for us 

 to attempt more than to suggest the pro- 

 priety of carefully investigating the parti- 

 culars of cases where the insensibility to 

 colour can be traced to this cause, and of 

 laying down such a plan of treatment, medical 

 and general, as seems best adapted to the 

 exigencies of each individual case. 



Hi/pcrchromatopst/ (virep, be\ond ; x.pwfj.a, 

 colour; ityis, vision). Our knowledge of 

 this condition of the vision which may be 

 regarded as the opposite to achromatopsy, is 

 at present very limited, and is chiefly derived 

 from the publications of Dr. Sachs * and Dr 

 Cornaz.f As we have never had an op- 

 portunity of investigating a case of the sort, 

 we can only draw our information from these 

 and some other sources. 



Dr. Sachs is, we believe, an albino, and is 

 in addition affected with hyperchromatopsy. 

 The first account of this very singular anomaly 

 of vision was published by him, and other 

 instances have since been discovered. Pro- 

 fessor Wdi'tmann, of Geneva, in a communi- 

 cation with which he recently favoured us, 

 thus writes: " Quant a 1'Hyperchromatopsie, 

 c'est une affection qui n'est probablement pas 

 extremement rare. Je connais deux personnes 

 qui m'ontditen etre atteintcs, et j'espt-re etre 

 un jour en etat de publier quelques recherches 

 sur ce sujet. Cet etat n'est point necessaire- 

 ment lie a ralbinisme." 



* Deuxieme Memoire, p. 46. Dr. Wartmann 

 enters at length into the discussion of this subject, 

 but our space will not admit of our extracting his 

 ingenious arguments. 



* Historic Naturalis duorum Leucrethiopum Par- 

 ticular diue. Erlangen, lll'. 

 j- De 1'Hyperchromatopsie, par le Dr. L. Cornaz. 



Bruxelles, 1801. 



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