156 
ArTIcLeE VI. 
Memoir on Daltonism [or Colour Blindness]. By M. Evie 
Wartmann, Professor of Natural Philosophy in the Aca- 
demy of Lausanne, &c. 
[Read at the Société de Physique et d'Histoire Naturelle de Genéve, 
April 16, 1840*.] 
i; 
INTRODUCTION. 
Many persons, whose eyes are sound and capable of perform- 
ing their most delicate functions, are nevertheless unable to 
distinguish colours. The number of such persons is much more 
considerable than is generally supposed, and it is surprising that 
the majority of physicians and physiologists are ignorant of the 
existence of, or pay so little attention to, so common a fact. 
It is known that every one can, in certain cases, receive 
abnormal sensations of colour; but it is only in an intermittent 
manner and for a limited time. Thus, whenever any one looks 
fixedly at a bright object placed on a surface of a dark tint, and 
then closes his eyes, or transfers them rapidly to another ground 
of a white colour, he immediately perceives an image more or 
less clear of the object beheld, but presenting a colour comple- 
mentary to its own. Buffon has called this the phanomenon 
of accidental colours. It ceases at the end of a certain time, 
during which the primitive impression is seen in its turn to take 
the place of the secondary impression. It also arises when the 
eye, fatigued by the prolonged observation of a coloured and 
very bright object, looks at another object of a different colour. 
Various theories have been proposed to account for these 
coloured perceptions (which the Germans call suwdyective, and 
which Goethe terms physiological), — among others that of 
Scherffer+, for which Professor Plateau has recently substituted 
* This Memoir had been communicated to the Société Vaudoise des Sciences 
Naturelles, March 5, 1840. (See Actes de la Soc. Helvet. des Sciences Natu- 
relles, 1841, p.194.) Its conclusions have also been pointed out (August 3, 
1841) at the Meeting of the British Association at Plymouth. (See Report for 
1841—Transactions of the Sections, p. 40. Silliman’s American Journal, 
January 1842, tom. xlii. p.62. L’Jnstitut of February 3, 1842, No. 428, p. 47.) 
Numerous additions have been subsequently made. 
t Dissertation on Accidental Colours.—Journ, de Phys. tom, xxvi. 1785. 
