118 Scientific Proceedings, Royal Dublin Society. 
le centre de la dépression, la lumiére devrait subir une absorption plus 
forte aux endroits ot les fibres sont paralléles au plan de polarisation. 
Si ce plan est vertical, il se formera des parties obscures au-dessus et 
au-dessous de la fovea, des parties claires 4 droite et gauche. De méme 
il devrait se présenter des parties plus sombres aux endroits ou les fibres 
ne sont plus obliques 4 la surface de la rétine, c’est-a-dire au centre 
méme de la fovea et vers le bord de la tache jaune. On a vu le 
phénoméne des houppes de polarisation répondre a ces conditions.’” 
The coincidence of Haidinger’s tufts with the yellow spot was 
first discovered by Clerk Maxwell, who, in a note communicated 
to the British Association in 1856, after showing how the yellow 
spot could be observed, remarks: ‘“‘ By using a Nicol, the brushes 
of Haidinger are well seen in connexion with the spot; and the 
fact of the brushes being the spot analysed by polarized light 
becomes evident.’ This, I believe, is the earliest suggestion of 
the true origin of the tufts. 
That Haidinger’s tufts are exactly coincident in position with 
the yellow spot of the retina can easily be proved by means of a 
coloured screen which transmits light containing no yellow rays, 
and thus enables anyone to see the yellow spot in their own eyes 
asa dark patch. The best coloured screen I have tried for this 
purpose is due to a suggestion made to me by Mr. Whitmell, 
author of an admirable treatise on colour. This screen consists of 
a weak solution of the double oxalate of chromium and potassium, 
which is quite opaque to the yellow and orange rays. Holding 
such a solution near the eye, before a brightly lighted white 
suriace, the yellow spot is seen most conspicuously as a reddish 
patch on the general bluish-green ground. If now a Nicol be 
held before the solution, Haidinger’s tufts, or, as I have suggested 
they should be called, the jascicula lutea, can be seen precisely 
coincident in position with the macula lutea or yellow spot. 
The retinal area of both the fascicula and the macula varies 
slightly in different people; it is difficult to fix the exact 
boundary of the former, but so far as they can be traced, their 
longer axis is practically coincident with the diameter of the 
macula or yellow spot. The latter is somewhat elliptical in shape, 
1 Helmholtz, Optique Physiologique, p. 554. 
2 British Association Reports, 1856, vol. ii., p. 12; also Maxwell’s Collected 
Papers, vol. i., p. 242. 
