158 Intelligence and Miscellaneous Articles. 



burner, apertures have been bored in order to produce a draught 

 of air. This arrangement permits higher . sounds to be obtaiued 

 than with the ordinary bellows. A manometer, communicating 

 with the entry-tube, indicates the pressure which corresponds to a 

 determinate sound. — Gomptes Hdiidas de VAcademie des /Sciences, 

 Dec. 18, 1876, p. 1235-36. 



OBSERVATIONS ON A PROPERTY OF THE RETINA, FIRST NOTICED 



BY TAIT. BY OGDEN N. ROOD, PROFESSOR OF PHYSICS IN 



COLUMBIA COLLEGE. 



In the Edinburgh ' Proceedings,' 1869-70, vol. vii. pp. 605-607, 

 Tait described an interesting observation which has perhaps some 

 bearing on Thomas Young's theory of colour. While suffering 

 from indisposition, he noticed each time, on awakening from a 

 feverish sleep, that the flame of a lamp seen through a ground-glass 

 shade assumed a deep-red colour, the effect lasting about a second. 

 He suggests that the nerve- fibrils in the retina also partook of 

 sleep, and, on awakening, the green and violet nerves resumed their 

 function somewhat later than the red. I have in my own case noticed 

 some instances which seem to point out that after a nervous shock, 

 sudden or prolonged, the green nerves (adopting the theory of 

 Young) recover their activity later than the red, and probably later 

 than the violet nerves. The first observation was made twenty 

 years ago, while recovering from the effects of chloroform which had 

 been administered by a dentist well known at that time in Munich. 

 Upon regaining consciousness and raising my eyes to the face of 

 the operator, I was a little surprised at not having previously re- 

 marked his unusually ruddy complexion, but the next instant saw 

 that this was due to an optical illusion ; for his hair appeared of a 

 bright purplish-red hue. The singular appearance lasted perhaps 

 a couple of seconds, when his hair resumed its natura] colour, which 

 was white. This observation corresponds with that made by Tait. 



I give now an instance where chronic effects of a similar charac- 

 ter were noticed by me for a couple of weeks continuously during 

 convalescence from typhoid fever. In this case white objects ap- 

 peared of a not very intense orange-yellow hue, the general effect 

 on a landscape being such as is produced by the orange-yellow rays 

 of the setting sun. Here the activity of the green and violet nerves 

 was diminished relatively to that of the red. The auditory nerve 

 was also evidently affected during the same period ; but precisely 

 in what way I did not ascertain. 



It is a mttter of yearly observation with me, that effects similar 

 in kind to those first noticed are produced by long exposure to 

 bright white light out of doors. Under such circumstances, white 

 objects no longer appear pure white, but are tinted plainly purplish- 

 red ; and rather dull greens assume a grey hue, as though all the 

 green in them had been neutralized, while strong greens are consi- 

 derably reduced in intensity (saturation). Upon leaving the blind- 

 ing glare and entering a darkened room, it often for several seconds 

 appears filled with a greenish haze. 



Two of these cases, and probably that of Tait, point out that our 



