Paper, 'Researches on the action of certain parts of the solar spectrum upon the iris' by [Charles Edward] Brown Sequard

Description

Sequard explains that in 1847 he discovered that 'light has the power of acting directly upon the iris so as to produce there a muscular contraction, manifesting itself by the constriction of the pupil. If an eye taken out from the orbit is alternately exposed to light and darkness, we find that the pupil becomes alternately constricted and dilated. It was interesting to know whether the stimulation of the muscular fibres of the iris is produced by the chemical power of light or not'. He goes on to describe a series of experiments made with 'light decomposed by the prism', electric light and direct solar light. He observes that, in all cases, 'the yellow part of the spectrum acted as well as undecomposed light, and that the other parts of the spectrum had either no action at all, or only a very slight one'. He suggests from the results of his experiments that the ability of light to stimulate the circular fibres of the iris relates to its illuminating elements rather than to its chemical or calorific parts.

Annotations in ink throughout.

Subject: Optics / Physiology

Received 10 July 1856. Communicated by Dr [William] Sharpey.

This paper was published in full in volume 8 of the Proceedings of the Royal Society as 'Researches on the action of certain parts of the solar spectrum upon the iris'.

Reference number

AP/39/3

Earliest possible date

1856

Physical description

Ink on paper

Page extent

2 pages

Format

Manuscript