428 SECTIONAL TRANSACTIONS.—I. 
subsequently are now presented. Simple methods are demonstrated by which 
the colours can be produced in a striking manner, particularly in black-and- 
white pictures. 
Studies have also been made on the colour changes produced in coloured 
after-images by intermitting the light from the ground on which they are 
viewed. The changes are essentially similar to those seen when external illu- 
minated objects are viewed with a rate of intermission below that required 
for fusion, and occur in the same general sequence, although the phenomena ara 
more complicated owing to the colour effects associated with the decay of the 
after-images themselves and other factors. 
15. Dr. R. A. Waup.—Demonstration of an Electro-polygraph. 
16. Dr. F. W. Eprwee-Green.—Temporary Colour-Blindness. 
Though congenital colour-blindness has chiefly occupied the attention of 
those who have paid attention to the subject, it is well known that colour- 
blindness may be acquired through disease or injury. These cases have been 
regarded as permanent. It is, however, not known that colour-blindness similar 
in character to a very bad dichromic may occur as a purely temporary condition. 
The colour sense, even with normal-sighted persons, varies according to the 
condition of the health. When a series of colour equations have been made 
by three normal-sighted persons it will be found that on certain days one of 
the three will put more or less green in the equation than en the previous 
occasion, whilst the other two observers will make the same equation as before. 
This condition, whilst a disturbing factor, usually varies within the limits of 
normal colour-vision. The nerve cells whose function it is to perceive colour 
seem to be much more liable to affection by disease, especially by toxic infiu- 
ences, than those of the visual centre. Acquired colour-blindness seems to be 
closely related in its general characters to the congenital form. A man suffering 
from general paralysis of the insane may pass through all the degrees of 
congenital colour-blindness. A woman became totally colour-blind after ear 
disease; she was examined when she was regaining a certain amount of colour 
perception and could distinguish between red and violet, the rest of the spectrum 
appearing grey. A signalman became totally colour-blind after tetanus, his 
visual acuity being partly 6/6; he had previously passed the wool test several 
times. 
The following is an illustrative case. The examinee was a man who had 
just recovered from influenza, but he appeared perfectly well and made no 
complaint of any kind. His form vision was 5/5 partly, both eyes being used. 
Examined with the lantern, he called green both white and red; red he called 
white, and white red. 
Examined with the spectrum, he called the region from 650 py-A 571 pp 
(red, orange, yellow, and yellow-green) red; the region from 571 pu to 538 up 
(green) white; the region from » 538 py to A 442 wy (green, blue, and violet) 
blue; and purple from \ 442 yp to the end. The apex of his luminosity curve 
was at the normal point A 585 uu. He made the following equations : 45 red 
d 665 wu mixed with 2 of green X 520 wu matched 15 white. The normal equa- 
tion is 45 red with 13 green equals 16 white, so that he was matching a bright 
red with white. He made an equation of 10 A 633 nu red with 6 \ 540 py green 
equals 22 white. He also agreed with the normal equation, which is 10 red 
and 10 green equals 20 white, but required the comparison white light increased 
in luminosity. Examined again five months afterwards his colour-vision was 
normal in every respect. 
17, Prof. V. E. Henperson.—The Movements of the Small Intestine. 
A study of intestinal peristalsis recently made Jed the author to consider 
that the nerve net played an important part in its production, and that it did 
not depend for its propagation on muscle alone. A further study has shown 
that the sensitivity of the gut to internal pressure changes at different levels 
differs, but that the upper parts are not more sensitive, but less so than the 
lower. Further evidence of the activity of the net is offered, 
