406 PROCEEDINGS OF SOCIETIES. 
measurements made by his own scale in accurate wave-lengths. 
Some interesting relations of spectra are at once shown by the 
wave-length method. 
May 5th, 1875. 
H. C. Sorsy, F.R.S., President, in the chair. 
Mr. Slack read a paper “ On Angle of Aperture, and its Rela- 
tions to Surface-markings and Accurate Vision,’ in which he 
advocated the use of objectives with a small angle of aperture 
especially by naturalists and physiologists, thinking that opticians 
had been encouraged to make excessive apertures substitutes for 
good corrections. He referred especially to the high powers 
made by Zeiss, of Jena, with a small angle. 
The President expressed his entire concurrence with Mr. 
Slack’s remarks. 
Mr. Stephenson, Dr. Pigott, and Mr. Stewart spoke highly 
of the glasses of Zeiss. 
A paper by Dr. Braithwaite “On Bog Mosses” was taken as read. 
On April 21st, 1875, a “Scientific Evening” was held in the 
Library of King’s College. 
June 2nd, 1875. 
Cuartes Brooxe, Esq., F.R.S., Vice-President, in the chair. 
Mr. Stephenson exhibited and explained “A Scale for the 
Measurement of Angular Aperture.” 
Mr. Stewart made some remarks on Bucephalus polymorphus. 
Mr. Slack read a paper “ On the Use of Mr. Wenham’s Reflex 
Illuminator.” 
The proceedings were then adjourned till October. 
Mepicat Microscoricat Sociery. 
Friday, March 19th, 1875. 
Dr. J. F. Paywnn, President, in the chair. 
Spinal Cord in Infantile Convulsions—Dr. Sidney Coupland 
exhibited specimens from the case of a child, et. 6 months, dying 
in convulsions, secondary to cancrum oris. He described great 
dilatation of the capillaries and small vessel: of the cord, especially 
in the commissural part of the grey cornua, and enlarged perivas- 
cular spaces, the maximum of enlargement being in lower part of 
medulla, particularly near the central canal, but the canal itself and 
its epithelial lining seemed perfectly healthy. He considered the 
perivascular dilatations are most probably secondary to the convul- 
