SECTIONAL TRANSACTIONS.—I. 367 
On this theory the following conclusions are drawn : 
(r) In fasting subjects pure fat is burnt. 
(2) Mild exercise tends to the greater burning of carbohydrate. 
(3) Fever may tend to the greater burning of carbohydrate. 
(4) If carbon dioxide, taken as a measure of basal metabolism, is com- 
pared with body weight, there is a definite change in direction of 
the curve between two and four years. A similar change occurs 
at this age period in the relation of height and weight. 
(5) Basal metabolism (CO,) depends on the weight and very little on the 
height of the individual. 
(6) In obese and thin subjects the relation, basal metabolism : weight, 
is not far removed from the normal ; fasting lowers the metabolism 
more than the weight. 
(7) The low specific dynamic action of carbohydrate compared with 
protein is due to heat absorption resulting from partial reduction 
towards fat. 
Dr. Marie C. Stopes.—Some points in the technique of contraception 
depending on temperature (10.25). 
Records of temperatures of the cervix uteri as contrasted with oral and 
anal temperatures considered ; the function of grease in contraceptive 
technique ; difficulty of practical problems raised by the narrow margin 
between cervical and atmospheric temperatures at certain times and 
localities ; unsatisfactory nature of current attempts at solution due to 
ignoring the essential melting points involved ; cumbrousness of some 
current devices, e.g. transit in vacuum flasks ; a simple but effective vehicle 
devised ; further desiderata discussed. 
PRESIDENTIAL ADDRESS by Prof. H. E. Roar on Normal and abnormal 
colour vision (10.45). (See p. 169.) 
Dr. F. W. EpripGe-GreeEn, C.B.E.—The theory of vision (12.15). 
It has been proved that the cones of the retina are the percipient elements 
for vision, and direct stimulation by light has been assumed without any 
evidence. Direct stimulation of the colourless transparent cones is against 
all photochemical laws, as no effect can be produced by light unless it is 
absorbed. Stimulation of the cones takes place through the photochemical 
decomposition of the liquid surrounding them, sensitised by the visual 
purple. The rods are not percipient elements but control the visual purple. 
This theory explains every known fact of vision, including numerous facts 
inexplicable on any other view. 
Dr. Ivy Macxenzie.—The physiological basis of visual sensation (12.35). 
The function of the anatomical substratum of human vision may be con- 
sidered from the point of view of physics or of biology or of psychology. 
Physical considerations predominate in the analysis of events in front of 
the retina; psychological interpretation plays a large part in the events 
behind the arez striate, while the processes between the retine and aree 
striate lend themselves to anatomical and physiological observation. The 
visual pathways between the retine and arez striate comprise the basis 
of visual sensation as distinct from perception. ‘This neural compendium 
is of bilaterally symmetrical conformation, and a knowledge of its constituent 
parts provides the main standard of reference in localisation of brain disease, 
