458 SECTIONAL TRANSACTIONS.—I. 
SECTION I.—PHYSIOLOGY. 
Thursday, September 24. 
Discussion on Lhe Physiological Basis of Sensation. (Prof. E. D. Aprian, 
F.R.S.; Prof. Frank Atten; Dr. C. S. Myers, C.B.E., F.R.S. ; 
Prof. D. W. Bronx; Dr. R. 8. Creep; Sir J. Herpert Parsons, 
C.B.E., F.R.S.; Prof. H. Harrripee; Prof. H. H. WooiLarp; 
Prof. H. E. Roar; Dr. E. P. Poutron.) 
Prof. E. D. ApriAn, F.R.S. 
What sort of change takes place in the sense organs and their nerves when 
the skin is touched and what happens in the brain to make us feel? The 
events in the brain which cause sensation are still uncertain, but we know 
what kind of messages are transcribed by the sensory nerves, for they can be detected 
electrically. They consist of a succession of impulses in the nerve fibres, each impulse 
being a brief surface reaction which spreads down the fibre accompanied by a change 
of potential. Their frequency varies with the intensity and abruptness of the stimulus, 
but in any one fibre they are all alike, and they are of the same general type in all 
nerve fibres. Then in its main outline the working of the sensory apparatus seems — 
to depend on physical and chemical changes of fairly simple character, but there 
are many outstanding questions when we consider all the different kinds of sense 
organ and different qualities of sensation. Problems concerning the eye and ear, 
the different sense organs in the skin, the nervous mechanism of pain, &c., are in 
urgent need of solution, and their discussion may show the complexity of the sensory 
apparatus, and may help to explain the variety of sensation which we experience in 
spite of the simple nature of the messages which are sent to the brain. 
Dr. C. 8. Myzrs, C.B.E., F.R.S. 
Relatively little light seems likely to be thrown on the physiological basis of 
sensation by the study of sensory nerve fibres of sensory end-organs. We are, at 
present, almost wholly ignorant of what occurs in the more important cerebral sensory 
‘centres.’ Although these centres are essential for sensation, they are not to be 
regarded as the seats of sensation. For sensation depends on the relation of their 
activity to that of that vast integration of central nervous activity on which ‘ self- 
activity ’ is dependent : where no self-activity is involved there can be no consciousness 
of sensation. The biological function served by the consciousness of sensation is the 
control of its specific efferent responses by the organism. Sensations have become 
differentiated from one another because the response is different for each. When the 
patterns of response for two different stimuli are too nearly identical, the respective 
sensations are indistinguishable: just indistinguishable (or just distinguishable) 
differences in sensation do not necessarily imply the activity of the same (or different) 
end-organs. It is conceivable that, just as muscular responses may be regarded as — 
clonic or tonic, or as combinations of these, so certain sensations may be fundamentally 
classified as ‘clonic’ (i.e., as explosive, all-or-none, punctately distributed, uni- 4 
phasic, and easily fatigable), and as ‘ tonic’ (i.e., as enduring, graded, diffusely dis- — 
tributed, bi-phasic, and subject to adaptation and contrast). On the future study — 
(a) of the integration of these two and perhaps other elementary classes of sensation, 
and (b) of the central responses involved, immediate additions to our knowledge of — 
the physiological basis of sensation seem likely to depend. | 
‘eae ee ee ee ee ee 
Pete «4. 
= ¥ 
Friday, September 25, P 
Dr. Marte Sropes.—Some Physiological Facts from Ten Thousand Clinical 
Cases dealing with the Control of Conception. 
Ten years ago the vaginal use of Quinine was widespread but without scientific — 
investigation or supervision: clinical observation thereon began in 1921: the absorp- 
tion of quinine by the vaginal walls, as distinct from the uterine, established in the 
human female : deleterious effects in approximately 5 per cent. of subjects : comment 
