604 SECTIONAL TRANSACTIONS.— I. 



is approached, the ratio of the E.M.F. of polarisation to the external E.M.F. will be 

 reduced. For the same reason, increase of alternating current should reduce the 

 value of the compensating inductance (L) required for a bridge balance. Both of 

 these expectations were confirmed by experiment, a result which is inexplicable on 

 the capacity theory. A crucial experiment was attempted by finding whether the 

 passage of a direct current large enough to produce saturation of polarisation would 

 reduce L to zero. This experiment proved impracticable. 



The P.G.R. was found to be present when measured by alternating current, but 

 reduced in magnitude and inappreciable with higher frequencies than about 2,500 p.s. 

 It must be regarded, therefore, not merely as a change in the total amount of polarisa- 

 tion in the skin but as a reduction in the polarisability of the skin. 



Dr. I. Leitch. — On the Metabolism of Iodine. 



Presidential Address by Prof. C. Lovatt Evans, F.R.S., on The 



Relation of Physiology to other Sciences. (See p. 150.) 



Prof. J. J. R. MACLEOD, F.R.S.- — Fatty Acid as a Source of Carbohydrate in 

 Diabetes. 



Tuesday, September 11. 



Dr. H. E. Magee. — Some Factors that influence the Movements of the 

 Surviving Mammalian Intestine. 



The occurrence of organic lesions in the alimentary canal of cavies fed on deficient 

 diets suggested that these might have a remote effect on the intestinal movements 

 as recorded in vitro. Groups of cavies were fed on diets deficient in fat soluble 

 vitamins and in Ca, Na and CI, and the movements of surviving ileum from them 

 recorded and compared with tracings from the ileum of control animals. In the 

 case of the former, varying degrees of disordered rhythm of a hypersensitive or of a 

 hyposensitive type were obtained. The responses to adrenalin, bicarbonate and 

 phosphate were also abnormal in type. Other experiments on the surviving intestine 

 of cavies and rabbits have shown that the musculature is relatively insensitive to 

 electrolytes of physiological importance with few exceptions when acting from inside 

 the lumen. 



Prof. F. G. Baily. — The Measurement of Ultra-violet Radiation. 



A method is described of measuring the ultra-violet radiation from any lamp in 

 definite units, or the dosage of a treatment. Photographic printing paper responds 

 to those radiations which are medically active. What is required is a reliable standard 

 and a scale based on the standard, by which measurements by different people may 

 be in definite units. An arc lamp is described which is constant and reliable, with 

 steady flame and uniform radiation over long runs and on successive runs. It is 

 not intended for medical use, but is a standard unit of ultra-violet radiation, and is 

 also suitable for work needing a steady source, the regulation requiring no skill and 

 the electrodes being cheap. 



For comparison of lamps a suitable medium is blue ferro-prussiate paper of a 

 particular make, which is uniform in quality, permanent in colour, and only requires 

 washing for fifteen minutes. Silver papers are not so uniform, but they are sometimes 

 convenient. A set of papers is exposed for a series of times, ranging from 30 seconds 

 to 13 minutes, to the standard lamp at three feet distance, yielding 27 shades easily 

 distinguishable. In the pale and dark shades the steps difier by 20 per cent., but 

 between one and six minutes a difference of 10 per cent, is distinct. With this 

 series, the effect of a standard exposure of similar paper to any lamp can be determined 

 on the scale and defined in terms of the standard. 



To ascertain the quality of the radiation, absorption glasses are used, Crookes 

 glass passing radiations to a wave length of 350 (ji[x, lead glass to 320, Vita glass to 

 280, and quartz to 200. The resulting tints are determined on the scale, and the lamp 

 is defined by the four numbers, showing the character of the radiation as well as the 

 strength. 



