December 15, 1923J 



NA TURE 



867 



direct electric lighting circuit. On a 240 volts circuit 

 the current used is 3-5 amperes with 120 volts across the 

 arc. It will be noted that a water supply is necessary, 

 a circulation of four pints per minute being required. 



Light Bath Treatment by the Carbon Arc Light. 

 -The experience of Re}Ti of Copenhagen, confirmed 



\- other observers, is that the best illuminant is 

 arbon arc light. The spectrum of the carbon arc more 

 early approaches that of the sun than does that of 



ercury vapour, and in the experience of the London 

 1 1 ospital, this is further increased by the use of carbons 

 with a tungsten paste core, tungsten giving a spectrum 

 of great richness* in ultra-violet rays. 



The installation is very simple. A large carbon arc 

 lamp, working at 50 amperes and 70 volts, is suspended 

 from the ceiling at three to three and a half feet above 

 the floor. Around this, at a distance of from three to 

 four feet, the patients, nude, are seated on stools. 

 The whole of the body is exposed, first the front and 

 then the back, the sittings being of half an hour's 

 duration at first, and these are gradually increased up 

 to four hours a day. When the front of the body is 

 under treatment the eyes are carefully protected by 

 a thick mask. The tungsten paste cored carbons used 

 are ( + ) cored, 25 mm., (-) solid, 18 mm., both 12 

 inches long. 



General Treatment by Mercury-vapour Lamp. — 

 The apparatus consists of a quartz lamp or " burner " 

 containing mercury vapour, behind which are placed 

 reflectors of various shapes. The lamp is mounted 

 on a stand which permits its being placed at an appro- 

 priate height. It is worked off any direct electric 

 current, and is inexpensive to run. The practical life 

 of a " burner " is, in the larger types, about 1000 

 hours. A very high actinic illumination is obtained. 

 The patient lies or stands while under treatment, usually 

 at a distance of about three feet, but with the larger 

 model supplied by the Hewittic Electric Company, the 

 maximum distance at which a patient is sensible of the 

 radiation is eighteen feet. At the beginning of the 

 treatment the exposures are given to small areas, and 

 l^oth the area and the duration may be gradually 

 increased until the whole of the back or front of the 

 body is exposed for half an hour. An inflammatory 



reaction, redness, slight vesication with subsequent 

 desquamation, are common, and after a series of 

 exposures, the skin in the majority of patients becomes 

 strongly pigmented. Several of these lamps may be 

 placed in a suitable apartment, the patients being 

 allowed to move about. The mercury- vapour lamp 

 has been used with success in the treatment of tuber- 

 culosis of the skin, glands, bones, and joints. Care is 

 required in the dosage, and it is advisable to estimate 

 the intensity of the actinic rays by a chromo-actino- 

 meter. This is specially necessary when a new " burner " 

 is installed. 



It has been shown that rickets can be prevented in 

 animals fed on a ricket-producing diet if the surface 

 of the body is exposed to the radiations from a mercury- 

 vapour lamp, and there is an important field of use- 

 fulness for this form of radiotherapy carried out with 

 due precautions in the treatment of early rickets in 

 children. 



Conclusion. — The sphere of usefulness of the light 

 bath is being explored in several directions. A com- 

 mittee appointed by the Medical Research Council is 

 studying the biological action of light, and several 

 valuable investigations have been made. Among 

 others it has been demonstrated that the bactericidal 

 power of the blood of animals can be greatly increased 

 by the exposure of the animal to actinic light. Clinical 

 observation shows that there is a remarkable effect 

 upon the metabolism of the human subject ; dull, 

 lethargic patients rapidly become bright, cheerful, and 

 active. The body weight increases in many instances. 

 Chronic tuberculous affections of the skin, mucous 

 membranes, bones, and joints heal rapidly. Other 

 chronic processes, such as rheumatoid arthritis, have also 

 been benefited. The value of light in the prevention 

 and treatment of rickets has been noted above. A 

 course of treatment usually lasts three to five months. 

 Patients whose skin pigments well usually do best, but 

 there is no evidence to show that it is the pigmentation 

 which is the curative factor. At present it can only 

 be considered an index. Evidence so far points to the 

 actinic rays producing some possibly chemical change 

 in the blood which gives it greater power to destroy 

 bacteria and their products. 



Some Aspects of the Physical Chemistry of Interfaces.'^ 



By Prof. F. G. Donnan, C.B.E., F.R.S. 



IN' recent years a great deal of attention has been 

 paid by chemists, physicists, and physiologists to 

 the phenomena which occur at the surfaces or inter- 

 faces which separate different sorts of matter in bulk. 

 Things could happen in these regions which did not 

 occur in the more homogeneous and uniform regions 

 well inside the volume of matter in bulk. A surface 

 nr surface layer represents a sort of thin cross section 

 which can be probed and examined much more readily 

 tlian any part of the inside bulk. The living organisms 

 of plants and animals are full of surfaces and membranes. 

 What can happen at surfaces is therefore a matter 

 <if great importance for the science of living things. 

 An essential characteristic of the ordering or arraying 



' From the presidential address driivcrcd to Section B (Chemistry) of the 

 Hiiiish Association at Liverpool on September 14. 



NO. 2824, VOL. I 12] 



of molecules and atoms which seems to occur at 

 surfaces may consist in special orientation. In the 

 chemical and physical actions occurring in a volume 

 of liquid the bulk of which is large compared with its 

 surface, the molecules or atoms prolmbly move towards 

 each other with every sort of orientation. Should, 

 however, some special orientation be characteristic of 

 interfaces, then it is clear that such interfaces will 

 exhibit new phenomena due to this special sort of 

 arraying. Moreover, if we are dealing with molecules 

 which are ionised into electrically polar con.stituents, 

 or which, if not actually dissociated, can be treated 

 as electrically bi-polar, it follows that, if orientation 

 occurs at interfaces and surfaces, then electrical double 

 layers and electrical potential differences may be set 

 up at such boundaries. 



