November 6, 1919] 



NATURE 



205 



majority of medical men have to work upon the 

 store of scientific ideas and facts with which they 

 set out in practice; onwards they may gain in 

 adaptiveness and technical facility, but can dig: 

 little deeper into the strata of knowledge ; but for 

 the modern academic spirit this would spell, as in 

 our history it has spelled, stagnation. 



Physics and Medicine. 



Let us glance, however hastily, towards some of 

 the fields in which new knowledge has been 

 gained. In the venerable study of anatomy in its 

 static aspects the student has long been taught 

 the value of precision ; but the recent tide of 

 anatomical study towards its dynamic aspects, as 

 by the work of Sherrington and Head, is bringing 

 in new currents, not of theory only, but also of 

 practice. Of other casements opening upon new 

 visions of medicine that from the chambers of 

 physics is perhaps the most arresting, at any rate 

 at present. How fascinating, in their application 

 to pathology, are the principles of osmosis with 

 its curious reversals, of surface action and adsorp- 

 tion, of electrolytic differentials and electric 

 methods of taking quantitative measurements, of 

 mechanical pressures in the circulation of body 

 fluids and, in the heart, as measured and graphic- 

 ally delineated by Hales, Ludwig, Gaskell, and 

 Mackenzie, of the behaviour of fluid veins, and 

 of the relative diameters, normal or variable, of 

 the cardiac chambers and their main outlets. I 

 need not do more than allude to the recent work 

 on the CO2 tension in the pulmonary alveoli, and 

 to its immediately practical bearing on so-called 

 acidosis, on the treatment of persons gassed in 

 military or civil operations, and so forth. 



By physics again we are shown, especially in 

 plants, how in life the less complex molecules, 

 working not only in planes below those in which 

 the higher functions are developed, but also up- 

 wards by pacific penetration, moderate where they 

 do not command. How instantly such researches 

 as these must govern the practice of medicine we 

 perceive, for example, in the gum-saline treatment 

 of surgical shock. It would seem indeed that some 

 of the most mysterious phases of immunity and 

 anaphylaxis, of phagocytosis, as also of narcotism, 

 may depend, at any rate in great part, on surface 

 action ; and that the behaviour of lipoids released 

 from disintegrating proteins may lower surface 

 energy, as in the retention of water in renal 

 dropsy ; or again in a different field may deter- 

 mine the touch or the permeability of synaptic 

 neurons. These, and such physical laws, as they 

 are revealed to us, teach that the multiplication 

 and co-ordination of surfaces, let alone their 

 chemistry, are operations which do not arise in 

 mere mixtures of the same ingredients. So far 

 it seems as if all biological reactions were deter- 

 mined by physico-chemical laws — that is, by 

 molecular structure. The laws of selective absorp- 

 tion, as revealed in incandescent vapours, might 

 throw some light upon those of biology ; for in 

 NO. 2610, VOL. 104] 



both fields we have to study vibration of molecular 

 systems in unison, harmony, or discord. 



When we rise from physics into systems of bio- 

 logical activity two conceptions especially strike 

 us as new and marvellous ; namely, those of 

 the colloids and the cell. But throughout these 

 systems we shall find the physical phases, if no 

 longer constructively dominant, yet still active 

 and effectual. We cannot even guess at the links 

 of these chains where physics recedes and bio- 

 chemistry takes the lead. The mere size of the 

 molecules now concerned alters their relation to 

 the spaces in or about which they move ; not only 

 so, but in organic compounds a mere change of 

 position of a radical profoundly alters the proper- 

 ties of the compound and leads to manifold 

 changes of function. 



Often, moreover, these changes, as in the cases 

 of immunity and susceptibility, do not vary gradu- 

 ally, but by leaps and bounds, as flames respond 

 to musical scales of vibration. Thus great 

 diversities, contrasts, and strange conjunctions of 

 morbid phenomena do not necessarily signify 

 great divergence of nature in the morbific agents ; 

 so that again we cannot get very far by grouping 

 phenomena by direct observation. Processes out- 

 wardly disparate may be alike at the core. A 

 small and latent change of chemical constitution 

 may turn a benignant into a virulent substance, 

 and conversely ; as we may see in such substances 

 as cacodylic acid and the cyanides, or as saliva, 

 serpent's poison, and trypsin; and so forth. On 

 a small deviation in a secretion we may be 

 destroyed by those of our own household. 



How far are hormones a particular category, 

 how far universals ? Do they differ in nature from 

 other secretions, enzymes, antisubstances, and so 

 on? Do they by their interactions, compensations, 

 and inhibitions cover the ground of concerted 

 chemical action in kind, as the nervous system 

 does in time ; or are they few and peculiar to 

 certain limited needs? Whether inhibitory or 

 stimulatory may often depend rather upon the 

 term of the series to which the hormone is applied 

 than to a difference in quality. Merely to glance 

 at such questions as these reveals to us how vast 

 is the realm of knowledge yet unconquered, nay 

 undiscovered — ■ 



mazes intricate, 

 Eccentric, intervolved, yet regular 

 Then most when most irregular they seem. 



A very interesting transition from physics to 

 chemical biology is found in the phenomena of 

 catalysis. By some elusive property certain in- 

 organic substances — spongy platinum, for example, 

 or manganese dioxide — themselves unaltered, 

 exercise an accelerating influence upon chemical 

 change ; properties which are utilised to-day on 

 an enormous scale in industrial processes. Now 

 by our increasing knowledge of biochemistry we 

 perceive that the function of which the inorganic 

 catalyst is a simple case is manifested also in 

 ■ more complex orders by certain enzymes, or col- 



