Physics in Medicine 3 



and adaptation. Coupled with the motion-picture camera, the 

 bronchoscope enables a film to be made during the removal of 

 an obstruction in a bronchus, and the observer is given a veritable 

 conducted tour around the lung. Body cavities have become 

 ''accessible" in a new sense. The influence of the rather more 

 subtle laws of physical optics may be found in instruments for 

 measuring the average diameters of blood cells by the haloes 

 they cause around a source of light, instruments descended di- 

 rectly from the "eriometer," invented by Thomas Young for 

 measuring the diameters of fine hairs, at the time when this 

 physician-physicist was laying the foundations of the experi- 

 mental proofs of the wave theory of light. We might recall the 

 rather obvious fact that the optical microscope is a physical 

 weapon, studied and sharpened to a point where this same wave 

 nature of light is itself the chief and impassible barrier to seeing 

 the still invisible, and recognize in the substitution of streams of 

 electric charges for the beam of light in the new electron micro- 

 scope the next, and perhaps supremely important, contribution 

 physics has to make to the science of microscopy. 



We might similarly range through all the branches of physics 

 and quote examples of the fundamental nature of the physicist's 

 contributions, either in technique or in generalizations of wide 

 and abstract character, which transform the nature of the prob- 

 lem. The use of specific electronic devices like the cathode-ray 

 oscillograph with its attendant amplifiers occurs to us immediately. 

 The science of electronics and electron optics has contributed 

 and will contribute to many of the problems of neurophysiology. 

 It may be noted in passing that "magnetism" seems a slightly 

 disreputable word in medicine, which is unfortunate as it appears 

 that a study of the magnetic properties, magnetic susceptibility, 

 for example, of body fluids or tissues, might well yield both useful 

 and interesting information. The study of sound and of modern 

 radio-frequency techniques has resulted in great advances in the 

 applications of acoustics, a subject once more intimately asso- 

 ciated with Thomas Young. We think, too, of the possible appli- 

 cations of high-frequency radio science, now making available, 

 both directly and indirectly, power of a hitherto undreamed of 



