THE SCOPE OF RADIOLOGY. 



By Jan Stephanus van der Lingen, B.A. 



{Abridged.) 



Radiology is the study of the physical, chemical and physio- 

 logical properties of all kinds of radiations. In order that we 

 may form some idea of the origin of radiations, it will be neces- 

 sary to consider very briefly the constitution of matter. 



Matter, on being subdivided, yields the fundamental unit — 

 the molecules of the particular chemical compound. These mole- 

 cules are built up of similar atoms or an assemblage of certain 

 groups of different kinds of atoms. The properties of the mole- 

 cules depend upon the arrangement and properties of the atoms. 



Atoms, again, are built up of constellations of electrified 

 units, which we name corpuscles. These corpuscles gyrate round 

 certain centres of force within the atom, and thus we mav 

 imagine the atom to represent a miniature universe with its 

 planets and fixed stars. From this we see that the properties 

 of the atom depend upon the corpuscular constellations. Should 

 these constellations be changed, the chemical properties will 

 also be changed, hence the \ari(ius elements rejjresent ])articular 

 constellations of corpuscles. 



When energy is communicated to the corpuscles, their 

 speeds will undergo a change, and this change in speed must be 

 balanced by the forces which keep the corpuscles in their orbits. 

 If the ;forces do not balance the new speed, the corpuscles 

 will fly oft' from the former orbits and become the comets of tliis 

 micro-cosmos. 



In the radio-active substances we have an instance of these 

 comets. 



The difference in our analogy is that these comets are large, 

 and thus disturb the equilibrium of the planetary system of the 

 atom. The debris of the original atom probably tends to re- 

 establish ec|uilibrium. The re-established system will be dif- 

 ferent from the former, hence a new atom is born. Thi^ atnrn 

 is probably not in harmony with its neighbours, and consequently 

 must part company. As an instance of this we have helium, a 

 ])roduct olf radio-active matter. Thus alchemy does exist, but 

 Nature alone, thus far, in her laboratories performs these trans- 

 mutations. 



These emitted corpuscles, which we have mentioned lioforc. 

 form the corpuscular radiations. The gyrating corpuscles in 

 the atom may, under certain conditions, set up periodic pulses in 

 the surrounding medium, and thus cause light to be emitted, 

 which is ])ro]jagated in the form of wave motion. 



The properties of these radiations will depend ujx)n the 

 frequency of the pulsation caused by the cor])uscle. The light 

 emitted is thus characterized by its wave-lengths — that is, the 

 distance which each component part of this wave motion pa^^^es 

 over between two consecutive pulses. 



