ON ARTIFICIAL CELLS 125 



substance obviously passes through states which are 

 inactive. 



The formation of these growths may not depend — 

 and, in fact, it seems does not depend — upon the 

 intensity of the radio-activity, but probably upon the 

 process upon which radio-activity depends. Thus 

 the intensity of this so rests upon the nature, 

 number, and velocity of the ions emitted by the body ; 

 whereas the power of producing molecular agglo- 

 merations may, and most probably does, depend 

 upon the nature of the ions emitted far more so than 

 upon their number and velocity. And most bodies 

 seem to be radio-active, to however small an extent, 

 as le Bon and others have shown. 



Now, the radiation consists of four types, namely, 

 the a-, /3-, 7-, and S-rays, the a- being positively elec- 

 trified particles, the /S- and S- negatively, whilst the 

 y-rays do not appear to carry a charge. These radia- 

 tions themselves, however, do not seem to produce 

 the aggregations in question when the radio-active 

 salt is placed at a slight distance, a millimetre 

 or so, from the surface of the gelatinous body, 

 possibly on account of their great velocity. But 

 when the salt is actually in contact with the culture 

 medium the agglomerations, which are limited in size, 

 result. 



Ions do tend to produce aggregations, the posi- 

 tive far more so than the negative ; so that, pro- 

 vided their speed is not too great, the required 

 aggregate should result, and nowhere more so than 

 round the atom itself, as it remains electrified owing 



