EXPERIMENTS WITH RADIUM 105 



often regarded as a test of life? The passage into 

 higher forms, or rather development in size and shape, 

 is not the test ; but only when subsequent decay ensues. 

 The passage through the cyclic process in time is 

 indeed the test of life. It is the stoppage of growth at 

 a particular size and of reproduction by fission or sub- 

 division, and then the total disintegration of the cell, 

 or whatever we may choose to call it, after its steady 

 regular growth up to that point, that is sugges- 

 tive of vitality. The subdivision, or fission, which 

 accompanies the cessation of development even in the 

 mechanism of adding to its size, shows the stage 

 when there is a balance between the accumulation of 

 energy and its expenditure. The bodies obtained 

 by M. Stephane Leduc in 1902, by the action of 

 potassium ferrocyanide on gelatin, or by allowing 

 metallic salts to crystallise in gelatin and other 

 colloidal solutions without sterilisation, do not 

 exhibit all these primary or elementary properties 

 of living things. They do not, in fact, manifest 

 more than a resemblance in appearance to the cells 

 or unit forms of life. Their properties are not 

 sufficient to justify the inference that they are 

 even approximately living things, nor even that 

 they possess to any marked extent the qualities 

 that are associated with organic matter as we- have 

 described. 



On the other hand, it has been suggested that 

 if radiobes are crystals, they subdivide by cleav- 

 age under the influence of internal strain, as, 

 for instance, South African diamonds are found 



