VITAL GROWTH AND CRYSTALLIZATION 41 



ments were soon advanced. That play of colors which 

 Naegeli regarded as indicative of crystallinity can also be 

 seen if pressure is exerted upon a substance like glass which 

 contains no crystals at all; under pressure the glass is 

 slightly distorted and thus gives rise to the play of colors 

 under polarized light. Naegeli 's opponents argued that a 

 stress might arise in fibers during the process of growth, 

 and that the assumption of crystalline particles was there- 

 fore unnecessary to explain that play of colors. 



But their contention is impossible since it fails to consider 

 the make-up of living fibers which is totally different from 

 that of glass. The fibers consist of an almost liquid mass 

 in which small solid particles are imbedded. These parti- 

 cles are freely movable, being held together only by soft 

 layers between them. Stress exerted upon the substance 

 as a whole leads only to a mutual displacement of the single 

 solid (crystalline) particles against each other; but it can- 

 not distort them. 



Naegeli thus had good reason to discard this argument. 

 But his opponents had still other doubts. A weary con- 

 troversy arose, the final outcome of which was that every 

 one lost interest ; the general impression was that hair- 

 splitting arguments were being debated by a small group of 

 scientific specialists. The great issue raised by Naegeli, 

 that is the nature and essence of vital growth, finally fell 

 into oblivion for more than half a century. 



6. X-RAYS FURNISH A MEANS OF PROVING THE EXISTENCE OF 

 CRYSTALS IN LIVING MATTER 



Fifty years elapsed after Naegeli's early experiments, 

 which had suggested a relationship between crystallinity 

 and living growth. Naegeli died without seeing his epoch- 

 making discoveries recognized. Yet the issue was not com- 

 pletely dead. In the minds of a few it remained as an 

 unsettled question until suddenly in 1912 and the years 



