42 life's beginning on the earth 



following, the question stood again in the limelight of the 

 world of science everywhere. 



The famous x-rays discovered by Roentgen in 1895 had 

 been employed as a means of investigating crystallinity. 

 In this manner, a new basis had been established for the 

 study of the crystalline state. It became possible to trace 

 crystals of the most diminutive size by means of these rays. 

 Applying this method to various products of living growth, 

 the existence of crystals in them was revealed. 



The ideas developed by Naegeli became definitely estab- 

 lished facts: science was now in a position to demonstrate a 

 distinct realtionship between the growth of a crystal and the 

 growth in living plants or animals, and even to determine 

 the mutual arrangement of the crystalline components in 

 the living organism in all their details. 



Figures 24 and 25 are reproduced here to convey to the 

 reader an impression of the method by which x-rays can be 

 used to trace crystallinity. If a single ray of x-ray light 

 strikes a photographic plate, it leaves a dark spot in much 

 the same manner that any light ray will. The same occurs 

 if a layer of any non-crystalline substance like cellophane or 

 paraffin is interposed between the ray and the plate. But 

 if a whole solid crystal is interposed there, a different pic- 

 ture appears on the plate (Fig. 24). The ray now also 

 leaves on the plate a large black spot with a hazy contour. 

 Around it appears a handsome symmetrical pattern of 

 smaller dark spots, which arise from deviating rays. These 

 rays form when the x-ray passes through the invisibly nar- 

 row openings between the molecules or atoms from which 

 the crystal is built. In these fine openings the x-rays are 

 entangled; some of them are held back by interference with 

 each other; other rays in turn intensify each other and thus 

 leave distinct marks on the photographic plate. In the 

 case of ordinary light, we observe a similar alternating ex- 

 tinction and intensification of light rays, if they have passed 



