STUDIES IN GELS 



127 



medium (Takahashi and Rawlins, 1948). There is some indication 

 that the rods are formed by linear aggregation of" roundish particles. 

 The diameter of the straight rods is 150 A (Wyckoff, 1949), which 

 corresponds to the lateral identity period of 1 5 2 A revealed by X-ray 

 investigation (Bernal and Fankuchen, 1937) in the hexagonal crystals 

 of the virus protein (Stanley, 1935, 1936). 



Contrary to expectation, virus diseases with rod-shaped particles 

 are rare, globular virus macromolecules occurring much more fre- 

 quently. When dried, a virus suspension of this kind crystallizes, and 

 Wyckoff (1949) succeeded in producing very beautiful pictures of 

 the lattice of those crystals (Fig. 84d). The arrangement of the molecules 

 revealed by the X-ray diffraction method can now be seen, and it is 

 most interesting to observe how frequently small disturbances within 

 the regular pattern of the molecule arrangement occur. 



Figs. 84a-c represent the dispersed particles of protein sols which 

 prove the applicabihtv of the electron microscope in biochemistry. 

 The biologist asks, therefore, what 

 information the electron microscope 

 may give on the structure of gels, 

 among which we classify the shaped 

 portion of the protoplasm. By way of 

 example we reproduce in Fig. 8 5 the 

 electron optical image of a V2O5 gel 

 serving as ultrafilter (Ardenne, 

 1940b). One recognizes the reticular 

 structure assumed on the basis of 

 results obtained by indirect methods. 

 The agreement with the scheme of 

 Fig. 53a (p. 69), proposed before the 

 electron microscope had been dis- 

 covered, is most striking. 



Fig. 85 is a rather indistinct picture 

 of a dry gel. The first clear-cut elec- 

 tron micrograph of a very loose gel 

 which, previously to preparation, 

 contained about 99*^0 water, is reproduced in Fig. 86a (Frey-Wyss- 

 ling and Muhlethaler, 1944). It displays a beautiful spatial frame- 

 work with big meshes and roundish interstices. Fig. 86a seems 



Fig. 85. Electron micrograph of an 

 ultrafilter of vanadium pentoxide, 

 image scale 35,000: i (from Ardenne, 

 1940b). 



