90 



The Electron Microscope 



altogether only about a million atoms, and some investigators 

 consider it as a giant protein molecule. 



Fig. 31. Lampbrush chromosome. Magnification X 11,000 



Figure 31 is a sample from another field of biological research. 

 It shows a giant lanipbrusJi chromosome. Genetics may become 

 one of the most important fields for the electron microscope in 

 the future. From experiments with electron bombardment of 

 the eggs of Drosophila Melanogaster, C. P. Haskins has derived 

 evidence that a single gene is confined to a space about the size 

 of a protein molecule. To see single protein molecules is not 

 beyond the range of the electron microscope as it is at present. 

 When we have learned to see at least some of their details, 

 important progress may be expected in the study of heredity. 



Figure 32 is a photograph of that fascinating borderland sub- 

 ject of living and dead matter, the tobacco mosaic virus. So far 

 the action of different chemical reagents and anti-sera on this 

 virus has been tested under the electron microscope ; in time we 

 may also learn the secret of its procreative power. 



One of the finest scientific achievements of electron micro- 

 scopical research is the elucidation of the development process 

 in photography.^^ As the electron micrograph in figure Z?) shows, 

 every silver grain appears as a tangled skein of a relatively very 

 long and thin silver filament. There is now enough evidence to 



