CHAPTER 10 

 ACHIEVEMENTS OF ELECTRON MICROSCOPY 



IT can be estimated that at the time of writing more than 

 two hundred electron microscopes are in operation in re- 

 search institutes all over the world, and new results are being 

 published almost daily in medical, biological, and physio- 

 chemical journals, the greater part of which is not accessible 

 to the author. Therefore, the following short selection cannot 

 claim to be fully representative or up to date. 



As soon as the preliminary tests had proved the usefulness 

 and reliability of the new instrument, the R.C.A. established 

 a Fellowship for Biological Research with the Electron Micro- 

 scope, under the auspices of the American Research Council. 

 Figures 28, 31, and 32 are taken from a survey of the first year 

 of this work, by G. A. Morton. ^^ The photographs are all taken 

 with the commercial Type B model of the Radio Corporation 

 of America. 



Figure 28 shows photographs of the typhoid germ and of 

 Bacillus Sttbtilis side by side with pictures obtained with an 

 optical microscope. It may be mentioned that the latter are not 

 fully representative of what the best microscopes can achieve, 

 especially those working with ultraviolet. In fact the flagellae 

 and the membrane of the typhoid bacillus were first discovered 

 with the ultraviolet microscope, in a magnification of about 

 1,500, but both are far better visible in the electron micrographs. 

 The Subtilis photograph shows also minute crystals adhering to 

 the bacillus body. Both electron micrographs are direct records 

 of the scattering power of the bacillus body which has not been 

 dyed in any manner. They are also approximate records of the 

 density. L. Marton and L. I. Schifif have devoted an interesting 

 study ^^ to the problem of the translation of the photographic 

 density in electron micrographs into data of object thickness and 



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