THE NEW MICROSCOPES? 
By R. B. Srwet, M. D., and M. ELIzABETH WINTER 
Philadelphia, Pa. 
[With 5 plates] 
It is, to speak conservatively, of extreme interest to review the 
recent progress made by the scientist in his endeavor to penetrate the 
unseen world of the minute and disease-causing organisms, in particu- 
lar a world of viruses—suspected, yet lying just beyond the scope of 
human vision and the power of the microscope to reveal; for the lab- 
oratory research worker, the doctor, the technician long have been 
familiar with the effects of these unseen enemies they have been called 
upon to treat and to cope with in man, animal, and plant, and while 
their knowledge of the infinitesimal has been growing steadily, they 
were, until very recently, unable to make the slight step “beyond” 
which would enable them to “see.” But today, science is exploring— 
looking for the first time upon totally new worlds through the eyes of 
totally new types of microscopes, microscopes new in principle of 
construction and in principle of illumination. 
THE ELECTRON MICROSCOPE 
One of these new instruments, the electron microscope, has received 
considerable attention and is now being used extensively in both in- 
dustrial and medical research. Based on the principles of geometric 
electron optics, this microscope utilizes electrons as a source of illumi- 
nation instead of the light source of the ordinary light microscope. 
Electrons, practically speaking, are the smallest, lightest particles of 
matter and electricity. Like light, they behave like corpuscles guided 
by waves. Unlike light, however, they travel in a straight line in a 
vacuum where, subject to the action of electric and magnetic fields, 
their behavior coincides with the laws and principles set down by Sir 
William Hamilton who, more than a century ago, demonstrated the 
existence of a close analogy between the path of a light ray through 
refracting media and that of a particle through conservative fields of 
force. 
We know that these negatively charged particles, the electrons, re- 
volving about in their various orbits in the atom, serve to maintain the 
1 Reprinted by permission from the Journal of the Franklin Institute, vol. 237, No. 2, 
February 1944. 
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