MIRACLES OF SCIENCE 



sure means of its prevention has been available since 

 the time of Jenner. 



THE ULTRA-MICROSCOPE 



In the attempt to discover the causal agent for 

 smallpox and the allied maladies whose germs have 

 hitherto eluded detection, it has been discovered that 

 a virus capable of transmitting the disease may retain 

 its noxious features after being passed through an 

 unglazed porcelain filter. Similarly Dr. Peyton Rous 

 of the Rockefeller Institute, who has had great 

 experience in cultivating cancer and in transferring 

 the abnormal virus from one animal to another, in- 

 cluding mice, rats, and chickens, appears to have 

 produced cancer in an animal by injecting a liquid 

 that had been passed through such a filter. This 

 means that no bacteria of a size visible under the 

 most powerful microscope remained. 



It is thought by some observers, that ultra-micro- 

 scopic particles, conceivably living germs of an order 

 almost infinitely smaller than bacteria, have been 

 detected. The particles in question, whether or not 

 they hold this relation to disease, are observed with 

 the use of the so-called ultra-microscope, which owes 

 its origin to Zsigmondy working in 1901 and to 

 Siedentopf in 1903. The method developed by these 

 workers consists of letting a concentrated beam of 

 light cut across the microscopic field without entering 

 the lens of the microscope. 



The rays of light beating against exceedingly 

 minute particles of matter are diffracted or dissipated 

 in every direction, and to the observer who peers 



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