HILARY KOPROWSKI 
than polio does. (Good old polio days!) And yet an almost 
perfect method of prevention of polio is available for the future. 
I refer here, humble as I am, to the live virus vaccine, the use 
of which should be hailed by the slogan: “‘ Do not eradicate, but 
replace.”” The attenuated virus substituting for the virulent 
one in the human gut may prevent upsets in the balance of the 
intestinal flora. 
To place a virus hors de combat, anyhow, is not an easy task. 
Rabies is one of the oldest known diseases of mankind. Rabies 
virus is characterized by its infectivity for all warm-blooded 
animals, and the disease always ends in death. No wonder that 
in the course of centuries man has turned his heaviest guns 
against the rabies virus and, except for the folly of the Pasteur 
treatment, used all the weapons in his armoury in an expedient 
way. I refer here not only to effective mass vaccinations of 
domestic animals but also to other campaigns, often involving 
quite drastic methods such as endless quarantine, elimination 
of stray dogs and of wild life, and so forth. How does the virus 
react to such concerted attacks? Because of certain chemical 
components of its capsule the rabies virus can attach itself to 
a wide variety of receptor sites in different species and tissues. 
The presence of rabies in vampire bats in South and Central 
America has been known since the early sixteenth century. For 
the next four centuries the rabid vampire bats seemed to respect 
the southern borders of the U.S.A. However in the last decade 
when the public health authorities in the U.S.A. were seemingly 
winning the battle for control of rabies, one state (Florida) 
reported, in 1953, the appearance of an insect-eating bat which 
attacked a young boy. This bat was rabid. In 1961, 29 states 
reported the presence of rabid bats in their territory at one time 
or another. The virus played still another trick to outwit its 
adversary. Rabies infection was always supposedly transmitted 
by contact, through the “incurable wound” of Fracastorius. 
However, during recent years two speleologists died in the 
United States without apparently being exposed to the bite 
of an animal. Exposure of animals to inhalation of the virus 
from bats’ excreta in the same caves led to the conclusion that 
202 
