108 
D. E. SALMON. 
vance of exotic pests, like cholera, yellow fever or the plague, 
causes any serious alarm. 
Notwithstanding this, however, we have among us a number 
of contagious diseases, from which the country is never entirely 
free, which cause far greater loss of human and animal life than 
the majority of people ever imagine. There is small pox, now 
robbed of many of its terrors by a general system of vaccination ; 
scarlatina, which is often responsible for ten per cent, of the an¬ 
nual deaths in entire States; diphtheria, which causes an equal 
mortality; typhoid and puerperal fevers, measles, whooping- 
cough, syphilis, pyaemia and septicaemia, all of which help to swell 
the mortality lists. Then as affecting animals, and communica¬ 
ble from them to man, there are such horrible and fatal maladies 
as charbon, rabies, glanders, and, overshadowing all other plagues 
in importance, tuberculosis. Finally, as affecting and causing 
immense losses among animals, we have pleuro-pneumonia (bovine)? 
rinderpest, Texan fever, swine-plague and fowl-cholera. Not less 
than one-seventh of our people die from tuberculosis alone, or, in 
the United States, one hundred and twenty-five thousand annually; 
and if we add the losses from other zymotic diseases, we will 
double this number, and have in all a mortality approaching that 
caused by the late civil war. 
With this introduction to indicate the importance of the most 
thorough knowledge of these diseases, I shall enter upon a dis¬ 
cussion of the germ theory as applied to charbon, in the hope of 
keeping my readers interested by the magnitude of the subject, 
even if I fail to present my views in an attractive style. 
Before 1876, we were totally without satisfactory evidence in 
regard to the nature of the virus of any zymotic disease, but 
Koch’s investigation of charbon, published in that year, made it 
so clear that this malady was due to bacterium, called the Bacil¬ 
lus anthracis , that the germ or bacteria theory of contagion re¬ 
ceived a new impetus, which has done much for the elucidation 
of the whole question. There have always been doubters, how¬ 
ever, particularly among English-speaking people, most of whom 
have been unable to follow the investigations as closely as is 
necessary to reach sound conclusions; and now, when Greenfield 
