BRIEF HISTORY OF BACTERIOLOGY. 
grain can grow from one kind of seed, so also 
only one disease can be produced by one form of 
germ or micro-organism. 
The theory that disease germs were living 
things capable of growth and reproduction did 
not, at this time, gain favorable consideration, 
and it is not again advanced until almost sixty 
years have elapsed. In the year 1821 , * *Henle, an 
anatomist and scientist of Germany, again gave 
expression to the conviction of the truthfulness 
of the theory, but only to be met with the oppo¬ 
sition which defeated Plenciz. Henle, however, 
is said to have successfully met and overcome all 
the objections of his opponents, and shortly after 
this time the relation of micro-organisms to dis¬ 
ease was scientifically proven although many still 
remained sceptical. 
One point over which there was a great deal 
of discussion during the century and a half be¬ 
tween the discoveries of Leeuwenhoek and the 
acceptance of the theories of Plenciz through the 
demonstrations of Henle, was the origin of these 
germs. “Do they generate spontaneously or are 
they the descendants of pre-existing creatures of 
the same kind ?” *Karl H. Schulze, also of Ger¬ 
many, was the first to throw any light on this 
rather mystifying question. In 1836 he demon¬ 
strated the fact that “if the air which gained 
access to the material which was being experi¬ 
mented upon could be. made to pass through 
*F. Gustav Henle, born at Furth, Bavaria, 1798; 
died at Gottingen, 1885 . Was professor at Zurich, 
1824; Heidelburg, 1844, and at Gottingen, 1852. 
*Karl Heinrich Schulze, physician and anatomist 
born at Ault, Ruppin, in 179$. Professor at Berlin in 
1833. 
Plenciz’s 
Theory 
Accepted. 
Theory of 
Schulze. 
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