Tue Microscope. 203 
evidences that the bacteria held some relation to disease, (first ser- 
iously suspected in the case of anthrax or splenic fever in cattle, 
afterwards demonstrated to be the cause of this dangerous malady 
by Pasteur and Koch), brought them prominently into notice. 
Now, for twenty years the literature upon the nature and effects 
of bacteria has been steadily growing, until to-day it is scarcely 
possible for any one man to keep track of the voluminous pages 
devoted to them. It is to these organisms that I now invite your 
attention. 
* 2K * * * * * 
First, what are bacteria? Nothing need here be said as to 
their appearance, structure, or place in a classification of natural 
objects, but we may especially ask whence their origin? It is cer- 
tainly important in our discussion of the origin and occurrence 
and recurrence of disease that we should understand as fully as 
possible all the circumstances and conditions connected with the 
disease agents. Let it be taken as scientifically settled that living 
organisms do not spontaneously come into existence through some 
transformation of inorganic materials. We need not say that this 
never has occurred, nor in fact, that it may not, under some pecu- 
lar circumstances or conditions, be true now, but evidence is so 
abundant that this process does not take place in the usual course 
of affairs, that we may exclude it altogether in our practical rela- 
tions with the objects. We have then only to ask, are the bacteria 
independent, autonomous existences, or are they temporary modi- 
fications of other living things. It has been held by competent 
observers, that in certain conditions, various species of fungi be- 
come so modified in their growth as to assume, temporarily, the 
form in which we observe them as bacteria. Various accounts 
have been given in scientific publications, of the observations upon 
such changes. These, however, are mostly by men not especially 
familiar with the actual developments of the organisms in ques- 
tion. We positively know that some of these assertions are untrue, 
for when less fallible means are employed in experiments of the 
same kind, other results are uniformly obtained. By many, how- 
ever, the idea is not entirely abandoned. During the last year in a 
reputable scientific publication in France, a series of articles, based 
upon elaborate and extensive experiments and observations, have 
appeared, in which the author endeavors to show that the so-called 
