CHAPTER IV 
CLASSIFICATION AND DESCRIPTION OF BACTERIA 
THE early investigators in bacteriology were impressed with the 
newness of the field and devoted more time to the isolation of new 
forms. At this time classification received less attention. They 
examined all sorts of substances and described many shapes and sizes. 
The condition for working also made it difficult to secure accurate 
data and this is quite essential in all systematic work. Pure cultures 
were difficult to secure and the microscope approached in no way the 
perfection of the modern instrument. Under such conditions it remained 
for them as for the pioneers in any field to reproduce the facts upon 
which the later -workers could build. Consequently the arrangement 
of bacteria into groups or related masses has been left for the bacteri- 
ologists of a later day. 
One of the most important ideas which deviated attention from 
classification was the conception of pleomorphism. The early con- 
ception of this theory has been well stated by Fischer (1900). ‘‘ The 
pleomorphists maintained that a coccus did not necessarily remain a 
coccus all its life long, but it could under certain conditions stretch 
itself and assume the shape of a bacillus, that this again could become 
curved and change into a vibrio, to return again later on to the coccus 
form that it commenced with. Words like Micrococcus, Bacillus, Vibrio, 
Spirillum, which we know now to have a definite taxonomic value, 
were in the eyes of the pleomorphists worthless designations of transient 
changes of shape.” Such a conception of bacterial forms easily pre- 
vented or inhibited attempts at the arrangement of the described 
forms into a classification. This idea had its origin in the beginnings 
of biology and botany. In the early days of chemistry it was’one of 
the earliest objects of the science to change copper into gold. 
In bacteriology this theory has constantly received some attention. 
Buchner revived it when he reported that he had changed Bacillus 
subtilis into the bacterium specific for anthrax. More recently Rosenow 
(1914) has reported that he has changed the streptococcus into the 
pneumococcus. He was able to repeat this several times. The serum 
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