• CHAPTER II. 
Classi¬ 
fication of 
bacteria 
Definition 
of bac¬ 
terium 
Structure 
THE CLASSIFICATION, MORPHOLOGY, BIOLOGY, AND 
DISTRIBUTION OF BACTERIA. 
We have referred to micro-organisms as germs, 
a popular term, but not exact enough for our use. 
The term “germs” may be taken to mean any micros¬ 
copic organism, animal or vegetable. 
In the animal kingdom the lowest forms of life 
are called Protozoa (sing. Protozoon), of which there 
are several types: Sarcodina, Mastigophora, and 
Sporozoa, The discussion of the protozoa will be re¬ 
served until a later chapter. 
In the vegetable kingdom we are particularly 
interested in the fungi, which are subdivided into 
Hyphomycetes or molds, Blastomycetes or yeasts, and 
Schizomycetes or bacteria. The bacteria are by far 
the most important of the three; so we will confine 
ourselves solely to them for the’present, and leave the 
yeasts and molds for a subsequent chapter. 
The word bacterium is derived from a Greek word 
meaning a rod; the plural form is bacteria. A bac¬ 
terium may be defined as a minute living organism 
composed of one cell, belonging to the vegetable 
kingdom. 
The structure of bacteria is difficult to make out 
but they appear to be but masses of protoplasm. The 
central portion is more dense and stains more deeply 
with aniline dyes, like the nuclei of animal cells so 
that some believe that bacteria have nuclei. The ex¬ 
treme outer margin may be very dense, too, and in 
some varieties it constitutes a capsule. 
(6) 
