2 Dairy Bacteriology. 



demonstrated. The bacteria as a class are separated from 

 the fungi (smuts, molds, etc.) , mainly by their method of 

 growth; from the lower green algae by the absence of 

 chlorophyll, the green coloring matter of vegetable 

 organisms . 



2. Structure of bacteria. As far as structure is con- 

 cerned the bacteria stand on the lowest plane of vegetable 

 life. They are single- celled plants. In its inner struc- 

 ture, the cell does not differ essentially from that of many 

 other types of plant life. It is composed of a proto- 

 plasmic body which is surrounded by a thin membrane 

 that separates it from neighboring cells that are alike in 

 form and size. 



3. Form and size. Where a plant is composed of a 

 single cell but little difference in form is to be expected. 

 While there are intermediate stages that grade insensibly 

 into one another, the bacteria may be grouped into three 

 main types (so far as form is concerned). These are 



FIG. 1. Different forms of bacteria, a, b, c, represent different types as to 

 form: a, coccus, b, bacillus, c, spirillum; d, diplococcus or twin coccus; e, staphy- 

 lococcus or cluster coccus; / and g, different forms of bacilli, shows internal 

 endospores within cell; h and *', bacilli with motile organs (cilia). 



spherical, elongated, and spiral, and to these different 

 types are given the names, respectively, coccus, bacillus, 

 and spirillum (plural, cocci, bacilli, spirilla), (fig. 1). 



