16 BACTERIOLOGY. 



ship to certain well recognized types of plant life. In their 

 characteristics of growth, multiplication and reproduction 

 they resemble the group of algae more than any other group 

 of living beings, and it is this general relationship, rather 

 than any one peculiarity, which has led to their being 

 placed in the vegetable kingdom. 



As will be indicated later, bacteria multiply by division 

 or fission, and for this reason they are spoken of as flssion- 

 fuhgi or scMzomycetes. The word germ or microbe is often 

 employed to designate bacteria. It should be understood, 

 however, that these two terms have a broader significance 

 and include all microscopic life, whether animal or plant. 

 Bacteria therefore constitute a definite group of germs or 

 microbes. 



In addition to their relationship to algae, the bacteria 

 resemble in many respects the moulds or fungi, and the 

 yeasts. These two groups will be discussed more in detail 

 in a subsequent chapter. It will be sufficient to indicate in 

 this connection the more marked distinctions between the 

 moulds, yeasts and bacteria. The former, as is well 

 known, appear in velvety or cotton-like spreading growths 

 which even the unaided eye can often resolve into a net- 

 work of threads. The moulds are therefore spoken of as 

 thread fungi or hyphomycetes. Growth results not by 

 division, as in the case of bacteria, but by the lengthening 

 of a cell or thread, that is to say by continuous end-growth. 

 Moreover, the moulds are relatively higher forms of plant- 

 life inasmuch as many species of this group possess special 

 fruit-organs. The threads which make up the mass of a 

 mould are much thicker than bacterial cells. 



The yeasts are uni-cellular plants which differ froni 

 bacteria in size, method of multiplication and in other 

 respects. The yeast cell may be considered as a giant in 

 comparison with the minute bacterial cell. Moreover, 

 yeasts multiply, iiot by fission, but by a process known 



