ESSENTIALS OF BACTERIOLOGY. 



PART I. 

 GENERAL CONSIDERATIONS. 



CHAPTER I. 



BACTERIA. 



THE bacteria occupy the lowest plane of plant life known to 

 us, though they are by no means as primitive in their biology 

 as was formerly supposed, and it is quite possible that still 

 simpler forms may be discovered. 



The numerous unicellular vegetable organisms which form 

 the lower limit of plant life as we know it multiply by fission 

 and are hence called the Schizophyta, or splitting plants. This 

 group is subdivided into two classes (a) the Schizophyceas, or 

 fission algae, and (b) the Schizomycetes, or fission fungi, or bac- 

 teria, as we usually call them. 



Lately it has Become customary to subdivide the bacteria 

 themselves somewhat arbitrarily into two classes the lower 

 bacteria and the higher bacteria. 



The lower bacteria are unicellular masses of protoplasm of 

 microscopic size, multiplying by fission and existing without 

 chlorophyll. Three main types are found : (1) Globular forms, 

 called cocci ; (2) straight rod-shaped forms, called bacilli ; (3) 

 curved or spiral rods, called spirilla. 



The higher bacteria show a tendency toward a more com- 

 plicated mode of organization in two ways : (1) They consist of 

 filaments made up of separate individuals, but which exhibit 

 enough independence to foreshadow the rudiments of a physi- 

 2 (17) 



