CHAPTER II. 

 What are Bacteria? 



Structure — Myco-protein — Limiting Membrane — Gelatinous Capsule — 

 Special Cell Contents — Oxide of Iron — Sulphur — Colouring Material 

 — Flagella — Modes of Multiplication and Development — Division — 

 Rate of Vegetative Multiplication — Endospores — Arthrospores — 

 Classifications of Cohn, Van Tieghem, Zopf, Winter and Rabenhorst, 

 De Bary and Hueppe, Fliigge Baumgarten, &c. 



Under the general term Bacteria may be included those 

 minute, rounded, ellipsoid, rod-shaped, thread-like, or spiral 

 forms of vegetable organisms sometimes spoken of as be- 

 longing to the class of lower fungi. They are also known as 

 Fission fungi (the Schizomycetes of the Germans) ; a term 

 applied to them because of their multiplication by a process 

 of division, transverse to the longitudinal axis in the case 

 of the rod-like forms, but varying somewhat in the case 

 of the rounded organisms. Each single organism consists 

 of a small speck of protoplasm or vegetable albumen, to 

 which may be given the name of cell, as although these 

 specks are so minute that they can be seen and studied only 

 with the aid of the very best optical appliances at our 

 command, it is found that they are by no means simple in 

 structure, nor are they in all cases even similar. This proto- 

 plasmic speck is differentiated into certain well-defined parts. 

 The round cells or micrococci, the simplest of all forms, 

 are seldom more than i-2S,oooth part of an inch in diameter ; 

 the elongated cells have, on an average, the same diameter, 

 or they may be a little more, and are from i-i 2,000th part 

 to i-6,oooth part of an inch in length, though there are 

 marked deviations from these dimensions in certain forms. 

 Accepting the above figures as being accurate, it would 

 require 25,000 of these spherical cells, placed in a row, or 

 the same number of the longer ones, placed side by side, to 

 make up a chain or band one inch in length. The vegetable 



