THE STRUCTURE OF THE BACTERIAL CELL 3 



splitting plants (German, Spaltpflanzen). And of the two divisions 

 forming these Schizophyta the splitting algae were denominated the 

 sehizophyceaj (German, Spaltalgen), while the bacteria or splitting fungi 

 were called the schizomycetes (German, Spaltpilzen). The bacteria were, 

 therefore, often spoken of as the schizomycetes. This classification in its 

 reference to splitting fungi reflects the view, now practically abandoned, 

 that the bacteria represent the last stage of a progressive degeneration 

 which parasitism has entailed in the fungoid plants. 



GENEKAL MORPHOLOGY OF THE BACTERIA. 



The Structure of the Bacterial Cell. On account of the 

 minuteness of bacteria the investigation of their structure is 

 attended with great difficulty. When examined under the 

 microscope, in their natural condition, e.g., in water, they appear 

 merely as colourless refractile bodies of the different shapes 

 named. Spore formation and motility, when these exist, can 

 also be observed, but little else can be made out. For their 

 proper investigation advantage is always taken of the fact of 

 their affinities for various dyes, especially those which are usually 

 chosen as good stains for the nuclei of animal cells. Certain 

 points have thus been determined. The bacterial cell consists 

 of a sharply contoured mass of protoplasm which reacts to, 

 especially basic, aniline dyes like the nucleus of an animal cell 

 though from this fact we cannot deduce that the two are 

 identical in composition. A healthy bacterium when thus 

 stained presents the appearance of a finely granular or almost 

 homogeneous structure. The protoplasm is surrounded by an 

 envelope which can in some cases be demonstrated by over- 

 staining a specimen with a strong aniline dye, when it will appear 

 as a halo round the bacterium. This envelope may sometimes 

 be seen to be of considerable thickness. Its innermost layer is 

 probably of a denser consistence, and sharply contours the, 

 contained protoplasm, giving the latter the appearance of being 

 surrounded by a membrane. It is only, however, in some of 

 the higher forms that a definite membrane occurs. Sometimes 

 the outer margin of the envelope is sharply defined, in w r hich case 

 the bacterium appears to have a distinct capsule, and is known 

 as a capsulated bacterium (vide Fig. 1, h; and Fig. 62). 

 The cohesion of bacteria into masses depends largely on the 

 character of the envelope. If the latter is glutinous, then a 

 large mass of the same species may occur, formed of individual 

 bacteria embedded in what appears to be a mass of jelly. When 

 this occurs, it is known as a zooglcea mass. On the other hand, 

 if the envelope has not this cohesive property the separation of 



