STRUCTURE OF THE BACTERIAL CELL. 3 



of both, they have been grouped together in one class as the Schizophyta or 

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

 these Schizophyta the splitting algEe are denominated the schizophyceas (Ger- 

 man, Spaltalgen), while the bacteria or splitting fungi are called the schizo- 

 mycetes (German, Spaltpilzen) . The bacteria are, therefore, often spoken of 

 as the schizomycetes. Certain bacteria which have been described as con- 

 taining chlorophyll ought probably to be grouped among the schizophyceas. 



General Morphology of the Bacteria. 



Thie 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, aniUne 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 homogetieous structure. The protoplasm is surrounded 

 by an envelope which can in some cases be demonstrated by 

 overstaining a, specimen with a strong aniline dye, when it will 

 appear as a halo round the bacterium. This envelope may some- 

 times 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 true membrane occurs. Sometimes 

 the outer margin of the envelope is sharply defined, in which 

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

 known as a capsulated bacterium {vide Fig. i. No. 4; and 

 Fig. Tj"). 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 in- 

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



