* 



WHAT ARE BACTERIA ? 25 



albuminoid or protoplasmic substance of bacteria was first 

 analysed and described by Nencki, who, because of the 

 nitrogen contained in it, and because of the similarity of 

 its structure to animal and vegetable protoplasm, looked 

 upon it as a proteid material ; he gave to it the name of 

 myco-protein or fungus protein. 1 During certain periods 

 of the existence of these micro-organisms, especially in cer- 

 tain species, this white of egg or jelly-like substance, which 

 invariably occupies the central part of the cell, is perfectly 

 transparent and is slightly more refractile than water ; at 

 other periods, or in other species, it may be finely or 

 coarsely granular ; under certain conditions still more marked 

 and characteristic changes may occur, vacuoles or clear spaces 

 making their appearance. It is usually extremely resistant 

 to the action of acids and even of alkalies. 



That this myco-protein cannot always be of the same 

 composition is evident from the fact that minute granules of 

 chlorophyll or of fat may be made out lying in the substance of 

 the protoplasm in special species, whilst in others small starch 

 or sulphur granules, or particles of different kinds of pigment 

 may be observed. This speck of vegetable albumen is really 

 the active part of the cell, and it is in this that we obtain 

 those histo-chemical colour or staining reactions that are so 

 characteristic of the protoplasm of the higher vegetable and 

 animal cells which, as is well known, seem to have a 

 peculiar affinity for certain dyes or stains. Carmine, for 

 example, is taken up most voraciously by the nucleus or 

 central portion of the cell which then assumes a brilliant 

 carmine hue, not by any means equal throughout ; in 

 consequence of this inequality the minute structure of 

 the nucleus may be readily and even accurately studied. 

 The surrounding protoplasm, which appears to be less 

 active, is much less vividly stained, whilst the cell wall, 

 which is the least active part of the cell and serves as little 

 more than a boundary wall of formed material, if present 

 at all, remains, in the majority of cases, quite unstained. 

 Logwood, the aniline dyes, or iodine may be substituted for 

 carmine, with the general result that the same staining 

 reactions as regards the different parts of these cells are 

 almost invariably obtained. 



1 Analysis of myco-protein : Water, 84.81; albumen, 13.207; fat, 1.198; 

 ash, 0.638; extractives, 0.327. 



