44 THE BACTERIAL CELL. 



central body. The individual species of the genus Granulobader 

 established by Beyerinck to which belong the instigators of the 

 butyric acid and butyl alcohol, &c., fermentations under certain 

 conditions of culture store up in their interior copious supplies of 

 granulose, owing to which circumstance they are stained a deep 

 blue by iodine. It should be mentioned that W. MIGUIA (I.) 

 could not detect any honeycomb structure of the cell plasma 

 during his researches into the structure of the Bacillus oxalaticus, 

 discovered by Zopf. 



It may perhaps be useful, though not exactly necessary, to 

 remind the reader of the well-known botanical fact that the living 

 plasma strives to prevent the access of colouring matters. In 

 this connection, also, the behaviour of the various kinds of fission 

 fungi differs. Some of them exhibit merely a slight resistance, 

 and absorb colouring matter without their vitality being impaired, 

 as Birch-Hirschfeld established with respect to phloxine red in 

 the case of the typhus bacillus. In the majority of instances, 

 however, this resistance is so great that the cells must be killed 

 before they can be stained. On this account most of the staining 

 solutions employed for bacteriological purposes contain additions 

 (e.g. alcohol) destructive to the vitality of the cell, which being 

 accomplished, the plasma readily absorbs the colouring matter. 

 According to the researches of DREYFUSS (I.), it is not the true 

 albuminoid matter, but the nuclein (also a constituent of plasma) 

 which fixes the colour. 



Thanks to the care bestowed on the subject by medical 

 bacteriologists specially interested therein, the art of staining 

 bacteria has reached a high degree of perfection during the last 

 fifteen years. Exhaustive directions thereon are to be found in 

 HUEPPE'S (I.) handbook and EISENBERG'S (I.) treatise, and BERN- 

 HEIM (I.) has issued a very cheap book highly useful for laboratory 

 work. In Fermentation Physiology the examination of the bac- 

 teria being usually performed on the living, unstained organisms, 

 the aid of staining is seldom required ; the principal occasions 

 being when so-called cover-glass preparations have to be kept 

 for purposes of future microscopical comparison. The preparation 

 of such is described in all the books just mentioned. 



36. Elementary Composition of the Bacterial Cell. 



Determinations on this point by micro-chemical analysis were 

 first attempted by KAPPES (I.), whose attention was principally 

 devoted to Micrococcus prodigiosus, cultures of which were made 

 011 solid nutrient media, and then, when they had arrived at suffi- 

 cient development and had expanded into mass cultures, examined 

 for the amount and composition of the dry matter therein. Cul- 

 tures of this fission fungus on agar-agar contained on an average : 

 Water 85.5 per cent., and dry matter 14.5 per cent., the latter 



