40 THE BACTERIAL CELL. 



1883. He gave the name of capsule to the mucinous integument, 

 a term still remaining in use, especially among medical bacteriolo- 

 gists. Consequently we understand by capsule bacillus, one 

 wherein the cell wall is found to be in a distended condition 

 under normal conditions of vitality. The Bacillus diatrypeticus 

 casei (Fig. 2 of Plate I.), described in a subsequent section, may 

 be mentioned as a second example. 



As already stated, these mucinous envelopes are not affected 

 by the ordinary method of staining. If, however, they are pre- 

 viously treated with a suitable mordant, the colour will be readily 

 absorbed and fixed. Recipes for capsule staining are given by 

 Friedlander, Ribbert, Loefner, and others. The annexed illustra- 

 tion (Fig. 8) is drawn from a preparation stained in this way. It 



FIG. 7. Bacillus Pneumoniae 

 cruposae. 



A and B, elongated rods ; C, D, E, 

 short rods ; G-I, cocci. All the 

 cells exhibit highly distended 

 membranes. Magn. about 1500. 

 (After W. Zopf.) 



FIG. 8. Bacterium Pasteurianum. 



Zooglcea formation in an old film on the 

 surface of lager beer. Fixed and 

 stained by Lceffler's method. Magn. 

 1000. (After Hansen.) 



represents Bacterium Pasteurianum, an acetic acid bacterium dis- 

 covered by Hansen. The chain seen at the left-hand side differs 

 from the remaining portions of the figure. The upper half pre- 

 sents no special peculiarities, and shows (like the remaining chains) 

 three darkened cells held together by the swollen membrane ; 

 whereas in the lower moiety the dark parts are wanting, the three 

 cells formerly present therein having been accidentally crushed 

 in making the preparation, so that only the mutinous envelope 

 remains behind. In a more closely investigated case (not, how- 

 ever, with this bacterium) the substance composing the capsule 

 was identified chemically as related to mucin, or probably identical 

 therewith. 



If the gelatinisation of the cell walls proceeds to a little 

 greater extent, it causes the individual cells to become joined or 

 cemented into a coherent mass, called zooglcea by COHN (V.), the 



