128 APPENDIX. 



BACILLI. 



Longer or shorter cylindrical cells, growing longitudinally, and 

 dividing by transverse cleavage. Ultimately they tend to grow into 

 long threads {Leptothrix), along the course of which highly refractile 

 round spores are produced. The spores are set free, and under 

 favourable conditions reproduce the bacillus form. Bacilli often form 

 clusters, but very seldom are found in zooglea masses. 



Bacillus subtilis. On Potato, dvc. — ^Forms a very moist, trans- 

 parent, jelly-like film, which rapidly spreads itself over the nutrient 

 surface, and has a clear glistening appearance. 



In Gelatine. — It causes liquefaction slowly from above downwards, 

 giving rise to a granular white precipitate at the bottom of the 

 liquefied portions, and growing downwards in the tracks of the in- 

 oculating needle as dense opaque spikes. 



Microscopically. — It consists of rods, usually about 2 it,, thick by 

 6 or 8 /i. long. Growth takes place rapidly ; and at a slightly ele- 

 vated temperature (35° C.) it is possible to observe the process of 

 longitudinal growth and transverse cleavage, which accompanies the 

 multiplication of these organisms, fully carried out within thirty or 

 forty minutes (Fliigge). In liquid media the organism moves 

 actively by two flagella — one at each end. The spores are of an 

 oval shape, and thicker than the rods. 



Bacillus anthracis. On Potato {ste Fig. 15, p. 58). — It forms a 

 cream-coloured layer of a succulent consistence, which grows rapidly 

 at slightly elevated temperatures. 



In Gelatine (see Fig. 37). — Causes liquefaction of the jelly, and the 

 characteristic reactions described on p. 84. 



In Liquid Media. — It forms a fine filmy cloud in the lower strata of 

 the liquid, and after a time is deposited as a fine powder on the floor 

 of the beaker in which it is cultivated. 



Microscopically, — It is indistinguishable from B. subtilis in its rod- 

 like stage. In liquid media the rods are described to be flagellate 

 and mobile, and similar to B. subtilis in all respects. In its spore 

 formation there is, however, a slight difference. The spores of 

 B. anthracis are spherical, and are not thicker than the lengthened 

 rods, in the continuity of which they appear ; and in this stage the 

 organisms can be easily differentiated. 



Bacillus tuberculosis. On Serum (see Fig. 55). — For description 

 see p. 104. It refuses to grow well in other nutrient media. 



Microscopically. — Consists of small thin nodules, often curved, and 

 frequently possessing a bearded appearance, due to spore formation. 

 The bacilli measure about 4 /i in length by o's /*. in breadth, and the 

 spores are not broader than the rods. For special methods of stain- 

 ing it, see § 27, p 39. 



