IX] BACILLUS 167 



the bacilli grow containing comparatively less nutritive 

 material : not only in bicilli, but also in the individuals 

 composing a spirillum, are these vacuoles to be observed. 

 In cylindrical bacilli these vacuoles may be, and sometimes 

 have been, mistaken for spores. 



The ends of bacilli are generally rounded, occasionally 

 straight, and less frequently more or less pointed or conical 

 at one or both ends. In bacillus anthracis the ends are 

 generally more or less straight ; in the bacillus of diphtheria 

 grown on gelatine many bacilli show one end pointed, the 

 other rounded or straight and thick. 



According to the stage and the rapidity of their growth, 

 the baciUi vary much in length ; this is the case not only 

 with the single bacilli and short chains, but also in an 

 eminent degree with the elements of a bacillus filament or 

 leptothrix. In each case, indeed, it is possible to ascertain 

 that all lengths occur, from the cubical or spherical element 

 to the cylinder or rod. The former elongate into the latter 

 and then divide. According to v^fhether the division occurs 

 in a short or long element, the daughter elements are 

 cubical or spherical in the former, cylindrical or rod-shaped 

 in the latter case. This applies to single bacilli, to short 

 chains, and to the leptothrix forms. 



There are a great many species of bacilli, differing 

 morphologically from one another in the shape of the 

 elements, in motility, in the power of forming filaments or 

 leptothrix, and particularly in the thickness and length of 

 the elements. 



There are some species of bacilli — e.g. hay-bacillus, 

 anthrax-bacillus, bacillus mesentericus, proteus vulgaris, 

 bacillus of malignant cedema (Koch^, &c. — in which in , 

 the single bacilli and in the chains and filaments the size 

 of the elements varies from that of a cubical or spherical 



