260 BACTERIA. 



commences ; when this occurs, however, the animals are 

 usually slaughtered. 



I may here summarize what is known of the history of a 

 colony in the words of M'Fadyean, who has given the subject 

 much careful study, and to whose authority in this matter 

 I attach much weight. 



" i. It has its starting point in one or more cocci trans- 

 ported by the plasma currents, or by the agency of a carrier 

 cell (leucocyte). 



" 2. The cocci multiply by elongation and subsequent 

 fission. When undisturbed by the surrounding leucocytes 

 their growth and multiplication are after the manner of a 

 streptococcus, but frequently they become irregularly 

 grouped together (Staphylococcus heaps). 



" 3. By elongation, some of the cocci give rise directly to 

 short bacillary forms, and through these to long filaments. 



" 4. The further extension of the colony is effected by the 

 growth and multiplication of both threads and cocci. The 

 former multiply by segmentation into bacillary elements, 

 which may again elongate to leptothrix forms. 



" 5. The leptothrix filaments may give rise by close 

 segmentation to coccus forms. 



" 6. The formation of clubs and similar forms is evidence 

 of diminished vegetative power of the filaments (possibly also 

 cocci), in connection with which they originate. 



" 7- The growth of a colony may be arrested at any stage 

 by the agency of the animal cells (leucocytes), or by failure 

 in the supply of the necessary pabulum. In that event the 

 majority of the threads tend to develop clubs at their outer 

 ends (involution forms). The central cocci and the remainder 

 of the filaments then disintegrate ; but the clubs which offer 

 a greater (passive) resistance to the surrounding cells may 

 persist for an indefinite period." 



From what is here stated, and from what I have already 

 said, it will be evident that we have here to deal not with 

 an ordinary " mould r fungus, but rather with a form of 

 streptothrix that undergoes dichotomous division at certain 

 points. It must therefore be looked upon as possibly 

 one of the Cladothrix algae, or more probably as one of 

 the Schizomycetes in which the Cladothrix formation occurs, 

 and which has been described as closely allied to the strepto- 

 thrix Forsteri. 



