TEXT-BOOK OF BACTERIOLOGY. 129 



days rabbits, those of six days sheep, etc., and this degree of par- 

 tially-diminished virulence can also be preserved throughout gen- 

 erations of cultures. 



And even if the above statements may not, perhaps, always be 

 borne out in practice with perfect exactitude in all cases, that 

 does not change the incontestably proven scientific fact that bac- 

 teria of a high degree of virulence may lose this quality for a 

 shorter or longer time, or even permanently, and to any extent, up 

 to its complete extinction. 



Something similar has been observed in the saprophytic species 

 also. Many pigment bacteria, under the influence of high temper- 

 ature or of culture in media little suitable to them, lose the faculty 

 of forming coloring matter, and sometimes do not regain it under 

 normal circumstances till after a considerable lapse of time. 



How is this extremely striking phenomenon to be explained ? 

 What distinguishes bacteria in their natural state from those arti- 

 ficially debilitated ? Why can the former grow and multiply in the 

 bodies of susceptible animals, and the latter not ? 



The circumstance that all the influences which rob the bacteria 

 of this their (for us) most important capacity are such as are in- 

 jurious and hostile to them, would lead to the supposition that an 

 extensive degeneration of the cell protoplasm took place, which 

 would show itself in other places also. Yet this is found to be the 

 case to a very limited extent only. The harmless anthrax has the 

 same appearance and the same form as the normal anthrax; its 

 separate members show the same formation, the contents are as 

 clear as crystal and homogeneous, the rods are motionless, they 

 divide and produce spores as before. On the gelatin-plate and in 

 the needle-point culture we observe the same sort of growth in 

 short, there are no really striking differences. It is true that on 

 closer examination some slight traces of degeneration may be per- 

 ceived. While the virulent anthrax bacillus multiplies so rapidly 

 in the bodies of susceptible animals that the newly-formed mem- 

 bers at once diverge and proceed immediately to further division, 

 the anthrax of diminished virulence for example, the mouse anthrax 

 frequently grows out to peculiar long threads in the organs, a sign 

 of disturbed vital energy. The observations of Smirnow lead to 

 similar conclusions. He found that the artificially-debilitated bac- 

 teria show in their cultures a slower, less luxuriant growth than 

 the virulent ones, and also that they yield more readily than the 

 latter to the influence of disinfectants. But these differences do 

 not present themselves by any means regularly, and even if they 

 did, they would not advance us far toward a veritable explanation 

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