MORPHOLOGY AND PHYSIOLOGY OF BACTERIA. 123 



spores are found mostly in the bacilli, rarely in spirilla. They 

 are what is meant when the word spore is used alone without 

 qualification. The existence of another kind of spore, de- 

 scribed as forming from the whole of the bacterium (called 

 arthrospore) , is doubtful. At all events, its significance is not 

 at present understood. Spores develop generally, though not 

 always, under adverse conditions of various kinds, as of tem- 

 perature and of nutrition. They are more resistant to un- 

 favorable influences of all sorts than are the fully developed 

 bacteria. Spores, as a rule, resist drying, light, heat and 

 chemical agents .to a remarkable degree, but the spores from 

 one and the same organism often differ in resisting power in 





FIG. 46. -Bacteria with spores. 



different cultures. Frankland* found that anthrax spores 

 which formed at 18-20 C. much more resistant than anthrax 

 spores formed at 35-38 C. Even individual spores in the 

 same culture differ in resisting power. 



Anthrax spores are said to have been found which could 

 withstand steam for twelve minutes, i-iooo mercuric chloride 

 for nearly three days, or 5 per cent, carbolic acid for more than 

 forty days.f The greatest resistance is displayed by the spores 

 of some of the saprophytic bacteria, particularly those of hay 

 and potato, which are sometimes not destroyed by several 

 hours of steaming; and bacteria which resisted 100 C. for six- 

 teen hours are said to bave been obtained from the soil. When 



*Frankland. Centralblat fr Bakteriologie,etc. Bd. XV., 1894, p. no. 

 tGiinther. Einfiihrung in das Studium der Bakteriologie. Leipzig, 1906, 

 p. 406. 



