MORPHOLOGY, REPRODUCTION, ETC. 17 



considered as in any way comparable to true spores. They are rep- 

 resented by the granular and globular appearances occasionally ob- 

 served in old cultures of some bacteria, notably streptococcus, cholera 

 spirillum, diphtheria bacillus, and others. It was believed that they 

 were due to a transformation of certain individuals of the cultures 

 into more resistant forms. It is probable, however, that such struc- 

 tures are merely to be regarded as evidences of involution or degen- 

 eration, since it has never been demonstrated that cultures contain- 

 ing them are more resistant either to disinfectants or to heat, than 

 cultures showing no evidences of such forms. The true spores or 

 endospores are most common among bacilli, and are rarely observed 

 among the spherical bacteria. They arise within the body of the 

 individual bacterium as a small granule which probably represents a 

 concentration of the protoplasmic substance. Nakanishi 78 claims 

 that there is a definite relation between these sporogenic globules 

 and the nuclear material of the bacterial cell. At the time at which 



o o m 



FIG. 4. VARIOUS POSITIONS OP SPORES IN BACTERIAL CELLS. 



sporulation occurs there is usually a slight and gradual thickening 

 of the bacillary body. After the formation of this thickening, a 

 spore membrane appears about the same thickened area. The com- 

 pleted spore is usually round or oval, has an extremely high refract- 

 ive index, and a membrane which is very resistant. Muhlschlegel 19 

 believes that the spore membrane is a double structure, and, as stated 

 before, Nakanishi believes that the spore contains nuclear material. 



The position of the spore in the mother cell is of some differential 

 importance in that it is usually constant for one and the same species. 

 Thus, the spores of the tetanus bacillus are regularly situated at the 

 extreme ends of the bacillary bodies, while those of anthrax are 

 situated at or near the middle. 



Physiologically, sporulation is probably to be regarded as a 

 method of encystment for the purpose of resisting unfavorable envi- 

 ronment, and it is indeed true that species of bacteria the vegetative 



18 Nakanislii, Munch, med. Woch., 1900, p. 680. 



19 Muhlschlegel, Cent, f . Bakt., II Abt., vi, 1900, p. 65. 



