34 BACTERIOLOGY. 



ditions of nutrition and temperature,, the same process is 

 seen to occur, but so soon as these conditions become 

 altered, either by the exhaustion of the nutrition, the 

 presence of detrimental substances, unfavorable tempera- 

 tures, etc., there appears the stage in their life cycle to 

 which we have referred as "spore-formation." This is 

 the process by which the organisms are enabled to enter 

 a stage in which they resist deleterious influences to a 

 much higher degree than is possible for them when in 

 the growing or vegetative condition. 



In the spore, resting, or permanent stage, as it is 

 called, no evidence of life whatever is given by the 

 spores, though as soon as the conditions which favor 

 their germination have been renewed, these spores de- 

 velop again into the same kind of cells as those from 

 which they originated, and the appearances observed in 

 the vegetative or growing stage of their history are again 

 to be seen. 



Multiplication of spores, as such, .does not occur. 

 They possess the power of developing into individual 

 rods of the same nature as those from which they were 

 formed, but not of giving rise to a direct reproduction 

 of spores. 



When the conditions which favor spore-formation 

 present, the protoplasm of the vegetative cells is seen 

 to undergo a change. It loses its normal homogeneous 

 appearance and becomes marked here and there by 

 granular, refractive points of irregular shape and size. 

 These eventually coalesce and leave the remainder of 

 the cell clear and transparent. When this coalescence 

 of highly refractive particles is complete the spore is per- 

 fected. In appearance, the spore is oval or round, very 

 highly refractive, and of a glistening appearance. It is 



