SPORE-FORMATION. 43 



With the spore-forming bacilli, under favorable con- 

 ditions of nutrition and temperature, the same is seen 

 to occur daring vegetation, but as soon as these condi- 

 tions become altered, either by the exhaustion of nutri- 

 tion, the presence of detrimental substances, unfavorable 

 temperatures, 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 

 repeated. 



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 by granular, refrac- 

 tive points of irregular shape and size. These eventu- 

 ally coalesce, leaving the remainder of the cell clear and 

 transparent. When this coalescence of highly refrac- 

 tive particles is complete the spore is perfected. In 

 appearance, the spore is oval or round, very highly re- 



