72 BACTERIOLOGY 



Spore Formation. With the spore-forming bacilli, under 

 favorable conditions of nutrition and temperature, the 

 same mode of segmentation is seen to occur during vege- 

 tation; but as soon as these conditions become altered by 

 the exhaustion of nourishment, the presence of detrimental 

 substances, unfavorable temperatures, etc., they enter, in 

 their life-cycle, the stage to which we have referred as 

 spore-formation. This is the process by which the organisms 

 are enabled to enter a state 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, dormant, or permanent state, as it is variously 

 called, no evidence of life whatever is given by the spores; 

 though as soon as the conditions which favor their germina- 

 tion have been renewed these spores develop 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 only 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, refractive points of irregular 

 shape and size. These eventually coalesce, leaving the 

 remainder of the cell clear and transparent. When this 

 coalescence of highly refractive particles is complete the 

 spore is perfected. In appearance the spore is oval or round, 

 and very highly refractive glistening. It is easily differen- 

 tiated from the remainder of the cell, which now consists 



