48 BACTERIOLOGY. 



the optimum of the organism to be examined. If at the 

 end of twelve, eighteen, twenty-four, thirty, thirty-six 

 hours, etc., specimens of the culture are observed first 

 unstained in the hanging drops, and then, if round or 

 oval, highly refractile bodies are seen, they should be 

 stained for spores. 



According to Fischer motile bacteria always come to 

 a state of rest or immobility previous to spore-forma- 

 tion. Several species first become elongated. The 

 anthrax bacillus does this, and a description of the 

 method of its production of spores may serve as an 

 illustration of the process In the beginning the pro- 

 toplasm of the elongated filaments is homogeneous, 

 but after a time it becomes turbid and finely granular. 

 These fine granules are then replaced by a smaller 

 number of coarser granules, which are finally amalga- 

 mated into a spherical or oval refractile body. This 

 is the spore. As soon as the process is completed there 

 appears between two spores a delicate partition wall. 

 For a time the spores are retained in a linear position 

 by the cell membrane of the bacillus, but this is later 

 dissolved or broken up and the spores are set free. 

 Not all the cells that make the effort to form spores, 

 as shown by the spherical bodies contained in them, 

 bring these to maturity; indeed, many varieties, under 

 certain cultural conditions, lose their property of forming 

 spores. The following are the most important spore 

 types : (a) The spore lying in the interior of a short 

 undistended cell ; (6) the spore lying in the interior of 

 a short undistended cell forming one of the elements of 

 a long filament ; (c) the spore lying at the extremity 

 of an undistended cell much enlarged at that end the 

 so-called " head spore ;" and (d) the spore lying in 



