76 ATLAS OF BACTERIOLOGY. 



guished from that due to the formation of spores. 

 We are acquainted to-day with: (1) Endospores, 

 strongly refracting oval or round bodies developing in 

 the interior of the cell, and which as a rule possess 

 considerable resistance to injurious influences (heat, 

 dryness, chemicals) ; and (2) arthrospores (De Bary, 



Hiippe), i.e., sprout-like 

 constriction of one end of 

 the cell. These spores 

 (Fig. 8) are also said to 

 FIG. a Arthrospores of vibrio exhibit increased resist- 



cholerae, according to Huppe. ^^ -g^ as ^ ^^ 



investigations have furnished no absolutely positive 

 proof of the formation of arthrospores which ex- 

 hibit increased resistance, the difficult question of 

 arthrospores, important as it is, must be regarded 

 as still open. 



In the following pages the term spores refers only 

 to endogenous permanent forms. 



In the different varieties the development of the 

 endospores runs a similar but not identical course. 

 In examining any definite variety for the development 

 of spores, we resort, as a rule, to agar streak or po- 

 tato cultures, which are kept at a temperature best 

 adapted to the variety in question. At the end of 

 twelve, eighteen, twenty -four, thirty, thirty-six hours, 

 we examine small tests of the streak culture, first un- 

 stained in water and with a narrow angle of aperture. 

 If it is thought that round or oval, strongly refracting 

 spores have been found, the spores are stained ac- 

 cording to Neisser's or Hauser's method (vide Tech- 

 nical Appendix) . For the careful study of the devel- 

 opment of spores, it is best to place a few bacilli in a 



