45 



EXERCISE XVII. 



STUDYING AND STAINING SPORES. 



§ 66. Explanatory note. In certain species of bacteria 

 and under suitable conditions, there appears within the 

 bacteria highly refractory granules or bodies known as 

 spores. The formation of spores is largely restricted to cer- 

 tain species of bacilli. The spores are oval in form and in 

 old cultures they can often be found outside of the bodies of 

 the organisms which produce them. They possess the power 

 of resisting drying, heat, and unfavorable environment 

 much longer than the bacilli themselves. Ordinarily they 

 do not stain by the usual methods employed in staining 

 bacteria so that special methods are required. Several pro- 

 cesses have been proposed, but the one here given seems to 

 be quite as efficient as any of the others. 



Bacillus subtilis, or the hay bacillus, is one of the most 

 widely distributed species of bacteria. It develops spores 

 which can be readily detected in either the fresh or stained 

 preparations from cultures. 



§ 67. General directions. Examine and carefully de- 

 scribe the three cultures of Bacillus subtilis. 



Make a hanging drop preparation from the bouillon and 

 one from the agar cultures and examine them microscopi- 

 cally. Describe the bacilli and observe carefully the appear- 

 ance of the spores both within and outside of the bacilli. 



Make a cover-glass preparation from each culture and 

 stain with alkaline methylene- blue. Examine carefully and 

 note the appearance of spores which remain unstained. 

 Make a drawing of a few of the bacteria containing spores. 



Make a few (about 3) cover-glass preparations and stain 

 them for spores. 



Inoculate a tube of agar with Bacillus cholerae stiis and 

 place it in the incubator for the next exercise. 



