50 LABORATORY BACTERIOLOGY 



EXERCISE XIX 



STAINING SPORES 



76. In certain species of bacteria and under suitable condi- 

 tions, there appear within the bacteria highly refractive bodies 

 known as spores. The formation of spores is restricted to cer- 

 tain species. The spores are oval in form, and in old cultures 

 they may often be found outside of the bodies of the organisms 

 which produce them. They possess the power of resisting dry- 

 ing, heat, and unfavorable environment much longer than the 

 baciUi themselves. They do not stain by the usual methods 

 employed in staining bacteria so that special methods are re- 

 quired. Several processes 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 either in fresh or stained prepa- 

 rations from cultures. 



References. — Methods for staining spores in text-books. 



77. Work for this Exercise. — Examine and carefully de- 

 scribe the two cultures of Bacillus subtilis made in Exercise 

 XVI. 



Make a hanging-drop preparation from the bouillon and one 

 from the agar culture and examine them microscopically. 

 Describe the bacilli and observe carefully the appearance of 

 the spores both within and outside of the organisms. 



Make a cover-glass preparation from each culture and stain 

 with alkahne methylene-blue. Examine carefully and note the 

 appearance of spores which remain unstained. Make a draw- 

 ing of a few of the bacteria containing spores. 



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

 them for spores. 



