6o LABORATORY BACTERIOLOGY 



EXERCISE XVIII 



STAINING SPORES 



90. 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 

 bacilli themselves. They do not stain by the usual methods 

 employed in staining bacteria, so special methods are required. 

 Several processes have been proposed, but the one here given 

 seems to be quite as efificient 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. 



91. Work for this exercise. Examine and carefully describe 

 the culture 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 without the organisms. 



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 draw- 

 ing of a few of the bacteria containing spores. 



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

 them for spores. 



