22 BACTERIOLOGY. 



sections the rods have a beaded appearance, but the intervals between 

 the granules are sometimes very long, and occasionally the protoplasm 

 appears to have collected only at the extreme ends of the rod. 



The appearances in the case of the bacillus of glanders and the 

 bacillus of hsemorrhagic septicaemia may be similarly explained. 



The fact that tubercular sputum preserves its virulence for 

 several months, even after desiccation, is to be attributed to the 

 formation of spores. Babfes claims to have succeeded in differen- 

 tiating them by double staining. 



In his definition of spirilla, Zopf gives the spore-formation as 

 absent or unknown. In comma-bacilli in sewage water the author 

 has often noted appearances suggestive of refractive spores ; and 

 the same also may be observed in vibrios, differing by their regular 

 contour from the irregular spaces occasionally observed in stained 

 preparations ; but they are only vacuoles. 



CI 



9 



Fig. 9.— Comma-bacilli in Sew- Fig. 10. Vibbios in Water con- 



age Water, stained with taminated with Sewage, 



Gentian Violet, x 1200. x 1200. 



Respiration and Nutrition. — Like all a-chlorophyllous vegeta- 

 bles, bacteria require for their nutrition oxygen, nitrogen, carbon, 

 water, and certain mineral salts. Many require free access to oxygen, 

 others can derive it from the oxidised compounds in the medium 

 in which they grow. Pasteur divided bacteria into two great classes 

 — the aerobic and anaerobic, and considered that the latter net 

 only had no need of oxygen, but that its presence was actually 

 deleterious. Though this view must be considerably modified, the 

 terms are convenient, and are stUl retained. They are well illus- 

 trated by the bacillus of anthrax, and the bacillus of malignant 

 oedema; and a simple plan of demonstration has been employed 

 by the author. A fragment of tissue from the spleen, for example, 

 known to contain anthrax bacilli, is deposited with a sterilised 

 inoculating needle, with the necessary precautions, on the surface of 

 nutrient agar-agar in a test-tube ; another tube of nutrient agar- 

 agar is liquefied, and when cooled down almost to the point of 



