26 BACTERIOLOGY. 



from sugar and bodies of like composition ; from glyce- 

 rine and many of the fatty acids ; and from the alkaline 

 salts of tartaric, citric, malic, lactic, and acetic acids. In 

 some instances carbon compounds which when present 

 in concentrated form inhibit the growth of the lower 

 organisms, may, when highly diluted, serve as nutrition 

 for these bodies. Salicylic acid and ethyl alcohol come 

 under this head. 



In addition to carbon and nitrogen, water is essential 

 to the life and development of bacteria. Without it 

 no development occurs, and in many cases drying the 

 organisms results in their death. Certain forms, on the 

 contrary, though incapable of multiplying when in the 

 dry stage, may be completely deprived of their water 

 without causing them to lose the power of reproduction 

 when favorable conditions present. 



The closer study of the bacteria, and a more intimate 

 acquaintance with their nutritive changes, demonstrate 

 an appreciable variability in the character of the sub- 

 stances best suited for the nutrition of different species, 

 one requiring a more concentrated form of nutrition, 

 while another needs but a very limited amount of pro- 

 teid substance for its development. Certain members 

 bring about most profound alterations iu the media in 

 which they exist, while others produce but little appa- 

 rent change. In one case alterations in the reaction of 

 the media will be most conspicuous, while in another no 

 such variation can be detected. With certain forms 

 oxygen is essential for the proper performance of their 

 functions, while with another group no evidence of life 

 can be detected under the access of oxygen, and in a 

 third group oxygen appears to play but an unimportant 

 part, for development occurs as well with as without 



