RELATION TO ENVIRONMENT— CLASSIFICATION 27 



tion and that oxygen was obtained by these microorganisms by a split- 

 ting of carbohydrates. As a matter of fact, for a large number of micro- 

 organisms, this is actually true, and the presence of readily fermentable 

 carbohydrates not only increases the growth energy of a large number 

 of anaerobic bacteria, but in many cases permits otherwise purely 

 aerobic bacteria to thrive under anaerobic conditions.'^ On the 

 other hand, the basis of anaerobic growth can not always be found 

 in the fermentation of carbohydrates or in the simple process of 

 reduction. 



The favorable influence of certain actively reducing bodies, like 

 sodium formate or sodium-indigo-sulphate, upon anaerobic cultivation 

 is probably referable to their ability to remove free oxygen from the 

 media and thus perfect the anaerobiosis.^ A number of strictly anae- 

 robic bacteria, however, may develop in the entire absence of carbohy- 

 drates or reducing substances, obtaining their oxygen supply from other 

 suitable sources, some of which may be the complex proteids. Thus 

 the tetanus bacillus may ^ thrive when the nutritive substances in the 

 media are entirely proteid in nature. (See p. 28.) 



As Hesse * has shown, the respiratory processes of aerobic bacteria 

 consist in the taking in of oxygen and the excretion of CO^. The CO, 

 excretion has been shown, in these cases, to be markedly less than is 

 represented in the intake of oxygen. 



Anaerobes, likewise, show an excretion of CO2 which must, in these 

 cases, be a result of bacterial katabolism. 



Certain bacteria, like the red sulphur bacteria, have the power of 

 utilizing atmospheric oxygen in the same way in which this process 

 takes place in the chlorophyll-bearing plants. 



^Tiile a profuse supply of oxygen absolutely inhibits the growth of 

 most anaerobes, a number of these may, nevertheless, develop when only 

 small quantities of oxygen are present. Minute quantities of free oxy- 

 gen in culture media have been shown by Beijerinck'' and others not to 

 inhibit the growth of Bacillus tetani and Theobald Smith " has recently 

 demonstrated that when suitable nutritive material in the form of fresh 

 liver tissue is added to bouillon, a number of anaerobic bacteria may be 



' Theobald Smith, Cent. f. Bakt., I, xviii, 1895. 



2 Kitasato and Weyl, Zeit. f. Hyg., viii, 1890. 



3 Chudiakow, Cent. f. Bakt., Ref., II, iv, 189a 

 'Hesse, Zeit. f. Hyg., xv, 1897. 



c Beijerinck, Cent. f. Bakt., II, vi, 1900. 



" Th. Smith, Brovm, and Walker, Jour. Med. Res., ix, 1906. 



