142 BACTERIOLOGY. 



in the amount of oxygen admitted, and many, indeed, 

 grow equally luxuriantly in the partial exclusion of 

 oxygen. Life in the animal body, for example, as in 

 the intestines, necessitates existence with diminished 

 supply of oxygen. Pigment formation almost always 

 ceases with the exclusion of oxygen, but poisonous 

 products of decomposition are more abundantly pro- 

 duced (Hueppe). 



It is important to note that, according to recent in- 

 vestigations, it has been shown that the aerobic devel- 

 opment of the anaerobes may be facilitated by the pres- 

 ence of living or dead aerobes. 



It has also been observed not infrequently that certain 

 species which on their isolation at first showed more or 

 less anaerobic development that is, a preference to grow 

 in the depth of an agar stick culture, for instance 

 after a while seem to become strict aerobes, growing 

 only on the surface of the medium. This observation 

 proves that the simple fact of an organism showing 

 aerobic for anaerobic growth is not sufficient for its 

 separation into a distinct species. 



While all facultative as well as strict anaerobes grow 

 well in nitrogen and hydrogen, they behave very differ- 

 ently toward carbonic acid gas. A large number of 

 these species do not grow at all, being completely in- 

 hibited in their development until oxygen is again 

 admitted for example, B. anthracis and B. subtilis 

 and other allied species. It has been found in some 

 species, as glanders and cholera, that the majority of 

 the organisms are quickly killed by CO 2 , while a few 

 offer a great resistance, rendering impossible complete 

 sterilization by means of this gas. Another group, 

 again viz., streptococcus and staphylococcus exhibits 



