go MICRO-ORGANISMS AND DISEASE [chap. 



careful examination, however, it is found that while some 

 bacteria cannot at all or only very feebly grow in air (or 

 oxygen), there are others which cannot at all or only very 

 feebly grow without it : the first are obligatory anaerobic, 

 the second obligatory aerobic. Further it is found that 

 some bacteria can grow fairly well without oxygen, but grow 

 very much faster and more copiously under free access of 

 oxygen (air) ; these are facultative anaerobic ; while other 

 bacteria can grow fairly well under free access of air but 

 grow much better without it ; these are facultative aerobic. 



Thus the bacillus of malignant oedema, quarter evil or 

 symptomatic anthrax, of tetanus Clostridium butyricum are 

 obligatory anaerobic, though also these are capable of 

 becoming more or less accustomed by subcultures to grow 

 on the surface under access of air. 



The bacillus of anthrax, bacillus mesentericus, bacillus 

 prodigiosus, bacillus tuberculosis, bacillus coli and typhosus, 

 bacillus diphtheriae, vibrio of cholera and many others grow 

 best aerobically and show either no growth or only very 

 feebly so in the absence of free oxygen. 



For a large number of bacteria it is difficult to assign a 

 correct place amongst the facultative anaerobic or faculta- 

 tive aerobic bacteria, because the boundary line between 

 these is somewhat ill defined. 



The growth and multiplication of bacteria is cmterh 

 paribus principally influenced by the nature of the nutritive 

 medium. Since the substance of bacteria contains 

 proteid, all bacteria obviously require for their growth and 

 multiplication nitrogenous matter which in most instances 

 of pathogenic bacteria must be of the nature of albumin. 

 While there are bacteria which can exist on extremely 

 simple nitrogenous matter — e.g. ammonium carbonate — as is 

 the case with the nitrifying microbes, there are others 



