PRINCIPLES OF VETERINARY SURGERY 101 



optional-anaerobic bacteria are equally appropriate desig- 

 nations for this variety, which possess the property of 

 growing either with or without free oxygen. These forms 

 are capable of thriving when exposed to the air or when 

 hidden in the recesses of a sheltered environment. Ex- 

 amples, the pyogenic cocci, the typhoid bacillus, cholera 

 spirillum, etc. 



According to their place of abode micro-organisms may 

 be classified into : saprophytic bacteria and parasitic bac- 

 teria. They may even be designated by the simple names 

 of saprophytes and parasites. 



1. Saprophytic bacteria are those which cannot live in 

 the living tissues, but depend upon decaying organic matter 

 for their existence. The purely saprophytic micro-organism 

 is incapable of existing in the living body of animals and is 

 devoid of harmful action, while others may, under certain 

 conditions, elaborate a poison and intoxicate the system. 

 The fact that certain bacteria are only encountered in the 

 lesions of disease, and that others are only found in 

 extraneous abodes, does not conclusively show that a dis- 

 tinct line of demarcation can be drawn between these two 

 classes. It is well known that many parasites may thrive 

 as saprophytes, which fact necessitates the grouping of 

 many important bacteria into a third class which might ap- 

 propriately be called optional bacteria. This group would 

 then include such highly important micro-organisms as the 

 bacillus of Nicolaier and the septic vibrion actinomyces 

 bovis and probably the bacillus of glanders, which is known 

 to live about the stable watering trough indefinitely. 



2. Parasitic bacteria include those micro-organisms 

 found only upon or within the living body of animals. 

 There are many microbes that up to the present time have 

 not been found except in the lesions which they have pro- 

 duced. Nothing is known of their exogenous existence, 



