PRINCIPLES OF VETERINARY SURGERY 97 



heat, cold, etc. Some are highly poisonous, as tetanic toxin, 

 while others may be tolerated in relatively large quantities, 

 or be successfully eliminated by the emunctories, as in ani- 

 mals recovering from septicaemia. 



Bacteria may also produce disease by mechanically ob- 

 structing the capillaries, by absorbing the oxygen essential 

 to the construction of tissues, by impairing the function of 

 vital organs, and by kindling exhausting fevers ; all of which 

 might occur independently of the absorption and dissemina- 

 tion of the toxins which most micro-organisms elaborate. 

 Some bacteria, in fact many, possess a combined! action of 

 provoking organic disturbance, intoxicating the system, 

 producing fever, and blocking the construction of tissues, 

 all of which in their totality determine grave disorders. 

 Others have strictly a local action, or at least a local 

 effect, which predominates over the slight systemic 

 disturbance. In animals the pyogenic cocci are capable of 

 producing local lesions of considerable magnitude without 

 causing much systemic disorder, and only produce death 

 through the constant and exhausting drain of prolonged 

 suppuration. Tetanus bacilli, on the other hand, produce 

 scarcely perceptible local lesions, and yet may inject the 

 system with a fatal dose of poison. 



The nxunber of micro-organisms inoculated in any given 

 infection has a patent influence upon the pathogenicity of 

 the microbe. While it is true that a single bacterium by 

 multiplying may reproduce numbers in the course of several 

 days that would seem improbable on mathematical calcula- 

 tion, it is, -nevertheless, proven over and over that unless a 

 sufficient number of them are injected the results are usu- 

 ally negative. It seems that they fall an easy prey to the 

 englobing phagocytes, and besides, in numerous instances 

 it has been shown that specific micro-organismis, unassisted 

 with other associated (favoring) microbes (which seem to 



