CHAPTER VII 

 BACTERIOLYSIS AND ALLIED PHENOMENA 



UP to the present we have dealt entirely with the mechanism by 

 which the injurious effects of the infective bacteria are nullified. 

 It is obvious that this is only one, though perhaps the most im- 

 portant, aspect of the question. We have now to study how the 

 bacteria themselves are removed. 



The bactericidal properties of the blood attracted attention very 

 early in the history of bacteriology, and long before the beginnings 

 of the science Hunter showed that blood had the power of resisting 

 decomposition longer than other animal fluids. It was, however, 

 the controversy which took place between Metchnikoff and the 

 humoralist school which first focussed attention on this question, 

 and led to the discovery of the alexins by Buchner, Nuttall, and 

 others. The controversy is best discussed subsequently, and it is 

 sufficient now to point out that it was found that the circulating 

 blood had the power of killing certain bacteria, and that this 

 property was even more marked in the serum. Thus, according 

 to Lubarsch, 16,000 virulent bacilli will kill a rabbit if injected 

 intravenously i.e., the blood has not the power of killing this 

 number ; yet i c.c. of fresh serum will destroy this number or 

 more. It is obvious that the bactericidal substance or substances 

 occur in the blood, and to a greater extent in the serum. 



The properties of these bactericidal substances or alexins were 

 investigated, and it was found that they were fragile bodies, readily 

 destroyed by a moderate temperature (55 C.), and that they 

 disappeared spontaneously if the serum were kept for a few days. 

 They were destroyed by acids and alkalis, and what was most 

 important of all was that they were selective in their action i.e., 

 those from a certain animal might be potent antiseptics as regards 

 certain bacteria and inert towards others, whereas the serum of 

 another species might have quite different actions. They appeared 

 to be formed by the breaking down of leucocytes ; hence their 



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