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micro-zymes do not appear to have become microbes. To 

 Pasteur's discovery of the corpuscles of 'pehrine in the eggs 

 of the silk-worm, he replies that eggs contain many micro- 

 zymes, and that the peculiar disease corpuscles are simply 

 micro-zymes which have inherited the bad tendency de- 

 veloped in the micro-zymes of the parent moth and chrysalis. 

 Without forming any decisive opinion on this mysterious 

 and profound question (for what can appear more astonish- 

 ing than the continued life of a parasite, not merely in the 

 body of the parent worms, but actually in the eggs laid by 

 the moths?) attention may be drawn to the analogy between 

 the remarkable variety in the susceptibilities of microbes 

 and the apparently specialised chemical work of different 

 ferments, and the specialised chemical elaborations of the 

 cells of different organs of the animal body. Are not many 

 diseases of the human system, for instance, apparently due 

 to the excessive activity of specialised secreting cells, or to 

 the development of similar power of chemical elaboration by 

 other cells ; to an apparent change of function, as though 

 secreting cells of a given order were working in the wrong 

 places ? And are not such phenomena analogous to the in- 

 troduction into the blood or tissues of disease microbes 

 endowed with special chemical activities of their own? 



17. — In the course of this paper, mention has been made 

 of the education of microbes. The idea has a bearing upon 

 Pasteur's astonishing protective vaccination discoveries, and 

 seems to have a relation to the mysterious phenomenon of 

 heredity. The microbes of particular diseases, when passed 

 from animal to animal, increase in virulence; thus, as Pasteur 

 has shown, the microbe, which was originally powerless to 

 kill a guinea-pig a week old, but which killed a guinea-pig 

 a day old, has been nursed into a breed capable of killing a 

 sheep. Yet there is apparently no specific change in the 

 successive generations of bacilli ; we must assume that the 

 chemical constitution of their bodies remains unchanged, 



