8 DISEASE GERMS. 



existed, necessitates a modification of this view. But 

 even if characteristic differences could invariably be 

 pointed out in the anatomical units or cells, it is quite 

 certain that the living -matter of the most virulent 

 cancer, or of the most inveterate contagious malady 

 could not be distinguished from that of the harmless 

 growth, or healthy tissue at any period of its ex- 

 istence. 



The old doctrine, that the disease-carrying particles, 

 are germs derived from and capable of producing 

 microscopic vegetable organisms, has been recently 

 revived and extended. Since the investigations of 

 Pasteur, and the publication of the observations of 

 Salisbury and others, the vegetable or fungus germ 

 theory of disease has received a large accession of 

 advocates. According to this view, there are different 

 species or varieties of fungi corresponding to the 

 several contagious maladies with which we are 

 familiar. 



We must not, however, conclude that if disease 

 germs really do consist of living bioplasm or germinal 

 matter, they must necessarily be of a vegetable nature 

 and have sprung from vegetable organisms, or have 

 originated spontaneously, for it is obviously possible 

 that, though living, their nature may be very different, 

 and that they may have been derived from a different 

 source. While I freely admit that the facts of the case 

 are conclusive as regards the living state of the active 

 matter of contagious diseases, I am quite unable to 



