CH. XI] THE ENZYME THEORY OF DISEASE 161 



meningococcus are virulent and ferment sugars. Again, 

 Hofimann's bacillus is non-virulent and non-fermenting while 

 the Klebs-Loeffler bacillus is virulent and ferments. B. coli 

 communis is a sugar fermenter and readily acquires virulence. 

 We may explain the association between the two properties 

 on the ground that both are examples of adaptation and that 

 an organism which possesses uimsual power of adaptability 

 in one particular direction may be expected to show a similar 

 power of adaptability in another direction ; but the associa- 

 tion between virulence and fermenting power lends some 

 support to the supposition that the former may depend upon 

 a process which we have every reason to believe is responsible 

 for the latter, namely ferment action. 



8. Bacterial invasion is met, on the part of the body, by 

 measures calculated to destroy the organisms and to counter- 

 act their toxins. These measures consist in the elaboration, 

 by the fixed cells of the body as well as by the leucocytes, of 

 various enzymes (Osier and McCrae). The class of weapon 

 forged by the tissue cells for purposes of defence might, 

 perhaps, be thought to give some indication as to the class of 

 weapon it is designed to meet. 



9. Many other functions of bacteria, besides the fermen- 

 tation of carbohydrates, are attributed to ferment action ; for 

 example, the formation of indol, the coagulation of milk 

 (Savage, 1910), the liquefaction of gelatin, the production of 

 pigment (Adami) and the development of agglutinins (Du- 

 claux). Moreover these other functions of bacteria, like their 

 power of fermenting carbohydrates, appear to be governed in 

 many instances by the same conditions which we have already 

 mentioned as influencing their virulence. Thus, the presence 

 or absence of oxygen, high and low temperatures, exposure 

 to and protection from sunlight, the presence of antiseptics, 

 are all conditions which markedly affect the production of 

 pigment by bacteria (Adami, 1892). 



10. Many of these ferments are separable from the bac- 

 teria with which they are associated. Twenty-five years ago 

 it was proved (Bitter, 1887, quoted Wood) that the lique- 

 faction of gelatin by bacteria was due to a ferment which 



D. 11 



