166 THE ENZYME THEORY OF DISEASE [CH. xi 



the second place, to reproduce faithfully the complete train 

 of symptoms and lesions characteristic of a disease in the 

 entire absence of the specific organism to which the disease 

 is commonly attributed. Both these results have actually 

 been observed. As regards the first, numerous examples have 

 already been given of virulent organisms, normally capable of 

 giving rise to a complex and characteristic train of symptoms 

 and lesions in the living body (e.g. the Klebs-Loeffler bacillus, 

 B. typhosus} being deprived of their power to produce a 

 single one of these symptoms or lesions although, in every 

 other respect, retaining their character and properties un- 

 changed (vide " Virulence," " Pathogenesis "). 



It is well recognised, for instance, that infection with B. 

 typhosus may occur without any of the clinical manifestations 

 of typhoid fever. Dudgeon (1908) quotes three cases of 

 patients whose stools contained enormous numbers of typhoid 

 bacilli and whose blood agglutinated these organisms in 

 dilutions of 1 in 200, who nevertheless failed to exhibit a 

 single symptom of typhoid fever. 



With regard to the second, examples may be cited of 

 diseases associated with the presence of certain bacteria but 

 now generally recognised as being due to "filter passers." 

 Hog cholera, for instance, is a highly contagious disease 

 associated with a certain bacillus, the " hog cholera bacillus." 

 A pig suffering from the disease can infect other healthy 

 pigs ; the latter develop the same symptoms and are found to 

 be invaded by the same organism and they are capable, in their 

 turn, of infecting other healthy animals in precisely the same 

 way. It has been shown, however, that a broth culture of 

 the hog cholera bacillus, from an infected animal, after it has 

 been passed through a Chamberland filter a process which 

 entirely removes any bacilli present nevertheless retains its 

 power to "infect" a healthy animal with hog cholera, the 

 disease running the same course as usual and exhibiting 

 precisely the same lesions and symptoms. 



Such a sequence affords a precise analogy to the ex- 

 periment of Sortinin, a quarter of a century ago, which led to 

 his discovery that after a culture of certain bacteria had been 



