450 BACTERIOLOGY. 



of irregular size and shape, giving a peculiar mottling 

 to the organ when present in large numbers. By micro- 

 scopical examination these were found to represent 

 places where the liver cells had undergone necrosis, 

 accompanied by emigration of leucocytes, and the cells 

 about them were in a condition of fatty degeneration. 

 In sections of the liver, masses of the bacilli were dis- 

 covered in and about the necrotic foci. The bacilli 

 were not found generally distributed through the body, 

 but only in the bile, liver, and occasionally in the 

 spleen. Gilbert and Lion found in addition that hemi- 

 plegia and paraplegia were often produced in conse- 

 quence of atrophy of the cells of the cord. These 

 observations have been confirmed by Thoinot and 

 Massilin, but in their experiments the nerve-lesions 

 were not commonly present. 



From experiments on animals it would, therefore, 

 appear that the true explanation of the palhogensis of 

 the colon bacillus is undoubtedly to be found in the 

 toxic effects of the chemical products of the organism 

 rather than in its mechanical presence in the tissues. 



Variation in Virulence. The virulence of the colon 

 bacillus varies considerably as derived from different 

 sources. An attempt has been made to establish 

 certain rules for this. Thus, Lesage and Macaigne 

 express the opinion that when obtained from a healthy 

 body it is only slightly virulent, while that isolated 

 from a diseased person is much more virulent. The 

 infective power is thought to bear a definite relation 

 to the severity of the disease with which the organism 

 is associated; for instance, to be greatest in cultures 

 taken from cholera patients and least in those obtained 

 from pus. Dreyfus also confirms this view. He found 



