DIPHTHERIA BACILLUS. 343 



culture of one bacillus will kill a guinea-pig, while it 

 would require 1 c.c. of the culture of another bacillus 

 to kill. The same marked variation occurs in the 

 amount of toxin produced by different bacilli in their 

 growth in media outside of the body. There are also 

 bacilli which produce no specific toxin whatever and 

 yet appear to have all the other characteristics of viru- 

 lent bacilli. Moreover, the diphtheria bacilli differ 

 greatly in the tenacity with which they retain their 

 virulence when grown outside the body. The bacillus 

 that we have used in the laboratory of the health de- 

 partment has retained its virulence unaltered for four 

 years in frequently renewed bouillon cultures. Other 

 bacilli have lost 50 per cent, of their virulence after 

 being kept for only a few months. The passage of 

 diphtheria bacilli through the bodies of susceptible 

 animals does not increase their virulence to any con- 

 siderable extent, this being probably due to the fact 

 that the bacilli multiply but little in the tissues. 



At the autopsy of animals dying from the poisons 

 produced by the bacilli the characteristic lesions de- 

 scribed by Loftier are found. At the seat of inocula- 

 tion there is a grayish focus surrounded by an area of 

 congestion; the subcutaneous tissues for some distance 

 around are oedematous; the adjacent lymph-nodes are 

 swollen; and the serous cavities, especially the pleural 

 and the pericardial, frequently contain an excess of 

 fluid, usually clear, but at times turbid; the lungs are 

 generally congested. In the organs are found numer- 

 ous smaller and larger masses of necrotic cells, which 

 are permeated by leucocytes. The heart and voluntary 

 muscular fibres usually show degenerative changes. 

 Occasionally there is fatty degeneration of the liver and 



