DIPHTHERIA. 229 



an attenuated form of the real bacillus. The chief points 

 of difference between the bacilli are that the pseudo- 

 bacillus is shorter than the diphtheria bacillus when 

 grown upon blood-serum ; that the cultures in bouillon 

 progress much more rapidly at a temperature of from 

 20-22 C. than those of the true bacillus ; and that the 

 pseudo-bacillus is not pathogenic for animals. These 

 slight distinctions are all exactly what might be expected 

 of an organism whose virulence had been lost, and whose 

 vegetative powers had been altered, by persistent manip- 

 ulation or by unfavorable surroundings. 



The diphtheria bacilli are always present in the throats 

 of patients suffering from diphtheria, and constitute the 

 element of contagion by being accidentally discharged 

 by the nose or mouth by coughing, sneezing, vomiting, 

 etc. Whoever comes in contact with such material is in 

 danger of infection. 



It is of great interest to notice the remarkable results 

 obtained by Biggs, Parke, and Beebe in New York, where 

 the bacteriological examinations conducted in connection 

 with diphtheria show that the virulent bacilli may be 

 found in the throats of convalescents as long as five weeks 

 after the discharge of the membrane and the commence- 

 ment of recovery, and that they exist not only in the 

 throats of the patients themselves, but also in the throats 

 of their care-takers, who, while not themselves infected, 

 may be the means of conveying the disease from the 

 sick-room to the outer world. The importance of this 

 observation must be apparent to all readers, and serves 

 as further evidence why most thorough isolation should 

 be practised in connection with this dreadful disease. 



From time to time reference has been made to the 

 toxin elaborated by the diphtheria bacillus. Roux and 

 Yersin first demonstrated the existence of this substance 

 in cultures passed through a Pasteur porcelain filter. 

 The toxin is intensely poisonous, and by the modern 

 improved methods can be secured in such concentration 

 that o. i c.cm. will kill a guinea-pig in twenty-four hours. 



