DIPHTHERIA. 227 



serving the changes of reaction brought about by the 

 growth of the bacillus. At first the alkalinity, which 

 is always favorable to the development of the bacillus, 

 is destroyed by the production of an acid. When the 

 culture is old the acid is replaced by a strong alkaline 

 reaction. 



Diphtheria as it occurs in man is generally a disease 

 characterized by the formation of a pseudo-membrane 

 upon the fauces. It is a local infection, due to the 

 presence and development of the bacilli on the pseudo- 

 membrane,' but is accompanied by a general toxemia 

 resulting from the absorption of a violently poisonous 

 substance produced by the bacilli. The bacilli are found 

 only in the membranous exudation, and most plentifully 

 in its older portions. As a rule, they do not distribute 

 themselves through the circulation of the animal, though 

 at times they may be found in the heart's blood. 



The most malignant cases of the disease seem to be 

 due to pure infection by the diphtheria bacillus, though 

 such cases are more rare than those in which the Strepto- 

 coccus pyogenes and Staphylococcus aureus and albus are 

 found in association with it. 



It may be well to remark that all pseudo-membranous 

 diseases of the throat are not diphtheria, but that some 

 of them result from the activity of the pyogenic organ- 

 isms alone. 



No more convincing proof of the existence of a power- 

 ful poison in diphtheria could be desired than the evi- 

 dences of general toxemia resulting from the absorption 

 of material from a comparatively small number of bacilli 

 situated upon a little patch of mucous membrane. 



In animals artificially inoculated the lesions produced 

 are not identical with those seen in the human subject, 

 yet they have the same general features of local infection 

 with general toxemia. 



Guinea-pigs, kittens, and young pups are susceptible 

 animals. When half a cubic centimeter of a twenty-four- 

 hour-old bouillon culture is injected beneath the skin of 



