DIPHTHERIA. 291 



Upon potato the bacillus develops only when the reac- 

 tion is alkaline. The potato-growth is not characteristic. 

 Welch and Abbott always secured a growth of the organ- 

 ism when planted upon potato, but do not mention the 

 reaction of the medium they employed. 



Milk is an excellent medium for the cultivation of the 

 Bacillus diphtheriae, and is possibly at times a means of 

 infection. Litmus milk is an excellent medium for ob- 

 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. 



Palmirski and Orlowski l assert that the bacillus pro- 

 duces indol, but only after the third week. Smith, how- 

 ever, came to a contrary result, and found that when 

 diphtheria bacillus grew in the dextrose-free bouillon 

 that he recommends no indol was produced. 2 



Diphtheria as it occurs in man is generally a disease 

 characterized by the formation of a pseudomembrane 

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

 presence and development of the bacilli in 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 are thought 

 to be due to pure infection by the diphtheria bacillus, 

 though such cases are more rare than those in which the 

 Streptococcus pyogenes and Staphylococcus aureus and 

 albus are found in association with it. 



In a series of 234 cases carefully and statistically studied 



1 Centralbl.f. Bakt. u. Parasitenk., Mar., 1895. 



2 Jour, of Exper. Med. t vol. ii., No. 5, Sept., 1897, p. 546. 



