COBYNEBACTEBIUM P8EUD0DIPHTHEBITICUM. 405 



The glycerin-agar plates appear correspondingly luxuri- 

 ant (58, VIII, a); when magnified sixty times, they present 

 dense, granular, dark colonies with ragged borders and 

 opaque centers (59, iv, a and 6). Upon potato, fairlj"- 

 abundant white growth. It is dry, elevated, lobulated, 

 often resembling the species of mycobacterium and actino- 

 myces (58, x). In bouillon the acid production (ex- 

 pressed in 1 : 40 normal alkali to 5 c.c. of bouillon), 

 according to all writers, is usually very slight {i. e., upon 

 ordinary bouillon after twenty hours, 0.3-0.7; after forty 

 hours, not more than 1.2; upon sugar bouillon after 

 twenty hours, 0.6-1.4; after forty hours as much as 1.3 

 to 2.1), or there is none at all. After two to four days 

 the alkalinity increases perceptibly. We have observed 

 cultures, nevertheless, which produced upon sugar bouillon 

 in forty hours as much as 3.2. 



Old agar tubes often exhibit a brownish-red to brown- 

 ish-black discoloration. ^ This phenomenon is inconstant, 

 but, according to Escherich, is never present in diphtheria 

 bacteria. ^ Upon gelatin there occurs a luxuriant growth, 

 even at 18°; bouillon shows a more rapidly forming tur- 

 bidity and a denser and later forming sediment than 

 occurs with diphtheria bacteria. 



In Gratz, v. Hofmann found this organism so frequently 

 (26 times out of 45 healthy persons) in the mouth that 

 he considered it a normal inhabitant of the mouth. Other 

 writers found it much more infrequently. Escherich 

 never found it in healthy persons in Gratz, twice in 100 

 cases of diphtheria, and ten times in association with other 

 diseases of the throat. In Wiirzburg we found it not 

 infrequently in healthy and diseased eyes and noses. 

 Escherich admits the possibility that this organism may 



' An organism, obtained from Honl, of Prague, was very similar in 

 every particular (staining, clubbing, branching, luxuriant growth, 

 staining well by Gram's method), but presented a reddish tint in all 

 cultures, especially intensely (rose) developed in the surface layer of 

 a milk culture. We have cultivated a similar one from the nose with 

 a luxuriant brownish -yellow growth (58, v). 



2 "We obtained a brownish color of glycerin-ascites-agar in one of 

 our cultures in ten to fourteen days, and in three others after a longer 

 time (six weeks). I'or the cultures we are indebted to Dr. Silber- 

 schmidt (Ziirich). 



