402 ACTINOMYCETES. 



They are then tested further as follows: 



4. Staining of granules in twenty hours' serum cultures 

 according to the method of Neisser. This is very highly 

 recommended by C. Frankel (Berl. klin. Wochenschr., 

 1897, 1087). 



5. Titration of the acid formed in 5 c.c. of non- 

 saccharine bouillon in twenty and forty hours. If not 

 less than 0. 7 and not more than 1.2-1.5 c. c. of 1 : 40 normal 

 alkali solution is required for neutralization, this speaks 

 in favor of diphtheria. It is recommended that a parallel 

 observation be made with known diphtheria bacilli in 

 order to see whether a casual absence of acid production 

 does not depend upon the constitution of the bouillon. 

 (See p. 395. ) 



6. Animal experiment: If the injection of 1 c.c. of a 

 twenty-four hours' bouillon culture produces the charac- 

 teristic symptoms and death in about forty-eight hours 

 (see p. 399), the diagnosis of diphtheria appears certain. 

 With lessened virulence only slight local symptoms occur, 

 and eventually only death from marasmus. (See p. 404. ) 



7. Demonstration of the protective action of antitoxin 

 against the infection in especially difficult or uncertain 

 cases. 



By following this scheme, a typical diphtheria bacillus 

 is easily diagnosed, usually only the means given in 1 to 

 4, and perhaps also 5, are required. 



However, there occur in the mouth in cases of diph- 

 theria, besides diphtheria bacilli which are typical in 

 every way, also most numerous variations. See, especially 

 Kurth (Z. H. xxvni, 409). 



1. Non- virulent D. B., typical in all morphologic and 

 biologic peculiarities. Kurth found 3 non- virulent out of 

 39 typical cultures. 



2. Virulent D. B., typical in everything, except that 

 they exhibit no granule staining (Neisser found 3 without 

 granules out of 39 typical cultures). We found a form 

 with very slight production of granules. This group 

 passes over into the following. 



3. Virulent D. B., typical in every way, but without 

 the usual acid production. We found 1 out of 4 cultures 

 examined. 



