Cultivation 42 1 



The true diphtheria bacilli appear brown, with a dark blue 

 body at one or both ends; the pseudo-diphtheria bacilli 

 usually exhibit no polar bodies. 



Park * in his large experience found that neither the 

 Neisser nor the Roux stain gave any more information 

 concerning the virulence of the bacilli than the Loftier 

 alkaline methylene-blue. 



When cover-glass preparations are stained with these 

 solutions, the bizarre forms already mentioned are par- 

 ticularly obvious, and the contrast between the polar 

 granules, which color intensely, and the cytoplasm of the 

 bacillus, which tinges slightly, is marked. Through good 

 lenses the organisms are always distinct bacilli, notwith- 

 standing; the fact that the ends stain more deeply than the 

 centers, and it is only through poor lenses that the organ- 

 isms can be mistaken for diplococci. 



The bacilli stain well by Gram's method, which is ex- 

 cellent for their definition in sections of tissue, though 

 Welch and Abbott found that Weigert's fibrin method and 

 picrocarmin gave the most beautiful results. 



Cultivation. The diphtheria bacillus grows readily upon 

 all the ordinary media, and is very easy to obtain in pure 

 culture, plates not being necessary. Material from the in- 

 fected throat can be taken with a swab or platinum loop 

 and spread upon the surface of several successive tubes 

 of Loffler's blood-serum media. Upon the first a confluent 

 growth of the bacillus usually occurs; but upon the third, 

 scattered colonies suitable for transplantation can usually 

 be found. 



Loffler has shown that the addition of a small amount 

 of glucose to the culture medium increases the rapidity of 

 growth, and suggests a special medium which bears his 

 name Loffler's blood-serum mixture: 



Blood-serum 3 



Ordinary bouillon -f- 1 per cent, of glucose .... 1 



This mixture is filled into tubes, coagulated, and sterilized 

 like blood-serum, and is one of the best known media to be 

 used in connection with the study of diphtheria. 



The studies of Michel f have shown that the development 



* "Bacteriology in Medicine and Surgery," 1900. 



f'Centralbl. f. Bakt. u. Parasitenk.," Sept. 24, 1897, Bd. xxn, 

 Nos. 10 and 11. 



