128 



ESSENTIALS OF BACTERIOLOGY 



Blood-serum (After ' Lqffler). Seep. 69. 

 In a few hours (eight to sixteen) on the white opaque sur- 

 face a slight moisture is noticeable which, if examined, is 

 composed of bacilli. In twenty-four hours small round 

 colonies are found which seem to ar- 

 range themselves concentrically. The 

 growth becomes more abundant, and 

 the individual colonies larger and yel- 

 lowish (Fig. 54). On blood-coagulum 

 (see p. 72) the growth is usually gray 

 and the margins of the culture crenated. 

 Often a diagnosis can be made in four 

 hours if the serum-tubes are kept in the 

 oven at 37 C. In milk, abundant 

 growth, without curdling. 



Bouillon. In bouillon an abundant 

 growth takes place, and this medium is 

 used to obtain the toxins. 



Staining. Is positive by Gram's 

 method. Stained best with Loffler's al- 

 kaline methylene-blue. Neisser's double 

 stain (see p. 52) shows granules, blue 

 black, and body, brown. 



Patho genesis. By inoculation, ani- 

 mals, which naturally are not subject 

 to diphtheria, have had diphtheritic 

 processes develop at the site of infec- 

 tion; hemorrhagic edema then follows, 

 and death. 



No agglutinins are developed in the 

 serum. 



In rabbits paralyses develop, and 

 when the inoculation occurs upon the 



trachea, all the prominent symptoms of diphtheria show 

 themselves. 



Manner of Infection in Man. The exact way is not yet 

 known. It is supposed that the mucous membrane, altered in 



Fig. 54. Bacillus 

 diphtherias; agar-agar 

 culture (photograph 

 by Dr. Henry Koplik) . 



