I 88 BACTERIA 



stocking; or (3) solid, staining uniformly throughout. The pleo- 

 morphic differences of various bacilli are most characteristic/ and 

 of diagnostic importance. This organism stains with all the basic 

 dyes, notably by Loffler's blue, or Neisser's special granule stain. 

 It is also stained by Gram's method. The length of the organism 

 differs much, according to the reaction of the medium in which it 

 grows. Alkaline media favor long forms, and acid the reverse. 

 Its length is from 1.5/1 to 3.5^. It does not form chains. Bizarre, 

 or involution shapes predominate in old cultures. (Fig. 66.) 



FIG. 66. Diphtheria bacilli involution forms. (Kolle and Wassermann.) 



Culture and Temperature Requirements. It grows best at 

 body temperature, and on glycerine agar, or in Lb'ffler's blood 

 serum mixture of alkaline reaction. 



Vital Characteristics. It resists drying for a long time, and has 

 lived on culture media for eighteen months at room temperature; 

 also in silk threads for several months in a dried condition. Re- 

 mains alive in healthy throats for months. Formalin vapor kills 

 it speedily; corrosive sublimate solution, i- 10,000 destroys it in a 

 few minutes; light is lethal to it in from two to ten hours, and heat 

 at 58 C. in ten minutes. 



