B. DIPHTHERIA 157 



rounded by soft cedematous tissue. On autopsy the sub- 

 cutaneous tissue in the region of the seat of inoculation was 

 cedematous and streaked with blood. The inguinal glands 

 were enlarged, firm, and deeply congested. Film preparations 

 from the juice of the incised gland showed numerous diphtheritic 

 organisms. A pure culture was obtained which was proved to 

 be B. diphtheria by the virulence test and also by the antitoxin 

 test. 



For the examination of milk for B. diphtherias, the serum 

 method undoubtedly offers the best chance of obtaining a posi- 

 tive result. 50 c.cms. of sample are centrifugalised at 2000 

 revolutions per minute fof twenty minutes and the cream layer 

 removed to a sterile dish. The milk layer is withdrawn by 

 means of a suction pump connected to a fine bore glass tube 

 until only 1-2 c.cms. remain. The sediment, and cream 

 layer, are used for inoculating either blood serum plates or 

 tubes. If tubes are used, one loopful is employed for smearing 

 the surface of a number of tubes in succession so that at least 

 one tube will be obtained in which the colonies are well isolated. 

 In this manner a total of from 40 to 50 tubes is used for one 

 sample and examined after sixteen or eighteen hours incubation 

 at 37 C. From the tubes containing well-isolated colonies, 

 subcultures are made of all colonies in any way resembling B. 

 diphtherias and examined as to their morphological character- 

 istics and biochemical properties. B. diphtherias is usually 

 found in fresh serum preparations as a slender rod about 3ju in 

 length and exhibiting well-defined polar granules when stained 

 with Loeffler's methylene blue or Ponder 's stain (see appendix). 

 The club-shaped bacillus is sometimes found, and also beaded 

 and barred varieties but the bipolar type (type c, Westbrook 

 classification) is the most typical. B. diphtherias does not 

 liquefy gelatine, is Gram positive, and ferments dextrose, 

 Isevulose, galactose, arabinose, and maltose without formation 

 of gas but not saccharose and mannite. Older cultures some- 

 times produce acid in lactose and glycerine. The bacillus is 

 non-motile and does not form spores. 



