CULTIVATION OF THE BACILLUS. 359 



favourable sign or the contrary, though on experimental 

 grounds the latter is the more probable. We know, however, 

 that some of the complications of diphtheria may be due to 

 their action. The extensive swelling of the tissues of the 

 neck, sometimes attended by suppuration in the glands, 

 and also various haemorrhagic conditions, have been found 

 to be associated with their presence, in fact, in some cases 

 the diphtheritic lesion enables them to get a foothold in the 

 tissues, where they exert their usual action and may lead 

 to extensive suppurative change, to septic poisoning or to 

 septicaemia. In cases where a gangrenous process is super- 

 added, a great variety of organisms may be present, some 

 of them being anaerobic. 



Against such complications anti-diphtheritic serum pro- 

 duces no favourable effect, as its action is specific and only 

 neutralises the toxines of the diphtheria bacillus. In view 

 of this fact, in some cases the anti-streptococcic serum has 

 been used along with it, and it is apparent that in such con- 

 ditions the bacteriological examination of the parts affected 

 may afford valuable indications as to treatment. 



Cultivation. The diphtheria bacillus grows best in 

 cultures at the temperature of the body ; growth still takes 

 place at 22 C, but ceases at 20 C. The best media are 

 the following: Loffler's original medium (p. 52), solidified 

 blood serum, alkaline blood serum (Lorrain Smith), blood 

 agar, and the ordinary agar media. If inoculations be made 

 on the surface of blood serum with a piece of diphtheria 

 membrane, colonies of the bacillus appear within twenty- 

 four hours, and often before any other growths are visible. 

 The colonies are small circular discs of opaque whitish 

 colour, their centre being thicker and of darker greyish 

 appearance when viewed by transmitted light than the 

 periphery. On the second or third day they may reach 

 4 mm. in size, but when numerous they remain smaller. 

 On the agar media the colonies have much the same 

 appearance (Fig. 91) but grow less quickly, and sometimes 

 they may be comparatively minute, so as rather to resemble 

 those of the streptococcus pyogenes. In stroke cultures 



