BACTERIACE.E : THE BACILLUS OF DIPHTHERIA 2QI 



taining the swabs are sterilized. The swab is wiped over the 

 suspected region in the throat, taking care that it touches nothing 

 else, and is then rubbed over the surface of the blood-serum mix- 

 ture. The swab is returned to its test-tube and the cotton plugs 

 are returned to their respective tubes. The plugs, of course, 

 are held in the fingers during the operation, and care must be 

 taken that the portion of the plug that goes into the tube touches 

 neither the finger nor any other object. The principles, in fact, 

 are the same as those laid down in general for the inoculation 

 of culture-tabes with bacteria (see page 107). In board-of-health 

 work these tubes are returned to the office. When it is desirable, 

 a second tube may be inoculated from the swab. The tubes 

 are placed in the incubator, where they remain for from 6 to 15 

 hours and a microscopic examination is then made of smear 

 preparations stained with Loffler's methylene blue. After use 

 the tubes and swabs should be most carefully and thoroughly 

 sterilized. 



On Loffler's blood-serum kept in the incubator the bacillus 

 of diphtheria grows more rapidly than most other organisms 

 which are ordinarily encountered in the throat, a property 

 which to a certain extent sifts it out, as it were, from them, and 

 makes its recognition with the microscope easy in most cases. 

 The appearance of the bacilli under the microscope is quite 

 characteristic. The diagnosis of the diphtheria bacillus in prac- 

 tice is made from the character of the growth upon the blood- 

 serum and the microscopical examination, taking into account 

 the size and shape of the bacilli, with the frequent occurrence 

 of irregular forms and the peculiar irregularities in staining, and 

 this usually suffices; but in doubtful cases a second culture should 

 be made from the throat, and at the same time another tube of 

 Loffler's serum should be inoculated from the first culture. 

 On the next day plate cultures on glycerin agar may be made 

 from which typical colonies should be transplanted to broth. 

 After 48 hours at 37 C. the broth is injected into two guinea- 

 pigs in doses of 0.5 c.c. and one of the guinea-pigs should receive 



