304 SPECIFIC MICRO-ORGANISMS 



the other contains a steel rod, around the lower end of which a 

 pledget of absorbent cotton has been wound. These tubes con- 

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

 suspected iregion 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- tubes with bacteria (see page in). In board-of-health 

 work these tubes are returned to the ofiice. 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 LofBer's methylene blue. After use 

 the tubes and swabs should be most carefully and thoroughly 

 sterilized. 



On LoflSer'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 charac- 

 teristic. The diagnosis of the diphtheria bacillus in practice 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 bacilh, 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 



