THE BACILLUS AXD THE BACTERIOLOGY OF DIPHTHERIA 219 



then, without being laid down, the swab is immediately inserted in 

 the blood-serum tube, and the portion which has previously been in 

 contact with the exudate is rubbed a number of times back and forth 

 over the whole surface of the serum. This should be done thoroughly, 

 but it is to be gently done, so as not to break the surface of the serum. 

 The swab should then be placed in its tube, and both tubes, thin cotton 

 plugs having been inserted, are reserved for examination or sent to 

 the laboratory or collecting station (as in New York City). If sent 

 to the health department laboratories for examination the blank forms 

 of report which usually accompany each " outfit" should be filled out 

 and forwarded with the tubes. 



Where there is no visible membrane (it may be present in the nose 

 or larynx) the swab should be thoroughly rubbed over the mucous 

 membrane of the pharynx and tonsils, and in the nasal cavities, and a 

 culture made from these. In very young children care should be taken 

 not to use the swab when the throat contains food or vomited matter, 

 as then the bacteriological examination is rendered more difficult. 

 Under no conditions should any attempt be made to collect the material 

 shortly after the application of strong disinfectants (especially solu- 

 tions of corrosive sublimate) to the throat. 



Examination of Cultures. The culture tubes which have been 

 inoculated, as described above, are kept in an incubator at 37 C. for 

 twelve hours, and are then ready for examination. W 7 hen great haste 

 is required, even five hours will often suffice for a sufficient growth of 

 bacteria for a skilled examiner to decide as to the presence or absence 

 of the bacilli. On inspection it will be seen that the surface of the 

 blood serum is dotted with numerous colonies, which are just visible. 

 No diagnosis can be made from simple inspection; if, however, the 

 serum is found to be liquefied or shows other evidences of contamina- 

 tion the examination will probably be unsatisfactory. 



In order to make a microscopic preparation a clean platinum 

 needle is inserted in the tube and quite a large number of colonies are 

 swept w r ith it from the surface of the culture medium, a part being 

 selected where small colonies only are found. A sufficient amount of 

 the bacteria adherent to the needle is washed off in the drop of water 

 previously placed on the cover-glass and smeared over its surface. 

 The bacteria on the glass are then allowed to dry in the air. The cover- 

 glass is then passed quickly through the flame of a Bunsen burner or 

 alcohol lamp, three times in the usual way, covered with a few drops 

 of Loeffler's solution of alkaline methylene blue, and left w ithout heat- 

 ing for five to ten minutes. It is then rinsed off in clear water, dried, 

 and mounted in balsam. When other methods of staining are desired 

 they are carried out in the proper way. 



In the great majority of cases one of two pictures will be seen with 

 the T V oil-immersion lens either an enormous number of character- 

 istic Loeffler bacilli, with a moderate number of cocci, or a pure culture 

 of cocci, mostly in pairs or short chains. (See Streptococcus.) In a few 

 cases there will be an approximately even mixture of Loeffler bacilli 



