METHODS OF DIAGNOSIS 413 



obtained, a scraping of the surface with a platinum loop may be 

 sufficient. Where the membrane is confined to the trachea the 

 bacilli are often present in the secretions of the pharynx, and 

 may be obtained from that situation by swabbing it with cotton- 

 wool (non-antiseptic), the swab being put into a sterile tube or 

 bottle for transport. A convenient method is to twist a piece of 

 cotton-wool round the roughened end of a piece of very stout 

 iron wire, 6 inches long, and pass the other end of the latter 

 through a cotton plug inserted in the mouth of a test-tube 

 (compare Fig. 46, the wire taking the place of the pipette), and 

 sterilise. In use the wire and plug are extracted in one piece, 

 and after swabbing are replaced in the tube for transit. A 

 scraping may be made off the swab for microscopic examination, 

 and the swab may be smeared over the surface of a serum tube 

 to obtain a culture. This method of taking and treating swabs 

 is that usually employed in routine public health work. The 

 results obtained ordinarily suffice for the diagnosis of cases 

 suspected to be diphtheritic in nature. 



The means for identifying the bacillus are (a) By Micro- 

 scopical Examination. For microscopical examination it is 

 sufficient to tease out a piece of the membrane with forceps and 

 rub it on a cover-glass ; if it be somewhat dry, a small drop of 

 normal saline should be added. The films are then dried in the 

 usual way, and stained with any ordinary basic stain, though 

 methylene-blue is on the whole to be preferred, used either as 

 a saturated watery solution or in the form of Loffler's solution. 

 After staining for two or three minutes, the films are washed 

 in water, dried, and mounted. As a rule no decolorising is 

 necessary, as the blue does not overstain. Neisser's stain (p. 1 1 5) 

 may also be used with advantage, although it is to be noted 

 that sometimes in a secretion the diphtheria bacillus does not 

 react typically to this stain. Any secretion from the pharynx 

 or other part is to be treated in the same way. The value of 

 microscopical examination alone depends much upon the experi- 

 ence of the observer. In some cases the bacilli are present in 

 characteristic form in such numbers as to leave no doubt in 

 the matter. In other cases a few only may be found, mixed 

 with large numbers of other organisms, and sometimes their 

 characters are not sufficiently distinct to render a definite opinion 

 possible. The bacillus may be frequently obtained by means 

 of cultures, when the result of microscopical examination is 

 inconclusive. As already said, however, microscopical examina- 

 tion alone is more reliable after the observer has had experience 

 in examining cases of diphtheria and making cultures from them. 



