426 DIPHTHERIA 



first. There is also the striking change in the peripheral nerves, 

 which is shown first by the disintegration of the medullary 

 sheaths as already described. It is, however, still a matter of 

 dispute to what extent these nerve lesions are of primary nature 

 or secondary to changes in the nerve cells. 



Methods of Diagnosis. The bacteriological diagnosis of 

 diphtheria depends on the discovery of the bacillus. As the 

 bacillus occurs in largest numbers in the membrane, a portion of 

 this should be obtained whenever it is possible, and transferred 

 to a sterile test-tube. (The tube can be readily sterilised by 

 boiling some water in it.) If, however, membrane cannot be 

 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 sterile 

 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 Loftier '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. 117) 

 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 



