374 DIPHTHERIA. 



are of great importance in relation to heart failure in the disease. 

 Changes of a somewhat similar nature have been recently 

 observed in the nerve cells of the central nervous system, those 

 lying near the capillaries, it is said, being affected first. There 

 is also the striking change on 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 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, six inches long, and pass the other end of the latter 

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

 (compare Fig. 54, 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 obtaifi a culture. 



The means f oy identifying the bacillus are {a) By microscopical 

 examination. — For microscopical examination it is sufficient to 

 tease out a piece of the membrane with forceps and rub it on a 

 cover-glass, or if it be somewhat dry a small drop of- distilled 

 water 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 LofHer'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 



