METHODS OF DIAGNOSIS 417 



walls of arterioles and capillaries, so often met with in diphtheria, 

 is another example of the action of the toxin. The toxins have 

 also a pernicious action on highly developed cells and on nerve 

 fibres. Thus in the kidney cloudy swelling occurs, which may 

 be followed by actual necrosis of the secreting cells, and along 

 with these changes albuminuria is present. The action is also 

 well seen in the case of the muscle fibres of the heart, which may 

 undergo a sort of hyaline change, followed by granular disintegra- 

 tion and associated with leucocytic infiltration. These changes 

 are of great importance in relation to heart failure in the 

 disease. Changes of a somewhat similar nature have been 

 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 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. — These include : (a) 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 ; 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 Lb'ffler'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. 114) 

 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. Diagnosis by 

 the microscopic examination is now little used, but it is some- 

 times justified in cases of urgency, though only in the hands of 

 an experienced observer. In some cases the bacilli are present 

 in characteristic form in such numbers as to leave no doubt in 

 the matter. 



(5) Cultivation. — For this purpose a piece of the membrane 

 should be separated by forceps from the pharynx or other part 

 when that is possible. It should be then washed well in a tube 

 containing sterile water, most of the surface impurities being- 

 removed in this way. A fragment is then fixed in a platinum 

 loop by means of sterile forceps, and a series of stroke cultures 

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