ACTION OF THE DIPHTHERIA BACILLUS 425 





and also in normal conditions. Morphologically it is practically similar 

 to the diphtheria bacillus, and even in cultures presents very minor 

 differences ; it, however, grows more slowly on serum, and its colonies 

 have a tougher consistence and a more irregular margin. It is non- 

 virulent to animals, and does not produce an acid reaction in glucose 

 bouillon, or does so to only a slight extent ; in this way it can be dis- 

 tinguished from the diphtheria bacillus. It is still doubtful whether it 

 is pathogenic to the human subject. Its morphological characters are 

 shown in Fig. 123. 



Action of the Diphtheria Bacillus Summary. From a 

 study of the morbid changes in diphtheria and of the results 

 produced experimentally 

 by the bacillus and its 

 toxins, the following sum- 

 mary may be given of its 

 action in the body. 

 Locally, the^ bacillus pro- 

 daces inflammatory change 

 with fibrinous exudation, 

 but at the same time 

 cellular necrosis is also 

 an outstanding feature. 

 Though false membranes 

 have not been produced 

 by the toxins, a necrotic 

 action may result when 

 these are injected sub- 

 cutaneously. The toxins 

 also act upon the blood 



vessels, and hence oedema and tendency to hemorrhage are 

 produced; this action on the vessels is also exemplified by 

 the general congestion of organs. The hyaline change in the 

 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 

 recently observed in the nerve cells of the central nervous 

 system, those lying near the capillaries, it is said, being affected 



FIG. 123. Xerosis bacillus from a young 

 agar culture, x 1000. 



