SUMMARY OF PATHOGENIC ACTION. 373 



origin and spread of the disease. As is well known, the disease 

 usually spreads by infection, direct or indirect, from patient to 

 patient; but sometimes it appears to start afresh, as it were. 

 In the latter case the existence of the non-virulent diphtheria 

 bacilli may possibly afford an explanation of the occurrence, as 

 such bacilli are sometimes found even in healthy subjects. 

 The possibility of the transformation of the pseudo-diphtheria 

 (" Hofmann's ") into the true diphtheria bacillus has been the 

 subject of much controversy, but it cannot be regarded as 

 sufficiently established that such a transformation may be 

 effected, "still less that the former organism is related to the 

 origin and spread of diphtheria. 



Xerosis bacillus. — The term has been given to an organism first observed by 

 Kuschbert and Neisser in xerosis of the conjunctiva, and which has been since 

 found in many other affections of the conjunctiva and even in normal condi- 

 tions. Morphologically it is practically similar to the diphtheria bacillus, and 

 even in cultures presents very minor differences. It is, however, non-virulent to 

 animals, and, according to Eyre, does not produce an acid reaction in neutral 

 bouillon ; in this way it can be distinguished from the diphtheria bacillus. 



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 summary may be given of its action in the body. 

 Locally, the bacillus produces inflammatory change with fibrin- 

 ous 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 subcutaneously. The toxins also act upon the 

 blood-vessels, and hence oedema and tendency to haemorrhage 

 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 dis- 

 integration or by an actual fatty degeneration. These changes 



