DIPHTHERIA. 4°3 



consists of a combined necrosis of the tissues acted upon 

 by the toxin and coagulation of an inflammatory exudate. 

 When examined histologically it is found that the 

 mucous membrane is chiefly affected in its superficial 

 elements. The superficial layers of cells are embedded 

 in coagulated exudate — fibrin — and show a peculiar 

 hyaline degeneration. Sometimes the membrane seems 

 to consist exclusively of hyaline cells ; sometimes the 

 fibrin formation is secondary to or subsequent to the 

 hyaline degeneration. Leucocytes caught in the fibrin 

 also become hyaline. From the superficial layer the 

 process descends often to the deepest layers, all of the 

 cells being incorporated in the coagulated fibrin and 

 showing the hyaline degeneration. The neighboring 

 capillaries also become hyaline and the membrane 

 becomes a coagulation-necrotic mass. The occasional 

 laminated appearance of the membrane probably depends 

 upon different depths having been affected at different 

 periods, or to a difference in the process by which it has 

 been formed. The pseudomembrane is continuous with 

 the subjacent tissues by a fibrinous reticulum, and is 

 removed with difficulty, leaving an abraded surface. 



The coagulation-necrosis of diphtheria seems to 

 depend upon the local effect of the toxin. In the 

 horses which receive large quantities of it in the course 

 of immunization for antitoxin production it is common 

 for a large subcutaneous inoculation to be succeeded 

 by a fluctuating necrosis, which commonly becomes in- 

 fected from the skin and suppurates. Morax and Elmas- 

 sian 1 found that when very strong diphtheria toxin is 

 applied to the conjunctiva of rabbits every three minutes 

 for eight or ten hours, typical diphtheritic changes are 

 produced. 



Herman Biggs, 2 in an interesting discussion of the 

 occurrence of the diphtheria bacillus and its relation to 

 diphtheria, comes to the following conclusions : 



1 Annales de P Inst. Pasteur, 1898, p. 210. 



* Am. Jour, of the Med. Sciences, Oct., 1896, vol. xxii., No. 4, p. 411. 



