DIPHTHERIA GROUP 



235 



tissue, rarely, if ever, entering the blood-stream, and brings about 

 the characteristic lesions of the disease by means of the toxins 

 which it produces. These are absorbed into the blood and bring 

 about changes in many of the organs of the body. Death is 

 sometimes due directly to asphyxiation by the false membranes 

 occluding the air-passages. 



Experimental Evidence of Pathogenesis. The typical diphtheritic 

 inflammation of the mucous membranes may be reproduced in 

 young animals by direct inoculation in the trachea, and in older 

 animals as well if the membranes are -injured previously. The 

 histologic lesions of the body organs can be produced by injections 

 of the toxin of the organ- 

 ism. Paralysis due to tox- 

 one poisoning may be 

 developed under certain 

 conditions. That this or- 

 ganism is the specific cause 

 of diphtheria is, therefore, 

 definitely established. 



Character of Disease and 

 Lesions Produced. The 

 pharynx is most commonly 

 affected; the larynx and 

 the nasal mucous mem- 

 branes are sometimes in- 

 volved. There may also 

 be diphtheritic conjunctiv- 

 itis, diphtheritic infections of the middle ear and of the mucous 

 membranes of the genital organs. The organisms remain localized, 

 rarely entering the blood-stream, cause necrosis and degenera- 

 tion of the epithelial cells and the deeper tissues as well. Blood- 

 serum and fibrin are exuded from the vessels, and, together 

 with fragments of the necrosed tissue, form the diphtheritic 

 membrane. Acute interstitial nephritis, fatty degeneration of the 

 myocardium, and sometimes of the nerve tissues, are due to the 

 absorption of the toxins. There is no constant ratio between 

 the extent of the diphtheritic process in the throat or elsewhere and 

 the severity of the symptoms and lesions produced by the toxin. 



Fig. 101. Bacillus diphtheria, twenty- 

 four-hour colony on agar ( X 100) (Frankel 

 and Pfeiffer). 



