THE DIPHTHERIA BACILLUS 181 



within six to eight hours. If the animal does not succumb to a 

 rapid intoxication signs of paralysis appear in the lower extremi- 

 ties, gradually extending to the entire body, and causing death by 

 paralysis of the heart or respiratory muscles. Upon autopsy the 

 site of inoculation is found to be congested and the neighboring 

 lymph nodes swollen; the adrenals are congested; an excess of 

 fluid appears in the serous cavities and in the heart; voluntary 

 muscle fibers and nervous tissue show signs of degeneration. 



In human infection the disease is characterized by a pseudo- 

 membrane on a mucous membrane, or occasionally upon the 

 surface of a wound and a general toxemia. The site of the pseudo- 

 membrane is usually the throat, larynx, or nose ; diphtheritic in- 

 fection of the middle ear is not uncommon ; infection of the con- 

 junctiva sometimes occurs as a result of a patient's coughing or 

 sneezing into the eye of another person. The local lesion is 

 the result of bacterial invasion, and consequent degeneration of 

 the epithelial cells gradually extends to the underlying tissues. 

 A profuse fibrinous exudate is poured out, and soon spreading over 

 the surface a false membrane appears composed of fibrin, leukocytes, 

 dead tissue cells, and bacteria. The pseudomembrane may be 

 so thick and firmly adherent as to leave a torn and bleeding sur- 

 face when displaced. 



The most serious injuries caused by the diphtheria bacillus are 

 the systematic lesions due to the absorption of its poisons. Diph- 

 theria is primarily a toxemia. As a result fatty degeneration 

 takes place in the muscle fibers of the heart, in the myelin sheath 

 of the peripheral nerves, and in the white matter of the brain and 

 spinal cord and in the kidneys. These changes in muscle and 

 nerve explain the paralysis and cardiac weakness so often follow- 

 ing an attack of diphtheria. When death occurs as a result of 

 the infection it is usually due to toxemia, laryngeal obstruction, 

 or broncho-pneumonia. 



Diphtheria Toxin. Diphtheria bacilli when growing in nutrient 

 broth produce a soluble toxin which diffuses from their bodies 

 into the surrounding medium. Loeffler assumed the presence of 

 such a poison but Roux and Yersin were the first to obtain it apart 



