432 MICROORGANISMS 



relation of the organism which Klebs had discovered to the 

 disease was made in 1888-89 by Roux and Yersin. These 

 men showed that the organism forms a toxine or poison which 

 may be isolated from the organism and which, when injected 

 into a susceptible animal, causes all the characteristic symp- 

 toms of the disease. 



500. Symptoms of the Disease. The organism usually 

 finds lodgment and develops on the mucous membrane of the 

 throat, nose, and rarely of the lungs. Even the eyes or the 

 middle ear may become the seat of infection, though, in the 

 great majority of cases, it is the pharynx that is affected. The 

 form of the disease that is sometimes called membranous 

 croup is an affection of the larynx. In rare cases, the organ- 

 isms enter the general circulation and give rise to septicemia 

 but usually they are confined to some local area of the mucous 

 membrane where they develop and secrete their toxine and 

 cause a white membrane to develop. The toxine is absorbed 

 into the system where it attacks certain vital organs, princi- 

 pally the heart, nerves, and kidneys. In these organs, it causes 

 a fatty degeneration and, therefore, a weakening of the organs. 

 This weakening of the heart is doubtless responsible for many 

 sudden deaths from what are apparently mild attacks of the 



disease, and the weakening 

 of the larger nerves and of 

 certain tissues of the brain 

 are the cause of many cases 

 of paralysis which follow 

 attacks of the disease. 

 501. Character of the 



FIO. 274.-Baciiius diphtheria. Organism.-The diphtheria 



bacillus is a slender rod- 



shaped organism of moderate and somewhat variable size 

 (Fig. 274). When it is stained by a method invented by 

 Loftier, it presents a sort of beaded or granular appearance 

 which is so characteristic that a trained bacteriologist can 

 recognize it with certainty. This makes possible certain 



