DIPHTHERIA 



97 



coughs. Quarantine is usually kept up until bacteriologic 

 examination shows the absence of diphtheria bacilli. 



In 1893 Behring, a German scientist, found that 

 animals could be accustomed to injections of diphtheria 

 poison, and that after a time the blood of these animals 

 had acquired the power to cure other animals injected 

 with many times a fatal dose of diphtheria poison. 



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Fig. 29. — 1, A tube of blood-serum; 2, a sterilized cotton swab in 

 test-tube. Rub the swab gently but freely against the visible exu- 

 date, and without laying it down, after withdrawing the cotton plug 

 from the culture-tube, insert it into the latter, and rub that portion 

 which has touched the exudate gently but thoroughly over the sur- 

 face of the blood-serum without breaking its surface. Now replace 

 the swab in its own tube, plug both tubes, and place them in the 

 box provided by the health officials. This is to be sent to the bac- 

 teriologic expert. In laryngeal diphtheria the swab is to be passed 

 far back and rubbed freely against the mucous membrane of the 

 pharynx and tonsils (Anders). 



We have already said that the diphtheria bacillus when 

 grown in broth produces a strong poison. In fact, the 

 diphtheria bacilli produce all their evil effects through this 

 poison. The bacilli remain on the surface, i. c, they do 

 not enter the blood, nor do they invade the deeper tissues. 

 In this respect they differ from streptococci, which, as 

 already stated, may also give rise t(^ a membranous in- 

 flammation of the throat. The streptococci penetrate the 



