344 BACTERIOLOGY. 



kidneys. The number of leucocytes in the blood is in- 

 creased. From the area surrounding the point of inocu- 

 lation virulent bacilli may be obtained, but in the in- 

 ternal organs they are only occasionally found, unless an 

 enormous number of bacilli have been injected. Paral- 

 ysis, commencing usually in the posterior extremities 

 and then gradually extending to other portions of the 

 body and causing death by paralysis of the heart or 

 respiratory organs, is also produced in many cases in 

 which ihe inoculated animals do not succumb to a too 

 rapid intoxication. In rare instances the muscles of 

 the neck or of the larynx are first paralyzed, and thus 

 characteristic symptoms are caused. In a number of 

 animals I have seen recovery take place three to six 

 weeks after the onset of the paralysis. 



Diphtheria Toxin. It is evident that a micro organ- 

 ism which, when injected subcutaneonsly, destroys the 

 life of susceptible animals and produces such marked 

 anatomical changes in the internal organs, while it is 

 found only at or near the point of inoculation, must 

 owe its pathogenic power to the formation of a poison 

 which, being absorbed, gives rise to toxaemia and death. 

 This poison or toxin has been partially isolated by Roux 

 and Yersin, and others, by filtration through porous 

 porcelain from cultures of the living bacilli. It has not 

 yet been successfully analyzed, so that its chemical 

 composition is unknown, but it has many of the prop- 

 erties of proteid substances, and can well be designated 

 by the term active proteid (see page 72). Diphtheria 

 toxin is totally destroyed by boiling for five minutes, 

 and loses some 95 per cent, of its strength when ex- 

 posed to 75 C. for the same time ; 73 C. destroys 

 only about 85 per cent, and 60 very little. Lower 



