'////. HACILLUS AXD Till. li.\ r TERIOLOGY OF DIPHTHERIA 193 



tory of the Board of Health lias retained its virulence almost unaltered 

 for ten years in bouillon cultures. Other bacilli have lost 50 per cent, 

 of their virulence after being kept only a few months. The passage of 

 diphtheria bacilli through the bodies of susceptible animals does not 

 increase their toxin production to any considerable extent. 



At the autopsy of animals dying from the poisons produced by the 

 bacilli, the characteristic lesions described by Loeffler are found. At 

 the seat of inoculation there is a grayish focus surrounded by an area 

 of congestion; the subcutaneous tissues for some distance around are 

 oedematous; the adjacent lymph nodes are swollen; and .the serous 

 cavities, especially the pleura and the pericardium, frequently contain 

 an excess of fluid, usually clear, but at times turbid; the lungs are gen- 

 erally congested. In the organs are found numerous smaller and larger 

 masses of necrotic cells, which are permeated by leukocytes. The 

 heart and certain voluntary muscular fibres and tissues of nerves usually 

 show degenerative changes. Occasionally there is fatty degeneration 

 of the liver and kidneys. The number of leukocytes in the blood is 

 increased. From the area surrounding the point of inoculation viru- 

 lent bacilli may be obtained, but in the internal organs they are only 

 occasionally found, unless an enormous number of bacilli have been 

 injected. Paralysis, commencing usually in the posterior extremities 

 and then gradually extending 'to the whole body and causing death by 

 paralysis of the heart or respiration, is also produced in many cases in 

 which the inoculated animals do not succumb to a too rapid intoxication. 

 In a number of animals we have seen recovery take place three to six 

 weeks after the onset of the paralysis. The occurrence of these par- 

 alyses, following the introduction of the diphtheria bacilli, completes 

 the resemblance of the experimental disease to the natural malady in 

 man. 



Diphtheria Toxin. It is evident that a micro-organism which, when 

 injected subcutaneously, 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 patho- 

 genic 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 suc- 

 cessfully analyzed, so that its chemical composition is unknown, but 

 it has many of the properties of proteid substances, and can well be 

 designated by the term active proteid. The poison produced is 

 probably composed of a mixture of several nearly related toxins. 

 Diphtheria toxin is totally destroyed by boiling for five minutes, and 

 loses some 95 per cent, of its strength when exposed to 75 C. for the 

 same time; 73 C. destroys only about 85 per cent, and 60 very little. 

 Lower temperatures only alter it very gradually. Kept from light and 

 air and in cold storage it deteriorates very slowly. The views of 

 Khrlich and Madsen as to the nature of toxins will be considered 

 in the chapter under its relations to antitoxin. 



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