TOXINS 747 



A fresh specimen of antistreptococcic serum is always 

 desirable, as its power to destroy streptococci is soon lost. 



Toxins. 



Tulercdin. — Koch's tuberculin is prepared by growing 

 tubercle bacilli in flasks, containing peptonized bouillon 

 and glycerin, in an incubator at 37° 0. for six weeks. The 

 cultures are boiled and filtered through porcelain to remove 

 the dead bacilli, and the toxic substance is concentrated to 

 one-tenth of its bulk by boiling. The result is a solution of 

 the toxins of the tubercle bacilli in glycerin, and to this 

 is added a | per cent, aqueous solution of carbolic acid for 

 injection. Tuberculin is used in veterinary medicine solely 

 as a diagnostic test for tuberculosis in animals, chiefly 

 cattle. It may be used with almost entire certainty for this 

 purpose, Koch claiming 99 per cent, of correct results* from 

 its injection. Injections in tuberculous animals cause a rise 

 of temperature of from one to three or more degrees F. in 

 about twelve hours from the time of injection. If there is 

 any focus of tuberculosis, as in the joints or bones, open to 

 inspection, there will be a notable reaction observed in this 

 locality, with heat, redness and decrease of function of the 

 part. Erlich explains the fever following the injection of 

 tuberculin to be due to a reaction of a zone of cells about 

 the tuberculous focus which have been made unusually 

 susceptible by the toxins of the disease so that they become 

 inflamed by the sudden extra amount of toxin injected. In 

 a tuberculous guinea pig, which has been killed by the 

 injection of an overdose of tuberculin, zones of hyperemia 

 may be seen surrounding each of the grey nodules charac- 

 teristic of the disease. The injection of an ordinary dose of 

 tuberculin is practically harmless and does not even render 

 the milk of a cow unfit for food. In an advanced stage of 

 tuberculosis the animal may not react to tuberculin, and 

 this may be explained by the fact that the tissues are 

 perhaps habituated to the toxins. 



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