The Cause and Preventiox of Lamziekte. 227 



to the quantity of toxin ingested. The difference between the acute 

 and sub-acute form of the disease is largely dependent upon the 

 amount eaten, and in experimental work an animal can be killed in 

 fiom seventeen hours to ten days almost at will, ])y varying the size of 

 the dose. Doses appruiu^hiug (lie " niiniruuni letl)al dose '' generally 

 produce typical symptoms in about five days. 



The toxin itself is thermo-liable, i.e. is easily destroyed b> heat. 

 It is destroyed in a few minutes at 80° C. and at 75° C. by more 

 ])rolonged heating. Sterilized hones, which were toxic before 

 heating, can be used to cure pica. 



The toxicity of 0.0001 c.c. per kilo, previously mentioned, refers 

 to the Berkefeld filtrate of a highly toxic culture in minced liver 

 < issue. The closest analogy we can find for the lamziekte toxin is 

 (lie toxin of B. hofiilhiris, but complete identity with this toxin is 

 excluded by its physiological l)ehaviour towards different animals. 

 AVith a species of animal for which botulinus toxin may be very 

 poisonous the lamziekte toxin apjjears to operate less powerfully, and 

 vice versa. . The symptoms of expeiimental botulism in catile are 

 also distinctly different from- lamziekte. 



Tn regard to n practical attemnt to break the -tioloQ-ical yhain at 

 Uie loxin point little need be siiid. The obvious thing to do is to 

 collect all material to which any suspicion of toxicity can attach, 

 burn it, bury it, or fence it up out of the reach of stock. 



The ToxTcoGENir Saprophytic Bacteria. 



The fact that an organism or group of organisms is responsible 

 for the toxin production was a priori obvious once the nature of the 

 toxic material was discovered. Direct proof was obtained by the 

 usual laboratory methods of sub-cultivation, and indeed the inost 

 toxic laboratory material we now possess was derived by sub-culture 

 in suitable media ''minced liver tissue) from the very sample of veld 

 bones which led to the discovery of the cause of lamziekte. 



The fact that the organisms concerned in producing the toxin 

 are saprophytic rather than parasitic, i.e. flourish in dead organic 

 matter rather than in the living animal, was at once suggested by the 

 obserA^tion that the experimental production of the disease was 

 quantitatively related to the amount of infected material fed. It was 

 also supported by the fact that all the experiments of earlier years 

 upon the transmission of lamziekte on the theory of a pathoffenic 

 bacterial cause, were negative, and that the disease had been shown 

 to be neither infectious nor contasrious in the scientifically accepted 

 sense. Further evidence was readily obtained by the injection and 

 drenching of sterile toxin obtained by passing extracts of toxic 

 material through a Berkefeld filter. Such a filter retained the 

 bacteria, as evidenced bv cultnral study of the filtrate, but allowed 

 the toxin to pass throusrh. As converse proposition, cultures which 

 were toxic in large amount were found to be non-infective in small 

 amount, and material in which the toxin was destroyed by a heat 

 treatment (75° C. to 80° C.) which did not destroy the spores, failed 

 to produce lamziekte. The toxin therefore produced the disease wheii 

 separated from the bacteria, but the spores did not produce the disease 

 when separated from the toxin. Apparently the living animal is able 

 to get rid of any bacteria with which it may happen to hero ^e 



