2o8 ECONOMIC BACTERIA IN MILK AND MILK PRODUCTS 



which he believed was the cause ; others have found a micrococcus. 

 Blue cheese is produced, according to Vries, by a bacillus, and black 

 cJuese is produced by a copious growth of fungi. 



{/) Poisonous cheese. — In 1883 and 1884 there occurred in 

 Michigan, U.S.A., an outbreak of cheese-poisoning. Three 

 hundred persons in all were affected, and the illness was traced 

 by Professor V. C. Vaughan to a poisonous ptomaine present 

 in the cheese, and to which he gave the name tyro-toxicon. It 

 is not improbable that this ptomaine is a product of bacterial 

 fermentation. It is one of a large class of substances said to 

 be formed by the action of bacteria upon nitrogenous com- 

 pounds. It is unstable, and easily destroyed by the action of 

 heat and moisture, and even by exposure to the air. Being 

 present in small quantities only, it has never been isolated in 

 sufficiently large quantities to allow of its composition being 

 definitely determined. Tyro-toxicon has been proved to be a 

 violent poison both to man and the lower animals. A minute por- 

 tion consumed by a child produced sickness and diarrhoea in a 

 manner almost identical to cholera infantum (Vaughan). Similar 

 symptoms were obtained with cats and dogs. Vaughan found 

 that three months are required for the formation of tyro-toxicon in 

 milk kept in tightly-stoppered bottles ; but under certain circum- 

 stances, and in the presence of butyric fermentation in milk, the 

 poison is produced in about eight or ten days. Similar, and 

 possibly identical, poisons occasionally occur in cream, rancid butter 

 and milk {lacto-toxicon and diazo-benzol). They have the same 

 poisonous effects. Vaughan has isolated a microbe growing readily 

 on ordinary culture media and upon fruit and vegetables. This 

 micro-organism, it is considered, may be the agent producing tyro- 

 toxicon, but the bacteriology of the subject has not been worked 

 out. 



The writer investigated a similar outbreak due to tyro-toxicon jin 

 Dutch cheese in London in 1901.^ Seventeen persons were affected. 

 The symptoms of illness in all these 17 cases occurred in from 

 two to eight hours after eating the cheese in question, which came 

 from the same consignment. Moreover, the symptoms were 

 similar, namely, epigastric pain, rigors, vomiting, diarrhoea, prostra- 

 tion, and some fever. The degree of sickness does not appear to 

 have depended upon the amount of cheese eaten. There was no 

 death attributed to the poisoning, and in general the symptoms 

 appear to have passed off in the course of forty-eight hours. A 

 * Report on the Public Health of Finsbury, 1 901, pp. no- 116. 



