No. 4.] REPORT OF (^ATTLK BURKAU. 317 



points where the disease prevaik'd during the autumn and 

 winter of 1902 and 1908. 



Prior to the time of the discovery and pulilic announce- 

 ment of foot and mouth disease, the middle of November, 

 1902, the New Enghmd Vaccine Company, of Chelsea, bought 

 the young cattle it used for the production of vaccine virus 

 from Mr. Clark, who would buy thrifty looking young cattle 

 from various sources, and when they had been used at the 

 Ne^v England Vaccine Company's establishment he would 

 take them home to his place, wdiere they were kept for a 

 while until he could dispose of them. 



The proprietor of the New England Vaccine Company 

 states that the vaccine virus produced there during the last 

 three or four years has retained its strength to a remarkable 

 degree, and that it has not been necessary to introduce new 

 "seed," as is often done at these establishments when the 

 virus is found to be deteriorating ; but it has been his custom 

 when inoculating animals to put in a couple of " control " 

 points of virus placed on the market by other producers, in 

 order to compare the fpiality of his with theirs, and to be 

 sure that his product was maintaining its standard of strength 

 as compared with others. 



During 1902 he used the product of six different American 

 manufacturers of vaccine virus, among others the same estab- 

 lishment from which Dr. Tyzzer's suppl}' was obtained, 

 which was used in the AVakefield experiments. 



During the summer of 1902 the proprietor of the New 

 England Vaccine Company was in Europe, and little was 

 done at that establishment ; but in order to keep the vaccine 

 virus from losing its vitality it was necessary for his assist- 

 ant to inoculate an animal every month or six weeks, for the 

 purpose of carrying the supply along at a standard strength. 

 When one of these inoculations was made, " control " points 

 were also put in for comparison. It does not seem unlikely 

 that a heifer may have been inoculated in July, and control 

 points used which were contaminated with foot and mouth 

 disease virus, enabling the animal to convey the disease to 

 Owen Clark's premises either late in July or early in Au- 

 gust, Avithout contaminating the vaccine virus produced by 



