188 ADDENDUM 



diminish and in some cases eliminate extraneous bacteria, while 

 exerting little or no pathogenic action upon any tubercle bacilli 

 present. 



6. Butter. 



Insufficient attention is probably given to this food from the 

 bacteriological Public Health point of view so that the following 

 additional methods and particulars should be of interest. 



To examine butter for the tubercle bacillus the technique 

 recommended by Eastwood and Griffith 1 may be employed. 



A quarter of a pound of the sample is cut up and transferred 

 to a sterile flask with a side-tube at the bottom. About 60 c.c. 

 of sterile normal saline solution, warmed to a temperature of 

 37 C., is added to the contents and the flask placed in the 

 incubator (37 C.) in a vessel filled with water at the temperature 

 of the incubator. The time required for thorough melting of 

 the butter is generally about two hours. It is important to get 

 the butter melted as soon as possible so as to avoid unnecessary 

 multiplication of extraneous organisms, but time must be 

 allowed for all the fat to rise to the surface. When the melting 

 is completed the lower milky portion is withdrawn through the 

 side-tube, made up to about 100 c.c. by the addition of more 

 saline, well shaken and centrifugalised for 20 minutes (centrifuge 

 running at about 3500 revolutions per minute used). The whole 

 of the deposit is then used to inoculate guinea-pigs. Eastwood 

 and Griffith inoculated two each with |ths and a third with -J-th 

 of the deposit. A fourth guinea-pig was generally inoculated 

 with 10 c.c. of the clear melted fat. 



1 08 samples of butter were examined in this way. 



40 samples were purchased in London and the suburbs with 

 the assurance that the material was of British origin. Of these 

 20 yielded inconclusive results, 1 8 were definitely negative, while 

 2 were found to be tuberculous. 



20 samples were obtained from Shrewsbury and produced 

 locally. Of these 2 yielded inconclusive results and the 

 remaining 1 8 showed no tubercle bacilli. 



1 Report of Medical Officer, Local Government Board, 191213, p. 295 : issued in 

 1914. 



