1903.] on Civilisation and Health Dangers in Food. 255 



means that, even after excessive baking, the temperature reached in 

 the centre of a pie does not in any case exceed hy many degrees that at 

 which bacteria of low resistance are killed. 



3. There was a difference of several degrees between the tempera- 

 ture of various pies. 



The importance of these results will be better understood in the 

 light of some experiments which I have conducted, with the assistance 

 of Dr. A. Sellers, to ascertain the resistance of the Bacillus Derhiensis 

 to heat. In these experiments care was taken to ascertain the exact 

 duration of exposures to certain temperatures. We found that the 

 bacillus isolated from the pies, and cultivated in broth, was not killed 

 when exposed in that fluid for twenty-four hours to a temperature of 

 50°C. (121°F.) in four experiments out of six. 



It was only when a temperature of 60° C. (150° F.) was reached, 

 that death of the bacillus was usually obtained in less than five 

 minutes. 



It is therefore obvious that the bacillus could easily resist the 

 temperature to which the central parts of several of the pies which I 

 examined had been raised, and that pollution of the meat in the 

 chop ping-house was quite sufficient to explain the Derby outbreak. 



Another property of the bacillus explains how large masses of 

 food may rapidly be infected. Its rate of multiplication is extra- 

 ordinarily high. Thus I found that, with a small particle of a pure 

 culture of the Bacillus enteritidis^ I was able to infect throughout 

 several ounces of broth, meat jelly or milk, in less than two hours ; 

 2 milligrammes of culture are capable of infecting in two hours 150 

 grammes of these materials, when they are kept at temperatures 

 ranging between summer temperature and blood heat. In other 

 words, 1 part of infective material may easily infect in two hours 

 70,000 parts of one of the foods mentioned. A single drop of polluted 

 water, or particle of excreted matter, would therefore be capable in 

 summer to infect a gallon of milk, broth or jelly in a few hours. 



Carriage of Food from a Didance. 



If time permitted, I would be able to show how frequently cows' 

 milk is infected at the farm or through dirty milk-cans, and how 

 infectious bacilli multiply in the milk sent from the country to towns 

 in hot railway vans. In this way a quantity of infectious matter, 

 originally too small to cause a definite danger, is capable of increasing 

 to such an extent as to render milk distinctly noxious. 



During the past few years a large number of samples of milk sent 

 to Manchester have been tested in my laboratory, by means of inocu- 

 lation experiments. A small quantity of wholesome fresh milk 

 injected under the skin of a guinea-pig causes no inconvenience to 

 the animal, but infectious milk produces various forms of illness, 

 some of which are rapidly fatal. Many of the cases of fatal illness 

 are due to bacilli resembling those which I have mentioned in 



