194 BACTERIA IN MILK AND MILK PRODUCTS 



" The inference to be drawn from these gross results is clear : a 

 certain proportion of the samples of milk contained bacteria which, 

 under favourable circumstances, gave to the milk noxious properties, 

 the development of which could be checked in many cases by pre- 

 venting the growth of these bacteria. ^The difference between 

 refrigerated and non-refrigerated milk would have been very much 

 greater, if the milk had invariably been cooled immediately after the 

 milking of the cows/ (Delepine). 



Therefore, it may be said that to refrigerate milk immediately 

 after drawing it from the cow is to reduce the number of bacteria and 

 to diminish the potential toxicity of the milk. Finally, Professor 

 Delepine writes : 



" When the clear relation existing between time of keeping, plus 

 temperature and the noxious properties of a certain number of 

 samples of milk, is contrasted with the ambiguous results obtained 

 when an attempt is made to connect these noxious properties with 

 disease of the udder (tuberculosis being excluded), it is difficult not 

 to feel convinced that infection of the milk outside the udder, and 

 the conditions under which milk is kept, are the most important 

 factors causing it to acquire infective properties."* 



Species of Bacteria found in Milk 



The kinds of bacteria occurring in milk may for purposes of con- 

 venience be classified in the following four divisions ; though of the 

 first two groups it is not necessary, to say much here : 

 ^ 1. Ordinary bacteria of air, soil, or water. 

 - 2. Bacteria of sewage or intestinal origin. 



3. Bacteria concerned in fermentation. 



4. Pathogenic bacteria, in particular those associated with tuber- 

 culosis, enteric fever, cholera, scarlet fever, diphtheria, sore-throat 

 illnesses, and epidemic diarrhoea. 



1. Ordinary bacteria of soil, air, or water readily gain access to 

 milk from their natural media. It is unnecessary to consider them 

 here. 



2. Bacteria of sewage and intestinal origin occur from time to time 

 in milk. The two chief representatives are B. coli and B. enteritidis 

 sporogenes. In Liverpool, from 1900-1902, 788 " country " milks were 

 examined, and 55 per cent, contained B. coli and 9 per cent, contained 

 B. enteritidis sporogenes ; of 722 " town " milks, 23 per cent, contained 

 the former bacillus, and 4 per cent, the latter.-f Chick found B. coli 

 present in 17 out of 239 new milks, and Balfour Stewart found B. 

 enteritidis sporogenes in 49 samples out of 213. When it is considered 



* Jour, of Hygiene, 1903, pp. 80-84. 

 f Bacteriology of Milk, p. 216. 



