172 ANTISEPTICS 



apart from actual disease in the cow or in those handling the 

 milk, organisms capable of causing disease to man may gain 

 access from external sources. The most important of these is 

 the bacillus enteritidis sporogenes and organisms of the food- 

 poisoning group. The first is a normal inhabitant of the cow's 

 intestine, but the source of the latter group is more difficult to 

 trace. In each case serious intestinal symptoms may be caused 

 (see Chapter XV.). 



The Sterilisation of Milk. The danger arising from milk 

 being contaminated by disease organisms has caused much 

 attention to be paid to the subject of their destruction before 

 the milk is consumed. The only practical method here is 

 sterilisation by heat, and it is fortunate that practically all the 

 important organisms to be considered are non-sporing forms and 

 thus are relatively easily destroyed. To obviate the development 

 of the rather unpleasant taste caused by boiling milk, Pasteur 

 introduced the method of heating the milk for twenty minutes 

 to between 60 and 80 C. This usually kills all but about 5 

 per cent, of the organisms present and will dispose of most 

 streptococci, the tubercle bacillus, and b. diphtherias. Sporing 

 putrefactive forms, however, often survive, and unless the 

 pasteurised milk be rapidly cooled, the action of the process as 

 an economic preservative is largely nullified, more especially as 

 the protective milk-souring forms are destroyed. The boiling 

 of milk for two or three minutes will kill all harmful organisms, 

 and although some spores may survive, this is by far the most 

 useful sterilisation procedure on account of its easy domestic 

 application, the consumer very soon ceasing to notice the altered 

 taste. Boiling has been objected to on account of the destruction 

 of certain ferments, mostly of a proteolytic nature, present in 

 fresh milk. The value of these from a dietetic standpoint is, 

 however, at present undefined, and the only evidence that the 

 process of boiling is harmful lies in the fact that if very young 

 children on an exclusively milk diet be given boiled milk alone, 

 in a certain small number of cases scurvy results. The com- 

 parative rarity of this affection and the fact that it readily yields 

 to simple therapeutic measures makes it unworthy of consideration 

 in face of the serious dangers to which such young children are 

 exposed if they be supplied with ordinary milk. 



ANTISEPTICS. 



The death of bacteria is judged of by the fact that, when 

 they are placed on a suitable food medium, no development 



