132 THE BACTERIAL CONTENT OF MILK 



We submit this table with all the more confidence in that we 

 had occasion to repeat several portions of it subsequently, and 

 although the figures, of course, differed materially, the same kind 

 of changes were invariably exhibited. It will be understood that 

 the milk was ordinary country milk, and offered no complications 

 or any special sources of contamination. We do not suggest that 

 great emphasis can always be laid upon experimental records of 

 this nature, and it would be undesirable to draw, from such data, 

 conclusions of a far-reaching nature. There are, however, one or 

 two points to which attention may be drawn, and which, we venture 

 to think, have a somewhat wide application in the study of milk. 



First, it will be noted that there was an extremely rapid in- 

 crease in organisms in the first four hours, particularly at 37° C. A 

 slight fallacy occurs (as regards 5° and 15°) respecting this point, in 

 that the milk would not fall immediately from 34° C , which tempera- 

 ture it was at the time of milking, to the two standards of 5° and 

 15°; and hence in all probability it should be assumed that the 

 increase from 812,000 to 2,066,000 in four hours at 5° is exceptional. 



Secondly, speaking in a general way, the following great prin- 

 ciple appears to emerge, namely, that there is at each temperature 

 {a) a sudden rise, ib) a sudden fall, {c) a steady rise to maximum, 

 and {d) a steady fall ultimately to sterility. In other words, 

 there are tides of organisms, and we have found this to occur in- 

 variably in our study of " natural " milks. We do not suggest that 

 it is an invariable phenomenon in all milks, but rather that it is 

 the rule in respect to " natural " milk examined immediately after 

 milking. It is obvious that if we had commenced our examina- 

 tion, as is frequently the case in the study of town milks, twelve 

 or twenty hours after milking, we should, even if we had obtained 

 the same figures, have drawn very different deductions, because 

 the initial rise and initial fall would have been lost sight of 



Thirdly, it will be seen that the maximum number of bacteria 

 occur in seventy-two hours at 37° C, six days at 1 5^" C, and ten days j 

 at 5°C.,and that the maximum is lowest at blood heat and highest | 

 at 5° C. It is evident, therefore, that what occurs in a short time I 

 at a high temperature occurs in a longer period at a low tempera- 

 ture, but at a low temperature the bacteria eventually become 

 most numerous. These facts are of great importance in relation 

 to the time which milk is kept before use, and to the injurious 

 properties which it may acquire during such a period in the 

 direction of increased bacterial toxin production. 



Fourthly, marked acidity commenced between the twelfth and 



