2 9 6 



MILK AND ITS HYGIENIC RELATIONS 



etc. They all, however, agree in the main principles. These 

 consist of a vessel which contains water and is of a sufficient depth 

 for the bottles to be immersed in the water up to the neck. After 

 heating to the required temperature, the bottles can be removed 

 together in the carrier, and plunged into cold water. 



Some form of stopper or cap for the bottles is usually provided. 

 In some cases the teat is put on the bottle before the heating is 

 commenced, but it is not unusual for a plug of cotton wool to be 

 placed in the neck of the bottle, this plug being subsequently 

 removed and the teat placed on the bottle at the time of feeding. 

 Where the milk has to be diluted or modified in any way, this 

 modification is carried out before the heating is commenced. In 

 practice it is not easy to ensure that the milk shall be heated only 

 up to a definite temperature. A rise of temperature in the water 

 does not show the precise temperature of the milk. Further, it 

 would be necessary to watch the apparatus the whole time, 

 otherwise it is likely that the temperature would frequently be 

 exceeded. 



The figures obtained by Freudenreich and by Rosenau show 

 that in practice it would be impossible to determine the precise 

 temperature for the milk in the bottles. There is considerable 

 difference in temperature between the water and the milk in the 

 bottles, and further between the temperature of the milk in different 

 parts of the bottles. Hence it is usual in practice to allow the 

 water in the vessel to boil, and in some cases the water is allowed 

 to boil for a few minutes. The figures given by Rosenau show 

 that the temperature of the milk is much below that of the water, 

 even when the water has been allowed to boil for over three minutes. 



Freudenreich's figures are as follows : 



The following figures afford an illustration of the results of 

 numerous experiments performed by Rosenau. 

 Experiment 



Quart mixed market milk. 



Bottle immersed in water to lip. 



Distinct cream-line from standing at least five hours. 



