344 MILK AND MILK PRODUCTS. XIV. 



The use of preservatives of any kind is probably not a 

 wholesome practice, for though the growth of most of the 

 micro-organisms' is prevented, all change is not stopped. 

 Moreover there is considerable probability that, with children 

 particularly, the use of preservatives is attended with danger 

 to digestion. Many of the substances used as preservatives 

 have been shown" to have an injurious action upon digestive 

 enzymes. 



Sodium carbonate or bicarbonate is sometimes added to 

 milk as a preservative. In reality it does not thus act, but 

 merely prevents the lactic acid, formed by fermentation, from 

 coagulating the casein, and by neutralising the acid as fast as 

 it is formed, probably aids the change of the sugar into lactic 

 acid. 



Milk as a Medium for the Spread of Disease. Milk is 

 peculiarly well fitted as a nutrient for the .growth of micro- 

 organisms. As has already been stated, the number of orga- 

 nisms present in ordinary samples is enormous. Fortunately 

 the majority of these bacteria are harmless so far as their 

 effect upon health is concerned, but unfortunately milk very 

 readily acts as a conveyer of pathogenic organisms. 



Diphtheria, scarlet fever, typhoid, and especially tubercu- 

 losis! have been in many instances communicated by milk. 

 Careful Pasteurisation of all milk is greatly to be desired, and 

 already dairies are being started in various parts of England in 

 which the milk is submitted to a modified Pasteurisation. 

 The milk is heated in bulk to a temperature of 60 to 65 and 

 maintained at this temperature for 20 minutes, then quickly 

 cooled and sent out to the consumer, best in closed glass 

 bottles. Eussell has lately shown that the tuberculosis ba- 

 cillus may be destroyed by heating to 60 for 20 minutes, 

 provided the milk is heated under such conditions (with con- 

 stant agitation and in a close'd vessel) as to prevent a pellicle 

 forming on the surface.^ The advantages of using a low 



* Leffmann, Jour. Franklin Instit. lbi9, 97. 



t It has recently been asserted that bovine tuberculosis is probably not communi- 

 cable to man ; but, though the opinion is that of the great authority, Koch, it is not yet 

 generally accepted. 



} v.Tke Times, Feb. 25th, 1901. 



