Chemical Preservatives 393 



enough not to interfere with the digestive processes, 

 yet large enough to hinder the multiplication of bacteria 

 in milk. It has been found that market milk that will 

 ordinarily sour in twenty-four to twenty-eight hours, 

 will remain uncurdled at the same temperature for forty- 

 eight to seventy-two hours when treated with formal- 

 dehyde at the rate of one part to 40,000 parts of milk. 



Since the experimental evidence at present available 

 gives us no reason to think that formaldehyde in this 

 proportion will prove injurious even to young children, 

 it follows that, under certain conditions, its use may be 

 found justifiable. A number of authorities state! that 

 formaldehyde, employed in the proportion of one to 

 40,000, or even in somewhat larger proportion, does not 

 affect the action of the digestive ferments, nor does it ' 

 decrease the digestibility of the food used. 



They show, likewise, that the addition of formal- 

 dehyde, in the proportion indicated, to milk, retards 

 the growth of the bacteria, but that the retarding effect 

 is not the same in the case of the different species. 

 It appears that the harmless lactic-acid bacteria are 

 comparatively resistant to the action of the formalde- 

 hyde,, as was evidenced in the samples in which the pro- 

 portion of formaldehyde was one to 5,000, or one to 

 10,000. The. law should not. allow the use of formalde- 

 hyde, of hydrogen peroxide, or . of other preservatives 

 in milk even within supposedly safe. limits, lest some one 

 be tempted to employ larger amounts. Then, too, the 

 addition of preservatives, even in quantities otherwise 

 permissible, would tend to encourage slovenly methods 

 in the production and handling of milk. 



