386 MILK AND THE PUBLIC HEALTH CHAP. 



example, Eothschild and Netter 1 concluded from their investi- 

 gations that the addition of 1 : 10,000 formaldehyde retarded 

 the lactic acid bacilli sufficiently for practical purposes, but that 

 the increase of the other saprophytic bacteria and the patho- 

 genic varieties is not sufficiently checked. 



Chako, using the number of bacteria as the test, found that 

 in milk containing 1 : 10,000 formaldehyde a slight diminution 

 resulted during the first twenty-four hours, followed by a slow, 

 then a very rapid increase in the germ-content. In milk con- 

 taining 1 : 20,000 formaldehyde there was a slow diminution 

 for the first twenty-four hours, followed by a rapid increase. 

 In milk containing 1:40,000 formaldehyde the bacteria 

 developed nearly as rapidly as in the control milk free from 

 preservative. 



The quantities of these preservatives actually found in 

 milk show wide variations. They have usually been found to 

 be markedly in excess of the amounts which experimental 

 determinations have shown to be required to preserve milk for 

 twelve to twenty-four hours. Thresh and Porter 2 give the 

 following table, compiled from the Eeport of the Departmental 

 Committee, showing the maximum and minimum quantities of 

 boric acid which have been found by different observers in 

 milk. 



Thorpe compiled for the Departmental Committee a list 



1 Revue cT hygiene et de me"d. inf. ami. de la polyclinique H. de Rotschild, 

 1905, iv. No. 4. 



2 Preservatives in Food and Food Examination, 1906, p. 102. 



