PUBLIC PROBLEMS 183 



for detecting them. Stokes, using one method, concluded that 

 milk should be condemned if it contained more than 12 leuco- 

 cytes per field of the microscope when studied with a one-twelfth 

 inch immersion lens. 1 Stewart's method modified by Slack (see 

 page 285) gives slightly different results, and when this method 

 is used it has been assumed that milk should be condemned if it 

 contains 25 or more cells to the field, which is equivalent to 

 about 100,000 per c.c. 2 Doane's method of determining the 

 number of leucocytes is more accurate and uniform. As de- 

 scribed in experiment 18, it gives much higher numbers. 3 Doane 

 regards 500,000 leucocytes per c.c. as sufficient to render th^ 

 milk suspicious and 1,000,000 per c.c. as indicating inflamma- 

 tion of the udder. 



None of the methods yet devised can be regarded as very 

 accurate or satisfactory. Considerable variations are found in 

 successive determinations of the number of leucocytes in the 

 same specimen of milk, and there is certainly no knowledge at 

 hand to-day which enables us to say how large a number is 

 sufficient to suggest that the milk really contains pus. All that 

 can be said is that if the number per field of the microscope is 

 much beyond 25, or the number over 500,000 per c.c., the milk 

 may be regarded with suspicion. When mixed market milk 

 shows a large number of leucocytes, it probably indicates that 

 some of the cows supplying the milk are suffering from in- 

 flammatory troubles of the udder, and if the milk of a single 

 cow should show large numbers, it probably indicates inflam- 

 mation. But our information is, to-day, admittedly too small 

 to make the determination of much value, and as a means of 

 municipal examination of milk the determination of the number 

 of leucocytes is not very satisfactory. 4 



1 Stokes. Ann. Rep. of St. Bd. of H., Maryland, 1897, 1898 & 1901. 



2 Stewart. Am. Medicine, ix., p. 486. 

 Slack. Jour, of Infec. Dis., p. 214, 1906. 



'Doane. Bui. 102, Maryland Exper. Sta. 



Savage. Jour. Hyg., p. 123, 1906. 

 4 Rullmann and Trommsdorff. Arch. f. Ilyg., LIX., p. 224, 1906. 



