EXPERIMENT STATION WORK RELATING TO PURE MILK. 283 



have been jiroposed, one of whicli has been studied and develoj)ed 

 by Doane." 



Doane's investigations Avere concerned primarily with the occur- 

 rence and significance of leucoc3^tes or pus cells in milk. Leucocytes^ 

 are white blood corpuscles, and as such are, of course, a perfectly 

 normal constituent of the blood. They are not, however, confined 

 entirely within the l)lood vessels. They may be found in nearly 

 every tissue and fluid of the body, and hence are often called wan- 

 dering cells. In all acute inflannnations they are present in large 

 numbers. The solid matter in pus, which is a product of inflamma- 

 tion, is composed mainly of dead leucocytes. The presence of leu- 

 cocytes in milk has long been known. They have often been referred 

 to as normal and often as abnormal constituents. Doane nought to 

 ascertain whether or not leucocytes are constantly present in the milk 

 of healthy cows and. further, if their presence in large numbers may 

 be accepted as proof of disease in the udder and hence a basis for the 

 condenmation of milk. 



The method employed in counting the leucocytes consisted in cen- 

 trifuging for 4 minutes 10 cubic centimeters of milk in a graduated 

 sedimentation tube at an a})proximate speed of 2,000 revolutions per 

 minute, removing the layer of fat with a swab of absorbent cotton, 

 centrifuging for 1 minute and repeating the eiforts to remove all the 

 fat, which interferes seriously with the success of the method, siphon- 

 ing the milk to within one-eighth of an inch of the sediment, stain- 

 ing by the addition of two drops of a saturated alcoholic solution of 

 methylene blue with sufficient shaking to secure a thorough mixing 

 of the contents, heating two or three minutes to facilitate the action 

 of the stain, making up to the 1 cubic centimeter mark by the addi- 

 tion of w'ater, and finally putting this mixture into the blood counter 

 and ascertaining the number of leucocytes in the entire field in the 

 way ordinarily followed in blood work in clinical laboratories. Mul- 

 tiplying the number of leucocytes in the counter by 1,000 gives the 

 number of leucocytes in 1 cui)ic centimeter of the milk sample. 



'I'll is method was applied by Doane to the milk of the dairy herd 

 of the Maryland Experiment Station. The leucocytes in the milk 

 of individual cows on December 15, January 4, and March 1 num- 

 l)ered for cow Xo. 39, 37,000, 400,000, and 190,000 per cubic centi- 

 meter; cow No. 50, 180,000, 10,000, and 300,000; cow No. 5G, 1,000,- 

 ()()(). l.C.OO.OOO. and 27,000; cow No. 78, 70,000, 17,000, and 124,000; 

 cow No. 80, 47,000, 480,000, and 52,000; cow No. 8(), 200,000, 040,000, 

 and 214,000, and cow No. 87, 3-i0,()00, 11,000, and 28,000. These 

 figures are cited merely afi illustrations. Leucocytes were invariably 

 present, their munbers ranging from 3,000 to 1,000,000 per cubic 

 centimeter. 



oMiiryliiiul Slii. I'.ul. 102. 



