46 MILK HYGIENE 



the secretion consist, in part, of an admixture of blood 

 plasma that is usually invisible and, in part, of blood. 

 The latter may appear in freshly drawn milk as drops 

 of blood or as little clots. When more bleeding occurs, 

 the milk is liable to be diffusely colored reddish and it 

 will color the milk from the other quarters, and even 

 colors the milk of other cows reddish when mixed with 

 it. This admixture of blood cannot be proven by the 

 common guaiac method, for fresh milk will give the 

 same reaction. The proof is most easily gained by 

 means of microscopic examination of the sediment 

 obtained by centrifuging the milk, whereupon the red 

 blood corpuscles are easily recognized among the milk 

 globules. 



2. Udder oedema. It may be supposed that in udder 

 oedema, which frequently is very severe soon after calv- 

 ing, there is an admixture of transudate with the secre- 

 tion, but, so far as known, no investigations have been 

 made in regard to this matter. 



3. Embolism and thrombosis occur occasionally in 

 the udder and cause gangrene of a gland or of a part of 

 one ; frequently there is gangrene of the skin and of the 

 teat of the quarter affected. Milk secretion ceases and 

 in its place there is a bloody serous exudate. 



4. Mastitis. Inflammations of the udder cause quite 

 characteristic changes in the secretion, which often stops 

 entirely to give place to a purulent exudate. 



a. Mucous catarrh. When drawn, the milk contains 

 small yellowish flakes and lumps which, upon standing, 

 unite into a slimy, dirty, grayish sediment or, together 

 with the cream, form a lumpy, dirty colored layer on the 

 top of the milk. In severe attacks the secretion may be 

 viscid, slimy and sticky. 



b. Purulent catarrh. In the beginning, the secretion 

 is unchanged but for the presence of small flakes of pus 



