No. 4.] MILK AND CREAM. 347 



These cisterns, four in number, situated above each teat, 

 extend upwards into the gland and downwards almost to the 

 end of the teat. The teats, two for each milk gland, are 

 encircled at the lower end with numerous fibres, forming the 

 sphincter muscle, which prevents the escape of the milk 

 under ordinary conditions. 



The individual lobules are enveloped in connective tissues, 

 which unite them in a glandular mass, and this connective 

 tissue is in turn covered with adipose tissue, and the whole 

 udder is enveloped by the skin. 



Formation of Milk. 

 In spite of the many investigations concerning the forma- 

 tion of milk there is very little positive knowledge on the 

 subject. Previous to 1840 it was held that the milk glands 

 separated the materials for the formation of milk directly 

 from the blood. Later it was proved that none of these ma- 

 terials existed ready formed in the blood, so the above the- 

 ory was abandoned. The second theory was suggested by 

 Virchow, formulated by Will, and supported by Viot. They 

 claimed milk to be a fatty degeneration of the epithelial cells 

 of the alveoli, — a liquefied cell substance. Heidenhain op- 

 posed this view, and claimed that the epithelial cells do not 

 sutler degeneration, but rather only their free ends, the re- 

 newal of the cell material taking place at the opposite end. 

 C. Partsch holds that the formation of milk fat is not a result 

 of fatty degeneration, "but rather a special activity of the 

 cell in the true sense of the word." 



Rauber advanced the idea, as a result of his studies, that 

 the fat, casein and milk sugar are derived from the white 

 blood corpuscles. He claims that the lymph rather than the 

 blood vessels are found in direct contact with the alveoli, and 

 that the white blood corpuscles are diffused through the veins 

 and the lymph vessels and then further into the epithelial 

 cells, and there are transformed into the various milk 

 constituents. 



It is probable that the milk is not gradually formed and 

 stored in the udder during the day, but rather that the epi- 

 thelial cells of the alveoli become very much enlarged with 

 various substances going to form the milk, and that just pre- 



