DAIRY FARMING DAIRYING. 273 



.'1 result of in.j<'cti<in dept'iids on tin' pi'viod of liu-taliou and also on tlic state of 

 nutrition, 'j'liis together with other cousideratious supports the view that it is 

 not variations in the conditions of the pituitary gland which give rise to tlio 

 cycle of changes which occur in the mammary gland. Histological evidence 

 points to a dli-ect action of the extract on tlie glandular epithelium. The tiat- 

 teued appearance of the cells of the full alveolus is caused by the expansion 

 which they have to undergo when the lumen becomes filled with milk. 



" The milk obtained as a result of injection is normal in composition except 

 for a higher percentage of fat; in the following milklngs. however, there is a 

 drop in the percentage of fat although that of the other constituents remains 

 normal. While the solids-not-fat (proteins, lactose, and ash) are secreted in 

 close connection with the water of the milk, the amount of fat secreted is in no 

 wise connected with the amount of water. The ratio 'nitrogen to lactose' is 

 relatively constant throughout. These facts suggest the theory that the 

 pituitary extract causes the combination of the precursor of milk protein and 

 lactose (possibly a glycoprotein) with water and salts of the blood, and so by 

 a purely secretory action produces this i)art of the milk. The suddenly altered 

 tensions so set up in the eiiithelial cells cause the fat globules which have 

 accumulated at the ends of the cells to be discharged and to produce milk which 

 is rich in fat. It is because of the relatively large amount of the pituitary ex- 

 tract injected and because of the suddenness of the change that the fat per- 

 centage goes up. The act of milking, which also causes rapidly altered ten- 

 sions, has the same effect. 



"Although there is considerable variation, yot the average results on varying 

 the dose of ])ituitary extract injected show that the smaller doses give less 

 milk with a lower percentage of fat. When the doses are relatively large it 

 does not matter how much is injected, for only a certain amount of milk can 

 be obtained. There is some indication that a goat in the early stages of lacta- 

 tion is more sensitive to small doses than one in a later stage. Experiments 

 with fractional milkings show that while the percentage of fat rises from 

 start to finish in normal milk, yet in milk obtained as a result of injection the 

 percentage remains constant throughout." 



Carotin, the principal natural yellow pigment of milk fat: Its relations 

 to plant carotin and the carotin of the body fat, corpus luteum, and blood 

 serum, L. S. Palmer and C. H. Eckles (Jour. Biol. Chem., 17 (191//), No. 2, 

 pp. 191-249, fig. 1). — This work comprises 5 papers. 



I. The chemical and physiological relation of the pigments of milk fat to the 

 carotin and xanthophylls of green planta (pp. 191-210). — The object of the in- 

 ■\estigation here reported was to classify the milk-fat pigment, not only as a 

 true lii)ochroioe, but also with respect to its rekuion to the cai'otin and xantho- 

 phylls of green plants, and to determine the relative influence of certain fac- 

 tors, such as character of ration and breed of cow, upon the color of the butter. 

 It was observed that " the fat of cow's milk owes its natural yellow color to 

 the pigments carotin and xanthophylls, principally carotin, the well-known, 

 widespread, yellow vegetable pigments found accompanying chlorophyll in all 

 green plants. The carotin and xanthophylls of milk fat are not synthesized in 

 the cow's body, but are merely taken up from the feed and subsequently .secreted 

 in the milk fat. 



" When feed practically free fron. carotin and xanthophylls, such as the cow 

 usually receives during the winter months, is given to a milk-giving cow, the 

 immediate supply of these pigments in the organism is greatly depleted and may 

 be entirely used up, on account of the constant drain upon the supply by the 

 milk glands. The butter fat accordingly approaches a colorless condition in pro- 

 portion to the supply of carotin and xanthophylls in the system, the length of 



