670 MILK. 



as food, and this proves that at least a part of the fat secreted by the 

 milk is produced from proteins or carbohydrates, or perhaps from both. 

 The question as to how far this fat is produced directly in the milk- 

 glands, or from other organs and tissues, and brought to the gland by 

 means of the blood, cannot be decided. 



The origin of milk-sugar is not known. MUNTZ calls attention to the 

 fact that a number of very widely diffused bodies in the vegetable king- 

 dom vegetable mucilage, gums, pectin bodies yield galactose as a 

 product of decomposition, and he believes, therefore, that milk-sugar 

 may be formed in herbivora by a synthesis from glucose and galactose. 

 This origin of milk-sugar does not apply to carnivora, as they produce 

 milk-sugar when fed on food consisting entirely of lean meat. The 

 observations of BERT and THIERFELDER l that a mother-substance of 

 the milk-sugar, a saccharogen, occurs in the glands, does not explain 

 the formation of milk-sugar, as the nature of this mother-substance 

 is still unknown. As the animal body has undoubtedly the power of 

 converting one variety of sugar into another, the origin of the milk- 

 sugar can be sought simply in the glucose introduced as food or formed 

 in the body. Certain observations of PORCHER indicate such an origin 

 as he found in sheep, cows, and goats whose mammary glands "were 

 extirpated, that glucose appeared in the urine after delivery. He also 

 found that milk secreting animals 'became glycosuric on the removal 

 of the mammary glands, and he explains this glycosuria by the fact that 

 the lactose-forming action of the gland was removed at the time of delivery, 

 when large amounts of glucose were being produced. The experiments 

 of KAUFMANN and MAGNE upon cows also indicate a formation of lactose 

 from glucose. They found that during secretion the glands took sugar 

 from the blood, so that the venous gland-blood was poorer in sugar than 

 otherwise. NOEL-PATON and CATHCART 2 have carried on experiments 

 on phlorhinized dogs which show a lactose formation from glucose. 



The passage of foreign substances into the milk stands in close connec- 

 tion with the chemical processes of milk secretion. 



It is a well-known fact that milk acquires a foreign taste from the 

 food of the animal, which is in itself a proof that foreign bodies pass into 

 the milk. This fact becomes of special importance in reference to such 

 injurious substances as may be introduced into the organism of the nurs- 

 ing child by means of the milk. 



Among these substances may be mentioned opium and morphine, 

 which after large doses pass into the milk and act on the child. Alcohol 



1 Muntz, Compt. Rend., 102; Bert and Thierf elder, footnote 1, p. 644. 

 2 Porcher, Compt. Rend. 138 and 141 and Bioch. Zeitschr., 23; Kaufmann and 

 Magne, Compt. Rend., 143; Noel-Paton and Cathcart, Journ. of Physiol., 42. 



