EFFECT OF THE NEBVES ON THE MILK. 765 



however, increases the relative amount of casein. Both in the human 

 subject and in animals, the nature of the food, and the quantity of 

 water taken in, or with it, must directly influence the specific gravity, 

 the amount of solid matter, and the relative quantities of the several 

 ingredients of the milk. -It has been observed in the cow, that the 

 last milk drawn, at any one time of milking, is richer than the first. 



The influence of the nervous system in modifying the quantity and 

 quality of the milk, is most important, and universally recognized. 

 Irritation of the nipple increases, by a reflex influence, the flow of 

 milk ; this is probably one cause of the rapid flow of the secretion 

 during the act of suckling. Continued local irritation, combined with 

 a strong desire for the occurrence of lactation, and a fixed attention 

 towards the mammary glands, have been known to produce this secre- 

 tion in women not recently mothers, to protract its flow for many 

 years, to excite it in aged women and in girls, and even, it is said, in 

 individuals of the male sex. In that sex, usually, however, the rudi- 

 mentary glands yield only occasionally, a thin clear fluid, the com- 

 position of which is uncertain. The influence of the nervous system, 

 as affected by mental states, upon the secretion of the milk, is further 

 evinced by the abundant flow, the so-called draught, often excited by 

 the sight, or even by thinking of the infant. Tranquil and pleasing 

 emotions favor the normal secretion; but anger, anxiety, grief, and 

 terror may produce serious modifications in the quality of the milk, or 

 may even suspend its formation. Violent passions may induce such 

 changes in this secretion, as to cause it to be poisonous, and even im- 

 mediately fatal to the infant. This probably arises from some modifi- 

 cation in the blood (p. 732). 



To secure the healthy performance of the function of lactation, an 

 ample amount of nutritious food, moderate exercise, tranquillity of 

 mind, and regular habits, are necessary conditions ; a defective or ex- 

 cessive diet, fatigue, and irregularities and excesses of all kinds, are 

 unfavorable. The influence of alcoholic stimulants, in moderation, is, 

 by promoting digestion indirectly, favorable to the supply of milk. 

 Medicinal agents, especially those of a powerful kind, should be 

 avoided ; many of them enter the milk, and may thus affect the child. 

 Mineral and saline substances, and the alkaloids, such as quinine and 

 morphia, pass more readily into the milk than vegetable aperients. 



The peculiarities in the milk of the cow and other animals, as compared 

 with human milk, are interesting in a dietetic and economic point of view : 



Woman Cow Goat Sheep A.BH Mare 



(Simon) (Simon) (Chevalier) (Chevalier) (Simon) (Luciscus) 



Water, 890 860 868 856 907 888 



Solid matters, .... 110 140 132 144 95 112 



Butter, 25 38 33 42 12 8 



Casein, 35 68 40 45 16 16 



Sugar, with extractives, . 48 30 53 50 { ^ ft o 



Salts, ....... 2 6 6 7 1 



According to this Table, the milk of the goat more closely resembles, in 

 chemical composition, the human milk than does that of any other animal ; 

 but it has been found that, besides having a peculiar odor, its curd is remark- 

 ably compact. The milk of the sheep differs a little more from human milk. 



