LACTATION 567 



for the child. Violent emotion or shock have been known to 

 lead to the complete suppression of the mammary secretion.^ 

 The employment of certain drugs also influences it. Thus 

 atropine, if given in sufficient quantities, stops the secretion 

 altogether, or if supphed in smaller amounts causes the milk to 

 become more concentrated. 



The occurrence of menstruation in women, or of heat in 

 certain animals, may have a deleterious influence upon the milk, 

 and so upon the offspring (see p. 334). In the case of cows, 

 oestrus generally has a marked effect on the milk-yield, which as 

 a rule shows at first a perceptible diminution, followed usually 

 at the next milking by a yield weU above the average. The fat 

 content is generally at first considerably reduced, but at the 

 following milking is sometimes abnormally high, or may be still 

 abnormaUy low. On the two or three days preceding the 

 outward manifestations of heat, the fat content tends to be 

 decidedly above the average. 



Castration is stated to have a beneficial effect upon goat's 

 milk, reheving it of the characteristic hircine odour, increasing 

 the quantity of butter, casein, and phosphoric acid (though 

 decreasing the lactose present), and producing a greater and 

 more long-continued secretion.^ The removal of the ovaries 

 in cows may also tend to improve the quality of the milk, 

 rendering it richer than when the animals have been some 

 months pregnant.^ 



The advance of lactation may be accompanied by changes 

 both in the amount and in the composition of the mammary 

 secretion, but the changes vary greatly in different individuals. 

 In cows, the milk fat secreted in the fiirst few days after parturi- 

 tion is poor in volatile acids, but it tends to improve rapidly 

 during the first few months, the improvement being maintained 

 until near the close of the lactation period, i.e. in most cases 

 near the approach of the next parturition.* 



' Williams, loc. cit. 



'"■ Oceanu and Babes, "Les Effets Physiologiques de I'Ovariotomie," 

 C. B. de I'Acad. des Sciences, vol. cxl., 1905. 



' Wallace, loc. cit. 



* In cows which are " drying off," the percentage of volatile acids in 

 the butter fat is very low. See Crowther, loc. cit. 



