SECTION V 

 THE SECRETION AND PROPERTIES OF MILK 



LACTATION 



DURING pregnancy the foetus obtains the whole of its nourishment from the 

 mother by means of the placenta. After birth the quality of the nutriment 

 supplied to the young child depends on the activity of the cells of the 

 mammary glands. Now, however, nutrition involves further activity on the 

 part of the young animal, the alimentary canal being concerned in the diges- 

 tion of the milk supplied by the mother, and the excretory organs, especially 

 the kidneys, being made use of for getting rid of waste material. The 

 preparation of the mammary glands for the subsequent nourishment of the 

 new-born child begins in the first month of pregnancy, and is marked by 

 swelling of the glands, rapid proliferation of the duct epithelium, and 

 production of many new secreting alveoli. The developing of these 

 glands in the rabbit has been already described, and there is no doubt 

 that in the human species the process follows very much the same 

 course, being, however, spread over nine months instead of four weeks, 

 as is the case with the rabbit. During the latter half of pregnancy 

 a watery fluid can generally be expressed from the nipple. In certain 

 mammals this watery secretion gives place to a secretion of true milk at the 

 end of gestation or during the process of parturition itself. In the woman 

 the secretion does not begin as a rule until the second or third day after 

 birth, though the formation of milk may be anticipated if a child has been 

 put to the breasts during the latter part of pregnancy. Secretion begins on 

 the second or third day, even if the child has been born dead and no attempt 

 at suckling has taken place. For the maintenance of the secretion the 

 process of suckling is absolutely necessary. If the woman does not nurse 

 her child, the swelling of the breasts gradually passes off, the milk disappears, 

 and the glands undergo a process of involution. Under normal conditions 

 the secretion of milk lasts for six to nine months and may in rare cases extend 

 over more than a year. The amount secreted increases at first with the 

 growth and size of the child. The Table on p. 1238 represents the average 

 amount of milk secreted during the thirty-seven weeks after birth. It will, of 

 course, be greater with strong, big children, and smaller with weakly children. 



COLOSTRUM. Before the secretion of true milk begins, the fluid which 

 is obtained from the breast is known as colostrum. It may be expressed 

 from the breasts immediately after birth and is ingested by the child during 



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