OF LACTATION. 1025 



lactation, and then gradually rises until it attains a nearly fixed proportion. 

 The quantity of Sugar, on the contrary, is at its maximum at first, and gradually 

 diminishes. The amount of Butter (as appears from the wide extremes shown 

 in the above tables) is more variable than that of any other constituent. That 

 some of the variations are due, moreover, to the character of the ingesta, and 

 others to the external temperature, amount of exercise, and other circumstances 

 affecting the individual, is proved by the inquiries of Dr. Playfair upon the 

 Milk of the Cow. He has shown that the amount of butter depends in part 

 upon the quantity of oily matter in the food, and in part upon the amount of 

 exercise which the animal takes, and the warmth of the atmosphere in which it 

 is kept : exercise and cold, by increasing the respiration, eliminate part of the 

 oily matter in the form of carbonic acid and water ; whilst rest and warmth, by 

 diminishing this drain, favor its passage into the milk. The proportion of 

 Casein, on the other hand, is increased by exercise. Dr. Playfair's experience 

 on this head seems to correspond with the results of common observation in 

 Switzerland ; for where the cattle pasture in very exposed situations, and are 

 obliged to use a great deal of muscular exertion, the quantity of butter yielded 

 by them is very small, whilst the cheese is in unusually large proportion ; but 

 these very cattle, when stall-fed, give a large quantity of butter and very little 

 cheese. 



1026. The change which naturally takes place, from the condition of Colos- 

 trum to that of true Milk, during the first week of lactation, is a very import- 

 ant one. The Colostrum has a purgative effect upon the child, which is very 

 useful in clearing its bowels of the meconium that loads them at birth ; and thus 

 the necessity of any other purgative is generally superseded. Occasionally, 

 however, the colostric character is retained by the milk, during an abnormally 

 long period ; and the health of the infant is then severely affected. It is im- 

 portant to know that this may occur, even though the milk may present all the 

 usual appearance of the healthy secretion ; but the microscope at once detects 

 the difference. 1 The return to the character of the early milk, which has been 

 stated to take place after the expiration of about twelve months, seems to indi- 

 cate that Nature designs the secretion no longer to be encouraged. The mother's 

 milk cannot then be so nutritious to the child as other food; 3 and every medical 

 man is familiar with the injurious consequences to which she renders herself 

 liable, by unduly prolonging lactation. 3 Cases are not unfrequent, however, in 

 which the secretion continues as long as there is a demand for it ; and sometimes 

 quite independently of this. It is the habit, among some nations, to suckle 

 the children until they are three or four years old, and to continue doing so even 

 though another pregnancy should supervene ; 4 so that the older child is only dis- 

 placed by the arrival of another infant. And it seems to be chiefly among those 

 who have thus forced the mammary gland into a state of unnaturally persistent 

 activity, that the spontaneous and irrepressible flow continues, after the demand 

 for it has ceased. 5 



1 See Donne, " Du Lait, et en particulier celui des Nourrices," and " Brit, and For. Med. 

 Review," vol. vi. p. 181. 



2 On the whole subject of Infant Nutrition, the Author would strongly recommend the 

 excellent little work of Dr. A. Combe, formerly referred to. 



3 One of these, which has particularly fallen under the Author's notice, is debility of the 

 retina, sometimes proceeding to complete amaurosis : this, if treated in time, is most com- 

 monly relieved by discontinuance of lactation, generous diet, and quinine. 



4 See Erman's " Travels in Siberia" (translated by Cooley), vol. ii. p. 527 ; and the 

 "Narrative of the United States' Exploring Expedition," vol. ii. p. 138. 



5 Thus Dr. Green has published (" New York Journ. of Med. and Surg.," Sept. 1844) 

 the case of a lady, aet. 47, the mother of four children, who had an abundant supply of 

 milk for twenty-seven years previously. A period of exactly four years and a half occurred 



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