652 OF SECRETION. 



I. II. III. 



Water SS3-G 914-0 861-4 



Butter 25-3 54-0 8'0 



Caseine 34-3 45"2 19'6 



Sugar of Milk and Extractive Matters 48'2 G2-4 39'2 



Fixed salts 2-3 2-7 1-G 



It also appears from the analyses of Simon, that the proportion of the differ- 

 ent ingredients is liable to variation, according to the time which has elapsed 

 since parturition. The quanthy of Caseine is at its minimum at the com- 

 mencement of 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 

 recent 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, 

 favour its passage into the milk. The proportion of Caseine, on the other 

 hand, is increased by exercise ; which would seem to show that this ingre- 

 dient is derived from the disintegration of Muscular tissue, and thus adds 

 strength to the Author's view ( 681) that of the matter thus set free, a part 

 only is destined to immediate excretion, and that a part may again be 

 subservient to the operations of Nutrition. Dr. Playfair's experience on this 

 head seems to correspond with the results of common observation in Swit- 

 zerland, where they pasture cattle 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. 



856. The change which naturally takes place, from the condition of Co- 

 lostrum to that of true Milk, during the first week of lactation, is a very im- 

 portant 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. Oc- 

 casionally, however, the colostric character is retained by the milk, during 

 an abnormally long period; and the health of the infant is then severely af- 

 fected. It is important to know that this may occur, even though the milk 

 may present all the usual appearances of the healthy secretion ; but the mi- 

 croscope at once detects the difference.* 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 indicate 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 ;t and every medical man is familiar with the injurious 

 consequences, to which she renders herself liable by unduly prolonging lac- 

 tation.:): 



* See Donne, "Du Lait, et en particulier oelui des Nourrices;" and Brit, and For. Med. 

 Review, vol. vi. p. 1S1. 



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

 excellent little \vork of Dr. A. Combe, formerly referred to. 



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



