44 MILK 



species and, in a measure, in different individuals. Lactation is a 

 necessity among animals who depend for food-supply upon the 

 mother for some time after birth. With development of the di- 

 gestive tract other food becomes available, and the duration of 

 lactation, therefore, is conditioned by the length of time required 

 by the young mammal to become self-dependent. As the animal 

 develops and begins to take increasing quantities of other food the 

 demand upon the mother decreases and milk secretion gradually 



ceases. 



It is not uncommon to find mothers who are able to produce 

 milk for twenty to twenty-four months. Pfaundler, in Sommer- 

 feld's Handbuch, mentions that some Indian tribes nurse for two 

 to twelve years, and tribes of Eskimos for fourteen to fifteen years. 

 These figures are probably extreme, while the actual duration of 

 lactation is no doubt rtiuch shorter. It is possible, of course, that 

 some tribes nurse their children for longer periods than others. 



The total quantity of milk produced during a lactation period 

 is dependent, as a rule, upon the number of infants nursed. If a 

 mother nurses one child the quantity is less than if more are nursed. 

 Pfaundler gives the following approximate figures: A woman nurs- 

 ing one child produces — 



During a 6 month period about 1.25 to 1 50 hectoliters. 

 During a 7-month period about 1,50 to 2 " 



During an 8-month period about 2 to 2.5 " 



Wet-nurses who nurse two or more babies produce — 



During a 6-month period about 3.5 hectohtera. 



During a 12-month period about 8 " 



During a 24-month period about 15 or more hectohtera. 



The statement is sometimes made that among civilized nationS 

 nursing is becoming less the rule than heretofore. Since compara- 

 tive statements are difficult to obtain, it cannot be determined 

 with accuracy whether the assumption is correct. . It is true that 

 more babies thrive on bottle feeding than formerly, but this does 

 not prove that breast feeding is less common, since science has 

 taught us how to raise children successfully by artificial feeding. 

 On the other hand, it may be argued that modern social conditions 

 compel many women to work for a livelihood, frequently under un- 

 sanitary conditions and at low wages, and that neglect or inability 

 to nurse their offspring is a consequence. Furthermore, it is 

 claimed that among certain classes there is a growing disinclir^a- 

 tion to nurse. It is difficult at present to form a decisive opinion 

 on a subject which can be cleared up only by carefully compiled 

 statistics covering a" long period of time. 



At the present time the cow is the chief milk producer for the 



