THE PHYSIOLOGY OF MILK SECRETION WITH NOTES 



ON THE EFFECT OF FOODS, DRUGS, EXPOSURE, 



EXERCISE AND ABNORMAL BODILY 



CONDITION. 



BY A. W. BITTING, M. D. , INSPECTOR, CITY BOARD OF HEALTH, LABORATORY 

 OF COMPARATIVE PATHOLOGY, INDIANA AGRICUL- 

 TURAL EXPERIMENT STATION. 



Lafayette, Ind. 



In reproduction among the higher animals, the offspring at birth are 

 not sufficiently matured to be able to subsist alone; neither are they sur- 

 rounded by food that is already prepared for them. It is therefore necessary 

 that Nature should provide for a part or whole dependence upon the mother 

 for subsistence, during such time as is required for development to a state* 

 capable of independent existence. As a means to this end we find a mam- 

 mary gland in a very large group of animals, the secretion from which is 

 known as milk, and is a perfect food. Milk contains all the nutriment 

 required by a growing body, in proper proportions, in a palatable and easily 

 digestible form. For these reasons persistent efforts have been made 

 to domesticate animals and develop this function to the highest degree 

 as a source of food for people. How successful these attempts have been 

 is exemplified in the milking capacities of several animals now used for 

 this purpose. Animals in a wild state furnish a quantity of milk only 

 sufficient for the young, and only for such time as is necessary for their 

 maintenance. Under domestication, the cow in particular, has been de- 

 veloped to produce a quantity sufficient to support several offspring, and 

 to keep up the secretion almost continuously. 



The mammary gland being an accessory organ of generation, it is 

 but natural that it should be rudimentary at birth and without function. 

 It remains in this condition until the reproductive function becomes active, 

 at which time it begins to develop quite rapidly, and continues to do so 

 until the end of the first period of gestation. Like other organs of the 

 body, it grows with the general growth, and from usage. Its functional 

 activity does not ordinarily begin until near the close of the period of 

 gestation, reaches its maximum at from ten to fifteen days thereafter, and 



