228 ACTION OF THE MAMMARY GLAND. 



Saline substances administered by the stomach or rectum do not al- 

 Extraneous ways appear in the milk ; thus the ferrocyanide of potassi- 

 saits in milk. unlj w hich may be quickly detected in the urine, can not be 

 found in the milk. It is curious, that when iodide of potassium has been 

 administered to the mother, in doses, for example, of three grains thrice 

 a day, it can be readily detected in the urine of the infant by the usual 

 test of starch and nitric acid. 



The diurnal quantity of milk yielded by the human female has been 

 Diurnal quan- estimated at from 32 to 64 ounces. This estimate is made 

 tity of milk, ^y determining the weight of the infant before and after suck- 

 ling. Although a certain proportion is present in the gland, the secre- 

 tion appears to take place for the most part with great rapidity. On the 

 application of the infant the blood flows suddenly, and the milk pours 

 into the ducts, constituting what is termed the draft. 



We now enter on a consideration of the function of the mammary 



Mode of action g^ an< ^ w ^ n a v ^ ew ^ determining whether it acts in virtue 



of the mamma- of its special construction, whether it fabricates in itself, by 



the agency of cells, the proximate constituents of milk, or 



whether it merely strains them from the blood in which they pre-exist. 



Due weight should here be given to the fact that, unlike the excretions 

 of the lungs, the kidneys, or even the liver, the milk contains a very large 

 percentage of histogenetic or formative bodies. Its casein can not be 

 considered as in the career of retrograde transformation, since in the body 

 of the infant it is presently changed into albumen. Such a fact might 

 even lead us to suspect that we should detect some essential structural 

 and functional differences between the mammas and other glands. 



The influence of special structure is, however, disposed of by the nu- 

 livfluence of merous well-authenticated cases now on record, in which por- 

 speciai struc- tions of the skin, or the stomach, the navel, intestines, the ax- 

 illa, and glands in the groin have assumed a vicarious action, 

 and secreted milk ; and though it has been said of the latter instance that 

 it may be nothing more than an obscure manifestation of an attempt in 

 the human species at a repetition of the mammary gland in a region near 

 which it is normally present in the lower mammals, such a remark has 

 no application in the other cases. We may therefore infer that the proxi- 

 mate constituents of the milk are not manufactured by reason of any 

 special structure of the gland which secretes them, since other structures 

 can assume a vicarious action. 



This therefore narrows our inquiry down to the point, Does the mam- 

 mary gland merely filter off from the blood substances already existing 

 in it, or, those substances not so pre-existing, are they made in this or- 

 gan by cells ? 



Of the proximate elements of milk, many, such as the entire group 



