60 THE SECRETIONS: 



not to be expected that all the substances which enter the cir- 

 culating fluid and are separated by the kidneys, should be 

 found in the milk, since the absorbents appear to exert a sort 

 of selective power, and would thus reject those substances which 

 occur in the blood, but which would produce an injurious effect 

 on the tender frame of the infant, if they entered into the milk. 



I have sought in vain for ferrocyanide of potassium in the 

 milk of women who were suckling, and to whom I have given 

 it in doses of six drachms. This salt is known to enter very 

 readily into the circulation, and is found after a very short in- 

 terval in the urine. After the lapse of two days I gave the 

 same woman twenty-three grains of iodide of potassium, but I 

 could detect no trace of this salt in the milk. Lastly, I at- 

 tempted in vain to detect sulphate of magnesia in the milk of 

 a woman who was suckling, and to whom I had administered 

 it in a sufficient dose to act as a laxative. 



For the particulars of these experiments I must refer to my 

 essay ' On the Milk of Woman, in its Chemical and Physio- 

 logical Relations/ From these observations I think that I 

 am justified in the conclusion that energetic substances, 

 which are foreign to normal milk, either do not enter into 

 that secretion at all, or if they do, they undergo modifi- 

 cations, which render them more compatible with the organism. 

 Although I could not detect the sulphuric acid of the sulphate 

 of magnesia in the milk, it is very probable that the magnesia 

 entered the milk as a lactate, while the sulphuric acid was car- 

 ried off by the urine as a sulphate. 



Peligot, however, has detected iodide of potassium in asses' 

 milk ; and Herberger in the milk of woman. [I have on several 

 occasions observed the ordinary indication of iodine on the ad- 

 dition of xyloidin, or of starch and a drop or two of nitric acid 

 to the urine of infants at the breast during the period of the 

 mother taking three grains of hydriodate of potash thrice a 

 day a convincing proof that the salt has entered the milk.] 

 Mercurial medicines used by women who are suckling have 

 never been traced in the milk, [although their effects on the 

 infant are undoubted.] 



