EXCRETION OF FOREIGN MATTER 49 



Reports differ as to what foreign substances are 

 excreted witli the milk. These differences of opinion 

 may be accounted for in part by the fact that many sub- 

 stances are not excreted in noticeable quantity until the 

 animal has taken relatively large amounts of them. 

 Sometimes individual peculiarities operate, for it may 

 be that some inflammation not entirely healed, local 

 induration or similar changes in the tissues of the udder, 

 in short, the injuries that remain after mammitis, favor 

 such an excretion. 



It has been mentioned before that the milk contains 

 only traces of iron, and this fact alone is a proof that 

 iron compounds are not usually excreted with the milk ; 

 even after the consumption of a great quantity of iron 

 "during a long time, the iron content does not rise. Con- 

 cerning other metals, compounds of copper, lead and 

 antimony'^ are excreted only in very small quantity, so 

 that even a prolonged adminstration of these substances 

 to milch cows usually brings about no harmful effects. 

 According to investigations by Baum and Seeliger, the 

 lead content of milk does not increase beyond 0.0009 to 

 0.002 per cent., even after treating cows with large doses, 

 and this quantity is without importance, even to quite 

 small children. 



On the other hand, mercury is easily excreted 

 through the udder, when this substance is taken through 

 the digestive organs or when absorbed after applications 

 to the skin. Iodine and arsenic also easily enter the milk 

 in considerable quantity. 



Opinions differ concerning alkaloids. It is a fact, 

 however, that morphine, strychnine, atropine and vera- 

 trin are, under certain circumstances, excreted with the 



' In the older literature, there are recorded a ntunber of observa- 

 tions which indicate that tartar emetic may be excreted with the 

 milk in large quantity 



