402 SALTS OF THE HEAVY METALS 



toxic action provided they are introduced into the body. (The 

 alimentary tract in this case is not within the body.) For instance 

 the main difference in the toxicity of arsenic and iron is due to the 

 fact that arsenic is easily absorbed and iron is not. With few excep- 

 tions (arsenic, mercury, and uranium), there are no metals absorbed 

 sufficiently rapid to cause acute poisoning, unless a corrosive dose 

 has-been given. Other metals, lead, silver, iron, are absorbed more 

 slowly. As discussed under the local action, all metallic salts in 

 strong solution produce corrosion of the digestive tract. They 

 would therefore be absorbed and produce the general action, if the 

 animal survived the local action." 



As in case of other substances, metals must be in a soluble form 

 to be absorbed. This solubility does not mean that they must be 

 given in soluble form, as it makes but very little if any difference 

 in what form they are administered, because they will be converted 

 into the insoluble chlorides in the stomach, the insoluble carbonates 

 in the duodenum or into double salts with the proteids (albuminates) 

 which are soluble in an excess of the proteids, in which condition 

 they may be absorbed. They may also pass into the large intestine 

 as the sulphide, escape absorption and render the feces black. 



The excretion of metallic salts is even slower than the absorption, 

 so that they frequently accumulate in the body and cause chronic 

 poisoning (cumulative action) when they have been taken for a 

 sufficient time in too small amounts to cause immediate results. A 

 single large dose may also cause chronic poisoning. The principal 

 channel of elimination is by the digestive tract, no matter in what 

 way they have been administered, although a small amount is ex- 

 creted by the kidneys. The intestines may be irritated at the points 

 of elimination, as is shown by diarrhea and enteritis. 



Sufficient amounts are eliminated by the kidneys to cause a 

 marked nephritis, characterized by the ordinary phenomena of that 

 condition. If the poisoning is of the chronic variety, there may be 

 interstitial nephritis or cirrhosis of the kidneys. 



The systemic effect is very similar with all metals and consists 

 of a fall in blood pressure due to paralysis of the blood vessels and to 

 direct action upon the heart. This is followed by or attended with 

 disturbances of the central nervous system. 



The local (astringent and irritant) effects of the salts of the 

 heavy metals are used therapeutically, but the systemic action is 

 of more importance from a toxicological standpoint. 



IRON 



Iron is an important constituent of the body and is essential for 

 life of the higher plants and animals. It is found in animals par- 

 ticularly in the. hemoglobin of the blood and has a close relationship 

 to the oxygen-carrying powers of the red blood cells. Since hemo- 



