ACTION OF IRON AND ITS SALTS 155 



upon their acid constituent, are strongly astringent and more or less irri- 

 tant — as the chloride, perchloride, sulphate, persulphate, and nitrate. 

 They contract tissue by coagulating albumin, when applied to raw sur- 

 faces or mucous membranes, and through this means, by compressing the 

 blood-vessels from without and plugging them from within with clotted 

 blood, arrest hemorrhage. The astringent salts may also induce some 

 contraction of the vessels besides. Iron — in the form of liquor ferri 

 chloridi or liquor ferri subsulphatis — is the most powerful of the metallic 

 hemostatic agents we possess. 



Internal. — Alimentary Canal. — Iron is a food rather than a medi- 

 cine. It exists as a natural constituent of vegetable foods and of the 

 body, and is found particularly in the hemoglobin of the blood — to the 

 extent of about half an ounce in that of the horse. There is a sufficient 

 quantity in the food to support healthy animals. If iron is ingested by 

 a normal animal in ordinary doses, it has little effect unless continued 

 for a long time in considerable quantity, when it may produce indigestion 

 and constipation. Large doses of irritant and astringent salts, as the 

 perchloride, may induce gastroenteritis by local irritation. 



Internally in the stomach the iron salts behave as they do externally. 

 Acid ions are set free from the iron salt and the metal combines with 

 albumin. The liberation of the acid ion leads to an astringent action 

 and, if large doses are ingested, actual irritation. The degree of astrin- 

 gency is due to the preparation also. Thus ferric chloride is especially 

 astringent because of the ease of dissociation and corrosive action of the 

 HCl ion. Ferrous sulphate is only a little less so; while reduced iron, 

 the oxide, carbonate, double salts and salts of the vegetable acids 

 (citrates, acetates and tartrates), and albuminates, are very slightly or 

 ■hot at all astringent. In the case of the salts of the organic acids and 

 double salts the acid ions are but slowly dissociated, and in, that of the 

 albuminate there is no acid to be freed. Acid salts, as the sulphate, are 

 more suitable for the horse than the dog. Iron may blacken the tongue 

 from formation of the sulphide. In the stomach all forms of iron are 

 converted into chlorides, by the HCl of the gastric juice, and then prob- 

 ably into albuminates or carbonates in the duodenum. 



Iron is naturally absorbed from the organic compounds of the metal 

 existing in the nucleoalbumins of food, and, either existing in this form or 

 when given in medicine in the inorganic state, it is probably absorbed 

 chiefly from the duodenum as the albuminate or carbonate. But in any 

 event the greater portion escapes from the bowel unabsorbed.. The route 

 which iron follows, after absorption, has been quite accurately ascertained 

 by many experiments. It is taken up from the duodenum by the epithe- 

 lial cells and leukocytes and carried by the blood into the spleen, in which 

 it is first deposited. From thence, through the blood, it is conveyed to the 

 liver and bone marrow. If it is needed for blood-making it is transformed 

 by many steps into hemoglobin in the liver. But if it is not so needed 

 it is eliminated by the large intestine and escapes from the bowel in the 

 form of the sulphide and albuminate— the feces turning dark on exposure 



to air. J .... . 



Constitutional Action.— This is not observed unless iron is given m- 



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