MINERAL METABOLISM 333 



ing the iodin content of the food and is probably closely dependent upon 

 it normally (Hunter and Simpson; Strauss; Cameron(a)). (For a dis- 

 cussion of iodin in foods see Forbes and Beegle ; for its distribution in 

 plant and animal tissues see Cameron.) Its absence in the pituitary has 

 very recently been confirmed (Seaman) as well as its presence in the blood 

 (Kendall and Richardson). The complex organic combination in which 

 iodin is found in the thyroid has been isolated and identified by Kendall 

 as 4, 5, 6 tri-hydro-4, 5, 6, tri-iodo-2-oxy,-beta indol-propionic acid, con- 

 taining 65 per cent iodin and to which most if not all of the physiological 

 effects of the thyroid gland can be ascribed, particularly the stimulation 

 of basal metabolism (Kendall (a) (c) (d) ; Kendall and Richardson; Cam- 

 eron and Carmichael). . 



Iodin compounds are absorbed by the intestine and since iodids are 

 sometimes excreted after administration of organic iodin, while ingested 

 iodids may serve to increase the amount of thyroid complex, the body 

 possesses the ability to ionize and also to deionize iodin (Buchholtz; Blum 

 and Griitzner). Inorganic iodids are excreted mostly by the kidneys, and 

 the time of their appearance after, ingestion may be used as the basis of 

 absorption tests though marked variation in different individuals is re- 

 ported. Ingested iodin (element) is quickly bound in the blood by protein 

 and the absorption of iodids by the thyroid is very rapid, but the iodin 

 complex is formed more slowly (Sollmann(&) ; Marine and Rogoff(a) (c) ). 

 The administration of various forms of iodin (non-toxic dose) has caused 

 temporary infertility in animals (Adler(a)(&) ; Loeb and Zoppritz). 



Lack of iodin in food and drinking water is considered the cause of 

 fetal and maternal athyrosis and as the result of successful treatment in 

 animals the administration of potassium iodid has been recommended 

 (Smith; Hart and Steenbock(6) ; Welch). The administration of small 

 amounts of iodid prevents simple goiter in man (Kimball and Marine), 

 and while this condition has been associated with a lack of iodin (Hun- 

 ziker), a voluminous literature has established no clear connection 

 between endemic goiter and water supplies (Clark and Pierce). The 

 literature upon metabolism in diseases of the thyroid and in thyroid feed- 

 ing is reviewed by Halverson, Bergeim and Hawk. 



Neutrality Regulation 



The maintenance of neutrality is one of the functions of the inorganic 

 constituents of the body. The production of acids in the body is contin- 

 uous, and the oxidation products of carbon, sulphur and phosphorus are 

 neutralized in the body by the alkali metals (to some extent probably by 

 the alkaline earths), by ammonia resulting from protein decomposition and 

 by the proteins (Klein and Moritz; Robertson (a)). The eliminatioD of 



