332 HENRY A. MATTILL AND HELEX I. MATTILL 



very greatly reduced (Goldschmidt, Pepper and Pearce; Pepper and 

 Austin), a result directly opposite to that obtained in normal animals. 

 In experimental anemia the store of iron in the liver and spleen increases 

 (Muir and Dunn), but some factor other than blood destruction is opera- 

 tive, perhaps a derangement of the mechanism for retaining iron (Dubin 

 and Pearce(a)). 



Sulphur 



In a discussion of mineral metabolism sulphur requires only a passing 

 mention, for the amounts of this element ingested in inorganic form are 

 very small. The various forms of sulphur found in the urine (inorganic 

 and ethereal sulphates, neutral and basic sulphur), and in the feces (sul- 

 phids) originate in the processes of digestion and utilization of the sulphur- 

 containing proteins in the food and from the catabolism of sulphur-contain- 

 ing tissue proteins. Since sulphates are thus always available in the body 

 it is obviously impossible to determine the requirements of the organism 

 for inorganic sulphur. That the organic form is necessary is indicated 

 by the experiments of Osborne and Mendel (g). It appeared that cystin 

 was a limiting factor in growth of rats on a diet containing 9 per cent of 

 casein, since the addition of cystin without any other modification made the 

 ration decidedly more adequate. The addition of cystin to diets low in 

 protein, Lewis(a) found, diminished the elimination of nitrogen in dogs 

 while the equivalent amount of nitrogen in sulphur-free compounds such 

 as tyrosin and glycocoll had no such effect. It has recently been shown 

 that rats cannot use inorganic sulphates in place of the necessary amino- 

 acid cystin (Daniels and Rich). 



lodin 



lodin was discovered in the thyroid by Baumann in 1895 in amounts 

 from 2 to 7 mg., in the normal gland; much higher values (3-44 mg.) 

 have been reported recently by Zunz whose data were obtained during the 

 war, and the literature contains widely divergent figures. It is present 

 in the thyroid of cattle long before birth, the female containing more 

 than the male, and it is present in the new-born infant and in the human 

 fetus at least during the last three months of intrauterine life (Fenger(a) 

 (6) (d) ; Pellegrini). The amount of iodin gradually increases with age, 

 being most abundant at about the age of 50. There is also a seasonal 

 variation in the iodin content of the thyroid (in cattle, sheep and hogs) ; 

 in the summer and fall the amount of iodin is considerably greater than 

 in winter and spring (Seidell and Fenger; Fenger(e)), and is to be 

 associated with external temperature and change in the size of the gland. 

 In cattle no difference was found between pregnant and nonpregnant ani- 

 mals. The iodin content of the thyroid may also be increased by increas- 



