MINERAL METABOLISM 375 



Florida. As time goes on, diseases cured by cobalt will probably be 

 studied elsewhere. Although the deficient pasture, hay, and fodder 

 lands are scattered, the total acreage is large, and the stock losses are 

 serious. 



Symptoms of cobalt deficiency include gradual loss of appetite, 

 emaciation, rough coat, scaly skin, reproductive failures, and espe- 

 cially anemia. Response to cobalt administration is usually rapid, and 

 complete recoveries are common. Calves and lambs seem to be more 

 susceptible than adult animals. In certain areas lack of cobalt is ac- 

 companied by a copper deficiency. 



Cobalt is toxic when ingested to excess. Therapeutic doses of 30 to 

 40 g. per 100 lb. of stock salt are about the upper limit. Larger quan- 

 tities are quite poisonous. Thus the quantity needed and tolerated for 

 health lies in a poorly defined but fairly narrow range. Large doses 

 of vitamin Bjo do not seem to be harmful, and the excess is rather 

 rapidly excreted in the urine. Some of the vitamin is eliminated in 

 feces. There is no information on the excretion of other forms of 

 cobalt. 



Copper 



This element is known to play several roles. It is a prosthetic group 

 of the respiratory pigments called hemocyanins, serving as the prin- 

 cipal oxygen-transporting proteins in the bloods of many marine 

 forms, including crabs, lobsters, octopi, and snails. Copper is quite 

 abundant in these and related species. In terrestrial animals copper 

 is apparently distributed in smaller concentrations throughout all 

 tissues. It functions in unknown ways to provide for absorption of 

 iron from the diet and in the formation of erythrocytes. Furthermore, 

 copper is a key component of several plant and animal enzymes and 

 proteins, particularly the flavoproteins necessary to electron-transfer 

 mechanisms. It circulates in the blood, mostly combined with protein, 

 to the extent of about 0.0001 per cent. 



Vegetables and meats contain sufficient copper for human require- 

 ments, and deficiencies are unknown. Milk is very low in copper, but 

 fortunately the fetus accumulates this element during pregnancy. The 

 newborn child has enough stored to last for a year or so and con- 

 sequently does not suffer from the milk diet low in copper. 



Plants grown on soils low in copper become deficient, and grazing 

 animals may not receive enough available copper. Cattle and sheep 

 seem to be the most susceptible domestic animals. The former are 

 believed to need 50 mg. daily, and sheep and swine about 5 mg. From 

 5 to 8 p. p.m. of copper in feeds on the dry basis is enough to meet 



