MINERAL METABOLISM 385 



growth of the animal as a whole. Yet, although the needs are well 

 established for these general roles, the mechanisms involved are quite 

 unknown. 



Perhaps the missing link lies in the activation of certain enzymes by 

 Mn+ + . Bone phosphatase, for example, needs this ion as a cofactor. 

 Some decarboxylases, like those for oxalosuccinate and oxaloacetate, 

 require manganous ion. Furthermore, many investigators believe that 

 the manganese of liver is a component of arginase. Muscle adenosine 

 triphosphatase, certain peptidases, and choline esterase may depend 

 upon Mn+ + . The possibility of participation in such diverse enzyme 

 systems as these and others still unknown can account for the de- 

 pendence of animals on this element. But we are still in the dark 

 about the causes of deficiency systems. One known role of obvious im- 

 portance played by manganese is that of the metal in the respiratory 

 blood pigment of the shellfish. Pinna squamosa. 



As is so often the case, the allowances needed by normal animals are 

 difficult to set. Once again, ingested material is not all absorbed, and 

 absorption varies with intakes of other ions, especially calcium, iron, 

 and phosphate. Since most practical problems have been encountered 

 with poultry, much work has been based on birds. As a result, the 

 only firm estimates are those for birds and depend upon the breed 

 and on intake of calcium, iron, and phosphate. 



Both immature and adult chickens need feeds containing a mini- 

 mum of 30 to 40 p. p.m. of manganese with the higher figure for 

 heavier breeds, New Hampshire, Barred Rocks, etc. This level is just 

 sufficient for normal growth of chicks, heavy egg production, hatchabil- 

 ity, and the prevention of perosis or slipped tendon. Rations below 

 this level should be supplemented with bran, middlings, or manganese 

 compounds. The form in which manganese is added seems to be im- 

 material except that perhaps the phosphate is not absorbed. If the 

 diet is particularly high in Ca++ and P04=, as with large supplements 

 of bone meal, the above level of manganese is not sufficient and defi- 

 ciencies occur unless the supply is increased. Fowl seem to have dis- 

 tinctly higher requirements than do mammals. Corn is a very poor 

 source of Mn++ and is inadequate for poultry from this point of 

 view. 



Manganese deficiency is unknown in man although the element is 

 presumably required. Tea, legumes, leafy vegetables, fruits, nuts, 

 meats, and sea foods are good sources. 



Deficiencies have been produced in rats, mice, rabbits, chickens, and 

 pigs. The bones are poorly mineralized and those of the legs are de- 

 formed. Observed changes are microscopically different from those 



