48 MASS. EXPERIMENT STATION BULLETIN 428 



tion of sulfanilamide, a strong inhibitor of this enzyme, resulted in an inhibition 

 of eggshell calcification. The present report presents a study of the effect of 

 inhibitors other than sulfanilamide on the action of carbonic anhydrase on egg- 

 shell calcification; namely NaCNS, KMn04, and MnS04. 



Rhode Island Reds of known laying capacity were held in confined laying 

 batteries. The chemicals were administered either subcutaneously or orally. 

 Meldrum and Roughton's manometric method was used for determining car- 

 bonic anhydrase activity in the blood and the shell gland. The quality of the 

 eggshell calcification was determined by the eggshell breaking strength. 



The administration of NaCNS was followed by (a) an inhibition in carbonic 

 anhydrase activity of both blood and eggshell gland, and (b) a lowering in quality 

 of the eggshell. These changes were similar to those observed following sulfa- 

 nilamide administration. In constrast, KMn04, although a good in-vltro in- 

 hibitor of carbonic anhydrase, had little effect when administered to hens. The 

 administration of MnS04, either orally or subcutaneously, was followed by an 

 increase in the carbonic anhydrase activity. Finally, a direct relationship was 

 found between carbonic anhydrase activity and well-known seasonal variations 

 in breaking strength of the eggshell. 



These studies provide further evidence that the formation of the eggshell is 

 controlled by carbonic anhydrase. It is suggested that this enzyme acts as a 

 catalyst in the shell gland for the decomposition of carbonic acid, thus allowing a 

 greater numiber of carbonate ions to be released. These carbonate ions unite 

 with calcium and are then precipitated as calcium carbonate, thus forming the 

 eggshell. 



The Requirement for Calcium During Growth. (Julia O. Holmes.) Since 

 nutrition literature carries conflicting statements concerning the calcium re- 

 quirement of children, an attempt has been made to clarify the problem. No 

 data could be found concerning the rate at which calcium is deposited in the 

 human body during growth. Neither could reliable information be found con- 

 cerning the weight of the skeleton at dififerent ages, an important consideration 

 since 99 percent of the total body calcium is located in the skeleton. A search 

 was therefore made for such information for farm and laboratory animals. 

 Suitable data were found only for Shropshire sheep and albino rats, and included 

 gains in weight of the body and of the skeleton, and increases in calcium content 

 of the body at dififerent ages. When the gains for various intervals during the 

 growth period were expressed as percentages of the total gains made between 

 birth and the attainment of maturity, the percentage gains in calcium were identi- 

 cal with the percentage gains in weight. 



Since this relationship between percentage gains in calcium and in body weight 

 was found in two strictly dissimilar types of animals, the assumption was made 

 that the same relationship would occur in all species, including man. If thi^ 

 assumption is valid, it follows, for example, that the child who has accomplished 

 11 percent of his total growth at the end of the first year has also stored 11 per- 

 cent of his total calcium. On this basis, the approximate daily storage of calcium 

 which might be expected in boys reared under satisfactory dietary conditions 

 was calculated and is shown in the accompanying chart, together with their daily 

 gains in weight. The storage of calcium by girls is not significantly different 

 during the early years of life. Their pubertal spurt of growth, however, starts 

 earlier than in boys, i.e., at 1 1 or 12 years of age; and the entire process of growth 

 is accomplished earlier than in boys, probably b^' the 17th year. 



In converting these values for calcium storage into terms of dietary calcium, 

 it must be recognized that infants utilize only about 35 percent of the calcium 

 they eat; preschool children, 20 percent; and older children, 25 percent. The 



