XI. REQUIREMENTS 385 



e. Weight of (he Adrenal GlaJids 



The \vciji;lil of tlie adivnal glands has recently tieen suggested as a crite- 

 rion of ascori)i(' acid adeciuacy for the guinea pig.'^^ J.arge numliers of ani- 

 mals ranging in weight from 190 to 900 g. were maintained on a scorbuti- 

 genic diet supplemented with \'arying amounts of ascorbic acid for a period 

 of 7 weeks. Quantitati\'e data were obtained as to height of the odontoblasts, 

 ascorbic acid content of the white blood cells, plasma, and adrenals, hemo- 

 glol)in level, weight of the adrenal glands, and water intake. Of all these 

 measurements the weight of the adrenals proved to be the most sensitive 

 criterion of the ascorbic acid requirement. The size of the adrenal increased 

 as the dietary' ascorbic acid decreased. As judged by this criterion the daily 

 requirement was found to be 0.65 mg. per 100 g. for animals weighing less 

 than 400 g. and 0.55 mg. for animals weighing more than 500 g. They con- 

 cluded that the requirement is related to the amount of metabolic tissue, 

 the proportion of such tissue being larger in the yovmg animals. The adrenal 

 weight procedure would be a simple and practicable one to employ if it 

 proved to be reliable. In recent tests, however, the writer has found the 

 adrenals of scorbutic animals to be only slightly enlarged as compared to 

 those of normal controls. It seems possible that some factor in the diet 

 may act in conjunction with variations in available ascorbic acid to affect 

 adrenal size, e.g., pantothenic acid. 



At the present time, the general consensus is that measurement of the 

 length of the odontoblasts is the most sensitive and reliable method for 

 determining the ascorbic acid requirement. This discussion has necessarily 

 been limited chiefly to procedures with guinea pigs. ]\Iuch still remains to 

 be done in determining their nutritional requirements of factors other than 

 \'itamin C. Acquisition of this knowledge could conceivably affect certain 

 aspects of the ^'itamin C picture and thereby improve the methods of de- 

 termination of the vitamin C requirement. 



2. Factors Influencing Vitamin Requirement 



a. Mode oj Administration 



Greater antiscorbutic efficiency with injected than with orally adminis- 

 tered doses of ascorbic acid has been observed in guinea pigs by several 

 investigators.""^- Hou'^ found that ascorbic acid given by subcutaneous 



3« W. H. Pfander and H. H. jNIitchell, Federation Proc. 10, 391 (1951). 



" D. J. Stephens and E. E. Hawley, J. Biol. Chem. 115, 653 (1936). 



" A. Grollman and W. M. Firor, J. Nutrition 8, 569 (1934). 



3»H. C. Hou, Proc. Soc. Expll. Biol. Med. 32, 1391 (1935). 



" L. DeCaro, Hoppe-Seyler's Z. physiol. Chem. 240, 179 (1936). 



« S. S. Zilva, Biochem. J. 30, 1419 (1936). 



« W. Klodt, Fortschr. Therap. 12, 335 (1936); Chem. Zentr. 1754 (1936). 



