774 VTTT. PROVITAMINS D AND VITAMINS D 



during the summer with a low vitamin D content, while in the winter the 

 livers contain less oil, but the latter has a higher vitamin D potency. The 

 vitamin D content of the Norwegian cod, w^hich is caught at the time when 

 the nutritional condition is poor, following spawning, is higher than that of 

 the Newfoundland cod, which is in a much better nutritional state when 

 obtained.^^^ Those fishes which have a low content of liver fat generally be- 

 long to the species in which the highest content of vitamin D is found. ^^^ 

 Fish roe^^'* and turtle eggs contain moderate amounts of the vitamin. In 

 the case of the latter, it has been demonstrated that the season of the year is 

 an exceedingly important factor, as is also the nature of the food. 



In addition to the fishes, such lower forms as the copepods of the zoo- 

 plankton contain some vitamin D.-^^'^-*^ This is a probable source of the 

 vitamin D in the cod, which consumes large quantities of zooplankton. 



There is practically no vitamin D in the fat of other animals. ^-^ The 

 marine birds, which live largely on fish, are an exception to this rule, but 

 here the vitamin D deposited is obviously the result of the large amount 

 constantly available in the diet. In the case of higher animals, a concen- 

 tration of vitamin D is found in the milk and eggs in sufficient amounts to 

 afford the essential quantity necessary to assure the growth of the new- 

 born. 



Cow milk is, in general, a relatively poor source of vitamin D.^^v Ordi- 

 narily it contains about 5 to 8 LIT. per quart, in the case of cows kept in- 

 doors, while values of 17 to 26 I.U. per quart are found in the milk of cows 

 kept outdoors in June."^ Bechtel and Hoppert"^ reported figures of 5 

 I.U. for winter milk and 44 I.U. for summer milk. The value of 35 I.U. per 

 quart is based upon the vitamin D content of butter, or 8-60 I.U, per 100 

 grams. ^^'' Human milk has a somewhat higher content of vitamin D than 

 cow milk; Drummond and co-workers^^^ obtained a value of 60 I.U. per 

 quart for this product. Colostrum, the milk secreted during the first few 

 days after the birth of the young, contains from 6 to 10 times the amount of 

 vitamin D that is present in mature milk in the case of the cow,^^^ and about 

 3 times the amount in the case of the human. 



"3 A. F. Hess, C. E. Bills, and E. M. Honeywell, J. Am. Med. Assoc, 92, 226-229 

 (1929). 



"^ E. P. Daniel and H. E. Munsell, U. S. Dept. Agr. Misc. Pub., No. 275, 1-176 (1937). 



225 A. M. Copping, Biochem. J., 28, 1516-1520 (1934). 



226 J. Drummond and E. R. Gunther, /. Exptl. Biol, 11, 203-209 (1934). 



227 H. E. Honeywell, R. A. Dutcher, and C. D. Dahle, J. Nutrition, 2, 251-256 (1930). 



228 J. E. Campion, K. M. Henry, S. K. Kon, and J. Mackintosh, Biochem. J., SI, 81-88 

 (1937). 



229 A. E. Bechtel and C. A. Hoppert, /. Nutrition, 11, 537-549 (1936). 



230 H. J. Heinz Co., Nutritional Data, Pittsburgh (1950). 



231 J. C. Drummond, C. H. May, and N. Iv G. Richardson, Brit. Med. J., II, 757-700 

 (1939). 



232 J. van Niekerk and M. S. C. Bliek, .\rtn Brevia Neerlnnd. Physiol. Pharmacol. 

 Microbiol, 9, 25-26 (1939). 



