318 



SCIENCE 



[N. S. Vol. LII. No. 1344 



The ultimate solution, or at least the one 

 that is most to be desired, it seems to me, wiU. 

 be a universal time scale which shall have its 

 basis in paleontology and shall adhere to the 

 classic names, and in which the cycles and 

 epicycles of diastrophism will be regarded as 

 probably the most useful criteria for delimit- 

 ing formational or larger sedimentary units, 

 but never per se as criteria for the division of 

 geological time. 



Edward W. Beery 



The Johns Hopkins UNrvERSiTY 



SPECIAL ARTICLES 



THE INFLUENCE OF DRY VERSUS FRESH 



GREEN PLANT TISSUE ON CALCIUM 



ASSIMILATION 



In early work on mineral metabolism with 

 both the cow and the goat we showed that 

 milking animals, receiving grains and dry oat 

 straw as a roughage, are brought into a 

 decided negative calcium balance. In the 

 case of a goat the interesting observation was 

 made that after a period of negative calcium 

 balance, followed by access to fresh green 

 grass, a positive calcium balance was observed, 

 using the same ration as was used in the 

 period preceding the access to green plant 

 tissue. In extensive experiments Forbes and 

 associates and Meigs and his associates have 

 observed negative calcium balances with milk- 

 ing cows receiving rations liberally supplied 

 with calcium. The rations used were from 

 air dried materials, supplemented in some 

 cases with silage. The striking feature of 

 all the data obtained in these experiments 

 was the large amount of fecal calcium, in- 

 dicating a failure to assimilate satisfactorily 

 this base. 



In these our preliminary experiments, we 

 have used milking goats. They have readily 

 been brought into negative calcimn balance 

 on a ration consisting of air dried grains and 

 air dried straw, with more calcium excreted 

 in the fecal residue than was ingested with 

 the ration. 'When the dry cereal straw was 

 displaced by an equivalent in dry matter of 

 fresh green material, with no increase in the 

 total calcium intake, the negative calcium 



balance was reduced in one animal from 

 1.6-2.7 grams CaO to .6 CaO per day. With 

 another animal it was reduced from 1.5—2.5 

 grams CaO per day to .3-.8 gram per day. 

 On the low calcium intake of 8 to 9 grams of 

 CaO per week we could not expect a positive 

 calcium balance to ensue, but this remarkable 

 difference in the amount of calcitmi assimi- 

 lated from the two rations we believe, has 

 very great significance. 



These changes in calcium assimilation are 

 not to be attributed to variation in water in- 

 take or to unavailability of the calcium. Ap- 

 parently there is something having its source 

 in fresh green materials, which controls or as- 

 sists calcium assimilation. It is suggested 

 that under the extra strain of rapid growth 

 or milk production not enough calcium can be 

 assimilated for the liberal uses made of this 

 element, unless there is present an abimdance 

 of calcium in the diet as well as an abundance 

 of this something that assists calcium as- 

 similation. Possibly we are dealing with the 

 anti-rachitic vitamine, assmned as the fourth 

 food accessory factor. In any case this prob- 

 lem touches growth, milk production and egg 

 production. In the case of nursing women 

 the relation of diet to a positive or negative 

 calcium balance and to dental conditions will 

 assume new aspects. 



The supposition . that we are dealing with 

 something influencing calcium assimilation 

 and which is more abundant in green than in 

 dried plant tissue and consequently variable 

 with the season's milk, would explain the 

 variations in the seasonal frequency of rick- 

 ets, as observed and commented upon by 

 Hess. 



Our data are not yet inclusive enough to 

 indicate definitely the factors involved in this 

 problem, yet we have been sufficiently im- 

 pressed with the constancy of the observa- 

 tions made that it appears desirable to re- 

 emphasize this relation to mineral metabolism 

 which we anticipated some years ago and 

 expressed in an earlier publication. 



E. B. Hart, 

 H. Steenbock, 



C. A. HOPPERT 



