The Journal of biological chemistry . f calcium intake withthe added precaution of keeping our animals on screens to pre-vent consumption of bedding as well as feces (16). We do, how-ever, believe that we are entirely justified in concluding that allof these salts are available to a considerable degree as a somce ofcalcium for. growth in the animal. In the earlier literature it is easy to understand why the ideagained credence that calcium salts insoluble in water or dilutealkali were unavailable because the content of the small intestineshortly distant from the pylorus was believed to be alka
The Journal of biological chemistry . f calcium intake withthe added precaution of keeping our animals on screens to pre-vent consumption of bedding as well as feces (16). We do, how-ever, believe that we are entirely justified in concluding that allof these salts are available to a considerable degree as a somce ofcalcium for. growth in the animal. In the earlier literature it is easy to understand why the ideagained credence that calcium salts insoluble in water or dilutealkali were unavailable because the content of the small intestineshortly distant from the pylorus was believed to be alkaline inreaction. It is now known, however, that the acidity of thechyme is neutralized gradually and an acid reaction often prevailsfor a considerable length of the small intestine and even some-times throughout its entire length (18). It is undoubtedly the acidity which makes possible the assimi-lation of the difl&cultly soluble calcium salts from the such as barium sulfate (insoluble in dilute hydrochloric acid). Steenbock, Hart, Sell, and Jones 385 are not absorbed to an appreciable degree, at least not sufficientlyto cause toxic symptoms. We determined this by feeding bariumsulfate to two groups of rats, one on the basal ration used for thecalcium work with salt 39, and one with the same plus salt each case 2 per cent of BaS04 was added. With salt 39, theincomplete salt mixture—which due to lack of calcium is unableto support growth^—four rats started at 42 to 52 gm. in weightat an age of 24 days maintained themselves with slight growthfor 18 weeks. At this time thej^ weighed 77 to 93 gm. with nosigns of immediate failure. All of them were, however, extremelyrickety as indicated by their walk due to the calcium the complete salt mixture, salt 32, in the basal ration, plusthe barium sulfate, the rats started at 42 to 52 gm. at an age of25 days grew normally, attaining weights of 178 to 275 gm. in18 weeks with no signs of failure. We
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