CALCIUM 221 



FECES AND PLANT MATERL\L. Approximately 20 s of fresh fcn-cs from 

 cattle and a 24-hr collection from rats are used for analysis. The sample 

 is dried and ashed in the muffle furnace. The ash is dissolved in a few 

 milliliters of 2 iV HCI and made to 50 ml with distilled water. Anj^ 

 insoluble residue is allowed to settle, and 10-ml alicjuots are taken and 

 treated exactly as described under Bones and Teeth. Here again there 

 will be sufficient calcium in the original sample so that the calcium oxalate 

 collected in the metal cup can be used for gravimetric; analysis as well as 

 for radioassa3^ 



BLOOD PLASMA. Chemical calcium may be determined by direct pre- 

 cipitation from plasma according to standard methods (Ca-15), and then 

 carrier calciimi is added for reprecipitation, as already described, and col- 

 lection of the calcium oxalate for counting. Colorimetric and flame 

 methods for estimation of calcium in small samples of biological fluids 

 have been reported (Ca-16, Ca-17). 



Ca-l. Sollmann, Torald: "A Manual of Pharmacology," 7th ed., W. B. Saunders 



Company, Philadcli)hia, 1949. 

 Ca-2. Harrison, Harold E., and Helen C. Harrison: Studies with Radioralcium: The 



Intestinal Absorption of Calcium, /. Biol. Chem., 188: 83-90 (1951). 

 Ca-3. Hansard, Sam L., C. L. Comar, and M. P. Plumlee: Effect of Calcium Status, 



Mass of Calcium Administered and Age on Ca*^ Metabolism in the Rat, Proc. 



Soc. Exptl. Biol. Med., 78: 455-460 (1951). 

 Ca-4. Migicovsky, B. B., and A. R. G. Emslie: Deposition of Radioactive Calcium 



in Rachitic and Nonrachitic Chick Tibia from Oral and Intramuscular Doses 



of Ca«, Arch. Biochem., 28: 324-328 (1950). 

 Ca-5. Comar, C. L., and J. Clyde Driggers: Secretion of Radioactive Calcium in 



the Hen's Egg, Science, 109: 282 (1949). 

 Ca-6. Comar, C. L., W. E. Lotz, and G. A. Boyd: Autoradiographic Studies of 



Calcium, Phosphorus and Strontium Distribution in the Bones of the Growing 



Pig, Am. J. Annt., 90: 113-125 (1952). 

 Ca-7. Hansard, Sam L., C. L. Comar, and M. P. Plumlee: Absorption and Tissue 



Distribution of Radiocalchim in Cattle, /. Animal Set., 11: 524-535 (1952). 

 Ca-8. Visek, \V. J., R. A. Monroe, E. W. Swanson, and C. L. Comar: Calcium 



Metabolism in Dairy Cows as Studied with Ca''^ J. Dairy Sci., 36: 373-384 



(1953). 

 Ca-9. Visek, W. J., R. A. Monroe, E. W. Swanson, and C. L. Comar: Determination 



of Endogenous Fecal Calcium in Cattle by a Simple Isotope Dilution Method, 



J. Nutrition, 50: 23-33 (1953). 

 Ca-10. Harris, Henry C, W. H. Maclntire, C. L. Comar, W. M. Shaw, S. H. Winter- 

 berg, and S. L. Hood: Use of Ca^^ Labeled Calcium Carbonate in Determining 



Proportions of Native and Additive Calcium in Lysimeter Leachings and in 



Plant Uptake, Soil Sci., 73: 289-298 (1952). 

 Ca-11. Ririe, David, and Stephen J. Toth: Plant Studies with Radioactive Calcium, 



Soil Sci.. 73: 1-10 (1952). 

 Ca-12. Blume, James M., and N. S. Hall: Calcium Uptake bj- Tobacco from Band 



Applications of Fertilizer Materials, Soil Set., 75: 299-306 (1953). 

 Ca-13. Norris, William P., and Blanche J. Lawrence: Determination of Calcium in 



Biological Materials, .Anal. Chem.. 25: 95(> 960 (1953). 



