CALCIUM CONTENT OF STIMULATED AND UNSTIMULATED SALIVA

The divergent figures in the literature for the calcium content of saliva made it desirable to determine the effects of different methods of collection of the saliva. Becks (1), Clark (2), and Hawkins (3) analyzed samples of "unstimulated " or "resting " saliva taken at least one hour after a meal and without undue movements of cheeks and jaws. Horton, Marrack, and Price (4) used acid drops to obtain saliva, while Karshan, Krasnow, and Krejci (5) analyzed saliva stimu-lated by the chewing of paraffin. McClelland (6) and Morris and Jersey (7) found that saliva was changed quantitatively and qualita-tively by stimulation with paraffin, but calcium is not mentioned. The pH is increased during paraffin stimulation, as shown by Starr (8), Peabody, Hall and Lewis (9), Forbes (10), and others. One hour after breakfast resting saliva was expectorated into a gradu-ated cylinder. Immediately afterward a number of equal samples were collected during stimulation with different substances. 30 minutes later another sample of resting saliva was taken. The time of collection for each sample was noted. 5 c.c. samples of saliva were transferred into a Kjeldahl flask; about 50 c.c. of concentrated nitric acid were added, and the mixture brought to boiling. When half the volume was evaporated a further quantity of nitric acid was added to cool the mixture, and 0.5 c.c. of perchloric acid added. The liquor was then evaporated to about 1 c.c. by boiling. If the solution was still brown, more nitric acid was added; otherwise evaporation was continued until a white residue appeared and about 0.5 c.c. of the liquor remained. The solution was pipetted into a centrifuge tube, washing twice with 10 drops of distilled water, and the calcium determined by the method of Kramer and Tisdall (11). In some of the cases saliva was not ashed, but centrifuged at 3500 revolu-tions per minute for 30 minutes. The saliva from children, clearer than that from adults, was centrifuged for 15 minutes only. The slightly opaqu