136 



Scientific Proceedings (106). 



It is known that individuals vary within very wide limits in 

 their reactions to injections of foreign proteins. These observa- 

 tions suggest that those individuals who are relatively insuscep- 

 tible have some protective mechanism either in the serum or in 

 the cells of the body which prevents or delays the union of the 

 antigen, in this case horse serum, with the cells of the body. 



Abstracts of the Communications, 

 Pacific Coast Branch. 

 Twenty-fourth meeting. 



San Francisco, California, February II, 1920. 



74 (1534) 



The determination of calcium in blood and plasma. 

 By Guy W. Clark (by invitation). 



[From the Department of Biochemistry and Pharmacology, University 



of California.] 



The method consists in a direct precipitation of the calcium 

 without removal of the blood porteins. The only reagents 

 necessary are ammonium chloride (to prevent the precipitation of 

 magnesium), and ammonium oxalate, both adjusted approxi- 

 mately to P H 7.4. 



Blood. — Citrated blood (5 c.c. in a 50 c.c. centrifuge tube), is 

 hemolyzed by the addition of four volumes (20 c.c.) of warm water 

 and after standing 15 to 20 minutes is centrifuged to remove the 

 stroma. An aliquot (20 c.c.) of the clear, red liquid is transferred 

 to a 50 c.c. centrifuge tube. One c.c. of 5 per cent, ammonium 

 chloride is added and, after mixing, 3 c.c. of 3 per cent, ammonium 

 oxalate are added. The oxalate should be added slowly and the 

 contents of the tube must be well mixed. After standing at 

 least 16 hours (the much shorter time recently reported by de 

 Waard 1 results in an incomplete precipitation of the calcium), 

 the mixture is centrifuged and the supernatant liquid siphoned off. 

 The tube is washed by the addition of 25-30 c.c. of cold water 



1 de Waard, D. J. Biochem. Z., 1919, 97-98, p. 186. 



