Diffusible Calcium in Blood. 



271 



the past year, we have worked with human blood and experi- 

 mental tetany dog blood. 



The method of dialysis is an important factor in the results 

 obtained. In the first place, collodion sacs are unsatisfactory, 

 because they do not hold back protein for a sufficient length of 

 time and because there is a progressive passage of fluid into the 

 sac. We have used parchment paper thimbles, which obviate 

 these objections. It was found that when serum was dialyzed 

 against a Ca-free Ringer solution, there appeared to be a pro- 

 gressive dissociation of Ca, so that, at the end of 5-7 days' dialysis, 

 90 per cent, of the total Ca had diffused out. Where, however, 

 compensation dialysis is employed, i.e., known amounts of Ca are 

 added to the dialyzing fluid outside the sac, equilibrium is ob- 

 tained in 24 hours, at ice box temperature, and the diffusible Ca 

 is found to be between 60-70 per cent. In all of our work, the 

 serum and dialyzing fluid were saturated with 6 per cent. C0 2 -air 

 mixture, and the buffer of the dialyzing fluid was such that when 

 so saturated, it had a ph of 7.4. 



The calculation of the diffusible Ca is simple and may be ex- 

 pressed in this formula: 



_ (Ca in dialysate X 2) — Ca added to dialysate 



Diffusible Ca = « ~ 



Serum Ca 



In the two tables our results are summarized. 



The calcium determinations were done by Lyman's method. 



Duplicate Analyses — Experimental Tetany, Dog No. 6. 





Ca in 



Ca in 



Ca in 

 Dial- 



Ca in 

 Dial- 



Serum 



Total Ca in System. 



Per 

 Cent. 



Series 

 NN. 



Serum 

 at Start, 

 mg. in 

 4 c.c. 



Serum 

 at End, 

 mg. in 

 4 c.c. 



ysate at 

 Start, 

 mg. in 

 4 c.c. 



ysate at 

 End, 



mg. in 

 4 c.c. 



Ca, 

 mg- in 

 100 

 c.c. 



Before 

 mg. in 

 8 c.c. 



After 

 mg. in 

 8 c.c. 



Diff. 

 mg. 



Dial- 

 yzable 

 Ca. 



% 



NN 1 

 NN 2 

 NN 3 

 NN 4 



0.248 

 0.248 

 0.248 

 0.248 



0.274 

 0.274 

 0.218 

 0.232 



0.210 

 0.210 

 0.105 

 0.105 



0.184 

 0.180 

 0.128 

 0.124 



6.1 



0.458 

 0.458 

 0-353 

 0-353 



0.458 

 0-454 

 0.346 

 0.356 



0 



0.004 

 0.007 

 0.003 



60 



63 

 61 

 58 



