474 



fatty acid compound can not lower the surface tension of water 

 to less that 52 dynes/cm. By tliis observation the hypothesis of 

 inactivalion of fatty acids by protein solely is |)roved to be in- 

 sufficient. Tiierefore we had to think of other possible compounds 

 und found a sulilicient explanation foi- constancy in the formation 

 of calcium soaps. The existence of this proces of inactivalion was 

 found in the following way: 



A. If the Calcium of serum or blood is precipitated by addition 

 of oxalate of ammonia, the surface tension can not be held con- 

 stant if small quantities of oleic acid are added. This is to be seen 

 in the next table. 



Surface tension of fresti human oxalate plasma 49 d. c.M. 



-f 0.001 N oleicacid in neutral emulsion 47 „ 



+ 0.002 N 45 „ 



+ 0.003 N „ „ „ „ • 42 „ 



+ 0.004 N „ . „ „ 40 „ 



+ 0.005 N , . „ „ 38 „ 



The same results are obtained, when NaFI plasma is used. 



B. A salt-solution containing the same amount of Ca as Plasma 

 can maintain its tension above 50 dynes on addition of a neutral 

 emulsion of oleic acid at 37°, to the same extent as plasma can. 

 This holds for a solution of CaCl,.6 Aq. 0,05 % as well as for 

 a solution composed of NaCl 0,7 "/„, NaHCO, 0,2 % KCl 0,02 »/„ 

 CaCI,.6 aq. 0.05 '/. and H,CO, till [H] = 0,4.10-7 \s reached. 



The following table gives the surface tension of the said salt 

 solution if small amounts of oleic acid were added very gradually. 



Surface tension of the balanced salt-solution 74 d. c.M. 



-(- 0.0001 N oleicacid in neutral emulsion 54 „ 



+ 10 X 0.0001 N „ . „ 53 „ 



+ 10 X 0.0001 N 52 „ 



+ 10 X 0.0001 N „ . 52 „ 



+ 5 X 0.0001 N . „ „ . 50 , 



+ 5 X 0.0001 N „ „ „ . 39 „ 



If the surface tension of the saline shall not be lowered unter 

 the plasma tension, it is necessary to add the oleic acid very gradu- 

 ally, and to leave the mixture for a half hour at 37° after each 

 addition ; only in this way it is possible to obtain a form of Oleate 

 of Ca, whose capillary activity is low enough. But this condition 

 is fulfilled in vivo. 



The question now arose, wether this mechanism of inactivation 

 would be equally important for the normal fatty acids of the blood 

 as it proved to be for oleic acid. It is certain, that about one third 

 part of the blood-calcium is present in the colloidal state; when we 



t 



