Phenomena of " Clot " Formations. 



367 



concentration, is of about the order of half saturation. It is proposed to inves- 

 tigate the relative clotting power of salt in greater detail later ; the present 

 communication deals mainly with the question of the influence of one parti- 

 cular factor on gel formation, viz., on the surface tension of the solution.* 



A preliminary account of the clot production by various calcium salts has 

 been given in the first paper (loc. cit.). It was then shown that in the case 

 of calcium salts which increase the surface tension of water, increase in the 

 concentration of the salt caused a diminution of the clotting time. In the 

 case of the calcium salts which lowered the surface tension, however, the 

 accelerating effect of the increase in the concentration of the salt was counter- 

 balanced by the diminished surface tension of the solution. In two cases (those 

 of calcium dichloracetate and of the sulphocyanide) an optimal point was 

 found. Increase in the concentration of the calcium salt above and below this 

 point caused a lengthening of the time required for gel formation. In the 

 case of calcium trichloracetate, the length of clotting time progressively 

 increased with increasing concentration within the limits investigated.! 



Method of Experiment. — The following was the method of experiment 

 adopted : — 1 c.c. of a 4-per-cent. sodium cholate solution and 3 c.c. of the salt 

 solution in the required concentration were heated in separate quartz tubes 

 of 10 c.c. capacity in a thermostat at 50°. As soon as the liquids had attained 

 the temperature of the thermostat, they were rapidly mixed ; the salt solution 

 * was poured into the cholate solution, and the mixture was then poured back 

 into the tube originally containing the salt alone. This was then clamped in 

 the (transparent) thermostat and watched. The formation of oily globules was 

 the first sign of clot formation. These at first moved rapidly in the liquid, but 

 as they increased in size, motion became less rapid, until, finally, movement 

 was hardly visible. At this point, at short intervals, steel balls of 3/32 inch 

 diameter, such as are used for ball-bearings, were dropped into the tube at 

 short intervals. The time of complete gel formation was taken as that at which 

 a ball stopped dead before it had fallen half-way through the tube. The time 

 was taken by a stop-watch, which was started at the moment of mixing the 

 solutions. Even when the clotting time was 5 minutes, control determinations 

 seldom differed by more than 10 seconds — they usually agreed with one another 

 within 5 seconds. In the first series of experiments on calcium salts, the cholate 

 solution was made by saturating N/100 sodium hydroxide with cholalic acidj 



* Throughout this communication by " sui'face tension '' is meant surface tension 

 measured against air. 



t The surface tension of the salt solutions is affected mainly by the anions. The series 

 of anions employed was that used in the investigations on aggregation (' Eoy. Soc. Proc.,' 

 B, vol. 83, p. 96 (1910) ). 



\ Prepared pure by the author's method (' Journ. Physiol.,' vol. 44, p. 265 (1912)). 



