320 



Mr. J. A. Craw. On the Filtration of [Dec. 1, 



Filtrates : Experiments Nos. 4, 5, 6 and 7, Table I, show the hemolytic 

 values of the succeeding fractions through 15, 11, 9 and 7'5 per cent, 

 gelatine respectively. The average indices for the whole nitrates were in the 

 order given above (1-5), (6'9), (31-7), and (36-9). 



In Experiment No. 8, Table I, 50 c.c. of 20 per cent, horse serum in 

 - 8 per cent. NaCl had previously been passed through a 7'5 per cent, 

 gelatine filter. In this case the permeability to lysin was slightly less than 

 that of a similar filter without serum, the average indices of the filtrates 

 being (30"6) and (36 - 9) respectively. 



Gelatine : On melting out the gelatine, after filtration, at 37° C, and 

 mixing with the test blood, the latter was in all cases rapidly and completely 

 haemolysed, index (100). Control experiments showed that saline on being 

 pressed through gelatine which had been used to filter lysin became strongly 

 hemolytic. The original gelatine had no hsemolytic effect in the standard 

 time. 



Eesidual Fluids : The residual fluids in all cases showed average indices 

 which were higher than that of the original fluid. The lowest portions of 

 residual fluid had generally higher indices than the portions towards the 

 upper surface. With rising concentration of gelatine the haemolytic power 

 increased, thus with 7'5 per cent, the residue had an index (52*7) whereas 

 with 15 per cent, it was (85). 



Conclusions. — Megatherium lysin is retained to a greater extent than 

 sodium chloride, and more is retained with higher concentrations of gelatine. 

 The residual fluids have higher concentrations than the original and the 

 concentration is greater with higher percentages of gelatine. Diffusion and 

 expression of lysin from the gelatine into the residual fluid are insufficient to 

 account for the increased concentration immediately after decompression, and 

 it seems as if the water of the original fluid could pass into the gelatine 

 more readily than the lysin. 



It seems possible, under the conditions of preparation, that during the 

 draining of the filters from the various percentages of gelatine at 30° C, the 

 filters with the higher concentrations would retain thicker surface layers of 

 gelatine and so exaggerate the differences in permeability. 



Filtration of a Typical Colloid, Ferric Hydrate, through 11 per cent. Gelatine 



under Varying Pressure. 



As ferric hydrate in colloidal solution shows no appreciable tendency to 

 diffuse, any redistribution of the colloid by the gelatine filter must be 

 explained on some other basis than that of diffusion. 



Method. — A 5-per-cent. solution of colloidal ferric hydrate was prepared 



