XQ2 : . : ; COLLQIPS^IN BIOLOGY AND MEDICINE 



[P. A. KOBER has devised a new and valuable form cf ultrafilter 

 based on the principle of selective dialysis through collodion and 

 evaporation of the dialysate (per-vaporation). See Jour. Am. Chem. 

 Soc., Vol. XL, No. 8, p 1226, et seq. Tr.] 



Applications of Ultrafiltration. Ultrafiltration as previously men- 

 tioned serves to separate colloids from crystalloids. It can fre- 

 quently replace dialysis, having the advantage of rapidity and 

 permitting separation without the unavoidably great dilution of the 

 dialysate. 



For this purpose it has been used for the separation of globulin 

 from the electrolytes holding it in solution, and the products of the 

 digestion of casein by pancreatin (H. BECHHOLD* 4 ). 



The most important recent applications of Ultrafiltration are, the 

 separation of colloids with particles of different sizes (fractional ul- 

 trafiltration) , and the determination of the colloid or crystalloid 

 nature of doubtful substances. We refer here to the separation of 

 various albumoses by H. BECHHOLD,* 4 the researches concerning 

 the nature of starch solutions by E. FOUARD,* and those concerning 

 diastase by PRIBRAM, and the experiment to explain fermentations 

 in the absence of cells by A. VON LEBEDEW,* the researches of GROS- 

 SER on milk (see pp. 174 and 350), the studies of KIRSCHBAUM on 

 dysentery toxin which are still unpublished, as well as those of H. 

 BECHHOLD on the separation of diphtheria toxin from toxon. By 

 Ultrafiltration, GROSSER was able to distinguish boiled from unboiled 

 milk (see p. 174). 



Ultrafiltration is of especial importance in the study of equilibrium 

 in solutions, because in this method there is no change in the balance 

 of crystalloid and colloid portions through the dilution of the solu- 

 tion. It is assumed that only small quantities are filtered, that the 

 differential is in some way ascertained so that no changes in concen- 

 tration occur; and that only moderate pressures are used in the 

 case of solutions containing electrolytes (see p. 59). The numerous 

 researches on iron oxid hydrosol by J. DUCLATJX and G. MALFITANO 

 depend on this, as does the work of R. BuRiAN* 1 on salt-albumin 

 mixtures. 



Ultrafiltration has been variously employed for the solution of 

 purely biological questions. R. BuRiAN* 2 has employed it in study- 

 ing the function of the kidney glomeruli, and H. BECHHOLD* 7 in the 

 question of "internal antisepsis." 



Finally, it must be mentioned, that by Ultrafiltration germ-free 

 fluids may be obtained, as well as optically pure water suitable for 

 ultramicroscopic experiments (H. BECHHOLD * 4 ). New paths have 

 been opened to the study of filterable infectious agents by ultra- 

 filtration (VON BETEGH). 



