416 COLLOIDS IN BIOLOGY AND MEDICINE 



ions, but that accompanying the abstraction of water by hypertonic 

 solutions a penetration or interchange of ions may occur. 



For the diuretic and purgative action of neutral salts see page 

 409 et seq. 



SALVES, LINIMENTS. 



Salves and similar preparations are frequently employed not only 

 to cover wounds but also with the object of introducing medicines 

 into the body through the skin. The skin absorbs only such sub- 

 stances as are soluble in fat; this has been established by the inves- 

 tigations of W. FILEHNE* and A. SCHWENKENBECHER.* 



The colloidal properties of fats deserve our attention. The cooling 

 sensation induced by cold cream depends on its capacity for holding 

 water; it takes up about 28 per cent water which is obviously the 

 dispersed phase. Wool fat is "hydrophile" to a still greater extent. 

 It enters commerce as lanolin and is the base for salves. We saw 

 that by means of hydrophile lecithin, water-soluble, though ordinarily 

 fat-insoluble, substances, such as sugar, become soluble in fat. Pos- 

 sibly we may attribute to this property, when it is present, the 

 penetration into the body through the skin by means of salves, of 

 medicaments for which the skin is otherwise impermeable. [Ax- 

 ELROD, Jour. Industr. and Eng. Chem., Vol. IX., p. 1123, gives the 

 method for preparing cetyl alcohol as a substitute for lanolin and 

 eucerin. Tr.] 



P. G. UNNA* showed that the hydrophile constituent of wool fat 

 is the oxycholesterin group. Five parts of this latter, mixed with 

 95 parts of paraffin ointment, are able to unite with 100 per cent of 

 water. (It enters commerce as eucerin.) 



