Physical Chemistry ani> Vktkkinary Sciknce. 191 



■of rise, existence and destruction of the membranes in the orf,'anisin 

 and their properties and importance for pliysiological and patliological 

 life (Zangger). 



The conditions of superficial condensation on colloidal solutions, 

 which are in contact with each other, are the differences of their 

 surface tensions, and the impossihility of mixing. These conditions 

 are realised in the organism. 



The principjil properties of the memljranes are — 



(1) Their typical colloidal character. 



(2) Their specific peculiarities as separating layers. 



(1) The membranes are colloidal. — [ mentioned that their origin is 

 from a colloid sijlution. They have therefore similar characters to the 

 mother liquid. Typical for them as colloids are the possibility of 

 imbibition with water, a certain electric charge, the influence of ions, 

 absorption of crystalloids or colloids with the same or adverse electri- 

 cal character. Their C(jnsistency is altered by those factors, either- in a 

 positive (precipitation) or negative sense (partial dissolution). The 

 alt/tn-ations are permanent or reversible, but the membrane has always 

 the traces of the life history. 



(2) The most typical character of the membranes is their selective 

 penneability. — The membranes are easily permeable for water, but not 

 as well for the substances dissolved in it. 



With regard t<j electrolytes the membrane can be (a) permeable 

 for the anion or kation alone ; (b) permeable for both ions. The 

 traversing of only one ion through the membrane causes a difference 

 of electrical potential whereby the surface tension is changed. The 

 permeability is altered (a) by alterations of the temperature ; (b) by 

 imbibition with water ; and (c) by absorbed substances which have 

 influenced the membrane, namely — 



n\ P 11 "1 ' ^^ ^^^® same electrical sign. 



^ ' {oi the other electrical sign. 



(2) Non-electrolytes (alcohol, urea, sugar). 



(3) Electrolytes (kations, anions). 



These alterations may be reversible or irreversible. Generally 

 speaking, we can say that (1) the longer a substance was in contact 

 with a membrane the less reversible are the alterations it had caused 

 in the membrane, with regard to permeability. (2) Every substance 

 more or less influences the permeal)ility of a membrane. The in- 

 fluence is especially intensified when the substance enters in chemical 

 reaction with the membrane or when fixed by absorption (impregnation 

 with fat, or lipoids). (3) The greater the density of a membrane tlie 

 less it is influenced. 



Fi'om a biological point of view the results of these facts are that 

 every cell has a membrane or a special superficial layer with other 

 physical pi-operties than the protoplasma. This membrane regulates 

 the entrance and departure of substances. Substances dissolved in the 

 interstitial lii[uid can only influence the cell life if the membrane is 

 permeable for them. Abnoiinal permeability of the membrane pro- 

 duces a pathological metabolism within the cell. Therapeutically 



