166 L. V. HEILBRUNN. 



contact with the egg contents. Both surfaces are solid-liquid 

 surfaces, and as such no doubt possess a high surface tension. 1 

 The arrow C represents the sum of the radial components of 

 the tension of both inner and outer surfaces of the membrane. 

 Suppose now that a substance which lowers the surface tension 

 of water, is added to some eggs in sea-water. By what is known 

 as the Gibbs-Thomson Law it will tend to accumulate at the 

 surfaces of the vitelline membrane. This will result in a lowering 

 of the surface tension of the membrane. 2 As a result equili- 

 brium no longer exists, the force pushing outward is now stronger 

 and the membrane is lifted away from the egg surface. Most 

 of the egg proteins do not follow the membrane as it is lifted 

 away, but remain in their original position. This is due to the 

 fact that they diffuse much less readily than the salts, which 

 can be thought of as pushing out the membrane. Around the 

 mass of egg proteins a membrane is rapidly formed. As prev- 

 iously pointed out, this "hyaline layer" is to be regarded as 

 similar to the precipitation membranes formed on egg fragments. 

 As a result of elevation, the vitelline membrane is no longer 



1 The surface tension of a solid-liquid surface has never been accurately deter- 

 mined, but there are various reasons for considering it the seat of an exceptionally 

 high tension. For the similar case of a solid-gaseous surface Freundlich ("Kapil- 

 larchemie," p. 90) following Quincke states that "die Oberflachenspannung fliissig- 

 gasformig steigt allgemein mit sinkender Temperatur. Wenn nun die Flussigkeit 

 stetig in einen amorph-festen Korper eine Flussigkeit mit sehr groszer innerer 

 Reibung iibergeht, musz man auch annehmen, das die Oberflachenspannung 

 bestehen bleibt, ja das sie zunehmend groszere Werte erhalt wenn sie sich auch 

 wegen der groszen Zahigkeit nicht auszern kann." With the aid of a formula 

 derived by Wilh. Ostwald, Freundlich calculates the tension of solid-liquid 

 surface BaSC>4- water to be several thousand dynes per cm., an enormous value. 

 In his wonderful treatment of capillarity Gibbs devotes a long section to the dis- 

 cussion of solid-liquid surfaces (Gibbs, Collected Papers, I., 314-331), and derives 

 various equations for them. In discussing the surfaces of the membranes, I have 

 for the sake of simplicity not considered the presence of the jelly of chorion, which 

 surrounds the egg. This is so diffuse a gel that it no doubt [has little if any effect. 

 In fact, after its removal (by shaking), the eggs behave just as they did before. 



2 Gibbs, loc. cit., p. 274: "Now the potential of a substance which forms a very 

 small part of a homogeneous mass certainly increases, and probably very rapidly, 

 as the proportion of that component is increased. (See (171) and (217).) The 

 pressure, temperature, and the other potentials, will not be sensibly affected (see 

 (98)). But the effect on the tension of this increase on the potential will be pro- 

 portional to the surface-density, and will be to diminish the tension when the 

 surface-density is positive (see (508))." The numbers refer to equations. When 

 a substance accumulates at a surface, its surface density is by definition positive. 



