Chapter V — 31 — Physical Chemistry 



minimum of solubility, a minimum of viscosity and of linkage with 

 peripheral electrolytes (i.e., minimum ability to combine), mini- 

 mum swelling in water, maximum rigidity and maximum insta- 

 bility in solution. At the isoelectric point the ampholyte is ex- 

 tremely apt to flocculate. It seems therefore that the fundamental 

 properties of cytoplasm must be dominated on the one hand by the 

 pB. of the intracellular liquids and on the other hand by the iso- 

 electric point of its constituents. 



Physical constitution of cytoplasm:- The classical researches of 

 Mayer and Schaeffer (1908) made an important contribu- 

 tion to the study of the colloidal state of cytoplasm in so far as 

 animal cells are concerned. These results apply equally well to 

 plant cells and must be considered first. 



Mayer and Schaeffer undertook first the study, with the ultra- 

 microscope, of colloidal solutions of different organic colloids. 

 They then in a comparative way were able to begin the study of 

 animal cells. They showed that these solutions may present 

 two very different optical appearances. Some, such as glycogen, 

 dialyzed albumin, and diastases, are characterized by a suspension 

 of a large number of micelles, brightly lighted and animated by 

 Brownian movement. These are the hydrosols. Others, such as 

 white of egg and nucleoproteins, appear optically empty and with- 

 out any visible micelles whatever. They are filtered with difficulty 

 and show very high viscosity. They are composed of micelles con- 

 taining a great deal of water, thus possessing a strong linkage with 

 the intermicellar liquid, i.e., water, so that the micelles do not 

 refract light and do not appear in the ultramicroscope. To these 

 latter liquids, Mayer and Schaeffer give the name fluid hydrogels. 

 Under certain influences, by hydration of their micelles, these hy- 

 drogels can be transformed into hydrosols. They appear as con- 

 fused luminous streaks — this is called the non-resolvable nebulous 

 stage — then as very fine granules which agglomerate progressively 

 and the field becomes completely starred with brilliant dots. This 

 is the resolvable nebulous state i.e., flocculation. This reversible 

 phenomenon may be succeeded by a more important and irreversible 

 modification, coagulation, accompanied by physical and chemical 

 phenomena which finally agglomerate the particles into a single 

 mass. 



So Mayer and Schaeffer set off against each other two dif- 

 ferent physical states: the hydrosol, appearing in the ultramicro- 

 scope as a suspension of micelles vividly lighted and animated by 

 Brownian movement, a state similar to that presented by pseudo- 

 solutions of metals; and the hydrogel appearing as an optically 

 empty pseudosolution which is very viscous. These investigators 

 designate by the name jelly the semi-solid state of the hydrogel 

 which is much more viscous and endowed with a very definite 

 rigidity. This terminology is not accepted by all authors. Some 

 writers distinguish the hydrophobic colloids (mineral colloids) 

 whose micelles do not have any affinity whatever for water and 



