Chapter V — 35 — Physical Chemistry 



appears optically empty as Mayer and Schaeffer described it. 

 What remains still obscure in the question is the physical structure 

 which can be attributed to that optically empty state which charac- 

 terizes the cytoplasm, both in plant and animal cells. From every 

 point of view the cytoplasm appears as a colloidal solution or a 

 fluid gel. It is not, however, miscible with water. This is a fact 

 of capital importance which distinguishes it essentially from all 

 gels or solutions. To designate the peculiarity of this gel-like sys- 

 tem of not being able to mix with the excipient, water, although 

 water represents 90% of its weight, the Italian physiologist, BOT- 

 TAZZI, has created the term gliode. The gliode is a colloidal system 

 existing exclusively in living cells, particularly in the cytoplasm. 

 Keuyt and Bungenberg de Jong in recent work have sought 

 to explain this peculiarity by considering the cytoplasm not as a 

 hydrogel but as a coacervate. They have shown that a very slight 

 addition of the precipitating agent may bring about, at first, a par- 

 tial separation of the colloid from the solution, in the form of a 

 mass retaining a considerable quantity of the solvent and still 

 showing, in consequence, a more or less marked fluidity. This col- 

 loid which is fluid but more concentrated than the original system 

 is miscible with an excess of the solvent. This phenomenon is 

 called coacervation and the fluid mass, separated as described, is 

 called the coacervate. Now coacervate systems are very reminis- 

 cent of cytoplasm. Such systems can be prepared in the laboratory. 

 Bungenberg de Jong has been able to produce coacervates in which 

 water, proteins and lecithins, i.e., the normal constituents of proto- 

 plasm, are actually associated in artificial cells, presenting striking 

 analogies with real cells and showing a central body, like the nu- 

 cleus, and globules of oil, separated by invisible films. What is 

 more, these systems are stable when the pH value is in the neigh- 

 borhood of 7.4, i.e., when the pH values are comparable to that 

 which seems to exist in the cytoplasm. Of course these resemb- 

 lances are of a purely physical nature and do not in any way con- 

 cern the absolutely inimitable physiological activity of living 

 cytoplasm. 



Cellular constants and equilibria:- Some substances exist in the 

 protoplasm in greatly varying proportions, depending upon internal 

 or external factors (nutrition of the organ and the condition of the 

 medium respectively). The glycerides are such substances and in 

 the cells constitute transitory deposits which, by their nature, are 

 capable of being mobilized. This is not true of the permanent 

 constituents of the cytoplasm, such as the proteins, lipides and 

 water. These latter show differing properties and keep their differ- 

 ing properties when in the cell. The stability of the cell is main- 

 tained only because its various properties are in equilibrium. The 

 permanent constituents are present in the cytoplasm in fixed pro- 

 portions, independent of external or internal conditions. 



Mayer and Schaeffer have done some work on animals, the 

 results of which it would seem possible to extend to plants. They 



