18 Prof. B. Moore and Mr. W. G. Evans. Forms of Growth 



supercooled solution of a crystalloid, but it differs in that the appearance of 

 the solid or " gel " phase of the colloid does not lead, as in the case of the 

 crystalloidal state, to almost instantaneous separation of the excess of salt 

 and establishment of a stable equilibrium, but instead of that, to a slow 

 drifting towards an equilibrium which may go on for days or weeks or months, 

 and vary in speed, or be actually reversed, with changing characters of 

 environment. 



It has been demonstrated by the work of Moore and Eoaf* on the effects 

 of variations in temperature upon the osmotic pressure of gelatine solutions, 

 that a similar metastable condition arises long before any precipitation or 

 passage from a hydrosol to a hydrogel occurs. If a mobile solution of 

 gelatine at a temperature high above the point of gel-formation be raised a 

 few degrees in temperature, the osmotic pressure is considerably increased in 

 3xcess of the amount demanded by the gas law, showing that there occurs 

 some dissociation in the solution-aggregate of the colloid. If, now, the 

 temperature be allowed to fall back to the original point, only a small drop in 

 osmotic pressure occurs at first and it requires some days before the original 

 level is reached. This peculiar hysteresis requiring a prolonged interval of 

 time for the passage from one condition to another is of great biological 

 interest and may lie at the root of those cyclic alternations, of varying times 

 in different tissues, so characteristic of living matter. 



The present communication is concerned with another interesting similarity 

 between inorganic colloids and living structures, namely, that the forms 

 assumed as a result of these slow metastable depositions, or growths, so closely 

 resemble lowly living organisms as to be, in many cases, most difficultly 

 distinguishable from them. In our view, it is this close mimicry between 

 colloidal deposits and living organisms which is responsible for more than one 

 previous observer having described as living organisms such slow growths in 

 metastable solutions. 



Eapid osmotic growths between strong solutions of colloids and of 

 crystalloids, capable in most cases of slowly precipitating one another and 

 so forming precipitation membranes, have been studied in most painstaking 

 and ingenious ways by a great host of observers.f These experimentalists 

 have shown that similar effects to production of cell-membranes, skeletons, 

 shells, and tests, and also of mitotic nuclear-division figures, and many 



* ' Biochemical Journ.,' vol. 2, p. 34 (1907). 



t Such as Gustav Rose, Bunge, Bottger, Traube, Harting, Monnier and Vogt, Quincke, 

 Leduc, Benedikt, Dubois, Herrera, Kuckuck, Albert and Alexandre Mary, and others. 

 Accounts of the literature of the subject are to be found in Leduc, ' Mechanism of Life,' 

 Bebman, London, 1911, and Quincke, ' Annalen der Bhysik,' 4te Folge, vol. 7, p. 631 

 (1902). 



