70 THE BEGINNINGS OF LIFE, 



to the rate at which they emerge from the state of 

 solution. Molecules which come together suddenly and 

 tumultuously aggregate into mere formless granules, 

 whilst those which come together more slowly are 

 enabled to collocate into that geometrical form in 

 which their molecules exist in a state of polar equi- 

 librium. The crystalline is, undoubtedly, a higher 

 mode of aggregation than the amorphous, and it is the 

 highest form which it is possible for the molecules of 

 a crystalloid to assume. But when we turn to the 

 different kinds of colloidal matter, we shall find, as 

 might be expected from a consideration of its superior 

 molecular complexity, that a still more marked differ- 

 ence exists between the various solid aggregates which, 

 under the influence of different conditions, can be made 

 to emerge from solutions containing such matter. 



When many albuminous fluids are heated to 140""- 

 2I2°F, it causes an isomeric modification of the pro- 

 tein substances and their precipitation throughout the 

 uid in the form of minute particles^. These are tole- 

 rably similar in size and form to those which appear 

 when a saline substance is precipitated in the condition 

 of an insoluble powder, owing to the rapid and simul- 

 taneous union of constituents whose affinity for one 



^ This is one of the best means of seeing Brownian movements of the 

 most typical kind, especially if a drop of the fluid be examined whilst 

 still warm. Heavier saline granules no larger in size may not exhibit 

 such movements at all, or else only very imperfectly. The albuminoid 

 molecules also cease to vibrate in syrup, glycerine, or fluids of similar 

 consistence. 



