110 



LIFE: ITS NATURE AND ORIGIN 



most of the enzymes, which, with the genes, mainly direct the 

 course of chemical change in bionts, are free particulate units of 

 colloidal dimensions. The establishment of colloidal dimensions 

 may come about in several ways. Some molecules are born col- 

 loids; some achieve colloidality by molecular growth or aggrega- 

 tion; and some have colloidality thrust upon them by adsorption 

 or chemical fixation on a colloidal carrier or an extended surface. 

 Whatever the underlying cause, increase in particle size causes 



SPECIFIC 

 SURFACE 



.KINETIC 

 MOTION 



SOLIDS 



SUSPENSIONS 



CURVE SHOWING RISE AND FALL 

 OF COLLOIDAL CHARACTERISTICS 



INCREASING PARTICLE SIZE 



Figure 16. Degree of colloidality related to particle size, specific surface and 

 kinetic activity. (From paper in "Colloid Chemistry," Vol. 5, by J. Alexander, Rein- 

 hold Publishing Corp., N. Y.) 



a reduction in kinetic motion, as may be readily seen in an ultra- 

 microscope. Particles at the lower ranges of microscopic resolu- 

 tion (about 0.25 micron) show only the feeble Brownian move- 

 ment. On the other hand the kinetic motion of small molecules 

 is so rapid that if a hydrogen molecule were large enough for the 

 eye to resolve, it would still be invisible, just as in the case of a 

 rifle bullet in flight. Between these two extremes lie all degrees 

 of the kinetic motion of particles, which increases at an accelerated 

 rate as molecular dimensions are approached. 



