ON COLLOID CHEMISTRY AND ITS INDUSTRIAL APPLICATIONS. 121 
It has frequently been felt to be a difficulty, from the standpoint 
of energetics, that cells use energy for purposes in which it is not 
easy to make out what has become of it. Warburg (1914) suggests 
that it may be required for the keeping apart of substances which 
would mix by diffusion, for the preservation of semi-permeable 
membranes, the restriction of osmotic interchange and so on, all 
of these phenomena being manifested in microscopic or even ultra- 
microscopic dimensions. A discussion of phase relations in proto- 
plasm in connection with equilibrium and energy will be found in 
the essay by Zwaardemaker (1906). 
A property of emulsoid colloids which has its importance in the 
present connection is their capacity of taking up water by what is 
ofven called “imbibition.” The distribution of water between the 
two phases can be varied to a large extent by the presence of 
electrolytes and other agents. Whether imbibition is mainly or 
entirely an adsorption of water at the swface of the constituent 
elements, as is indicated by the experiments of Posnyak (1912) and 
by some which I did myself on gelatin (‘General Physiology,” 
p. 101), it is clear that the concentration of solutes in the liquid 
phase must be raised thereby. Since the position of equilibrium in 
reversible hydrolytic reactions, catalyzed by enzymes, depends on 
the concentration of water present, we see how at one time a 
synthetic product, such as glycogen, is hydrolyzed, and at another 
time glucose is synthesized to glycogen by the same enzyme. What 
is required is merely a means of varying the free water, and the 
possibility of this is provided by the presence of highly dispersed 
emulsoid colloids. 
In addition to the highly dispersed systems discussed above, 
protoplasm usually contains various larger aggregates and structures. 
Chambers (1917) calls the small particles visible under the ordinary 
microscope, “ microsomes,” and the larger ones, ‘‘ macrosomes.” He 
shows that the former are stable, the latter very sensitive to 
injury. There are also certain granules, of various forms, called 
‘mitochondria.’ Cowdry (1916) has devoted special attention 
to these and finds that they are stained in the living state by dyes" 
which contain a diethyl-safranin group, such as Janus-green B, and 
are apparently composed of albumin and lecithin. Ih the living 
state they are cqntinually changing shape, and especially in cells 
during activity. 
In the present state of knowledge, it would be unprofitable to 
speculate further on the functions of these different inclusions. 
The same may be said of the nucleus of the cell. That this is 
essential to continued life, growth, and subdivision is clear. Much 
attention has been given to the series of changes which it under- 
goes in the last process, called “ mitosis,” or “ karyokinesis.” They 
are obviously due t» the ordered arrangement of certain vectorial 
_ forces, having a definite focus of origin, but we are still in the 
dark as to their meaning. Much importance has been attached to 
the number of distinct staining elements, ‘“ chromosomes,” produced 
ata particular stage of the process. 
Unwarranted conclusions are sometimes drawn as to the chemical 
nature of substances found in cells from their behaviour to dyes. 
