LIFE: ITS ORIGIN AND NATURE 23 
is a highly complex substance, and is, in turn, 
built up of a number of complex compounds. 
Recent researches have shown that life depends 
upon the presence of basic “colloids” as they 
are called,—known as colloidal substances or 
solutions. Colloids are gummy, semi-fluidic 
substances, which may be either organic or in¬ 
organic in nature. A typical example of the 
latter would be gum arabic. A c ystalloid, on 
the other hand, would be exemplified by a solu¬ 
tion of common salt. 
Colloids show two distinct forms of molecular 
arrangement, known respectively as “hydro- 
sols” and “hydrogels.” Thus a solution of glue 
or gelatine at such a temperature that it is 
fluid and mobile is a hydrosol; at a lower (or 
higher) temperature it sets into a solid jelly, 
and is then a hydrogel.. The white of an egg 
(uncooked) would be a good example of 
an organic hydrosol. When it is cooked, how¬ 
ever, it is converted into a hydrogel. 
The living body, as we know, is built up of 
proteins, fats, carbohydrates, water, and minute 
traces of various “salts,” in organized form. 
These various substances are supplied to the 
body in the form of food, are constantly being 
converted into bodily substances by the various 
processes of digestion. Carbohydrates are con¬ 
verted into fats; glycerine and soaps are form¬ 
ed in the body; various amino-acids are formed, 
new proteins are developed, and in fact the 
substances which we eat are converted and re¬ 
converted, in the body, into a number of sub¬ 
substances, before they are finally utilized. A 
great deal of work has been done in the past, 
