COMPARATIVE ZOOLOGY. 
CHAPTER I. 
MINERALS AND ORGANIZED BODIES DISTINGUISHED. 
Nature may be separated into two great kingdoms— 
that of mere dead matter, and that of matter under the 
influence of life. 4 These differ in the following points: 
(1) Composition.— While most of the chemical elements 
are found in different living beings, by far the greater 
part of their substance is composed of three or four—car¬ 
bon, oxygen, and hydrogen ; or these three with the addi¬ 
tion of nitrogen. Next to these elements, sulphur and 
phosphorus are most widely distributed, though always 
found in very small quantities. The organic compounds 
belong to the carbon series, and contain three, four, or 
five elements. The former class, comprising starch, sugar, 
fat, etc., are relatively stable. The latter, possessing the 
three elements named, with nitrogen and sulphur or phos¬ 
phorus, are very complex, containing a very large number 
of atoms to the molecule, and are usually unstable. Here 
belong albumen, myosin, chondrin, etc., the constituents 
of the living tissues. The formula for albumen is said to 
be C 72 H 112 N 18 S0 22 , or some multiple of this formula. 
These compounds also contain more or less water, and 
usually exist in a jelly-like condition, neither solid nor 
fluid. All organic compounds are formed through the 
chemical activities of protoplasm , which is the only living 
substance. Inorganic may, under its influence, be changed 
