ORGANIZATION. 
31 
the division of labor emerges. First comes a distinction 
between the governing and governed classes; then follow 
and multiply the various civil, military, ecclesiastical, and 
industrial occupations. 
In like manner, as we advance in the animal series, we 
find the body more and more heterogeneous and complex 
by a process of differentiation , i. e ., setting apart certain 
portions of the body for special duty. In the lowest 
forms, the work of life is carried on by very simple appara¬ 
tus. 12 But in the higher organisms every function is per¬ 
formed by a special organ. For example, contractility, 
at first the property of the entire animal, becomes centred 
in muscular tissue; respiration, which in simple beings 
is effected by the whole surface, is specialized in lungs 
or gills; sensibility, from being common to the whole or¬ 
ganism, is handed over to the nerves. An animal, then, 
whose body, instead of being uniform throughout, is made 
up of different parts for the performance of particular 
functions, is said to ie organized. And the term is as ap¬ 
plicable to the slightly differentiated cell as to complex 
Man. Organization is expressed by single cells, or by 
their combination into tissues and organs. 
1 . Cells.—A cell is the simplest form of organized life. 
In general, it is a microscopic globule, consisting of a del¬ 
icate membrane enclosing a minute por¬ 
tion of protoplasm. The very simplest 
kinds are without granules or signs of 
circulation; but usually the protoplasm 
is granular, and contains a defined sep¬ 
arate mass called the nucleus , within 
which are sometimes seen one or two, 
Fig. 1.—Parts of a Cell: 
rarely more, dark, round specks, named <*, t>,y, ceii-waii ; *>,nu- 
nucleoli. The enveloping membrane is cleus ’ w ’ micleolus ‘ 
extremely thin and transparent, and structureless: it is 
only an excretion of dead matter acting as a boundary to 
