ORGANIZATION. ol 
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, 7. 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 apparatus.” 
But in the higher organisms, every function is performed 
by a special organ. For example, contractility, at first the 
property of the entire animal, becomes centred in mus- 
cular tissue ; respiration, which in simple beings is effect- 
ed by the whole surface, is specialized in lungs or gills; 
sensibility, from being common to the whole organism, is 
handed over to the nerves. An animal, then, whose body, 
instead of being uniform throughout, is made up of differ- 
ent parts for the performance of particular functions, is 
said to be organized. And the term is as applicable to 
the slightly differentiated cell as to complex Man. Or- 
ganization is expressed by single cells, or by their combi- 
nation 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 deli- 
cate membrane inclosing 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 nwclews, within 
which are sometimes seen one or two, 
Fira. 1.—Parts of a Cell: 
rarely more, dark, round specks, named _ a,»,», cell-wall; p, nu- 
nucleolt. The enveloping membrane is cau ieee 
extremely thin and transparent, structureless and minutely 
perforated: it is only an excretion of dead matter acting 
as a boundary to the cell-contents."* The nucleus is gen- 
