A Practical Physiology | Page 3

organisms are studied usually
from two points of view: first, as to their form and structure; second, as
to the processes which go on within them. The science which treats of
all living organisms is called biology. It has naturally two
divisions,--morphology, which treats of the form and structure of living
beings, and physiology, which investigates their functions, or the
special work done in their vital processes.
The word anatomy, however, is usually employed instead of
morphology. It is derived from two Greek words, and means the
science of dissection. Human anatomy then deals with the form and
structure of the human body, and describes how the different parts and
organs are arranged, as revealed by observation, by dissection, and by
the microscope.
Histology is that part of anatomy which treats of the minute structure of
any part of the body, as shown by the microscope.
Human physiology describes the various processes that go on in the
human body in health. It treats of the work done by the various parts of
the body, and of the results of the harmonious action of the several

organs. Broadly speaking, physiology is the science which treats of
functions. By the word function is meant the special work which an
organ has to do. An organ is a part of the body which does a special
work. Thus the eye is the organ of sight, the stomach of digestion, and
the lungs of breathing.
It is plain that we cannot understand the physiology of our bodies
without a knowledge of their anatomy. An engineer could not
understand the working of his engine unless well acquainted with all its
parts, and the manner in which they were fitted together. So, if we are
to understand the principles of elementary physiology, we must master
the main anatomical facts concerning the organs of the body before
considering their special functions.
As a branch of study in our schools, physiology aims to make clear
certain laws which are necessary to health, so that by a proper
knowledge of them, and their practical application, we may hope to
spend happier and more useful, because healthier, lives. In brief, the
study of hygiene, or the science of health, in the school curriculum, is
usually associated with that of physiology.[1]
6. Chemical Elements in the Body. All of the various complex
substances found in nature can be reduced by chemical analysis to
about 70 elements, which cannot be further divided. By various
combinations of these 70 elements all the substances known to exist in
the world of nature are built up. When the inanimate body, like any
other substance, is submitted to chemical analysis, it is found that the
bone, muscle, teeth, blood, etc., may be reduced to a few chemical
elements.
In fact, the human body is built up with 13 of the 70 elements, namely:
oxygen, hydrogen, nitrogen, chlorine, fluorine, carbon, phosphorus,
sulphur, calcium, potassium, sodium, magnesium, and iron. Besides
these, a few of the other elements, as silicon, have been found; but they
exist in extremely minute quantities.
The following table gives the proportion in which these various
elements are present:
Oxygen 62.430 per cent Carbon 21.150 " " Hydrogen 9.865 " "
Nitrogen 3.100 " " Calcium 1.900 " " Phosphorus 0.946 " " Potassium
0.230 " " Sulphur 0.162 " " Chlorine 0.081 " " Sodium 0.081 " "
Magnesium 0.027 " " Iron 0.014 " " Fluorine 0.014 " " ----- 100.000

As will be seen from this table, oxygen, hydrogen, and nitrogen, which
are gases in their uncombined form, make up 3/4 of the weight of the
whole human body. Carbon, which exists in an impure state in charcoal,
forms more than 1/5 of the weight of the body. Thus carbon and the
three gases named, make up about 96 per cent of the total weight of the
body.
7. Chemical Compounds in the Body. We must keep in mind that, with
slight exceptions, none of these 13 elements exist in their elementary
form in the animal economy. They are combined in various proportions,
the results differing widely from the elements of which they consist.
Oxygen and hydrogen unite to form water, and water forms more than
2/3 of the weight of the whole body. In all the fluids of the body, water
acts as a solvent, and by this means alone the circulation of nutrient
material is possible. All the various processes of secretion and nutrition
depend on the presence of water for their activities.
8. Inorganic Salts. A large number of the elements of the body unite
one with another by chemical affinity and form inorganic salts. Thus
sodium and chlorine unite and form chloride of sodium, or common
salt. This is found in all the tissues and fluids, and is one of