A Practical Physiology | Page 3

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 the most important inorganic salts the body contains. It is absolutely necessary for continued existence. By a combination of phosphorus with sodium, potassium, calcium, and magnesium, the various phosphates are formed.
The phosphates of lime and soda are the most abundant of the salts of the body. They form more than half the material of the bones, are found in the teeth and in other solids and in the fluids of the body. The special place of iron is in the coloring matter of the blood. Its various salts are traced in the ash of bones, in muscles, and in