# The New Student's Reference Work/Biology

See also Biology on Wikipedia, and the disclaimer.
​Biology, a subject of great interest and importance, not only to scholars and medical men, but to all intelligent people who care for living nature. All questions in regard to the living world belong here. An animal or plant is wonderfully constructed, but, after all, the most wonderful thing about it is that it is endowed with life. While it is interesting to observe the structure of animals and plants, it is even more interesting to learn the purpose of the structure and to determine what is taking place within their bodies, what has been their past history, how they behave in reference to their surroundings, etc. This is, of course, very difficult; it requires observations with and without the microscope, experiments, and the use of the best powers of the mind.
Biology is an attempt to analyze the activities of life and finally, if possible, to give an explanation of the same. It is one of the natural sciences and is related to many branches of learning. It is easily separated from physics and chemistry, both of which deal with lifeless matter, but is is closely connected with natural history, medicine, physiology, botany, zoölology, psychology and with many affairs of everyday life.
Biology in its modern sense is of recent origin. It is customary to consider it as having taken rise about 1860, but in order to understand the reason for this way of looking at the matter, it will be necessary to trace the growth of the subject. It is ​a long story, reaching over several centuries, but it can be briefly told.
Among the ancient Greeks observations directly upon animals and plants led to many facts of natural history. Aristotle (384-322 B. C.) is the best representative of the knowledge of his time about life. But after a few centuries the mind of mankind was turned away from nature. In due course of time, there was a complete arrest of inquiry into all things relating to the external world.
During this period, other branches of learning might make a little advance, but the knowledge of nature suffered the most, because we cannot know anything about natural phenomena without turning the mind outward and making direct observations upon the external world. Therefore, it was an epoch of great importance when men began again to observe, to use their eyes, and to turn to the great world of nature outside themselves. The men who started independent observations deserve much credit, for the authorities of both church and state were unfriendly to unbiased inquiry, and they went against every motive of self-interest in becoming pioneers in the new intellectual life. Vesalius (see Anatomy), Galileo and Descartes were among the reformers in the 16th century, and in the 17th century the work of Malpighi, Swammerdam and Leeuwenhoek is worthy of especial mention. Their great work consisted chiefly in this, that “they broke away from the thraldom of book-learning, and, relying alone upon their own eyes and their own judgment, won for man that which had been quite lost, the blessing of independent and unbiased observation.”
Thus awoke again the good spirit of inquiry and thereby the foundations of modern science were laid. When attention was turned to animals and plants, the first things noticed were, of course, the simplest and most obvious: external form, color, habits. This is the period in which the organism was studied as a whole, for each plant and animal is an organism. The naturalist of the time knew relatively little about the internal structure of animals and plants but many general facts about them. Linnæus and Ray represent this level of knowledge. For them, the study of nature consisted in observing and collecting widely, grouping or classifying animals and plants, learning about their habits, etc. Linnaeus made an epoch by introducing a method of naming plants and animals by giving to each two names—a generic and a specific name. This made knowledge more definite. He used Latin, which was the language of science, and, as his method was universally adopted, the same name came to apply to the same animal or plant in all countries. This directed the attention of naturalists to species or particular kinds, and thereby prepared the way for the discussion of the origin of species, which is the fundamental question in the doctrine of organic evolution.
But another advance was to come. The next natural step after the study of the organism as a whole was to think of its architecture or the way in which it is constructed. Men began, therefore, to observe the organs or parts that are united together to make up animals and plants. This was a study of internal structure. The construction of animals was studied very widely and they were compared with one another, so that there arose the new science of comparative anatomy (see Anatomy) of which Georges Cuvier (1769-1832) was the founder. Similar work was done for plants by Jussieu. But knowledge of nature was becoming so much extended that it was necessarily subdivided, and investigations into the uses of the organs were being made by physiologists like Haller and J. Müller (see Physiology) at the same time that structure was being studied by the anatomists.
The next step was based on the observation that organs are composed of simpler parts called tissues. Often several different kinds of tissue will unite into one organ; for example, the heart is not all muscle but connective tissue and nerves enter into it; the walls of the stomach also contain glands, muscles, nerves, connective tissue, etc., all united to form the one organ—the stomach. The leaf of a plant is not all one kind of tissue, but several different kinds enter into it. We are thus approaching step by step the finer structure of living beings. Bichat (1771-1802) studied the tissues extensively, and at the beginning of the 19th century laid the foundation of microscopic anatomy or histology.
The next step was based upon the perfection of the microscope. This instrument had been introduced, in a crude form, into natural history in the 17th century, and had opened a new world to naturalists. About 1840 great improvements were made in manufacturing the magnifying glasses for the microscope, and observers began gradually to see that the tissues are not the simplest parts of animals and plants, but that tissues are composed of very small units or particles, brought together and built into the tissues as bricks might be fitted together into a building. This idea took definite form about 1839-40, principally through the observations of two men, Schleiden and Schwann. The former was a botanist, and he came to the conclusion that all the parts of plants are built of little box-like compartments or cells. The latter, his friend, was an anatomist and zoölogist, who, from his studies with the microscope on animals, reached ​similar conclusions. This great discovery unites all animals and plants on a broad plane of similitude of structure. It is known as the cell theory, and has done much toward unifying the knowledge of animals and plants. This, taken in connection with the fact that all animals and plants arise from a single cell, has great meaning. The discovery that the egg of all animals is a single cell, shows that the starting-point is one of the single bricks of organic architecture, which by successive divisions gives rise to all the others that enter into the construction. Plants also proceed from a single cell. These are among the most remarkable facts in all nature. In its original form, however, the cell theory was very imperfect. Both Schleiden and Schwann supposed that the cell wall was important, and looked upon the cells as little box-like compartments. This had to be changed by later students, and the cell theory was reformed and modified into the protoplasm theory.
The progress, thus far, had brought out the facts that cells are joined to make tissues, the tissues to make organs, and organs to make the organism, but there was one further step to be taken to bring this line of advance to its proper goal. It was soon discovered that the cell wall of cells is not important, but that the jelly-like viscid fluid within is the substance that is actually alive. This substance is the seat of all life and is called protoplasm (see Protoplasm). We see that observations began on the outside and led by a series of steps to the true seat of life, just as a flight of stairs, uncovered by some good genii in the old fairy tales, led from the surface to a treasure cavern, but it took a good many years for naturalists to take each step. Max Schultze, in 1860, placed the ideas about protoplasm on a firm basis, and from that time dates modern biology, which is all about this living substance—-what it is like in its various manifestations, what it is doing, and what it has done in the world.
Therefore, a great deal of the work of the biologist is the study of this living substance at first hands. He can place under his microscope the simplest plants and animals, and if they are translucent enough to let the light through, he can see many things that are taking place within the protoplasm. One of the common organisms of great interest to biologists is the amœba—a simple microscopic particle of living jelly in which the processes of life are reduced to their simplest expression, and it meets all the requirements for observation. This organism is really an animal and a single cell, and, therefore, it lies near the bottom of the animal series.
By suitable experiment and observation it can be shown that the amœba, simple as it appears, is really very complex, on account of the powers and activities which it exhibits by virtue of being alive. A list or catalogue of its activities will be the same as those occurring in the various tissues and organs of higher animals. Therefore, we have in it the germ of all the activities of the higher creation. Its body is a little mass of protoplasm, and anything determined about it holds good for protoplasm. This substance is the only one in the world that is endowed with life, and biologists have come to the conclusion that it is practically identical in plants and animals, but at the same time exhibits a wide range of variations and differences, not in kind, but depending on the degree of perfection and specialization.
Protoplasm has properties which, taken together, distinguish it absolutely from every form of non-living matter. These are: (1) its chemical composition; (2) its power of waste and repair and of growth; (3) its power of reproduction. Other substances are simpler in composition than protoplasm, in fact, it is the most complex substance in the universe. Common chemical elements like carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus, enter into it, but they are combined in a very much more complex manner than in any other substance, and they are all present at the same time. Living matter is also continually undergoing a process of breaking down, by a sort of internal combustion, and making good the loss by the manufacture of new protoplasm out of the simpler food particles. It also has the power of growth, and “lastly, living matter not only thus repairs its own waste, but also gives rise, by reproduction, to new masses of living matter; which, becoming detached from the parent mass, enter forthwith upon an independent existence.”
“We may perceive how extraordinary these properties are by supposing a locomotive engine to possess like powers: to carry on a process of self-repair in order to compensate for wear; to grow and increase in size, detaching from itself at intervals pieces of brass or iron endowed with the power of growing up step by step into other locomotives capable of running themselves, and of reproducing new locomotives in their turn. Precisely these things are done by every living thing, and nothing like them takes place in the lifeless world.”—Sedgwick and Wilson, General Biology.
The higher animals, all of which are many-celled, may be looked upon as combinations of amœba-like elements, variously modified and built into the tissues. In passing from the condition of a single cell to that of many there has been not only an increase in the number of cells, but there has been also a physiological division of labor, so that particular groups of cells ​have been set apart to perform a certain particular round of duties, while other cells have been set aside for other work. For example, the protoplasm of certain cells has become very contractile and forms the muscles; in certain other cells the protoplasm has become highly irritable and responsive, and makes the nervous tissues; and so on for the other groups. This physiological division of labor has led to the different tissues.
Plants show very nicely the gradations between the single-celled and the many-celled condition. There are first linear aggregates, in which the cells are united end to end in a single row. The next step is groups of cells arranged in a single layer to form an expanded surface; and finally the combination of cells into a solid mass having length, breadth and thickness.
In biology, animals and plants are considered from a variety of view-points: as to their Structure, or the way in which they are constructed (see Anatomy); as to their Development, or the stages through which they pass from the egg or seed to the adult (see Development); as to their Physiology, or the uses of the different organs and the changes that are taking place in the protoplasm of the tissues; as to their Distribution. Biology is, therefore, a complex science, and is the result of the concurrent progress in all these departments. It may be likened to a great stream into which a number of smaller streams have united to make the main one, and it contains mixed together the product of all.
The main divisions of biology are, of course, greatly subdivided; for example, under structure, we might consider animals and plants in reference to their surroundings, and show that the structural peculiarities are the result of responses to the surrounding conditions, and we might further show how likeness in structure indicates relationship, and is the basis upon which animals and plants are classified or arranged into systematic groups. Moreover, development and physiology are very extensive branches, and must be divided into smaller topics for practical consideration. In reference to the distribution of animals and plants, it must be said that it takes two directions: first, their geographical distribution, and, secondly, their distribution in time. The first will be clear without further statement, but the second requires a word. We know that there are entombed in the rocks countless numbers of animals and plants that lived centuries ago and became extinct. The succession of life in the rocks is very interesting, beginning as it does with the lowest forms, in the earliest formed rocks, and passing to the higher ones in the later formed rocks. In this succession of stages we can read the past history of life on the earth, and this has helped greatly in establishing the doctrine of organic evolution.
It is an indefinite line that separates biology from botany and zoölogy. Modern botany and zoölogy embrace all that is known about plants and animals respectively, but the plant kingdom and the animal kingdom are considered separately. In biology the facts are approached from a different standpoint, and the emphasis is differently placed. The phenomena of life are brought into union in both animals and plants, and the attention is especially directed to the activities of protoplasm, and its responses to surrounding conditions. General biology is a term in common use to indicate the consideration of certain general facts about animals and plants. It is recognized as a distinct branch, and frequently studies of these general topics are made to precede studies that are mainly botanical on the one hand, or mainly zoölogical on the other.
These facts should make clear how the department of biology arose and what it is about; but before leaving the subject we should at least glance at its 19th century features. The three things that most distinctly mark biological advance during the 19th century are: (1) The cell-doctrine (which see),—the discovery of the fact that, with the exception of unicellular forms, plants and animals are composed of groups of cells, and moreover, that they all begin their existence as eggs or ovules, in the single-cell condition. (2) The discovery of protoplasm (which see), and the recognition of the rôle it everywhere plays in animal and plant life. (3) The doctrine of organic evolution, or the discovery of the genealogy of animals and plants.
There are in addition other things to be mentioned: The great extension of knowledge in reference to microbes and bacteria (which see) has been characteristic. Advances in this direction have led to the discovery of the nature of fermentation, of decay, to the germ theory of disease, etc.; and have also brought in their train an unusual number of practical applications: antiseptic surgery, the canning of fruits and meats, infecting insects with disease to stop the ravages of the injurious kinds; and also the protection of silk-worm culture, etc.
The growth of information regarding the development of animals and plants has been very great, and has been turned to account in reading the past history of life.
The question of the spontaneous origin of life was revived in 1858. That is the belief that the simplest microscopic forms of life are sometimes formed, spontaneously, from lifeless matter. But it was ​again answered in the negative, as it had been in the 18th century, and finally it was put to rest through the work of Pasteur, Tyndall and others.
In the latter part of the century experiments on living forms became prominent. The eggs, the larvae and the older stages have been placed under different conditions of temperature, light, food, chemical and mechanical surroundings, and the effect of these changes watched. Many important facts have been brought to light by these experiments.
Biology is a body of rapidly expanding knowledge of intense interest and great service to mankind. Much was accomplished by it in the 19th century, but much more is to be expected in the 20th century.
For books about biology, see Sedgwick and Wilson's General Biology, Parker's Elementary Biology and Thompson's The Science of Life. Additional titles will be found under Anatomy, Botany, Zoölogy.