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in scientific study should always try to follow these steps exactly. First comes actually making the experiment. This includes collecting and putting together such materials as we may need, a statement of the work we perform, and most important of all, a definite statement of the problem that we are attempting to solve. The second step is to make observations on the experiment which we have set up. These observations may extend over a period of several days or even weeks. They must be noted in such form that we can use them in the third step of the experiment. This step, the hardest of all, consists in drawing conclusions from the observations we have previously made. Every experiment should be illustrated with drawings to show all the apparatus used at each stage of the process.
USE OF NOTEBOOK. Scientific work should be carefully and accurately performed, and the results should be recorded in some permanent form. For this purpose a notebook is used, in which the student makes a complete record, not only of experiments but also of all other work performed in the schoolroom, outdoors or at home. The notebook best adapted to this purpose is one in which the leaves may be added from time to time. For work done outdoors, field trips and the like, it is better to have a separate notebook. This may be used as a working book, in which observations are jotted down in a brief form and later copied in ink in the laboratory notebook. It is of advantage to have all your notes under one cover. •
DRAWING. - Drawing constitutes a very important part of your laboratory work. In scientific drawing, every line made should mean something; the lines should be firm and bold; sketchy work should not be allowed. A hard (HHHHH) pencil should be used. If you are expert with the drawing pen, then make your drawings in ink. Do not attempt to shade your drawing. Every part of the drawing to which you wish to call attention must be carefully labeled. Place a neat index of the parts so labeled directly underneath the drawing, near the bottom of the page. Only one. side of the paper should be used in any scientific work, whether written work or drawings.
THE LABORATORY.-For convenience, science work is usually performed in a room called a laboratory. This room may be fitted up with certain appliances to make the work easier. But in biology the great out of doors makes a much more useful laboratory than any schoolroom. However, observations made at home or out of doors should, when possible, be verified in the laboratory under the supervision of a teacher.
Frequently the laboratory differs little if at all from an ordinary schoolIt should always be well lighted and, if possible, should have north
light as well as some direct sunlight. A corner room is best if it can be obtained. If tables are used, they should be arranged so that each student may get as much light as possible without shading his neighbor.
INSTRUMENTS USED. - Every pupil ought to provide himself, in addition to the laboratory notebook and a hard pencil, with the following articles: a hand lens (a small brass-mounted tripod lens, one mounted in vulcanite, or the small lens known as a linen tester), two or three darning needles mounted in elder pith or in wooden handles, a good eraser, and a ruler marked with the metric system. A small pair of forceps, scissors, and a light, thinbladed knife or scalpel are useful, but not essential for most laboratory work.
INTEREST IN LABORATORY WORK ESSENTIAL.-It is not, however, the laboratory or the equipment that makes the laboratory work a success. It is rather the spirit of the pupils. Interest in the work is the first essential. When at work on what may seem to be only dry details, look ahead and think about what you are doing. Try to find a purpose in everything that you do. It is possible to make any piece of biological work interesting by keeping in mind that everything in nature is part of a great plan and has a purpose. It is your place to find out just how the given part that you may be studying is fitted or adapted to its work in the general plan.
At the end of each of the following chapters is a list of books which have proved their use either as reference reading for students or as aids to the teacher. Most of the books mentioned are within the means of the small school. Two sets are expensive one, The Natural History of Plants, by Kerner, translated by Oliver, published by Henry Holt and Company, in two volumes, $11; the other, Plant Geography upon a Physiological Basis, by Schimper, published by the Clarendon Press, $12; but both works are invaluable for reference.
Two books stand out from the pedagogical standpoint as by far the most helpful of their kind on the market. No teacher of botany or zoölogy can afford to be without them. They are: Lloyd and Bigelow, The Teaching of Biology, Longmans, Green, and Company, and C. F. Hodge, Nature Study and Life, Ginn and Company. Other books of great value from the teacher's standpoint are: Ganong, The Teaching Botanist, The Macmillan Company; L. H. Bailey, The Nature Study Idea, Doubleday, Page, and Company; and C. B. Scott, Nature Study and the Child, D. C. Heath and Company.
II. INTRODUCTORY EXPERIMENTS IN CHEMISTRY AND PHYSICS
In the introductory chapter we learned that science concerns itself with matter, and that the science of biology is concerned with the study of this matter when it is in a living state. order to understand this definition we must first get a conception of what matter really is.
Matter. If you take a piece of ice in your hand, you are aware that it is cold, and that it has weight and a certain form. We call it a solid. A few minutes' exposure to the warmth of your hand will change this solid into a liquid. If the water thus formed be heated over a flame until it boils, it may be changed again, this time into a gas which passes off into the air and becomes invisible. The ice has successively changed from a solid to a liquid and then to a gas. In each state we could measure it and weigh it. In each form it occupies space. It must be considered matter, whether in the form of a solid, a liquid, or a gas.
Physics and Chemistry. The sciences which treat chiefly of the properties and forces of inorganic or dead matter, and of the relations of the parts of the substances composing it, are known as the sciences of physics and chemistry.
Chemical Element. All the building materials of this universe, both living and lifeless, are classified by chemists as either chemical elements or chemical compounds. A chemical element is so simple in its structure that it cannot be broken or decomposed into a simpler substance. Examples of such substances are oxygen, making up about one fifth of the atmosphere; nitrogen, composing nearly all the remainder of pure air; carbon, an element that enters into the composition of all organic living things or those that once possessed life; and over sixty others of more or less importance to us in the study of biology.
Preparation of Oxygen. Oxygen may be easily prepared in the schoolroom or at home in the following manner.1
Heat half a teaspoonful of black oxide of manganese with a little more than its bulk of chlorate of potash in a test tube over a bunsen flame or a spirit lamp. Vapors will be seen to arise as the mixture becomes heated. After a moment insert a glowing match into the mouth of the test tube; it bursts into a bright flame. In what form does oxygen pass off from the two chemicals in the test tube? How could you determine the presence of oxygen in a substance?
Properties of Oxygen.
The physical properties of oxygen are those which we determine with our senses. Oxygen, when carefully prepared, is Preparing oxygen. found to be a colorless, odorless, and tasteless gas. It is known to form nearly one half of the earth's surface, to form eight ninths of all water and over three fourths of the weight of the plants and animals inhabiting this world of ours. It has the very important chemical property of causing things placed in it to burn. If, for example, a piece of picture wire is heated red-hot, and then placed in a jar of oxygen, the metal will burn with a bright flame.
Oxidation. Light carefully a small piece of magnesium wire and then place it in a test tube in which you have previously made oxygen. Notice the very brilliant flame. A light-colored ash remains. This is magnesium oxide. In the above experiment the oxygen in the test tube unites with the magnesium so rapidly as to form a flame. This process is known as a combustion.
The chemical union of oxygen with any other substance is called oxidation. Can you distinguish between combustion and oxidation? Oxidation takes place wherever oxygen is present. These facts, as we shall see later, have a far-reaching significance in the understanding of some of the most important problems of biology.
Oxidation in a Match. The simple process of striking a sulphur match gives us another illustration of this process of oxidation. The head of the match is formed of a composition of phosphorus, sulphur, and some other materials. Phosphorus is a chemical element distinguished by its extreme inflammability. It unites with oxygen at a comparatively low temperature. Sulphur is another chemical element that combines somewhat easily with oxygen but at a much higher temperature. The rest of the match head is made up of red lead, niter or some other substance that will release oxygen, and some glue or gum to bind the materials together. The heat
1 For a concise statement of this and following experiments in the scientific form expected from the pupil, see Hunter and Valentine, Laboratory Manual of Biology, Henry Holt and Company, pages 213 ff.
caused by the friction of the match head against the striking surface is
Experiment.-Oxidation may take place with very little heat present, although heat is always a result of oxidation.
Place an iron nail in a bottle of water, and cork and seal the bottle. Place another nail in a saucer in which is kept a little water. Note the formation of rust on the nail in the saucer and the absence of rust on the nail in the bottle. Rust is iron oxide and is formed by the union of iron and oxygen. This kind of oxidation
is said to be a slow oxidation. Slow oxidations are constantly taking place in nature and result in the process of decay and breaking down of complex materials into simpler materials.
Oxygen in the air
In the Smoke
Diagram of combustion or rapid oxida-
Heat given off as result of Oxidation. One of the most important effects of oxidation lies in the fact that, when anything is oxidized, heat is produced. This heat may be of the greatest use. Coal, when oxidized, gives off heat; this heat boils the water in the tubes of a boiler; steam is generated, wheels of an engine turn, and work is performed. The energy released by the burning of coal may be transformed into any kind of work power. Energy is the ability to perform work.
Carbon. Another chemical element of much importance to us is carbon. This element makes up an important part of all things that now have or at any time had life. Such matter we call organic. Carbon is found making up part of the bodies of plants and animals, of coal, and in a nearly pure state in the diamond. The presence of carbon can often be detected by the fact that the substance containing it turns black upon being heated in a flame.
Experiment. - Heat separately on a tin plate some leaves, sticks of wood, gravel, sand, and rich black earth. Place them over a hot flame for some minutes. Which of the above materials contains carbon?
If some substance that contains carbon, as a piece of wood, is burned in a jar with a tight-fitting cover, the flame will be seen to go out after a short HUNTER'S BIOL. -2