FOR TEACHERS 
 
 TO ACCOMPANY 
 ELEMENTARY BIOLOGY " 
 
 v 
 
 GRUENBERG 
 
GIFT OF 
 Agricultural Educ.Div. 
 
 THWF n- 
 
 BIOLOGY 
 
 LIBRARY 
 
 G 
 
MANUAL OF SUGGESTIONS 
 FOR TEACHERS 
 
 TO ACCOMPANY 
 
 "ELEMENTARY BIOLOGY" 
 
 BY 
 
 BENJAMIN C. GRUENBERG 
 
 n > > n , 
 
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 v 
 
 GINN AND COMPANY 
 
 BOSTON NEW YORK CHICAGO LONDON 
 ATLANTA DALLAS COLUMBUS SAN FRANCISCO 
 
BIOLOGY 
 
 LIBRARY 
 
 G 
 
 MAIN LIKAKV.A<imCUCttme DEFT. 
 
 COPYRIGHT, 1919, KY 
 BENJAMIN C. GRUENBERG 
 
 ALL RIGHTS RESERVED 
 319.9 
 
 
 
 atftcnaum 
 
 GINN AND COMPANY PKO 
 PRIETORS ' BOSTON ' U.S.A. 
 
PREFACE 
 
 This manual is intended to aid the teacher in organizing in- 
 struction material and ideas for effective presentation in connec- 
 tion with the author's " Elementary Biology." It is no substitute 
 either for a knowledge of the subject matter or for the technique 
 of teaching. 
 
 Since the text which the manual is to accompany is largely 
 concerned with showing how a knowledge of living things helps 
 human beings, the notes here offered are largely concerned with, 
 suggesting interpretations and applications. The method of treat- 
 ment implied throughout assumes a changing body of knowledge 
 tor the teacher, and a changing civic and intellectual environment 
 for the pupil. New problems and new needs calling for additional 
 knowledge, new discoveries enlarging the horizon, new thought 
 bringing new insight and new significance these represent the 
 permanent stream, to be surveyed in its main ramifications even 
 while it flows. This means imagining as well as remembering, it 
 means doubting as well as believing, but it means also, of course, 
 learning much more outside the book than in it. 
 
 The references are all useful ; but even the most specific and 
 authoritative are transients. Here the intention is to guide teacher 
 and pupil to the use of the printed page with some judgment as 
 to relative values. It is assumed that there will be available mono- 
 graphs and encyclopedias, manuals for the identification of various 
 groups of plants and animals, textbooks, and current publications 
 of all sorts. 
 
 The teacher should be constantly on the lookout for develop- 
 ments that suggest new problems and new applications in which 
 biology is significant. Many lines of publication are currently 
 available for the mere asking ; others have to be ordered as they 
 
 iii 
 
 674620 
 
iv MANUAL FOR TEACHERS 
 
 appear. There should be in every high-school or college library 
 the monthly circular of new publications issued by the United 
 States Department of Agriculture; the one from the Public 
 Health Service ; and the one from the Bureau of Education. 
 The local and state departments of health and of. agriculture, the 
 nearest Experiment Station, the Bureau of Fisheries, and similar 
 agencies may be drawn upon for helpful and pertinent material. 
 And every teacher should keep within hailing distance of what 
 appears in the technical journals. B C G 
 
MANUAL FOR TEACHERS 
 
 PART I. THE WORLD IN jCR WS-' lVE 
 
 I. INTRODUqXiOK V 
 
 Ask pupils to report such examples as they may happen to have 
 of applied biology ; that is, of practical use being made of knowledge 
 or understanding about living things. The history of civilization is 
 a continuous record of the displacement of superstition by insight. 
 Get examples of superstitions that have to do with health and 
 disease ; with the phases of the moon in relation to crop production ; 
 with lucky and unlucky signs in relation to fishing and hunting 
 or the performance of other practical tasks. Why do we call these 
 beliefs superstitions, and how do we distinguish them from our 
 own true beliefs ? 
 
 Have a committee of two or three students prepare a composite 
 list of all the examples that have been submitted, with some classi- 
 fication of the material. 
 
 Have students bring together what they can of the usages of 
 former generations with relation to epidemics and other diseases ; 
 with relation to insuring good crops, etc. Compare the average 
 length of life and the death rates at various periods and in dif- 
 ferent countries. Compare yields per acre of various crops at 
 different periods and in different countries. How have these 
 changes come about ? How have they been brought about ? 
 
 References. LOCY, W. A., Biology and its Makers, pp. 1-8. WHITE, 
 ANDREW D., Warfare of Science and Theology, chap. i. Yearbooks of 
 the United States Department of Agriculture. Annual Reports of the 
 State Department of Health ; City Board of Health ; Surgeon General, 
 United States Public Health Service; Surgeon General, United States 
 Army. National Vitality," Bulletin No. 30 of the Committee of One 
 Hundred on National Health, Government Printing Office. Work of 
 Vesalius. Life and work of William Harvey. 
 
MANUAL FOR TEACHERS 
 
 II. WHAT GOES ON IN THE WORLD 
 
 The purpose of these lessons is to acquaint the pupils with 
 some of the common physical and chemical processes. Some of 
 these are directly concerned in vital processes ; others are helpful 
 toward aii^underst^din^ pf more complex relations. Incidentally, 
 we may, lay the foundations of whatever thinking our pupils are 
 capable, pf ; sttta{n{g: by introducing the first laws of matter and 
 motion, and the idea of evolution in the broad sense of continuity 
 and causality. Where students have already studied elementary 
 science this part may be omitted, or perhaps reviewed briefly. 
 
 The laboratory work should be in the nature of demonstrations, 
 rather than experiments in the strict sense. The first few lessons 
 might well be carried out with the text in the hands of the pupils, 
 and the exercises completed, or at any rate started, in the class. 
 
 Things change. After reading section 7, have the pupils divide 
 a sheet of paper into four columns, headed as below : 
 
 WEATHER 
 
 PLANTS 
 
 HUMAN BEINGS AND 
 OTHER ANIMALS 
 
 NON-LIVING OBJECTS 
 
 
 
 
 
 In each column are 'to be listed as many kinds of changes as the 
 pupils can think of that happen to the kinds of things suggested 
 by the heading of the column. 
 
 Physical changes. Section 8 may be illustrated by melting a 
 lump of ice in a pan, through applying the flame of an alcohol or 
 Bunsen lamp. After calling attention to the change, the heat is 
 again applied until the water is all gone. Melt a piece of paraffin 
 or a bit of candle and continue to heat, without, however, starting 
 decomposition or igniting. 
 
 Make three lists of substances with which you are acquainted. In 
 the first list place the names of those that may exist in all three states ; 
 in the second, those that exist in only two states; and in the third, 
 those that exist in only one state. 
 
MANUAL FOR TEACHERS 3 
 
 Note that the metal mercury is liquid at ordinary temperatures, and 
 that practically all metals may be volatilized at high temperatures. 
 
 Demonstrate solution by placing sugar, salt, marble, starch, etc. 
 in tumblers of water. 
 
 Chemical changes. Prepare three large test tubes or tumblers, 
 a solution of washing soda (about four tablespoons to the pint), a 
 solution of barium chloride, a solution of phenolphthalein, and 
 some dilute hydrochloric acid. Before the class call attention to 
 the similarity in appearance of the four, solutions. That they are 
 not really the same kind of stuff is to be demonstrated. Place the 
 soda solution in the three test tubes ; in succession add portions 
 of the three other solutions. You will obtain a precipitate, a 
 change in color, and an effervescence. The three distinct reactions 
 indicate the occurrence of chemical changes. 
 
 Have the pupils describe these examples of chemical change, 
 not in terms of the materials used and the materials produced, 
 but in terms of the phenomena observed. Two apparently similar 
 liquids produce, when mixed, a solid, insoluble substance and a 
 new liquid, one that can be shown to have properties different 
 from those of either of the two used in the first place. Two others 
 produce some gas, and so on. It is possible in each case to show 
 that some distinct kind of substance has disappeared and that 
 some new kind of substance has been formed. 
 
 Demonstrate the reversibility of the chemical changes manifested 
 when a solution containing litmus or phenolphthalein is alternately 
 changed from acid to alkali and the reverse. Use dilute HC1 and 
 dilute NaOH solution. Have students suggest all the examples 
 of color changes with which they are familiar ; some of these will 
 be chemical changes. 
 
 Have students give examples of chemical changes that have not 
 yet been brought to the attention of the class. Make as complete 
 a list as possible of physical changes and one of chemical changes. 
 
 Get a committee of students to compile the lists of the whole 
 class, indicating the number of times each particular kind of change 
 is mentioned and bringing in for class discussion and conclusion 
 all doubtful cases. 
 
4 MANUAL FOR TEACHERS 
 
 Complexity of matter. Use magnifying glasses and bits of 
 granite, gneiss, marble, and other minerals to get the idea of 
 heterogeneity, not necessarily the word. 
 
 Milk may be analyzed, to show that it is made up of several 
 distinct parts. The specimen of milk is allowed to stand over- 
 night in a four-ounce wide-mouthed bottle, covered against dust. 
 
 The cream, oifat, sepa- 
 rates out. In regions 
 that are acquainted with 
 dairy processes, the time 
 may be shortened by the 
 use of a centrifuge, or 
 separator. If the milk 
 has not soured, and there 
 is nothing to be gained 
 by delaying the demon- 
 stration, the milk may 
 be immediately curdled 
 by the addition of a few 
 drops of acetic or some 
 diluted mineral acid. 
 (The casein is held in 
 solution by the natural 
 
 alkalinity of the milk, and is precipitated on neutralizing or acidi- 
 fying.) Separate the curd and the whey by filtering through paper. 
 The whey may be further analyzed by evaporating over a flame, 
 in a porcelain dish. This shows the whey to be made up of water 
 and solid. The solid residue may now be further broken up by 
 ignition, showing that it is made up of a part that can burn and 
 a part that cannot burn, the ash. 
 
 Have pupils make a list of the fractions of the milk that can be 
 readily recognized as distinct, as fat, curd, water, solids-in-whey-that- 
 can-burn, ash. 
 
 Have ready for inspection specimens of alcohol, ether, benzine, 
 gasoline, etc. as examples of liquids that appear to be homogeneous ; 
 
 FIG. 
 
MANUAL FOR TEACHERS 
 
 c 
 
 and rock candy, a lump of glass, and a clear crystal of quartz 
 or alum as examples of solids that appear to be homogeneous. 
 
 Wherever it can be managed, it is worth while to demonstrate 
 electrolysis of water, with a test of each of the 
 two gases produced. If a eudiometer is not 
 available, set up two large test tubes, filled with 
 the acidulated water, over the two poles of a 
 direct-current system (see Fig. i). 
 
 If you have a eudiometer, burn the hydrogen 
 from a small glass jet and collect the vapor in a 
 cold bell jar or battery jar held above the flame. 
 
 Elements and compounds. Have a collection 
 of elements ; these can usually be borrowed from 
 the chemical laboratory. The pupils should see 
 elementary sulfur, phosphorus, carbon, sodium 
 or potassium, iodin, iron, magnesium, and 
 silicon. It is not difficult to get specimens of 
 platinum, gold, silver, nickel, aluminum, lead, 
 tin, copper, and zinc. 
 
 Energy ; energy and matter. Reexamine the 
 first list of changes prepared, or the list of 
 physical and chemical changes ; next to each 
 item of change have students write the name 
 of the kind of energy that brings the change 
 about. Heat has already been shown to cause 
 changes in state ; it produces motion, as in the 
 thermometer. This can be demonstrated on a 
 large scale by gently heating a flask full of 
 water closed by a pierced stopper carrying a 
 glass tube (see Fig. 2). A little red or blue 
 ink may be added to the water to make it 
 visible in all parts of the room. Magnetism may be demonstrated 
 with an electromagnet or with a permanent magnet (bar or horse- 
 shoe). The other forms of energy mentioned, with the excep- 
 tion perhaps of the X rays, have either been studied before or 
 may now be demonstrated, so far as needed. 
 
 FIG. 2 
 
6 MANUAL FOR TEACHERS 
 
 Students should get the idea that all events are connected in 
 series, and this study may well end by having them describe, in 
 writing, one or two chains of happenings, in which the change 
 in energy as well as the change in matter is indicated for each link. 
 
 Conservation of energy. Many children come to school with the 
 superstition that machines are devices for increasing the amount 
 of energy. It is well to clear up any misgivings or misunder- 
 standings on this point. Machines vary as to efficiency, that 
 is, as to the proportion of all the energy they receive that they 
 make available in the special work for which they are intended, 
 but in all machines the output of energy is exactly equal to 
 the income. 
 
 References. PEARSON, KARL, Grammar of Science, chap. i. Have 
 students report on readings in any accessible textbooks in physics, chem- 
 istry, or general science on such topics as physical changes, chemical 
 changes, work, states of matter, conservation of matter, conservation of 
 energy, elements, compounds, forms of energy, transformation of energy, 
 perpetual motion, the philosophers' stone, efficiency, etc. 
 
 III. FIRE 
 
 The concern of the student of life with fire is sufficiently indi- 
 cated in the text. The experiment suggested in section 1 7 is not 
 practicable for the ordinary laboratory, and would not in any case 
 convince the skeptic. 
 
 Air and fire. Here we meet problems that lend themselves 
 readily to experimental treatment, and the opportunity should be 
 utilized to make clear the method of the experiment. A candle flame 
 furnishes the most convenient " fire " for these experiments, and 
 a Bunsen or an alcohol flame, or both, will be convenient to have 
 at hand. 
 
 The flicker of the flame suggests that burning liberates motion 
 in addition to light and heat, but it may well be that this motion 
 is imposed upon the flame by air currents, as is the case with 
 the trembling of leaves, for example, or the movement of the shirt 
 on the clothesline. Here we may find out by trying, that is, by 
 experiment. Emphasize the important fact that we have here a 
 
MANUAL FOR TEACHERS / 
 
 problem the solution of which we shall seek not in authorities, or 
 in the records of other people's beliefs and opinions, but in the 
 materials and forces at hand. Have the problem formulated clearly 
 by the pupils, that there may be no ambiguity as to just what we 
 are trying to find out. How, then, shall we find out? A second 
 item involves the use of various materials. Record should be made 
 of the things used. Then what is to be done with the things ? The 
 generalized scheme for the experiment is, to shut off air currents. 
 Many suggestions may be made by the pupils, and the suggestions 
 will in turn be criticized. There should be substantial agreement 
 on the most reasonable or the most convenient method to be 
 pursued or material to be used. A lamp chimney 1 has the advan- 
 tage that it may surround the flame on all sides, and that it is trans- 
 parent. Produce the lamp chimney and set it over the burning 
 candle. The flickering stops, and this result may be sufficient to 
 satisfy the pupils with the conclusion that the flicker is due to out- 
 side disturbances. If there is any disposition to discuss the matter 
 further, be careful to remove the chimney before the flame is ex- 
 tinguished ; it may be put on and taken off several times before 
 the question is closed. As the discussion nears its end, leave the 
 chimney over the candle, and the flame will expire. This will at 
 once suggest new issues, and many of the pupils will be prepared 
 to explain that it is the exclusion of the air that resulted in the 
 dying out of the flame. But before that can be taken up, make 
 
 1 In general it is well to have the materials to be used in the day's work 
 readily accessible in the laboratory or recitation room, but not laid out. 
 When you. that is, the teacher and the pupils decide that a lamp 
 chimney would be desirable, the teacher's resources must be equal to the 
 occasion. But no matter how carefully the teacher has prepared the day's 
 demonstration, the procedure should never give the impression of being 
 " cut and dried " in advance. Exception should be made for demonstra- 
 tions that involve rather elaborate arrangements, or that take more time 
 for setting up than the usual session allows. In that case, however, there 
 is either no pretense that the experiment is performed in response to a 
 problem that has arisen in the class, or, if you have led up to the problem, 
 the plans for the experiment may be agreed upon at one session, with the 
 understanding that the preparations will be made in anticipation of a future 
 meeting of the class. 
 
8 MANUAL FOR TEACHERS 
 
 a complete record of the first experiment, insisting upon the logical 
 sequence and clear analysis rather than upon the mechanical form 
 of the record. These points should stand out clearly, whatever 
 designations may be used: 
 
 1 . The problem : the question to be solved. 
 
 2. Materials and apparatus : what was used. 
 
 3. Operations performed : what was done. 
 
 4. Results : what happened, what phenomena were observed. 
 
 5. Conclusions}: the answer to the question, so far as it may be 
 inferred from the results. 
 
 In insisting upon a correct record of the first experiment, we 
 must shift the emphasis from the performance, as an interesting 
 " stunt," to the argument involved in formulating the problem, 
 in selecting materials and operations, in selecting the significant 
 elements from the results, and in drawing conclusions. 
 
 When we have established this routine of thinking about ex- 
 periments, less time will be required in the .matter of form of 
 records etc. 
 
 The second experiment, suggested by the expiration of the 
 flame, centers on the question whether the flame uses tip something 
 in the air or gives off something that interferes with burning. The 
 air being invisible, we must have some means of showing the in- 
 crease or decrease in the volume of air. It may be that after 
 several suggestions from the pupils, it will devolve upon the teacher 
 to find a feasible plan. A cylinder large enough to go over the 
 candle, and closed at one end, inserted over the lighted candle 
 standing in a dish of water, will meet all the conditions. If the 
 flame gives off gas(es), bubbles should be forced through the water, 
 out of the cylinder ; but if the flame uses up part of the air, what 
 would happen ? The possible results should be anticipated as part 
 of the argument, before the operation is actually performed, but 
 with the apparatus in hand. 
 
 Some of the pupils will probably jump to the conclusion that 
 the flame uses up part of the air. But we must not be too sure. 
 It is quite conceivable that both processes are going on at the 
 
MANUAL FOR TEACHERS 9 
 
 same time, but at different rates. Here is a problem for the 
 chemist to identify the gases concerned. 
 
 When the cylinder is finally placed over the lighted candle, the 
 flame begins to fade, it flickers a few times, and finally expires. In 
 the meantime the level of the water inside the cylinder changes 
 in a way that indicates a reduction in the amount of gas included. 
 We may also observe the condensation of moisture on the inside 
 of the cylinder, and the ascent of the thin column of smoke from 
 the wick. Which are the phenomena that are significant in relation 
 to our problem ? Obviously, the change in level of the water. 
 What does that show ? Probably that something in the air has 
 been removed by the action of the flame. By means of a ruler 
 held alongside the cylinder it may be possible to get an approxi- 
 mate idea of what proportion of the air has been thus used up. 
 
 But let us not overlook the possibility that something may be 
 present in the jar (the air) that was not there before. We shall 
 have to come back to the question whether the flame gave off 
 something. There is the smoke, for example ,' and perhaps there 
 are some invisible fire products. We may need the assistance of 
 the chemist to answer the question. At this time we may be cer- 
 tain only that something has been taken from the air by the burning. 
 
 Now as to the chemical nature of the remaining gas (or mixture 
 of gases), we should need some knowledge of chemistry to pro- 
 ceed farther. It is futile to test this air further with relation to 
 fire, as some of the students are almost sure to suggest ; for 
 the failure of a flame to burn in this residual air cannot tell us 
 anything that we did not already know. The teacher, drawing 
 upon his fuller experience, produces a reagent, a substance that 
 reacts distinctively with the various gases in this case lime- 
 water. Yes, it is the same kind of limewater as is sometimes used 
 in the baby's milk bottle. It is prepared by shaking up some 
 calcium oxid (unslaked lime) with water, and filtering through 
 paper. This should be kept .in tightly stoppered bottles (cork is 
 better than glass ; but if glass-stoppered bottles are used, smear 
 a little vaseline on the stopper, to make sure of an air-tight joint 
 that will not become caked). A little limewater is placed in the 
 
10 MANUAL FOR TEACHERS 
 
 bottom of a cylinder similar to the one used in the experiment. 
 Place a glass plate or the palm of the hand over the open end 
 of the cylinder and shake up vigorously. The limewater does not 
 change its appearance perceptibly. A little limewater is placed in 
 the cylinder in which the flame had expired, the cylinder being 
 quickly turned up and then quickly covered. When the limewater 
 is shaken up, it turns cloudy or milky. This shows us at least 
 that the two masses of air are different, although it does not tell 
 us just what the difference is. We may therefore conclude that 
 the burning process not only removes something from the air 
 but also sets free something that was not there before. 
 
 The question may here be raised as to the relation between the 
 products of combustion to the fuel, on the one hand, and to the 
 materials removed from the air, on the other. 
 
 Burning a synthesis. It is a reasonable hypothesis that the 
 product, like the visible ash of some other fires, is either some 
 portion of the fuel thus set free, or a portion of the fuel or of 
 the air modified in some way, or a new combination of materials, 
 containing elements from the fuel, from the air, or from both. 
 
 The technique of testing these variations of the hypothesis is 
 rather too complex for the schoolroom. We can, however, test the 
 supposition that the product of a burning contains fuel substance 
 plus air substance. For this purpose we must have a fuel the 
 burning of which gives us a product that is easily gathered and 
 weighed. We use magnesium ribbon, magnesium because the 
 product of its combustion is solid, and ribbon because it is con- 
 venient to handle. 
 
 A trip balance has a large funnel, closed with cotton wool in 
 the stem, on one platform, with a strip of ribbon about eight 
 inches long. This is counterbalanced until the platforms are level. 
 A wire loop or hook may be hung into the funnel before adjusting 
 the balance. The magnesium ribbon is hung from the loop and 
 ignited with an alcohol or Bunsen flame, and the funnel is imme- 
 diately replaced upon the platform of the scale. If the operation 
 has been carefully conducted, the accumulated smoke or ashes will 
 be found to weigh more than the original ribbon of magnesium. 
 
MANUAL FOR TEACHERS 
 
 II 
 
 Since the addition to the solid matter on the scale platform could have 
 come only from the air, we are tempted to conclude that the air 
 stuff that takes part in burning combines 
 with something in the fuel. 
 
 The gases in the air. The three principal 
 gases of the atmosphere may be prepared 
 for laboratory use as follows : 
 
 Carbon dioxid. A wide-mouthed bottle 
 or flask is fitted with a two-holed stopper. 
 Into one hole is fitted a glass "thistle" 
 tube reaching nearly to the bottom of the 
 bottle. Into the other hole is fitted a bent 
 glass tube reaching only a fraction of an 
 inch below the cork or rubber and having 
 a rubber tube attached to the outside arm 
 (Fig. 3). This apparatus, or gas genera- 
 tor, may be used for generating hydrogen 
 and for other purposes. To make carbon 
 dioxid, place some marble chips (calcium 
 carbonate) or limestone bits in the bottom 
 of the bottle ; insert the stopper with the 
 tubes and pour water through the thistle 
 tube until the chips are covered. Pour 
 dilute hydrochloric acid (commercial will 
 do) slowly into the thistle tube until effer- 
 vescence begins. Place the free end of 
 the rubber delivery tube in a pneumatic 
 trough or in a dish of water. The bubbles 
 coming through the water indicate the rate 
 at which gas is being liberated. Carbon 
 dioxid can be collected either with the 
 
 help of a pneumatic trough or with a large dish of water, the 
 tubes or bottles to be filled being held in the hand over the 
 delivery-tube opening, after being filled and inverted. Be careful 
 not to raise the mouths of the vessels out of the water while the 
 gas is being collected. Four-ounce wide-mouthed bottles are 
 
 FIG. 3 
 
12 MANUAL FOR TEACHERS 
 
 convenient for these experiments. Glass squares smeared with 
 vaseline may be used as covers for these containers ; and if there 
 is not too much water left in the bottles after the gas is collected, 
 several bottles of gas may be prepared in advance and may be 
 relied upon to react properly when wanted. 
 
 Nitrogen. To produce this gas there are needed a Florence or 
 an Erlenmeyer flask, 250 cc. or 500 cc. ; a rubber stopper with 
 one opening carrying a short glass tube with a long rubber delivery 
 tube ; some ammonium chloride (sal ammoniac) and some sodium 
 nitrite, NaNO 2 . (Be careful not to use sodium nitrate, NaNO 3 .) 
 There will also be needed a pneumatic trough or other means 
 of collecting gas over water, bottles with glass covers smeared 
 with vaseline, and an alcohol or Bunsen flame. Place about a tea- 
 spoonful (level full or less) of sal ammoniac and about an equal 
 volume of sodium nitrite in the flask ; pour in just enough water 
 to cover the salts, and insert stopper carrying the delivery tube. 
 Warm the mixture gently over the flame, holding the flask in the 
 hand all the time so as to be able to regulate the heat by moving 
 the flask nearer to or farther from the flame. When the chemical 
 action begins, a great deal of heat is generated within the flask ; 
 then it is necessary to apply only enough heat from the outside 
 to keep up a steady action. After some gas has escaped from 
 the delivery tube, displace the water in one or two bottles to 
 make sure that there is no more air^in the generating flask. Then 
 collect the gas in the usual way. At the conclusion of the work, 
 or when the generation of gas is stopped for any reason, be care- 
 ful to take the delivery tube out of the pneumatic trough. The 
 teacher should try out the making of nitrogen before attempting 
 it in the classroom. 
 
 Oxygen. This gas can be produced by hydrolysis, if there is 
 available a direct current of electricity, or by chemical methods. 
 For small quantities, the decomposition of red oxid of mercury in 
 a small tube by the application of heat is convenient. For making 
 larger quantities to be used in experiments, the decomposition of 
 potassium chlorate is the best method. A mixture of about equal 
 parts of potassium (or sodium) chlorate and manganese dioxid 
 
MANUAL FOR TEACHERS 13 
 
 (both powdered) is placed in a large test tube or in a copper 
 or iron still. If a test tube is used, close the end with a rubber 
 stopper carrying a delivery tube ; if a still is used, connect the 
 outlet with a rubber delivery tube. The mixture of chlorate and 
 dioxid is heated steadily (the glass tube being rotated to prevent 
 melting the glass at one point), and the evolved gas is collected 
 in the usual way. Be careful to remove the delivery tube from 
 the water when the heat is withdrawn. 
 
 To demonstrate the fact that there are three distinct substances 
 here, notwithstanding their resemblance to each other and to the 
 air, a bottle of each gas, labeled, is set out, and we proceed to 
 test them in turn, in relation to burning. A lighted splinter (cigar 
 lighters are convenient) is inserted into a bottle of air for a few 
 moments and then taken out; it is inserted thus in turn in the 
 bottle of nitrogen, where the flame is instantly extinguished. The 
 splinter is relighted and placed in the carbon dioxid, with the same 
 results. It is finally placed in the oxygen, where it instantly blazes 
 up into a more intense flame. Take the splinter out and extinguish 
 the flame by shaking it or by blowing it out. While a spark still 
 remains on the stick it is again inserted into the bottle containing 
 oxygen. The spark bursts into flame. There can be no doubt left 
 in the minds of the pupils that it is the oxygen of the air that is 
 the significant factor in burning. Recall the experiment in which 
 the portion of the air removed by the fire was seen to be approxi- 
 mately one fifth, and compare this with the known (from authorities) 
 proportion of oxygen. 
 
 Oxidation. Review all that has been learned about burning, and 
 get the idea of the products of combustion being specific kinds 
 of compounds. It is well to have at hand specimens of sulfur, 
 charcoal, magnesium, etc., for demonstration of burning elements. 
 Get the generalization about burning that will include the burning 
 of liquid fuels (alcohol, oils, benzine, gasoline, etc.), as well as of 
 gaseous fuels (illuminating gas, marsh gas, hydrogen, gasoline 
 vapor, etc.) and of solids. 
 
 If there is time, it is interesting and instructive to demonstrate 
 the burning of iron with a flame, and to compare the product 
 
14 MANUAL FOR TEACHERS 
 
 with the rust produced by weathering of iron or by rusting under 
 water. Ordinary picture cord may be used, the strands being un- 
 wound and a single strand at a time being employed. Use a quart 
 jar full of oxygen, and ignite by dipping the looped end of the wire 
 into sulfur (flowers) and igniting the sulfur. Now dip this into the 
 jar of oxygen, and the iron will ignite and burn with a visible flame. 
 
 "References. In any available books on chemistry, general science, or 
 the history of science, or in encyclopedias and other books of reference, 
 have pupils find material for special reports on such topics as air, oxygen, 
 fire, Priestley and oxygen, Scheele and oxygen, Lavoisier and oxygen, 
 Cavendish and the synthesis of water, explosion of gases, internal- 
 combustion engines, spontaneous combustion. 
 
PART II. LIFE PROCESSES OF THE 
 ORGANISM 
 
 IV. LIVING THINGS AND NON-LIVING THINGS 
 
 With the more direct approach to living things as the object 
 of contemplation, and eventually of study, the students should 
 have before them constantly as many different kinds of living 
 things as may be conveniently kept in the workroom. This does 
 not mean that we should convert our laboratories or recitation 
 rooms into menageries ; but it is not unreasonable to have on 
 hand a number of growing plants, in pots or in window boxes, one 
 or two aquaria (both fresh and salt water if possible), a vivarium 
 containing frogs, lizards, newts, various insects according to season, 
 slugs and other animals, and a hay infusion. In addition there 
 should be exposed prepared specimens, under glass, of as many 
 plants and animals as the available cabinets will hold without 
 making the collection a jumble. These should be supplemented 
 with pictures of interesting forms that cannot otherwise come 
 within the common experience of the children. Where there is an 
 abundance of material the teacher will from time to time change 
 the aspect of the collection, adding to the interest through novelty, 
 and shifting the attention as the need for emphasis may direct. 
 
 As a preliminary exercise have the pupils prepare two lists of 
 the names of objects, one list comprising living things, the 
 other, non-living things. It may be necessary to explain that a 
 thing, or object, is not to be confused with a material. For example, 
 the earth may be considered an object, like the sun or the moon or 
 a baseball ; but earth is the name we give to a kind of stuff, like 
 iron or wood or leather. We often call an object by the name of 
 its most important or distinctive or sole material, as when we 
 call a branding tool the iron, or a washer the leather, or a document 
 
 15 
 
1 6 MANUAL FOR TEACHERS 
 
 the paper. The point of this exercise is twofold: (i) It should 
 help to clear up confusion between objects and classes of objects, 
 on the one hand, and unformed matter on the other. (2) It should 
 bring clearly into consciousness the relative paucity of formed 
 objects in nature, other than organisms, and the practically universal 
 fact that life is related somehow to formed matter. 
 
 It is well to have on view as many types of crystals as can be 
 conveniently exhibited. 
 
 Before the study of the text the pupils should be encouraged 
 to analyze their concepts of living things by listing all the 
 characteristics of organisms that they can think of. These lists 
 may then be used as a basis of criticism and discussion. 
 
 In the discussion of differences or similarities between living 
 and non-living, the pupils should be encouraged to formulate their 
 concepts in good sentences ; and they should be encouraged then 
 to modify their generalizations by expanding their observations to 
 types that do not appear to agree with these concepts. Reference 
 to the plants (that do not walk about), to the worms (that have no 
 stomachs or brains), to the organisms without blood,, etc., are 
 largely in the nature of challenges, and pains must be taken to 
 avoid driving the pupils to desperation. But it is possible gradu- 
 ally to get them to see that life is not to be comprised in a word 
 or in a single differential. 
 
 About a week before the class is ready to consider growth, 
 arrange a demonstration of inorganic growth as follows : 
 
 In the bottom of a battery jar or large fruit jar place a layer 
 of clean sand. On the sand place a number of crystals, as of 
 copper sulfate, ferrous sulfate, chrome alum, zinc sulfate, etc. 
 Pour slowly into the jar a mixture of sodium silicate (water 
 glass) and water, about one part to fen. The prepared jar is to 
 stand undisturbed where it may be observed without being moved. 
 
 Saturated solutions of sugar, alum, and other substances that 
 crystallize readily may be prepared, and the growth of crystals 
 watched. By suspending a thread (weighted) in such a solution, 
 the crystallization may be started, and the growth of the mass 
 about the string as an axis may be watched. Compare rock 
 
MANUAL FOR TEACHERS I/ 
 
 candy. It may be feasible to have the children prepare such 
 growths at home. 
 
 Compare the assimilation of foreign peoples, or of new 
 pupils in a school. 
 
 If there is not common familiarity with photographic materials 
 and processes, demonstrate the modification of blue-print paper or 
 printing-out paper under the influence of light. 
 
 In the study of functions the idea can be made more clear 
 by emphasizing the fact that we think of use chiefly in terms 
 of human advantage, and then contrasting function with use. For 
 this exercise, have each student prepare two sheets of paper (or 
 pages of the notebook) by dividing the space into four columns, 
 headed as below : 
 
 NAME OF ORGANISM 
 
 PART USED 
 
 How USED 
 
 FUNCTION 
 
 
 
 
 
 One sheet is to be used for plants, the other for animals. 
 A few illustrations will appear in the course of the discussion ; 
 these may be used to start the lists, and each pupil may then be 
 required to bring say ten or a dozen on each list. The most com- 
 monly used parts of the more familiar plants and animals will serve 
 as the most striking means for emphasizing the contrast between 
 use 2X\&. function, for example, the tongue of the cow, the tail of 
 the ox, the root of the carrot, the bark of the hemlock, etc. 
 
 Be careful at this point, as always, to keep clear of the pre- 
 conceived notions of purpose. It can easily be made plain to even 
 the least mature pupils that the function of a given organ is by no 
 means an indication of purpose on the part of the organism. You 
 have but to ask, " For what purpose did you grow yourself a 
 liver ? " or " What was your purpose in building four chambers 
 into your heart ? " and the child sees at once that he grew up 
 without purpose on his own part ; and this repudiation of purpose 
 may be extended to other organisms. It remains then a question 
 
1 8 MANUAL FOR TEACHERS 
 
 of Nature's purpose or God's purpose, which imply assumptions 
 that we do not need for our purpose, or which imply interpreta- 
 tions that are of no use to us. At any rate, purpose must not be 
 allowed to interfere with the purposes of our study. 
 
 References. HUXLEY, T. H., On the Physical Basis of Life, in his 
 " Methods and Results," Essay 3 ; JORDAN and KELLOGG, Evolution and 
 Animal Life, chap, iii ; LOCY, W. A., Biology and its Makers, chap, xii ; 
 LOEB, JACQUES, The Organism as a whole, chap, ii ; MORGAN, T. H., Evo- 
 lution and Adaptation, chap, i; WILSON, E. B., The Cell, pp. 17-30. 
 The abler pupils can read the first two of the above ; have all look up in 
 available books on botany and zoology such topics as protoplasm and cell. 
 
 V. THE LIVING STUFF 
 
 In comparing plants and animals, have living specimens within 
 sight and within reach. See suggestions under IV. 
 
 Hay infusions prepared for protozoa usually die out in a 
 short time. To keep a supply on hand use this method : Prepare 
 a culture medium by boiling hay in water, with a little corn meal, 
 until the liquor is of a dark brown color. Leave a small amount 
 of the hay in the liquor. This may be kept indefinitely in sealed 
 bottles. For use, expose some hay infusion in a battery jar for a 
 day or two, in order to inoculate with bacteria from the air. Cover 
 with a glass plate and leave until a scum appears. Then add some 
 water, mud, etc. from a pond or ditch. Several jars may be pre- 
 pared, and inoculated with material from different sources. In a 
 few days the protozoa will be sufficiently abundant; the supply 
 should last for several months. It is well to inoculate a fresh 
 hay infusion every three or four months, using some of the old 
 culture for this purpose. 
 
 Leaves of Elodea, myriophyllum, or other delicate water plants, 
 filaments of spirogyra or other algae, epidermal cells of almost any 
 kind of leaf, or onion skin, will give sufficient material for forming 
 the idea of cells as structural units, as well as something of the 
 nucleus, vacuoles, and non-living bodies within the cell. Animal cells 
 are better shown from prepared slides. Call attention to the fact 
 that the colors in such specimens are due to the artificial stains 
 used for the purpose of making the structural details visible. 
 
MANUAL FOR TEACHERS 19 
 
 It may be worth while to give the pupils some instruction in the 
 use of the microscope. To familiarize students with the inversion 
 of the image, it has been found helpful to prepare a set of slides 
 by mounting permanently in balsam tiny bits of paper cut from 
 some printed matter (small type, one side of paper only), each 
 containing two or three letters. These slides are studied with the 
 naked eye, with the simple microscope, and with the. low power 
 of the compound microscope. The making of drawings of the 
 object under these three conditions, with the slide always kept 
 in the same position in front of the student, will accelerate the 
 formation of the ideas needed in the control of the instrument. 
 
 In most cases it will suffice to set up the microscopes with the 
 demonstration material already centered and focused, and have 
 the students look at the preparations. 
 
 Chromosomes, if they are to-be seen, must not be searched for 
 in fresh preparations. If desired, prepared slides may be made 
 or purchased, as, for example, root-tips of onion. 
 
 If it is not feasible to place protozoa and living tissues under 
 the observation of the students, for the purpose of forming a 
 definite idea of the appearance of protoplasm, it is often worth 
 while to prepare an emulsion of oil and salt water. This emulsion 
 exhibits constant movements of a kind that are in some ways 
 similar to those seen in living protoplasm ; and while the students 
 may not know anything of surface tension, they do know that 
 " oil and water will not mix," a"nd that the movements in the 
 emulsion are due to the "unmixing" of the oil and water. 
 
 References. LOCY, \V. A., Biology and its Makers, chap, xi; LOEB, JACQUES, 
 The Dynamics of Living Matter, chap, iii ; WILSON, The Cell, chap. i. 
 
 VI. THE CONDITIONS OF LIFE 
 
 Before beginning the study of the relation between the environ- 
 mental factors and life processes, it is well to make an inventory of 
 what the members of the class already know on the subject. We 
 shall find many beliefs that are unsupported, many that will not 
 stand critical examination. On the other hand, it is not worth while 
 to demonstrate anew what is already well established for all of us. 
 
2O MANUAL FOR TEACHERS 
 
 By contrasting the conditions that obtain in a jar containing 
 seeds that do not sprout, with the conditions in the ground, where 
 seeds do sprout, we are enabled to analyze the environment for 
 the purpose of selecting the significant factors, or for the purpose 
 of formulating hypotheses that can be subjected to experimental 
 test. The fact that seeds behave in one way in the storage bin 
 and in quite a different way in the soil furnishes the occasion and 
 the opportunity for seeking in the sprouting conditions of seeds 
 the answer to our general question. 
 
 Have a list of all the suggested factors made on the board ; 
 check out those that are the same for seeds in storage and seeds 
 in the soil. There will be left for immediate experiment hardly 
 anything more than water; for although other factors may be 
 related to the sprouting, they appear to be the same for the resting 
 seeds and for the developing embryos. Before proceeding with 
 any experiments, therefore, it is well to emphasize the idea that, 
 while we are seeking for single determining factors, we must be 
 prepared to consider the possibility of a determining combination 
 of factors. 
 
 Have students formulate the general problem, What is the 
 relation of this facto?' to the sprouting of seeds ? Then have a 
 plan of campaign worked out by the class. When a satisfactory 
 plan is agreed upon, have committees of the students arrange a 
 demonstration series for the class ; those who are in a position 
 to do so should be encouraged to perform special experiments 
 at home. 
 
 A satisfactory plan must include the control. This should appear 
 in the course of the discussion ; the teacher should avoid present- 
 ing the idea as authoritative or as standard practice. 
 
 Whatever plan is used for determining the relation of moisture 
 to sprouting, occasion should be found or made for introducing 
 the problem of quantity, Does an increase in moisture acceler- 
 ate the process ? This should offer opportunity for experimental 
 demonstration leading to the idea of the optimum. 
 
 Have reports of the experiments made out in good form (see 
 p. 8), and so far as possible have data presented in tables. For 
 
MANUAL FOR TEACHERS 21 
 
 example, the conditions and results of the experiment can be pre- 
 sented in tabular form, or the results on successive days may be 
 tabulated. 
 
 After the students have formulated their conclusions as to the 
 relation of moisture to sprouting, it is in order to take up some 
 of the factors that have been laid aside as being the same in the 
 two contrasted situations. For example, What is the relation of 
 air, of temperature, of light, to sprouting? 
 
 As before, have the problems and the plans formulated by the 
 students, giving suggestions only where necessary, yet not unduly 
 prolonging the preliminaries. 
 
 Differential air conditions may be obtained by using vessels of 
 different sizes for a given number of seeds or by placing different 
 numbers of seeds in a series of vessels of the same size. Of 
 course the seeds are to be soaked in water in advance, since we 
 know that moisture is essential. Another method would be to 
 exclude different amounts of air from bottles of the same size, 
 by means of soil or plaster of Paris. A practical vacuum may be 
 obtained by inverting a test tube full of mercury into a mercury 
 bath (avoiding the entrance of air bubbles), and then carefully 
 slipping in a few soaked peas. The tube may be held in place 
 with a clamp on a ring stand. 
 
 For differences in temperature use a refrigerator, the classroom 
 and the boiler room, or a place close to the radiator or stove. 
 The difficulty of obtaining constant temperatures of three or four 
 grades would usually preclude this experiment Where ovens or 
 incubators with thermostats are available, the experiment is well 
 worth performing. 
 
 Problems as to light and other factors may well be left to the 
 initiative and ingenuity of individual pupils who are especially 
 interested. It is well to have the experiments performed according 
 to different methods, and to have the results compared and dis- 
 cussed in class. For example, in the experiment on the relation 
 of moisture to sprouting, some may use soil, others sand, or saw- 
 dust, or blotting paper, and so on ; while in one series the glass 
 vessels, the water, and the seeds are used without any matrix. 
 
22 
 
 MANUAL FOR TEACHERS 
 
 References. ANDREWS, E. F., Practical Course in Botany, pp. 10-12, 
 30-40, chap, vii; BERGEN and CALDWELL, Practical Botany, pp. 139-141; 
 BERGEN and DAVIS, Principles of Botany, chap, i; COULTER, J. M., Ele- 
 mentary Studies in Botany, pp. 174-176; DUGGAR, B. M., Plant Physiology, 
 pp. 280-296, chap, xv ; MORGAN, T. H., Experimental Zoology, chap, i ; 
 OSTERHOUT, W. J. V., Experiments with Plants, chap. i. Morgan is for the 
 teacher only ; in the others will be found many suggestions for individual 
 experiments and projects for pupils. 
 
 VII. AIR AND SOIL IN RELATION TO SPROUTING 
 
 To show which of the gases in the air is related to sprouting, 
 prepare flasks of carbon dioxid, of nitrogen, and of oxygen, with 
 seeds that have been soaked in water. 
 The control consists of a flask of the 
 same size, containing the same number 
 of seeds but ordinary air instead of any 
 special gas. All the flasks are sealed 
 with paraffin, and they are kept together 
 for the sake of the uniform temperature 
 and light. It is well to wash the gases 
 used in this experiment by passing 
 through clean water in a bottle con- 
 nected as shown in Fig. 4. 
 
 We can test the gases left in the flasks 
 wherein the seeds sprouted, for an in- 
 crease in the amount of carbon dioxid. 
 To show that the sprouting seeds give 
 off heat, fill two large bottles with seeds 
 that have been soaked for twenty-four 
 hours ; to the contents of one of the 
 vessels add a little formalin, to kill the 
 seeds without altering their appearance. In each bottle insert a 
 thermometer; and if a third thermometer is available, have that 
 in the air beside the bottles. Place the two bottles together in 
 a suitable box and pack in with cotton waste, sawdust, or other 
 material, to prevent rapid change of temperature. Read the ther- 
 mometers from time to time and have the results tabulated. Under 
 
 FIG. 4 
 
MANUAL FOR TEACHERS 
 
 favorable conditions there should be a difference of several degrees 
 (centigrade) between the temperature of the sprouting seeds and 
 that of the soaked seeds that did not sprout, or the surrounding air. 
 
 Compare the sprouting seeds to other living things and to engines. 
 
 The suggestion 
 that animals and 
 human beings re- 
 semble the germi- 
 nating seeds in that 
 they give off heat 
 and use up oxy- 
 gen can be carried 
 farther by testing 
 at the same time 
 the exhaled air and 
 the ordinary room 
 air in their effect 
 upon limewater. 
 The set of bottles 
 shown in Fig. 5 
 will facilitate the 
 demonstration. 
 
 Have the idea 
 of soil analyzed in- 
 to sand and other 
 insoluble constit- 
 uents, salts, and 
 organic remains. 
 Since the salts ap- 
 pear to be the 
 
 factors most likely to influence the plants, the experiments would 
 center about them. After formulating the problems and making 
 the plans, arrange to grow seedlings in clean sand moistened 
 with pure water ; that is, water free from dissolved matter. 
 Use distilled water and explain how the purity of this differs 
 from the purity of pure drinking water. As a control, make a 
 
 FIG. 5 
 
 When the free end of the Y-tube is used as a mouthpiece, 
 inhalation of air draws the gas through one of the bottles, 
 and exhalation drives the gas through the other bottle. 
 Limewater placed in both bottles will show the difference 
 between inhaled air and exhaled air very strikingly 
 
24 MANUAL FOR TEACHERS 
 
 parallel growth in garden soil, and another in clean sand moistened 
 with tap water, well water, or the like, or a special solution known 
 to contain salts. 1 A comparison of the condition of the plants after 
 a prolonged growth, or at the time when some begin to show evi- 
 dence of deterioration, will throw light on the relation of soil salts 
 to the life of the plant. 
 
 The nutritive solution may be used either as root medium (in 
 contrast with distilled water) or for watering the sand. In the 
 latter case it may be diluted with an equal volume of distilled 
 water. 
 
 In the case of every experiment the students should be called 
 upon to formulate the problems and to indicate at least the gen- 
 eral form of the experimental procedure. The results should be 
 tabulated so far as possible. 
 
 It is impossible, for a considerable time, to draw conclusions from 
 the experiments suggested for this chapter ; it is therefore well, 
 immediately after setting up the experiments, to undertake further 
 studies on the structure of seeds, coming back to conclusions and 
 summary later. 
 
 References. ANDREWS, Practical Course in Botany, pp. 30-40; BERGEN 
 and CALDWELL, Practical Botany, pp. 447-448; COULTER, Elementary 
 Studies, Part II, chaps, ii, iii ; DUGGAR, Plant Physiology, chaps, vii, viii. 
 
 1 A culture medium for growing plants without soil may be prepared 
 by dissolving in each liter of distilled water 
 
 Potassium nitrate i.o gram 
 
 Calcium sulfate 0.5 gram 
 
 Calcium phosphate 0.5 gram 
 
 Magnesium sulfate 0.5 gram 
 
 Sodium chlorid 0.5 gram 
 
 Ferric chlorid, or ferrous sulfate solution A few drops 
 
 Another formula for a nutritive solution is the following : To each liter 
 of distilled water add 
 
 Calcium nitrate i.oogram 
 
 Magnesium sulfate 0.25 gram 
 
 Potassium chlorid 0.25 gram 
 
 Monopotassium phosphate 0.25 gram 
 
 Iron solution A few drops 
 
v MANUAL FOR TEACHERS 25 
 
 VIII. SEEDS AND SEEDLINGS 
 
 For the study of seed structure, kidney beans, pumpkin or 
 squash seeds, large peas, and corn will furnish convenient illus- 
 trative material. Seeds to be taken apart should be soaked at 
 least twenty-four hours; a few drops of formalin in each jar 
 containing soaked seeds will prevent decomposition. 
 
 For the study of the main parts of a plant, any small weeds 
 that can be pulled up by the roots and gathered in quantities may 
 be used. 
 
 In making drawings of structures studied, we should avoid, 
 on the one hand, hasty and careless sketches that do not really 
 show the significant features, and, on the other hand, elaborate 
 and artistic drawings that show too much, often concealing the 
 significant features amid a mass of unessential detail. To make 
 large, clear, diagrammatic figures that show forms and relation- 
 ships is a trick worth cultivating. It is worth while to suggest 
 convenient methods of arranging and labeling drawings, as well 
 as suitable lettering and location for names, dates, class designa- 
 tions, etc. But it is easy to lose a great deal of time in elaborat- 
 ing on these details, and a great deal of energy in insisting upon 
 uniformities that are in the end unimportant. 
 
 Where the students take an interest in classification it may be 
 suggested that a committee prepare a chart with three columns, 
 on which are to be entered the names of plants as they come to 
 the attention of the class, according to the number of cotyledons 
 in the seeds. This device will tend to place the more familiar seed 
 plants in their main divisions, and will also help to fix the idea that 
 there are many plants that never bear seeds. 
 
 Collections of economic seeds should be encouraged, and some 
 should be made for the school museum. 
 
 The experiments on the relation of the accumulated food in the 
 seed to the life of the young plant are easily performed by the 
 students themselves or may be done in the laboratory for demon- 
 stration. After sprouting soaked corn grains, the bulk of the 
 endosperm is cut away and the hypocotyl is passed through a 
 
26 
 
 MANUAL FOR TEACHERS 
 
 small hole in a piece of cheesecloth or muslin stretched over the 
 top of a bottle or tumbler rilled with water. Pea seedlings with 
 the cotyledons removed are arranged in a similar way. The con- 
 trol consists of the seedlings with the endosperm or cotyledons 
 undisturbed. Fig. 6 shows the results of such experiments. 
 
 Corn 
 seedlings 
 
 FIG. 6 
 
 To discover whether there has been any loss of material from 
 the cotyledons of the growing plantlets, dig up seedlings that have 
 been grown in sand or soil, and compare with the cotyledons of 
 fresh-soaked seeds. . 
 
 Seedlings should be started in flat boxes of soil or sand (or 
 sawdust) at intervals of two days for two or three weeks before 
 they are to be used. They will serve for comparative study of 
 structure and of emergence. 
 
MANUAL FOR TEACHERS 2/ 
 
 References. ANDREWS, Practical Course, pp. 40-47 ; BERGEN and CALD- 
 WELL, Practical Botany, pp. 136-144; BERGEN and DAVIS, Principles of 
 Botany, chap, iii ; COULTER, J. G., Plant Life and its Uses, pp. 348-353; 
 COULTER, J. M., Elementary Studies, Part II, chap, iv ; COULTER, BARNES, 
 and COWLES, Textbook of Botany, pp. 270-275 (for the teacher) ; OSTER- 
 HOUT, Experiments with Plants, chap. i. 
 
 IX. EXTERNAL FORCES AND PLANTS 
 
 The demonstration of geotropism with the aid of the centrifuge or 
 the clinostat is not satisfactory for high-school students who have not 
 yet studied physics, since it involves the identification of centrifugal 
 acceleration with gravity. To get this clearly requires too much digres- 
 sion. It is better to use an arrangement that permits the inversion of 
 the seedlings from time to time. 
 
 A convenient arrangement for the study of geotropism consists 
 of two panes of glass (any size will do), one serving as a base and 
 the other as a cover. The bottom glass is covered with cotton 
 wool or wrinkled filter paper, upon which soaked seeds are placed. 
 In placing the cover on top of the seeds, it is well to insert bits 
 of cork under the corners, to prevent crushing the seeds. The 
 two panes are held together by means of rubber bands. The wet 
 cotton or paper extends beyond the end of the glass. The whole 
 arrangement is set up vertically in a shallow dish containing a 
 little water in the bottom. The cotton or paper protruding beyond 
 the top of the glass is turned back into the water. In this way 
 the absorption of water to keep the seeds moist is not altogether 
 from below. After the seeds have sprouted, the position of the 
 hypocotyls is noted, and every day or two the glasses are 
 turned over. 
 
 Students can be interested in carrying out this experiment at 
 home. If there are not enough suitable pieces of glass available, 
 the bottom can be made of a piece of thin wood. By using small 
 seeds (radish, flax, or mustard) and blotting paper, enough 
 moisture can be supplied without extending the absorbing material 
 beyond the edge of the glass. The edges may then be loosely 
 inclosed with dry paper, to prevent excessive evaporation. 
 
28 
 
 MANUAL FOR TEACHERS 
 
 If the material is kept in condition long enough, the negative 
 geotropism of the shoots can also be demonstrated. In making 
 experiments with the geotropism in shoots of older plants, be 
 careful to avoid one-sided illumination. 
 
 In the experiment on the geotropism of the root, it should not 
 be difficult to make the class see that downward growth is some- 
 thing different from falling down ; occasionally, however, a student 
 becomes confused on this point. In such a situation the fact that 
 
 the pressure of the root down- 
 ward is far in excess of the 
 weight of the plant may be 
 conveniently shown by mak- 
 ing a hypocotyl penetrate 
 into mercury. Windsor beans 
 are convenient for this ex- 
 
 ^^J^^^IJI periment, and the sprouted 
 seed is pinned to a cork fast- 
 ened over the dish of mer- 
 cury, with a little water over 
 it, as shown in Fig. 7. 
 FIG. 7 An ingenious device for actu- 
 
 ally measuring the downward 
 
 pressure of a root is described in Osterhout's " Experiments 
 with Plants," pp. 81-85. See also Ganong's " Plant Physiology." 
 To demonstrate the growth movements in roots, use peas that 
 have been allowed to sprout in moist paper, having fairly straight 
 hypocotyls about an inch long. Mark off intervals of about i mm. 
 from the tip of the root, using india ink and a scale. For apply- 
 ing the ink use a very fine pen or a bow made of a horsehair or a 
 fine silk thread stretched between the ends of a piece of spring 
 steel. Replace the young plants among the folds of moist paper, 
 with the tips in a horizontal position but free to bend down. The 
 results after a day or two will show not only the region of maxi- 
 mum growth in the tip of the root, but also the fact that the curva- 
 ture is brought about by more rapid growth on one side than on 
 the opposite side. 
 
MANUAL FOR TEACHERS 29 
 
 The response of plants to light stimulation may be shown by 
 comparing plants grown in different degrees of illumination, or 
 by watching the behavior of plants exposed to one-sided illumina- 
 tion. For the first experiment divide a lot of seedlings of about 
 the same stage of development into two sets. Cover one set with 
 a pasteboard box that will effectually exclude the light without 
 excluding adequate ventilation. In the course of a few days it will 
 be possible to see differences in the height of the two groups: In 
 a few days more it will be possible to observe the blanching of 
 the plants deprived of light. It is fair to conclude from these 
 results that light retards the growth of plants, and that the green 
 of the plant can be maintained only in the presence of light. 
 Emphasize the fact that darkness is a negative condition ; it 
 is not darkness that makes plants grow faster, but light that 
 retards the growth. 
 
 Plants grown in flowerpots inside the window will frequently 
 present the effect of one-sided illumination, in that the leaves will 
 be turned with the flat surface parallel to the window or with the 
 tips inclined toward the window. Geraniums are very good for 
 this. To show that the position of the leaf is not a random one, 
 the pots should be turned through an arc of 180 degrees and the 
 positions marked, on successive days. Have students look up 
 " compass plants " and bring in evidences of phototropism from 
 field and garden or from house plants. 
 
 It is not worth while to demonstrate chemotropism, although 
 any students who are sufficiently interested to do so should be 
 encouraged to work out plans and carry out experiments by 
 themselves, and report to the class. . 
 
 Hydro tropism is easily demonstrated. Fill a small flowerpot or 
 a Zurich germinator with sphagnum, kept moist. On the outside 
 of the pot place some mustard seeds, which will adhere because 
 of a mucilaginous substance they secrete. Suspend the pot under 
 a bell jar or a large battery jar. The roots, instead of growing 
 down, will cling to the moist surface of the pot. The control con- 
 sists of an identical arrangement in a jar containing a vessel of 
 water, to keep the atmosphere saturated ; in this jar the roots 
 
30 MANUAL FOR TEACHERS 
 
 will grow downward. Another arrangement consists of a wire 
 basket filled with wet sphagnum or excelsior, in which the seeds 
 germinate. After the roots have projected beyond the basket, 
 suspend the latter with the bottom inclined, so that the nearest 
 water for each root is not down but to one side. This should 
 be placed under a jar, to prevent drying of the roots. 
 
 References. For the teacher: COULTER, BARNES, and COWLES, Text- 
 book, pp. 458-479; DARWIN, CHARLES, Movement in Plants; LOEB, 
 Dynamics of Living Matter, Lect. VII, VIII. For the pupils : ANDREWS, 
 Practical Course, pp. 47-52; COULTER, Plant Life, pp. 131-134; DUGGAR, 
 Plant Physiology, chap, xx, pp. 415-420; OSTERHOUT, Experiments, chap. ii. 
 
 X. ABSORPTION FROM THE ENVIRONMENT 
 
 To' introduce the subject of osmosis, it is well to begin with 
 practical demonstrations of diffusion. Open a bottle containing 
 acetic acid, ether, chloroform, alcohol, formalin, or some other 
 substance with a decided odor. Open the gas cock for a few 
 moments. When it is evident that the odorous substance has 
 reached some distance from its source, the subject of diffusion 
 may be taken up. 
 
 For diffusion in liquids, prepare some bottles or tumblers of 
 water and place in each a lump of sugar or salt. Into a beaker or 
 jar of water that has been standing for some time, so that there 
 are no movements or currents in it, let fall a drop of red ink 
 (eosin solution or some other water-soluble pigment will do). The 
 diffusion of the salt or sugar, and that of the ink, are visible and 
 demonstrate the action of some form of attraction that, in the one 
 case, raises the material from the bottom of the jar to the surface 
 of the water (since in time the diffusion will result in an equal 
 distribution of the material throughout the liquid), and in the other 
 case spreads it through a quiet body of water. 
 
 To illustrate absorption without diffusion, sheets of glue or of 
 gelatin may be used. Wood, leather, and paper behave in much 
 the same way, except that the glue and gelatin are practically 
 homogeneous substances, whereas the other materials represent 
 structures with visible (microscopic) pores. 
 
MANUAL FOR TEACHERS 31 
 
 An artificial root hair or cell may be made of goldbeater's 
 skin or of celloidin. The latter is to be preferred because it 
 gives a homogeneous membrane that the students can see in the 
 course of formation. Use a pure celloidin dissolved in alcohol and 
 ether, free from acetone. Pour a little of the celloidin into a clean, 
 dry bottle (4-oz. wide-mouthed) and then slowly pour out what you . 
 can (back into the original container), turning the bottle all the 
 while so as to spread the celloidin evenly over the inner surface 
 of the bottle. Allow to stand for several minutes, blowing into 
 the bottle from time to time, to accelerate the evaporation of the 
 ether and alcohol. Prepare for each bag a two-hole rubber stopper 
 (size No. 4 or No. 5), a thistle tube, a rubber band, and a glass 
 plug to fit into one of the holes in the stopper. There will also 
 be needed a mixture of sirup or molasses and water, a jar of clean 
 water, and a support 
 
 After all of the ether has evaporated from the " newskin " 
 membrane in the bottle (as you can tell by the odor), add a little 
 water, which will accelerate the removal of- the alcohol. With a 
 little careful manipulation it is possible to remove the bag from 
 the bottle without breaking it. Insert the rubber stopper in the 
 neck of the bag, and make fast with a few turns of the rubber 
 band. Insert the thistle tube, and the bag is ready to be filled 
 with the sirup. After a little practice the teacher should be able 
 to make the bag in a few minutes, and thus to complete the whole 
 operation in the presence of the class. 
 
 After pouring in the sirup until the bag is quite full, plug the 
 vent, wash off the outside, and place in the jar of clean water, 
 suspending the cell so that it does not come in contact with the 
 sides of the jar. Note the height of the liquid on the inside, and 
 watch the rise of liquid in the thistle tube. If it is desired to con- 
 tinue the rise of liquid beyond the limits of the thistle tube, this 
 should be replaced by a long glass tube say three feet long 
 before closing the vent and clamping in place. 
 
 Parallel demonstration of starch paste, various salts and sugars, 
 or of different concentrations of salts and sugars may be made by 
 different members of the class. The diffusion outward should not 
 
32 MANUAL FOR TEACHERS 
 
 be overlooked in the presence of the striking inward diffusion of 
 water. The discussion of the results should bring out all the 
 important facts associated with the idea of osmosis. 
 
 Examples of diffusion and of osmosis in everyday experience, 
 with practical applications, should be called for and recorded. 
 
 References. For the teacher: COULTER, BARNES, and COWLES, Text- 
 book, pp. 297-311 ; LOEB, Dynamics of Living Matter, lect. iii. For the 
 pupils: ANDREWS, Practical Course, pp. 52-58; BERGEN and DAVIS, Prin- 
 ciples, chap, v; COULTER, Plant Life, 35-36; DUGGAR, Plant Physiology, 
 chap, iv ; OSTERHOUT, Experiments, chap. iii. 
 
 XI. ROOTS OF PLANTS 
 
 To obtain root hairs suitable for class study, place radish seeds 
 on wet blotting paper (blue or green) in Syracuse watch glasses 
 or Petri dishes two or three days before they are to be used. 
 There should be no free water standing above the blotters. Have 
 dishes, with magnifying glasses, ready to pass out at the beginning 
 of the study. As the root hairs shrivel up on exposure to the air, 
 the dishes should be taken up again at the conclusion of the study, 
 and stacked up for use with another class. If carefully handled, 
 the preparations should serve two or three days. Have root hairs 
 of tradescantia, flax, or radish mounted for examination through 
 the compound microscope. 
 
 Fresh woody roots, as well as the fleshy roots mentioned in the 
 text, should be on hand for examination, unless it is feasible to 
 study them in the woods or fields. 
 
 Have on exhibition preparations for microscopic views of the 
 principal kinds of root tissue, including the two kinds of growing 
 tissue, cambium and terminal meristem. 
 
 To show the dependence of root-hair formation upon external 
 conditions, keep roots of seedlings in water, with parallel growths 
 in sand or paper. Those in the water will not form hairs. 
 
 To demonstrate sap pressure or root pressure, take a vigorous 
 hydrangea plant with stem at base about half an inch thick, place 
 pot and base of plant in pail of water, and in this position cut off 
 the stem about two inches from the surface of the soil. Connect 
 
MANUAL FOR TEACHERS 33 
 
 the stem with a glass tube by means of a rubber-tube coupling. 
 Remove from the water and arrange a support for the long glass 
 tube. The preparation is made in water to prevent the entrance 
 of air-bubbles. 
 
 To get adventitious roots, place various twigs, bits of begonia 
 leaf or bryophyllum leaf, leaves of india-rubber plant or of English 
 ivy in bottles of water. 
 
 References. BERGEN and CALDWELL, Practical Botany, chap, iii; 
 BERGEN and DAVIS, Principles, chap, iv ; COULTER, Elementary Studies, 
 Part I, chap, xiii; COULTER, Plant Life, chap, iv ; COULTER, BARNES, and 
 COWLES, Textbook, pp. 311-316; DUGGAR, Plant Physiology, chap, iii; 
 OSTERHOUT, Experiments, chap, iii ; United States Department of Agri- 
 culture yearbooks ; farmers' bulletins. 
 
 XII. WHAT FOOD IS 
 
 The idea of activator as something needed to keep a process 
 going may be illustrated by the spark in the gasoline engine. 
 The drop of acid added to water to make the latter a conductor, 
 as in hydrolysis, takes no part in the main process, but makes the 
 latter possible. 
 
 Regulator is illustrated by the pendulum of a clock and by 
 the balance wheel of a watch. If we place salt in the water before 
 cooking corn meal or oatmeal, we thereby regulate the temperature 
 at which the water will boil, since salty water has a higher boiling 
 temperature than pure water. The gyroscope is another example 
 of a mechanical regulator. 
 
 The school museum should gradually accumulate specimens of 
 foods in a pure state, casein, albumens of various kinds, and 
 other proteins may be obtained in the market. Starches, sugars, 
 and fats, with the sources indicated on the bottles, are helpful in 
 making the terms stand for something concrete, and in correlating 
 with geography on the one hand and with domestic science on 
 the other. 
 
 References. COULTER, Plant Studies, pp. 41-42, 343-347 ; COULTER, 
 BARNES, and COWLES, Textbook, pp. 356-363; HOUGH and SEDGWICK, 
 The Human Mechanism, pp. 86-95. 
 
34 MANUAL FOR TEACHERS 
 
 XIII. THE ORIGIN OF FOOD 
 
 For conducting the experiments in photosynthesis, hydrangea, 
 coleus, and geranium are convenient plants to use. 
 
 To show the relation of air to starch-making, exclude the air 
 from a leaf upon a vigorous live plant, by smearing vaseline over 
 both surfaces, on one side of the midrib only. After exposure to 
 bright sunlight for a whole day, remove the treated leaf, to be 
 tested for the presence and distribution of starch. To remove the 
 chlorophyl and to fix the starch, boil in water a few minutes, then 
 place in alcohol. The bleached leaf is tested for starch by placing 
 in a solution of iodin in 10 per cent solution of potassium iodid, 
 about the color of weak tea. It is necessary to explain that starch 
 is the only substance known to turn blue with iodin. 
 
 The question as to which of the three chief gases in the air is 
 concerned in starch-making could be answered by means of an 
 experiment, if it were desirable to do so in the laboratory. Large 
 bell jars connected with aspirators for drawing a current of air 
 through are used. A live potted plant is placed in each jar. The 
 inlet pipe of one jar is connected with a wash bottle containing 
 caustic soda solution, to withdraw the carbon dioxid ; a second jar 
 is thus connected with a phosphorus container for removing the 
 oxygen ; a third has both of these gases removed. The control is 
 allowed to get the ordinary atmospheric mixture of gases. 
 
 The relation of light to photosynthesis may be demonstrated 
 either by using two plants, one in the light and one in the dark, 
 or by shielding a portion of a leaf from light while the rest of the 
 plant is exposed. The latter method is attained by pinning two 
 pieces of black paper on the opposite sides of a leaf so as to 
 exclude the light from the covered portion without excluding the 
 air, and leaving the rest of the leaf exposed to light as well as to 
 air. At the close of the first sunny day the leaf is removed from 
 the stem, boiled in water, and soaked in alcohol. The application 
 of iodin brings out the distribution of starch. 
 
 To show that oxygen is liberated during photosynthesis, place 
 a healthy potted plant under a large bell jar (with an opening at the 
 
MANUAL FOR TEACHERS 35 
 
 top) on a plate of glass. Seal the base of the bell with vaseline. 
 Remove the oxygen from the jar by burning a taper lowered 
 from above. Seal the top opening.' At the close of one or two 
 sunny days, open the top and lower a lighted taper into the jar. 
 The difference between the burning conditions at the beginning of 
 the experiment and the burning conditions at the close points to 
 the entrance of oxygen, and the plant is the only apparent source 
 of the new gas. 
 
 To explain the general chemical relations of the materials 
 involved in photosynthesis, it is not necessary to elaborate much 
 detail. It is sufficient to bring out the fact that the hydrogen- 
 oxygen ratio in carbohydrates is the same as that in water, and 
 that the utilization of water and carbon dioxid as the sources of 
 the elements entering into the carbohydrates leaves a surplus of 
 oxygen corresponding to that brought in with the carbon dioxid. 
 
 In connection with this study, the results may be recorded in a 
 table showing the parallel between photosynthesis and a manufac- 
 turing process. It is interesting, if there is time, to bring out at 
 this point our ultimate dependence upon the sun for all the energy 
 that we utilize, fuels and waterfalls as well as organic processes. 
 " Every action is a transformed sunbeam." 
 
 References. For the teacher : COULTER, BARNES, and COWLES, Textbook 
 of Botany, pp. 363-380; DUGGAR, Plant Physiology, chap. ix. For the pupils: 
 ANDREWS, Practical Course, pp. 168-174; BERGEN and CALDWELL, Prac- 
 tical Botany, pp. 15-17; BERGEN and DAVIS, Principles, pp. 107-110; 
 COULTER, J. G., Plant Life, pp. 43-44, 228-234; COULTER, J. M., Ele- 
 mentary Studies, Part I, chap, iii ; OSTERHOUT, Experiments, pp. 182-203. 
 
 XIV. THE CHEMICAL CYCLE OF LIFE 
 
 Have specimens of clover, alfalfa, partridge pea, or other wild 
 or cultivated legume pulled up for a study of the tubercles. The 
 balanced aquarium can be studied profitably with reference to the 
 essentials of the balance. Encourage students to represent their 
 ideas of the " cycles " etc. diagrammatically. 
 
 Have students bring news items bearing on the current or local 
 status of the nitrogen problem. 
 
36 MANUAL FOR TEACHERS 
 
 References. BERGEN and CALDWELL, Practical Botany, pp. 374-378, 
 447-451; BERGEN and DAVIS, Principles, pp. 231-235; DUGGAR, Plant 
 Physiology, chap, x; SEDGWICK and WILSON, General Biology, chap, xvii; 
 STILES, Human Physiology, pp. 25-36. 
 
 XV. THE SOIL AS THE SOURCE OF OUR MATERIALS 
 
 The purpose of this chapter is to combat, on the one hand, gen- 
 eral indifference toward the problem of soil use and conservation, 
 and, on the other hand, a certain fatalistic Malthusianism. We 
 should make clear that population and prosperity are directly re- 
 lated to the amount and character and condition of the soil ; and 
 that applied science can help us extend our power and resources 
 indefinitely, without thought of exploiting the lands of other 
 peoples. Have students gather data on reclamation, irrigation 
 projects, etc., and data as to increased production per capita and 
 per unit of area. 
 
 References. See references to VII; L>UGGAR, Plant Physiology, chap. vi. 
 
 XVI. THE LEAF AS STARCH FACTORY 
 
 The concept leaf should include more than the familiar types. 
 It is better to examine cursorily a large number of varieties than 
 to study minutely a few forms. All the extremes afforded by the 
 resources at hand from the rhubarb to the asparagus, from the 
 cactus to the cedar, from the mullein to the tradescantia should 
 be brought together until the student is quite convinced that the 
 definition of leaf is not to be found in a description of a few or 
 of many shapes. 
 
 Examine with the microscope bits of epidermis peeled from any 
 convenient leaves, and cross sections thin enough to show the 
 tissues and if possible the stomata. 
 
 Comparing the leaf to a factory, have students make diagrams 
 showing the route followed by materials received from the air and 
 from the stem until they are finally disposed of. 
 
 To measure the transpiration of a potted plant, inclose the 
 pot and earth in rubber sheeting and weigh the whole. Weigh 
 
MANUAL FOR TEACHERS 37 
 
 again at intervals and note the loss. For a qualitative demonstra- 
 tion, the prepared potted plant may be placed under a bell jar; 
 the condensation of moisture on the glass will indicate loss of 
 water from the plant surface. 
 
 To show the pulling force of the transpiration current, insert 
 the stalk of a healthy leaf in the end of a glass tube, and seal the 
 joint with paraffin. Fill the tube with water and set over mercury. 
 The rise of mercury in the tube is a measure of the mechanical 
 equivalent of the transpiration from the leaf's surface. 
 
 Special readings and reports on insectivorous leaves. 
 
 References. ANDREWS, Practical Course, pp. 189-195; BERGEN and CALD- 
 WELL, Practical Botany, pp. 13-15, 18-20, 385-389; BERGEN and DAVIS, 
 Principles, pp. 88-96, 102-106 ; COULTER, Plant Life, pp. 234-241, 251-255 ; 
 COULTER, BARNES, and COWLES, Textbook of Botany, pp. 521-530, 551-578, 
 385-388,616-620; DARWIN, Insectivorous Plants; DUGGAR, Plant Physi- 
 ology, chap, v; OSTERHOUT, Experiments, pp. 173-181, 203-223. 
 
 XVII. OUR DEPENDENCE UPON LEAVES AND CHLOROPHYL 
 
 This is in part a repetition of the thought in XIV, The Chemical 
 Cycle of Life, but from a somewhat different point of view. The 
 attention is directed to the concrete materials that we actually use. 
 Materials used in connection with the study of leaf forms and 
 structure, and museum material, may be used here. Connect the 
 study with the local market and industrial conditions. 
 
 For the study of algae, there should be microscopic prepara- 
 tions or good charts. Homemade charts that will serve adequately 
 can be prepared with a little effort. 
 
 This topic furnishes an excellent opportunity for a synthetic review. 
 
 References. COULTER, Elementary Studies, pp. 378-383; SARGENT, 
 Plants and their Uses, 36, 137. Yearbook of the United States Depart- 
 ment of Agriculture, an variety, magnitude, and values of crops. 
 
 XVIII. STARCH-MAKING AND DIGESTION 
 
 Digestion of starch can be demonstrated by using a very thin 
 starch paste, (a) with some takadiastase and () with some human 
 saliva. Use large test tubes ; keep at room temperature or warmer. 
 
MANUAL FOR TEACHERS 
 
 Demonstrate starch test with iodin on small portion drawn off 
 at the beginning of the experiment. Draw off at intervals of five 
 or six minutes and test again. When there is no more starch 
 present, test portion from each test tube with Fehling solution. 
 The disappearance of the starch and the appearance of the sugar 
 (the absence of which may be demonstrated at the beginning 
 of the experiment) indicate that something has happened to the 
 starch which probably has something to do with the formation of 
 
 sugar. It is well to 
 test the diastase with 
 Fehling solution at the 
 beginning, since some 
 commercial diastase 
 contains reducing sub- 
 stances. 
 
 A more striking and 
 otherwise more satis- 
 factory demonstration 
 consists of showing 
 the formation of dif- 
 fusible substances by 
 the action of diastase 
 
 and saliva. Place the thin starch paste with saliva in a celloidin 
 bag (see p. 31 of Manual), and starch paste with diastase in an- 
 other bag. A third bag (control) contains merely starch paste. 
 The three bags are suspended in three jars or tumblers contain- 
 ing clean water. After the expiration of fifteen minutes, withdraw 
 some of the surrounding water and test with Fehling solution. 
 Repeat from time to time until there is a positive reaction. Then 
 put a few drops of iodin inside each bag. The bags containing 
 saliva and diastase will have lost their starch and will have diffused 
 sugar into the surrounding water ; the control shows no change. 
 
 Corn grains that have been soaked in water overnight may be 
 tested with Fehling solution (after being cut open, some length- 
 wise and some crosswise). Allow some of the soaked grains to 
 sprout, then cut them open and test them. The presence of sugar 
 is due to the action of a diastase upon the starch. 
 
 FIG. 8 
 
MANUAL FOR TEACHERS 
 
 39 
 
 References. For the teacher : COULTER, BARNES, and COWLES, Textbook 
 of Botany, pp. 397-402 ; DUGGAR, Plant Physiology, pp. 265-271, 277-278 ; 
 GREEN, Vegetable Physiology, chap, xvi ; LOEB, Dynamics of Living 
 Matter, lect. ii. For the pupils: ANDREWS, Practical Course, pp. 6-10; 
 BERGEN and CALDWELL, Practical Botany, pp. 144-146; COULTER, Plant 
 Life, pp. 350-352; OSTERHOUT, Experiments, pp. 155-169. 
 
 XIX. DIGESTIVE SYSTEM IN MAN 
 
 If microscopic preparations of the tissues of the alimentary canal 
 are available, students will be interested in examining them ; but 
 they are not essential. Specimens of fresh materials obtained from 
 the butcher may be shown to those who are not squeamish. None 
 of the students would probably object to examining sausage casing 
 that has been allowed to soak in water until soft. A satisfactory 
 demonstration of peristalsis consists of placing a marble in a long 
 piece of sausage casing and driving it through to the other end 
 by pulling the casing through the fingers (see Fig. 8). 
 
 Ordinarily it is not worth while to demonstrate the action of the 
 various digestive ferments of the alimentary canal. If the notion 
 of digestion or fermentation is clear, it is sufficient to show speci- 
 mens of pepsin, peptone, pancreatin, ox-gall, etc. 
 
 A good way to summarize this study is to have students make 
 a simple diagram representing the alimentary canal, and to label it 
 with the names of the organs on one side of the drawing, and the 
 names of the processes involved on the opposite side. 
 
 Have students prepare a table like the one below, and fill in 
 all the blanks : 
 
 THE ACTION OF DIGESTIVE JUICES ON FOODS 
 
 
 ACTIVE JUICES 
 
 FOODS DIGESTED 
 
 RESULT OF ACTION 
 
 Mouth .... 
 
 
 
 
 Stomach . . . 
 
 
 
 
 Intestines . . . 
 
 
 
 
 Another form of summary is to have students describe the fate 
 of an imaginary mouthful of food containing all the nutrients, in 
 its course from the mouth to the large intestine. 
 
40 MANUAL FOR TEACHERS 
 
 References. HOUGH and SEDGWICK, The Human Mechanism, chap, viii ; 
 STILES, Human Physiology, chaps, xiii-xv; STILES, Nutritional Physiology, 
 chaps, xiv-xvi. Have pupils make special reports on digestive systems and 
 on special organs of various vertebrate and invertebrate types or groups. 
 
 XX. HEALTH AND FOOD STANDARDS 
 
 It is important to establish a clear distinction between stand- 
 ards that represent customs or usage, and norms established as 
 the result of experiment or measurement. Have students present 
 examples of usage among certain people who have remained be- 
 hind the best thought and knowledge of the same or other com- 
 munities. Get them to think of the reasons for this, and of methods 
 for accelerating the standardization of practice. 
 
 Get examples of food fads or other standard usages, with the 
 principles offered in justification. 
 
 Determining units for measurement ; get examples of as many 
 kinds as the students happen to know. As a demonstration, deter- 
 mine the time needed to raise a quantity of water to the boiling 
 point in a given vessel, with the burner in use ; compare with 
 results when using double quantity of water. Or use similar 
 quantities with different size of flame. 
 
 Explain principle of calorimeter ; if there is one in town, arrange 
 to visit with the class and have its workings demonstrated. 
 
 Study cases in which standards have come into general use 
 after scientific determination. 
 
 In the matter of food standards, bring out the principle of indi- 
 vidual variation. This should be referred to as occasion offers, as 
 one of the fundamentals of modern thinking about organic and 
 social problems. 
 
 To give the daily requirements more concrete significance, 
 have the students calculate the mechanical equivalent of the energy 
 represented by the daily ration. For example, compare the 
 energy consumed by the organism in one day with the moving of 
 a ton of freight, with the raising of passengers in an elevator a 
 given .height, with the lifting of a quantity of ore or bricks, 
 and so on. 
 
MANUAL FOR TEACHERS 41 
 
 The mechanical equivalent of one calorie is about 3,060 foot- 
 pounds. One horse-power is 550 foot-pounds per second. 
 
 References. HOUGH and SEDGWICK, Human Mechanism, pp. 211-217; 
 ROSE,- Feeding the Family, chap. i. The teacher should constantly consult 
 publications of research laboratories, such as those of Mendel, Lusk, 
 Chittenden, Benedict, etc. See United States Bureau of Standards, 
 Circular No, 55. 
 
 XXI. FOOD REQUIREMENTS 
 
 Have each student prepare a schedule of one meal, or of a day's 
 meals, and then go through the calculations according to the 
 methods used in the text. After the calculations are finished, have 
 the food assortments of specimen charts criticized by the various 
 standards. Have students formulate their own suggestions for 
 the improvement of their diet, as, eat less ; eat less fat or 
 protein ; eat more vegetables ; and so on. 
 
 References. FISHER and FISK, How to Live, pp. 28-35; HOUGH and 
 SEDGWICK, Human Mechanism, pp. 217-233; LEE, ROGER I., Health and 
 Disease, pp. 31-45; ROSE, Feeding the F'amily, chap, iii ; STILES, Human 
 Physiology, chap. xxv. Current publications. Have special reports made 
 on rations for soldiers or for various institutional groups. 
 
 XXII. FOOD AND DIETARIES 
 
 It would be interesting and illuminating to collect examples of 
 superstitions, folklore, and family traditions on what to eat and 
 what to avoid. Misleading suggestions on the choice of food are 
 frequently found in advertisements of special food preparations, and 
 in more dogmatic forms. Many obscure pathological conditions 
 have come to be recognized in recent years as due to disturbances 
 in nutrition that may be corrected through proper adjustment of 
 the diet. The students should be encouraged to note and report 
 experiences and observations bearing on these points. Where 
 there is an opportunity to correlate the study of food with the 
 domestic-science work of the school, this should not be overlooked. 
 
 In the study of food economy there is an opportunity for a great 
 deal of practical work, and this is readily correlated with the 
 domestic science. Using Fisher's tables, have students obtain 
 
MANUAL FOR TEACHERS 
 
 current prices of the various foods, and calculate the cost of stand- 
 ard (100 calorie) portions. An interesting piece of outside work 
 consists of preparing a series of bottles or specimen jars showing 
 the standard quantity of each of a series of food articles, together 
 with the price of each. A parallel series might be prepared by an- 
 other group of students, showing the quantity of each kind of food 
 that may be obtained for a given amount of money, say ten 
 cents or five cents. The labels on these jars should contain, of 
 course, all the significant data, as in the two labels below : 
 
 SERIES A 
 
 TEN CENTS' WORTH 
 
 OF 
 CORN MEAL 
 
 Quantity . 
 Calories 
 Protein 
 Prepared by 
 Date 
 
 SERIES B 
 100 CALORIES 
 
 OK 
 OYSTERS 
 
 Quantity . 
 Protein 
 Cost . . 
 Prepared by 
 Date 
 
 Dry food materials need merely to be sealed in the jars or 
 bottles. Meats, fish, fresh vegetables, etc. can be preserved in 
 4 per cent formalin solution. Each student need prepare but one 
 or two specimens; and the information gathered is exchanged 
 by comparison of costs and other data. The specimens may be 
 kept indefinitely, and the collection may grow from year to year. 
 
 References. FISHER and FISK, How to Live, pp. 35-40; HOUGH and 
 SEDGWICK, Human Mechanism, pp. 233-243 ; JORDAN, E. O., Food Poison- 
 ing, chap. ix. LEE, Health and Disease, pp. 54-68, 46-51 ; RAPEER, Edu- 
 cational Hygiene, pp. 68-77. Special readings in ROSE, Feeding the Family. 
 Have students compare special rations established for domestic animals, 
 from reports of agricultural experiment stations and from the United States 
 Bureau of Animal Industry. Current matter on vitaminesand on deficiency 
 diseases. See XX. 
 
MANUAL FOR TEACHERS 43 
 
 XXIII. FOOD HABITS 
 
 The practical value of these studies should of course issue in 
 habits, habits of attitude as well as habits of conduct. It is, how- 
 ever, extremely difficult to gauge the extent to which the studies 
 have influenced the habits of the pupils. With discretion a teacher 
 may from time to time put forth a question or a suggestion that 
 will bring an illuminating reaction on this problem. 
 
 For a study of the teeth, it is usually easy to obtain instructive 
 specimens from a dentist. Cross and longitudinal sections may be 
 prepared by means of a grindstone. But it is easy to spend too 
 much time on the study of tooth structure and form ; these are not 
 worth much unless it is desired to make a fuller study of compara- 
 tive morphology of mammalian teeth. The important facts are 
 few and quickly grasped, and are related to decay. 
 
 A striking demonstration of the danger of exposing the teeth 
 to rapid alternation of temperature consists of heating a test tube 
 and then casually dipping it into a jar of cold water. 
 
 It has been found very instructive to make a census of the 
 proprietary drugs on sale or advertised in the neighborhood, for 
 the purpose of determining the proportions of those offered as 
 remedies for headaches and constipation. Labels or wrappers 
 from such preparations make an interesting exhibit. 
 
 References. FISHER and FISK, How to Live, pp. 44-51, 51-57? 78-89; 
 HOUGH and SEDGWICK, Human Mechanism, chap, xix ; LEE, Health and 
 Disease, pp. 51-53; ROSE, Feeding the Family, chap, ii; STILES, Human 
 Physiology, chap, xxvi ; STILES, Nutritional Physiology, chaps, xxii, xxiii. 
 Special readings in JORDAN, Principles of Nutrition, and in SHERMAN, 
 Chemistry of Food and Nutrition. Teacher should be familiar with work 
 of Cannon and of Carlson. See CANNON, Bodily Changes in Pain, Hunger, 
 Fear, and Rage, chap. i. 
 
 XXIV. THE SOCIAL SIDE OF THE FOOD PROBLEM 
 
 Have the students find out the local situation in regard to the 
 protection of the water supply, and classify the functions involved 
 in this protection in order to see how much depends upon 
 biological principles. 
 
44 MANUAL FOR TEACHERS 
 
 Have the students obtain copies of local regulations concerning 
 food standards, food protection, and food sales. Reports of the 
 state and municipal departments of health, bureaus of weights 
 and measures, milk committees, etc. should be consulted. 
 
 Collect labels from various food packages, showing the publica- 
 tion of facts concerning preservatives, artificial coloring, etc., in 
 accordance with specified laws, or of claims as to purity of materials 
 used. It is impossible to know ordinarily the extent to which food 
 is " faked." But reports are constantly appearing that throw light 
 on this question, and students should know both how to obtain 
 the information contained in such reports and how to interpret it. 
 For example, the New Hampshire Board of Health issued one 
 report in which it appeared that of three hundred and sixty-three 
 samples of food taken in the market, nearly one half (164 45.2 
 per cent) were adulterated. Changes in the attitude of official and 
 semiofficial bodies toward this matter are constantly being made, 
 and students should know how to keep in touch with such 
 changes. For example, in New York City the Board of Health 
 began in 1914 to publish every week the names of all dealers or 
 manufacturers convicted of selling foods not in accord with offi- 
 cial standards. The plan of publishing names and addresses of 
 violators has been especially valuable in connection with the milk 
 business, since the ordinary milk buyers are practically helpless 
 in their dealings with unscrupulous sellers. Newspaper clippings 
 should be pasted in notebooks or posted on the class bulletin. 
 
 Have students report on conditions in stores and markets 
 where food is sold. After comparing notes in class, have them 
 draw up a scale for scoring or grading the shops. 
 
 Have students report on conditions in workshops, stores, fac- 
 tories, and offices, in relation to lunch-rooms, opportunity for wash- 
 ing up, etc. Much of this information can be obtained by inquiry 
 among relatives and acquaintances. 
 
 Where there is a school lunch service, it should be possible to 
 cooperate for the purpose of establishing in the minds of the pupils 
 standards in regard to conditions as well as in regard to the food, 
 balanced rations, quantities, etc. Have students prepare schedules 
 
MANUAL FOR TEACHERS 45 
 
 of food values for the various items served in the lunch-room, and 
 arrange to have the figures used in connection with the menus. 
 If this is already the practice, sample menus may be used as basis 
 for discussion of balanced rations etc. 
 
 Where there is time, it is worth while to devote a whole period 
 to the subject of National Food Resources. Begin with a compari- 
 son of the proportion of the population engaged in farming at the 
 close of the Civil War with the proportion so engaged at the time 
 of the last census. Then compare the per capita production of 
 various food materials at the two periods ; compare the yield per 
 acre under cultivation, and so on. The point to be brought out 
 is the increased control and the increased resources through the 
 application of biological and other exact knowledge. Assign indi- 
 vidual students to report on the various governmental activities 
 related to the food yield that are mentioned in the text. Bring 
 out the realization that the problem of food conservation means 
 more than adequate production ; it involves matters of transporta- 
 tion, marketing, storage and preservation, and, finally, adequate 
 distribution in the economic sense, that is, the ultimate consump- 
 tion of the food in a way that will contribute the utmost to the 
 welfare of the nation or the community. 
 
 References. HOUGH and SEDGWICK, Human Mechanism, pp. 505-514; 
 JORDAN, Food Poisons, chaps, v, vi, viii ; LEE, Health and Disease, 
 pp. 69-73. Special reports on war food administration ; on local and state 
 regulations of food production, food distribution, and food standards ; on 
 current studies pertaining to character and extent of malnutrition among 
 children or other groups ; on current or local efforts to remedy defects of 
 nutrition in large groups. Material can be obtained from the departments 
 of health, commerce, and agriculture, and from the United States 
 Children's Bureau. 
 
 XXV. STIMULANTS, NARCOTICS, AND POISONS 
 
 In getting the idea of acclimatization, the students will be led 
 to draw upon their own experiences and observations. The point 
 to emphasize is that the modified organism becomes dependent 
 upon the new environment. Whether it works as well under 
 
46 MANUAL FOR TEACHERS 
 
 the new conditions as it can under the natural conditions is a 
 different question, although an important one. 
 
 The difficulty that many students have in forming chemical con- 
 cepts may in part be met by the use of mechanical analogies, which 
 are more readily visualized. For example, in thinking about the 
 action of drugs or chemicals upon protoplasm, compare this action 
 to the effects that may arise from introducing a foreign body into 
 a piece of machinery. If a boy should stick his finger into the 
 business region of a buzz-saw, the machine would keep right on 
 working as though nothing had happened ; this corresponds to an 
 indifferent chemical body, or to a " subliminal dose." If the boy 
 should drop a bar of iron in among the wheels, it might catch be- 
 tween the spokes and stop the machinery altogether; or it might 
 catch against a moving part, simply slowing up the machinery. 
 This corresponds to a narcotic, up to the " lethal dose." Finally, 
 he could push his bar of iron against the belt connected with the 
 governor of the engine and disconnect this part ; in that case the 
 engine might suddenly begin racing at increased speed. This 
 would correspond to the effect of a stimulant, or accelerator. 
 
 References. FISHER and FISK, How to Live, pp. 64-78, 250-268 ; HOUGH 
 and SEDGWICK, Human Mechanism, pp. 357-363 ; LEE, Health and 
 Disease, pp. 125-134; "The Great American Fraud" (American Medical 
 Association) ; Farmers' Bulletin, " Habit- Forming Drugs." 
 
 / XXVI. ALCOHOL AND HEALTH - XXVII. ALCOHOL 
 AND SOCIETY 
 
 We must be on our guard against the temptation to resort to 
 the hortatory method in dealing with this subject ; it is necessary 
 to maintain a more calm and more tolerant spirit than that which 
 characterized the campaigners of a generation or two ago. It 
 happens altogether too frequently that intelligent, honest, and 
 likable people are also alcohol drinkers. The awful things predi- 
 cated about drinkers in the older books do not find confirmation 
 in the daily experience of the students. Instead of discrediting 
 the drinkers, these experiences discredit the books and the whole 
 tribe of physiology and hygiene teachers. 
 
MANUAL FOR TEACHERS 47 
 
 There are available verified and verifiable data that help to 
 demonstrate the undesirability of alcohol as a beverage, but these 
 data are to be used in a common-sense way. We must avoid the 
 fallacy of arguing from statistical generalizations to individual 
 application. It is impossible to say " You will suffer " so and so 
 if you drink. The very most that we can say is, " If you drink, 
 your chances of becoming sick are increased by so many per cent ; 
 and when you are sick, your chances of recovery are reduced by 
 so many per cent." In other words, the data show simply group 
 effects. We may therefore teach only that a society, or community, 
 or class of people stands to gain by adopting this or that course 
 of conduct. Our problem is to socialize the interest and make the 
 individual resolve that, so far as he is concerned, the group of which 
 he is a member is to profit from his learning. So long as our 
 health teaching in regard to alcohol (and in regard to many other 
 matters) was based on the sentiment of competitive advantages 
 for the individual, it resulted simply in placing before the child 
 the betting odds against the practices condemned. And since 
 most children are fairly good " sports," the teaching did not suc- 
 ceed in intimidating them. The individual can often afford to take 
 chances ; the only certainty we can teach from our statistical studies 
 is that the group suffers from the use of alcohol. 
 
 To demonstrate the effect of alcohol upon proteins, add alcohol 
 to the raw white of an egg ; this is a suggestion of how alcohol 
 may injure protoplasm. Supplement with parallel demonstration 
 of the coagulating effect of mercuric bichlorid solution and other 
 " poisons." The point is to show that alcohol is one of a class 
 of substances that are unquestioned poisons, and not something 
 unique in its relation to protoplasm. 
 
 Have students gather data on usages of local employers, in 
 selecting workers for responsible positions, in the matter of drink- 
 ing. Have them get information as to regulation of the patent- 
 medicine trade by local or general authorities. Have reports 
 made on fraudulent cures for alcoholism. What are the current 
 and local developments in meeting the social requirements of the 
 human animal that had been left to the exploitation of the alcohol 
 
48 MANUAL FOR TEACHERS 
 
 interests in the past ? Agitation and legislation since the entrance 
 of the country upon the war. The soldier and alcohol. Opportuni- 
 ties for special reports and studies are almost limitless. 
 
 References. For the teacher: BILLINGS, Physiological Aspects of the 
 Liquor Problem ; KOREN, Alcohol and Society. For the pupils : FISHER 
 and FISK, How to Live, pp. 227-250; HOUGH and SEDGWICK, Human 
 Mechanism, pp. 363-379; LEE, Health and Disease, pp. 113-125. An 
 excellent condensed summary of all the significant data has been prepared 
 by the D'Abernon-Newman Committee (British) under the title " Alcohol : 
 its Action on the Human Organism." An American edition is issued by 
 Longmans. 
 
 XXVIII. AIR AND LIFE 
 
 Review briefly the important ideas already learned on' the rela- 
 tion of oxygen to energesis in burning. Have live plants and 
 animals on hand for demonstration of breathing. 
 
 If drawings have been made of cross sections of the leaf, refer 
 to them and add further notes on the path of the air exchange 
 involved in breathing. If there are no drawings and there is not 
 time to make any, use wall charts, blackboard drawings, and 
 microscopic demonstration. 
 
 If the season permits, use live insects for the study of spiracles 
 and breathing movements ; otherwise use prepared specimens. 
 Study tracheae from microscopic mounts and from pictures 
 and charts. 
 
 Compare live earthworms with sandworms, bloodworms, or 
 other gill-bearing worms near the coast. Use preserved speci- 
 mens of mollusks and crustaceans for comparison of different 
 types of gills. The course of the water in breathing is easily 
 studied in crayfish and in fish. The breathing process in frogs 
 should also be studied in the living specimens. The test of the 
 students' grasp of the mechanism of breathing in the frog lies in 
 their answer to the question, " What would happen to a frog that 
 was forced to keep his mouth open indefinitely ? " 
 
 Prepare in advance dissections showing the connection between 
 the throat and the gill slits in the fish, and between the throat and 
 the lungs in the frog. Some of the older students can make such 
 
MANUAL FOR TEACHERS 
 
 49 
 
 dissections under direction. Preserve good preparations in 4 per 
 cent formalin for future use. 
 
 References. BIGELOW, Applied Biology, pp. 502-503. Special reports 
 on course of air (oxygen) in the breathing of various vertebrate and 
 invertebrate types, from descriptions in available books on zoology 
 
 XXIX. BREATHING IN MAN 
 
 Obtain lungs of calf, sheep, or 
 ox from a butcher. Use models 
 of lungs, showing diagrammati- 
 cally some of the detail structure. 
 For making clear the mechanics 
 of the diaphragm action, the appa- 
 ratus pictured in Fig. 9 should be 
 set up in advance. If there is a 
 skeleton in the school, show the 
 relation of rib curvature and rib 
 movements to the expansion and 
 contraction of the chest cavity. 
 
 Have students study the move- 
 ments of the chest and abdomi- 
 nal wall with the hands while 
 breathing slowly. Students, es- 
 pecially boys, are interested in 
 comparing lung capacity. If an 
 aspirator is available, or records 
 from the physical-training de- 
 partment, compare lung capacity 
 with chest expansion. Compare 
 the number of breaths taken by 
 different members of the class 
 in one minute ; individual variation ; variation in depth of breath- 
 ing of different pupils at the same time and of the same pupils at 
 different times. Compare the number of breaths per minute before 
 and after some vigorous setting-up exercises in the laboratory. 
 
 FIG. 9 
 
 A bell jar, closed at the bottom with 
 rubber sheeting, and at the top with a 
 two-holed stopper carrying (i) a Y-tube 
 with two rubber balloons, and (2) a glass 
 vent with a rubber tube closed by a 
 pinchcock 
 
50 MANUAL FOR TEACHERS 
 
 Demonstrate by the pupils themselves relation of posture to chest 
 expansion, breaths per minute, tidal air. Compare notes on the 
 effects of a tight belt or corset and other features of the clothing. 
 
 References. BIGELOW, Applied Biology, pp. 503-505 ; FISHER and FISK, 
 How to Live, pp. 18-28; HOUGH and SEDGWICK, Human Mechanism, 
 chap, x; STILES, Human Physiology, chap. xx. 
 
 XXX. VENTILATION 
 
 In speaking of ventilation standards, it is not enough to learn 
 figures for cubic feet per hour and the like. Have students 
 measure off from a corner of the room enough space to represent 
 say one thousand cubic feet ; have them get an idea of the cubic 
 capacity of the classroom, of the home living-room, of the bedroom, 
 and so on. 
 
 To show the meaning of relative humidity in relation to the 
 work of the lungs, set up two bell jars (or inverted battery jars), 
 suspending in each a piece of wet filter paper. Under jar A place 
 a dish of water; under jar B, an empty dish. Note the time in 
 which the papers become dry ; that in A may remain moist for 
 weeks. Compare the drying of clothes on a clear day and on a 
 muggy day. Introduce the wet-bulb thermometer and show how 
 differences between wet-bulb and dry-bulb readings are to be 
 interpreted. Compare the lower temperature of the wet bulb with 
 the feeling of a wet spot on the skin. Make clear how perspiration 
 helps to regulate the body temperature. Use the illustration of 
 the Australian water bottle. 
 
 Have students report on standardized usage in mines, where 
 low oxygen pressure is maintained to prevent explosions. 
 
 Establish committees of students to be responsible for the 
 ventilation and temperature of the classroom. 
 
 References. FISHER and FISK, How to Live, pp. 7-14; HOUGH and 
 SEDGWICK, Human Mechanism, chap, xxviii ; LEE, Health and Disease, 
 pp. 74-83. Reports of current investigations, especially on ventilation in 
 industrial establishments. 
 
MANUAL FOR TEACHERS 51 
 
 XXXI. CONTAMINATED AIR 
 
 The dusty trades of the neighborhood or of the community, and 
 those that yield injurious vapors or fumes, should receive special 
 attention. Have students find out what these industries are and 
 what conditions prevail for the safeguarding of the health of the 
 workers. Are there any regulations or difficulties about the con- 
 tamination of the community's air by smoke or fumes ? 
 
 In the study of the effects of tobacco, keep in mind the limita- 
 tions of the statistical method, as suggested in the notes on Chapters 
 XXVI and XXVII, and the further sources of error that come from 
 the possibility of the tobacco habit being in itself largely a selec- 
 tive agent, as suggested in the text. In a school containing large 
 numbers of boys it may be possible to collect data as to smok- 
 ing and non-smoking, and to correlate these with physical and 
 scholastic records. The data from your own school, or from a 
 school in your own city or state, will carry more weight than those 
 from some remote institution. Note especially the current and 
 local sentiment and tendencies. 
 
 References. HOUGH and SEDGWICK, Human Mechanism, pp. 377-379; 
 Bulletin 231, United States Bureau of Labor Statistics ; Report of Y. M. C. A. 
 committee on experimental study of the effects of smoking. 
 
 XXXII. FIRST AID AND HYGIENE IN RELATION TO 
 BREATHING 
 
 Time the period during which members of the class can hold 
 the breath. See whether those with unusually high records have 
 any special technique that enables them to exceed the performance 
 of the others. 
 
 Artificial respiration, by the Schaefer or by the Silvester method, 
 should be demonstrated and practiced by the members of the class 
 on each other. If there is an emergency hospital, a life-saving 
 station, a fire-house, or other similar institution within reach, 
 arrangements should be made for the demonstration of a pulmotor 
 
52 MANUAL FOR TEACHERS 
 
 or other like device for the establishment of normal respiration 
 after asphyxiation, drowning, or electric shock. 
 
 In summarizing, make an attempt to get a survey of the prevailing 
 habits of students and of prevailing home conditions with reference 
 to these matters, as open-air sleeping, mouth breathing, and so on. 
 
 References. Miners' 1 Circular No. j, United States Bureau of Mines ; 
 Technical Papers Nos. 77 and 82, United States Bureau of Mines ; RAPEER, 
 Educational Hygiene, chap, xv, " Open-Air and Open-Window Schools." 
 
 XXXIII. TRANSFER OF MATERIALS IN PLANTS 
 
 In anticipation of this study, place various kinds of twigs (pref- 
 erably willow twigs) in jars of water to form roots. Three weeks 
 or longer may be required. Girdling some of the twigs will enable 
 you to make- clear the relation between the bark vessels (phloem) 
 and the transfer of elaborated food in the stem. 
 
 Have on hand microscopic preparations, especially of longitudinal 
 sections of fibrovascular bundles. For the isolated bundles, use 
 corn stalks or celery, either fresh or preserved in from 2 per cent 
 to 3 per cent formalin. For explaining the exogenous type of 
 structure and growth, get sections of various dicot or coniferous 
 twigs, one inch or more in diameter. 
 
 To show the distribution through the wood vessels (xylem) of 
 stem and leaves, place seedlings, stalks of celery, or small succu- 
 lent plants with roots, in tumblers containing dyed water (a few 
 drops of red ink added to the water will do). 
 
 In connection with the problem of the ascent of sap, recall the 
 pull of the transpiration current and the demonstration of root 
 pressure. If necessary, repeat. Get the idea of capillarity clear by 
 means of glass tubes of various dimensions, including old thermom- 
 eter tubes or the finest tubes you can get by drawing out a glass 
 tube softened in a Bunsen flame. Place the tubes in pigmented 
 water and compare the heights to which the fluid rises. Suggest 
 the greater .capillarity of the microscopic vessels in the plant. 
 
 In connection with the problem of the descent of sap, discuss 
 thoroughly the behavior of girdled trees. Is the sap of the maple 
 
MANUAL FOR TEACHERS 53 
 
 obtained from the ascending or from the descending current ? 
 What is the evidence ? 
 
 Study commercial fibers (chiefly bast, such as flax, hemp, jute), 
 bark fibers, etc. Correlate with commercial geography. 
 
 References. For the teacher : COULTER, BARNES, and COWLES, Text- 
 book of Botany, pp. 388-397, 678-696 ; DUGGAR, Plant Physiology, pp. 272- 
 273, 278-279. For the pupils: ANDREWS, Practical Course, pp. 112-118; 
 BERGEN and DAVIS, Principles, chap, viii ; OSTERHOUT, Experiments, 
 pp. 224-258. 
 
 XXXIV. THE BLOOD 
 
 Obtain blood from a butcher or from a slaughterhouse. Add a 
 little formalin to prevent decomposition. 
 
 Demonstrate clotting and the formation of serum by allowing 
 the blood to stand quietly in a covered battery jar or beaker. 
 
 Whip some blood in a battery jar with an egg-beater or a whisk 
 of small twigs. The beating withdraws the fibrin from the blood 
 as fast as it is formed. Allow some of this whipped blood to 
 stand alongside the other ; when the clot is formed in the first, 
 the second still remains fluid. 
 
 Wash the corpuscles out of the clot with cold water ; show its 
 fibrous structure and its protein composition, using nitric acid 
 followed (after washing) with ammonia. 
 
 Examine human blood under the microscope, placing a drop in 
 a little salt solution. 
 
 Pass oxygen through defibrinated blood contained in a tumbler ; 
 pass carbon dioxid through another specimen. See pages 11-13 
 for the preparation of gases. 
 
 Compare the lymph to the ocean as the medium of primordial 
 life. 
 
 Point out that certain types of bleeders suffer from the failure 
 of the blood to form a clot, whereas in other cases the defect is 
 in the texture of the capillaries. 
 
 References. BIGELOW, Applied Biology, pp. 53-55, 482-486; HOUGH 
 and SEDGWICK, Human Mechanism, pp. 132-135; STILES, Human 
 Physiology, chap. xvi. 
 
54 MANUAL FOR TEACHERS 
 
 XXXV. THE CIRCULATION OF THE BLOOD 
 
 Demonstrate the circulation of blood in the web of a frog's foot 
 or in the tail of a tadpole. To keep the animal quiet while on the 
 stage of the microscope, it may be chloroformed ; but you must 
 be careful not to expose it too long to the fumes of the anesthetic. 
 Place the frog in a battery jar in which is suspended a wad of 
 cotton containing the chloroform, and cover. The low power of 
 the microscope is sufficient Point out that the large pigment cells 
 are not in the blood ; these cells are often confusing. 
 
 Demonstrate the structure of a beef or calf heart ; get good 
 models if these are available. 
 
 Have students tabulate data as to the circulation and as to the 
 changes that take place in the blood in various parts of its course. 
 
 Note the exception to the rule that " blood goes from arteries to capil- 
 laries and from capillaries to veins," namely, the portal circulation. 
 
 References. HOUGH and SEDGWICK, Human Mechanism, pp. 136-149; 
 STILES, Human Physiology, chaps, xvii, xviii. 
 
 XXXVI. HYGIENE OF THE CIRCULATORY SYSTEM 
 
 Have students find and count their pulses for a given time 
 (as for one minute), and record. Have the class stand up and go 
 through setting-up exercises, and then record the pulse again. 
 
 If a stethoscope is available, have them listen to their own 
 heartbeats and to any particularly interesting cases, as of mur- 
 murs etc. Call attention to the evidence of danger in overtraining 
 in athletics, for example, the experience of naval cadets in 
 after life. 
 
 Present a collection of antiseptics suitable for the treatment of 
 wounds and scratches. Study bandages. 
 
 Demonstrate methods for stopping bleeding, including nose- 
 bleed. Demonstrate the use of the tourniquet. Study the use 
 of astringents. 
 
 Have students tabulate the results of their study, types of 
 situations and treatment, appliances, etc. 
 
MANUAL FOR TEACHERS 55 
 
 Have students tabulate the factors that have an influence upon 
 the condition of the blood, and the results of various derangements, 
 as food, bowel habits, breathing, rest and fatigue, stimulants 
 and narcotics, and so on. 
 
 References. For the teacher : CANNON, Bodily Changes in Pain, Hunger, 
 Fear, and Rage, chaps, iii, v, ix, x ; HOUGH and SEDGWICK, Human 
 Mechanism, pp. 149-161; LEE, Health and Disease, chap, v; STILES, 
 Human Physiology, chap. xix. 
 
 XXXVII. THE BLOOD AS A LIVING TISSUE 
 
 Review white corpuscles in terms of the properties and behavior 
 of naked protoplasm, emphasizing especially types of irritability. 
 Have on hand specimens of antitoxin, vaccine for typhoid and 
 smallpox, and other serum preparations. Culture tubes and swabs 
 for diphtheria cultures should be seen and handled, and their use 
 demonstrated. 
 
 The idea of a precipitate can be represented very easily : add 
 some sulfate solution to a solution of barium chlorid. 
 
 The subject is usually very interesting to young people, and 
 leads to many questions. The teacher should be prepared to 
 answer some of these concretely and specifically, as the dosage 
 for antitoxin, the unit, and how it is determined ; the use of serum 
 methods in diagnosis and in the specific identification of animal 
 or other organic material ; the use of the opsonic index ; the 
 diseases against which vaccination has been successfully used ; the 
 arguments pro and con on compulsory vaccination ; the phenomena 
 of anaphylaxis ; and so on. 
 
 Get examples of individual variations in natural immunity and 
 racial variation. Experience of students with acquired immunity, 
 whether the result of disease or of special treatment ; data on the rela- 
 tion of temperature, fatigue, nutritive conditions, etc. to immunity. 
 
 The subject of heredity often obtrudes itself insistently and 
 must be handled firmly. To differentiate between the inheritance 
 of a disease and the inheritance of a natural susceptibility is not 
 difficult if the specific relation between bacteria and disease has 
 been first made clear. But when it is necessary to speak of a 
 
56 MANUAL FOR TEACHERS 
 
 possible infection of an infant within the body of the mother, 
 many teachers balk and make trouble for themselves. Draw upon 
 the local department of health and the hospitals for help. 
 
 References. BUCHANAN, Household Bacteriology; HOUGH and SEDG- 
 WICK, pp. 497-504. Special reports on the history of smallpox vaccina- 
 tion ; on experience of the army with typhoid vaccination ; on the work 
 of Behring, Metchnikoff, etc. 
 
 XXXVIII. WASTES AND BY-PRODUCTS OF ORGANISMS 
 
 Review chemical changes, with special emphasis upon the forma- 
 tion of new substances. Cell metabolism involves the formation 
 of new substances ; some of these are indifferent (water), some 
 are useful (proteins), and some (carbon dioxid, urea, various acids) 
 are injurious, at least in excessive quantities. 
 
 Grow some young seedlings in a moist chamber or under wet 
 paper, in contact with a polished piece of marble. The etching 
 of the stone shows the action of some add, but chemical studies 
 fail to reveal any organic acid secreted by the roots. The car- 
 bon dioxid (respiration product) in the water is sufficient to 
 dissolve the carbonate of lime. Guard against the teachings of some 
 of the older books, which still point to the etching as indicating an 
 adaptation for dissolving mineral matter. Some of the dissolved 
 mineral may be absorbed by the roots, but the secretion is of the 
 same character as our exhalation of carbon dioxid through the nose. 
 
 Compare the accumulation of insoluble materials in the tissues 
 of plants with the deposit of starch etc. in tubers and other 
 storage organs. 
 
 Microscopic demonstration of pigments ; chloroplasts as well as 
 sap pigment may be found in the corolla of the pansy. 
 
 Study museum specimens of tannin and its sources. Give a 
 demonstration of tanning (as of white of egg) and of tannery 
 products. Study specimens of other plant products, essential 
 oils, alkaloids, acids, etc. Correlate with commercial geography. 
 
 Microscopic demonstration of silica and raphides in plant cells : 
 use scouring rush (Equisetum) for the former, and Indian turnip 
 (Arisfzmd) for the latter. 
 
MANUAL FOR TEACHERS 57 
 
 Study the Paramecium again, with special attention to the con- 
 tractile vacuole. Any other available protozoa would do as well. 
 
 Cut kidney of calf or sheep lengthwise to show gross structure. 
 Show microscopic preparations of kidney for gland structure. 
 Microscopic sections of the skin are usually not satisfactory for 
 those unskilled in the use of the microscope. A better idea of 
 skin structure is to be obtained from a good model. 
 
 References. COULTER, BARNES, and COWLES, Textbook of Botany, 
 pp. 412-416, 620-626,718-725; HOUGH and SEDGWICK, Human Mechanism, 
 pp. 177-186 ; SARGENT, Plants and their Uses, chaps, iv, v ; STILES, Human 
 Physiology, chap, xxiii. 
 
 XXXIX. HYGIENE OF EXCRETION 
 
 What are the local and state regulations regarding the provision 
 of drinking water in shops, factories, etc. ? What are the local 
 usages in this respect, and as to public drinking fountains ? 
 
 To what extent is there need for official regulation regarding 
 the provision of adequate toilets and washing facilities in industrial 
 and commercial establishments ? public comfort stations ? 
 
 What are the public bathing facilities ? What are the tendencies 
 as to home bathing ? 
 
 How much water (and fluid with food) does each of us take 
 in during the day ? 
 
 Relation of physical exercise to circulation and excretion ; why 
 perspiration is healthful. 
 
 References. FISHER and FISK, How to Live, chap, iv; HOUGH and 
 SEDGWICK, Human Mechanism, pp. 413-424; LEE, Health and Disease, 
 chap. iv. 
 
 XL. EXCRETION AND FATIGUE XLI. FATIGUE AND 
 THE WORKER 
 
 Use a dynamometer from the gymnasium, or a spring scale 
 from the physics department, to explain the principle of the ergo- 
 graph. Have a number of students make records at the beginning 
 of the day and again at the close ; or get records of gymnasium per- 
 formance, as "chinning," made at intervals involving work and rest. 
 
58 MANUAL FOR TEACHERS 
 
 Compare experiences with fatigue and endurance. 
 
 Have students make special reports on the introduction of 
 " scientific management," or " standard motions," in local indus- 
 trial or commercial establishments, or on readings upon the sub- 
 ject. Have special reports on the findings of the Health of 
 Munitions Workers Commission. 
 
 Collect data on hours, variations in work, pauses, and overtime 
 in local establishments. What are the local or general regulations 
 in these matters ? To what occupations do they apply ? What 
 occupations are explicitly exempted ? Why this discrimination ? 
 
 Get information on the distribution of accidents in industries 
 during the day ; during the week ; during the year. Have students 
 plot graphs and analyze on physiological grounds. 
 
 Compare also records of school tests made with a view to 
 measuring the influence of accumulating fatigue upon attention etc. 
 
 Show how exercise of the large muscles helps to rest the 
 sedentary worker by accelerating the blood flow and facilitating 
 perspiration. 
 
 References. CANNON, Bodily Changes in Pain etc., chaps, vi-viii; 
 GOLDMARK, Fatigue and Efficiency ; HOUGH and' SEDGWICK, Human 
 Mechanism, chap, v, pp. 314320; LEE, Health and Disease, chap. v. 
 Bulletins and current reprints of the United States Public Health Service ; 
 Bulletins of the United States Bureau of Labor Statistics. 
 
 XLII. NERVES AND THE REACTIONS OF ORGANISMS 
 
 Demonstrate some of the common reflexes by the students 
 themselves. The knee-jerk is interesting and amusing when intro- 
 duced for the first time, and it gives food for thought. Feed live 
 worms to frogs in the laboratory, or use a dangling bit of red 
 worsted. Have students report experiences in fishing, or with 
 wild birds, or with domestic animals. Refer to the coughing reflex, 
 and to sneezing and vomiting. Have students report their own 
 observations and examples. The gland reflex that is most familiar 
 is that of the mouth watering, but the cold sweat is perhaps not 
 altogether strange (although this is not the same kind of reflex as 
 the others mentioned). 
 
MANUAL FOR TEACHERS 59 
 
 Have prepared microscopic slides showing nerve structure. It 
 is hardly worth while to study the muscle under the microscope. 
 
 Under chloroform dissect out the long muscles of a frog's leg, with 
 the associated nerve ; stimulate with the electric current from two 
 battery cells. Show contraction in response to the stimulation of the 
 nerve and in response to the direct stimulation of the muscle itself. 
 
 The dependence of the muscle upon the nerve connections may 
 be suggested, though not strictly demonstrated, by bending the 
 middle finger forward until the tip is opposite the palm of the 
 hand, as in Fig. 10. The nerve fibers connected with the muscles 
 controlling the end segment are com- 
 pressed and apparently inactive. The end 
 joint may be moved about (by the other 
 hand) and seems lifeless. 
 
 Use a pithed frog or one in which the 
 cord is severed back of the medulla, to 
 demonstrate the persistence of useful re- 
 flexes independently of the higher centers. 
 Refer also to the chicken that runs around 
 after the head is cut off. Have students 
 suggest other examples. 
 
 Recall the increase in pulse rate on FlG 
 
 taking exercise, as an example of a reflex 
 
 that does not shunt any impulses into the brain cortex. The 
 increased heart work is due to a series of reflexes involving 
 chemical stimulation (the partial pressure of carbon dioxid in 
 the blood) and muscular reactions, but no conscious sensation 
 and no voluntary influence upon the heart muscles or upon the 
 breathing mechanism. 
 
 Point out the fallacy of assuming that the reflexes, or the natural 
 behavior, of organisms are necessarily adaptive. The feeding 
 of nearly all animals depends upon reflexes, and the escape from 
 enemies also involves reflexes. If the reflexes were perfect, the 
 frog would catch every fly he tries to catch, and the fly would 
 escape from every frog that tried to catch him ; the victim (food) 
 would be assured to the feeder, and the safety of the prey would 
 
60 MANUAL FOR TEACHERS 
 
 be equally assured, and the feeder would starve. Have pupils find 
 illustrations of the principle that some reflexes are indifferent, that 
 some are even injurious, and that none are perfect as adaptations. 
 
 References. For the pupils: HOLMES, Animal Biology, chap, xxiii; 
 HOUGH and SEDGWICK, Human Mechanism, chaps, vii, xv. For the 
 teacher: DONALDSON, Growth of the Brain; LOEB, Comparative Physiology 
 of the Brain ; STILES, Human Physiology, chaps, vii, vi, viii, ix ; STILES, 
 The Nervous System. 
 
 XLIII. TROPISMS AND THE BEGINNINGS OF SENSE 
 
 The idea of a general reaction is not so strange as it may at first 
 appear. Recall that the child winks not only when something 
 approaches the eye, but also when he hears a sudden, loud sound, 
 or when he is startled. The flight of the bird may be initiated by 
 many different stimuli; a worm contracts in response to many 
 different stimuli ; the ameba shrinks into a spherical mass in 
 response to many different stimuli ; and so on. Compare seeing 
 stars when the head is struck. The students will no doubt brin^ 
 further examples, once they get the idea. 
 
 Experiments on the senses are always interesting and may be 
 devised in endless variety. Have the students work in pairs. 
 
 To get differences between various parts of the skin in respect 
 to discrimination in touch, use compasses with the points close 
 together and gradually opened apart, noting the smallest separation 
 that can be distinguished as two points in the different parts of 
 the skin tried, as the back of the hand, the neck, tips of fingers, 
 tip of tongue, wrists, face, etc. 
 
 For the hot and cold points, try series of points on the palm 
 of the hand, guiding by the folds. Use bits of wire or nails 
 about two inches long. Place nails in hot water (about 80 degrees 
 C.) and some in cold water (about 5 degrees to 10 degrees C.). 
 Change as soon as the temperature of the nail approaches that 
 of the skin closely. Have the students try the hot and cold points 
 on the cheeks. 
 
 For experiments with taste, use dilute solutions of salt, sugar, 
 acetic acid (vinegar), and very dilute solutions of quinine or aloes. 
 
MANUAL FOR TEACHERS 6 1 
 
 With a glass rod drawn to a very fine, rounded point (and rinsed 
 clean after each use), have the students find and chart the 
 distribution of the various papillae on the tongue. 
 
 For showing the relation of odors to flavor, have various sub- 
 stances (foods, spices, condiments) placed in the mouth of a 
 blindfolded student, holding his nose to prevent the inhalation of 
 vapors from the air or from the pharynx. Record the discrimi- 
 nations made, either by naming the substances recognized or by 
 describing them. 
 
 Call attention to the danger of interpreting movements of 
 organisms in terms of likes and dislikes in the absence of real 
 knowledge about the emotions involved. Earlier natural philosophy 
 of all peoples appears to take this form, and it is indeed difficult 
 to think of energies except as attractions and repulsions ; but we 
 may learn to use these terms without implying what usually goes 
 with them when applied to human conduct. 
 
 References. For the pupils: CLODD, The Childhood of the World, 
 Part II ; HOLMES, Studies in Animal Behavior, chaps, i-v ; HOUGH and 
 SEDGWICK, Human Mechanism, pp. 263-265. For the teacher: HOLMES, 
 -Evolution of Animal Intelligence, chaps, iii, iv ; LOEB, Forced Movements ; 
 LOEB, The Organism as a Whole, chap, x ; MORGAN, Evolution and Adap- 
 tation, chap, xi ; WATSON, Behavior, chaps, i-iii. 
 
 XLIV. EYES AND LIGHT 
 
 It is not difficult to keep Euglena in the aquarium, and in suffi- 
 cient quantities to show the collection of the organisms on the 
 illuminated side and the reversal of the tropism on exposure to 
 direct sunlight. The idea of reaction depending on physiological 
 state should offer no serious difficulties. Compare the effect of 
 seeing tempting food before a meal and after a meal. The mouth 
 does not water so readily when one is replete. So, a tired boy is 
 not aroused by temptations that would ordinarily lead him to great 
 exertions ; when one is ill, he wants none of the amusements that 
 ordinarily appeal to him ; and so on. The students can furnish 
 abundant illustrations from their own experience. The point to 
 keep clear is that the protoplasm can be modified in its conduct 
 
62 MANUAL FOR TEACHERS 
 
 by the presence or absence of various substances, by temperature, 
 by light, and by other incident forces. 
 
 Hydra and frogs are also valuable for showing the light 
 tropisms and the influence of intensity. Earthworm habits are 
 known to many boys. Assign for special report the behavior of 
 earthworms under varying intensity of illumination; and the 
 behavior of various water animals, including fishes. 
 
 Compound eyes of insects or other arthropods should be 
 examined ; have also microscopic preparations of eye surface 
 and eye section. 
 
 A good model of the human eye is almost essential for a satis- 
 factory study of this topic, but good charts may be acceptable 
 substitutes. A box camera that is readily taken apart will be of 
 help ; get one that has a focusing screen of ground glass. Have 
 the students study the pupil reflex with changing illumination, 
 working in pairs. Rarely a person is found who can control the 
 movement of the iris. It is probable that in most cases the control 
 is indirect, the subject produces the movements by changing the 
 focus while appearing to be staring fixedly, or he does so by 
 imagining sudden changes from extreme light to extreme dark; 
 or the reverse. This is in a way similar to making the mouth 
 water by thinking of good things to eat. 
 
 The students should finish this study with the conviction that 
 many of the movements of organisms are quite as mechanical as 
 those of a machine ; and they should be as ready to give up 
 attributing to emotions the movements of animals as they would be 
 to deny emotion to a phonograph reproducing sentimental ballads. 
 In the case of the animals, as in that of the phonograph, the 
 phenomena, including the emotions, are produced because the 
 thing is built thus and so. 
 
 References. For the pupils : HOUGH and SEDGWICK, Human Mechanism, 
 pp. 244-258. For the teacher: HOLMES, Evolution of Animal Intelligence, 
 chap, vii; STILES, Human Physiology, chap, xi ; WATSON, Behavior, chap. xi. 
 For reversal of tropisms : LOEB, Forced Movements, chaps, v-xi, xii, xix. 
 
MANUAL FOR TEACHERS 63 
 
 XLV. HYGIENE OF THE EYES 
 
 Where students' eyes are not regularly examined, arrange for 
 examination with Snellen's test cards and with astigmatism charts. 
 
 Make clear the fact that glare depends not upon the intensity 
 of the high lights but upon the contrasts. Have students collect 
 information about light conditions in local establishments, with 
 reference to abundance and distribution of illumination, presence of 
 flicker, glare, etc. Have students collect information about special 
 dangers to eyes in local establishments, and about methods of guard- 
 ing the eyes. Make a study of goggles used for special purposes. 
 
 What are the local and state regulations concerning conditions 
 inimical to people's eyes ? Are there any local regulations requiring 
 the administration of silver nitrate to the eyes of the newborn ? 
 Give statistical data as to the prevalence, increase, or decrease of 
 blindness ; preventive and remedial measures. 
 
 Demonstrate the administration of eye-drops and the use of the 
 eye-cup. Show how a foreign body is to be removed. 
 
 Demonstrate the proper and improper placing of reading, writ- 
 ing, and other work in relation to illumination. Point out the 
 objection to illumination of work by direct sunshine. 
 
 References. For the pupils: HOUGH and SEDGWICK, Human Mecha- 
 nism, pp. 395-401 ; LEE, Health and Disease, chap. vii. For the teacher: 
 PYLE, Personal Hygiene, pp. 169-274. 
 
 XLVI. SOUND SENSATIONS 
 
 Have some students report on the methods used by physicists 
 for determining the vibration rates for light and sound waves. 
 Come to a common-sense conclusion as to the old paradox about 
 there being no sound if there were no ears. 
 
 Some experiments may be made on pitch discrimination ; and 
 you may find one or two students who can recognize absolute 
 pitch. 
 
 Museum and demonstration specimens for various types of 
 sound-perceiving organs. Note the lateral line in fishes, the 
 eardrum in the cricket and locust, and so on. 
 
64 MANUAL FOR TEACHERS 
 
 Good models are essential for the study of ear structure, but 
 good charts are helpful. It is not worth while, however, with most 
 classes, to give much time to the detailed study of structure. 
 
 References. For the pupils : HOUGH and SEDGWICK, Human Mechanism, 
 pp. 258-262, 401-402 ; STILES, Human Physiology, pp. 143-148. For the 
 teacher : WATSON, Behavior, chaps, xii, xiii. 
 
 XLVII. RESPONSES TO GRAVITY 
 
 Have students report on insects and other animals in which 
 they may have had an opportunity to observe evidence of response 
 to gravity, including balancing and righting movements. 
 
 Demonstrate the idea of the statolith with a covered stender 
 dish containing a cork. Show with blindfolded students that we 
 are aware of our posture without seeing our environment. 
 
 With the frog it is easy to demonstrate compensatory move- 
 ments. Place the live frog in a glass jar. Tilt the jar so as to 
 bring the animal's snout down, and reverse. Tilt laterally. Turn 
 on vertical axis. If the movements are properly timed, the 
 responses of the animal are immediate and striking. It is possible 
 to show that these movements are due to semicircular canal 
 reflexes by eliminating the function of the eyes, either by covering 
 them with an opaque mixture of cotton, vaseline, and lampblack, 
 or by cutting the optic nerves, or by surrounding the jar with 
 a large piece of paper or cloth that offers no point for fixation. 
 On the other hand, it may be shown that many of these responses 
 arise from eye reflexes, by destroying the semicircular canals or 
 by cutting the nerves leading from them. In that case, however, 
 there remain disturbances in locomotion, showing that the animal 
 depends upon the semicircular canals for its orientation in space. 
 
 Have students make comparative tests of sensitiveness of hearing 
 by determining the distances at which each may distinguish the tick- 
 ing of a watch. The same watch will of course be used in all the tests. 
 
 References. For the pupils : HOUGH and SEDGWICK, Human Mecha- 
 nism, pp. 262-263. For the teacher : WATSON, Behavior, chap. xiv. There 
 will be numerous reports and monographs on the testing of candidates for 
 aerial service, giving results of investigations conducted during the war. 
 
MANUAL FOR TEACHERS 65 
 
 XLVIII. INSTINCTS 
 
 Have students note examples of instincts in animals and in 
 young children of their acquaintance, and then attempt to analyze 
 these instincts, so far as possible, in terms of reflex chains. 
 
 Note that instincts, like reflexes, cannot be perfect in the 
 adaptive sense. 
 
 Have students make note of variations in the manifestations of 
 instincts brought about by changes in the physiological state or 
 by the concurrence of two or more stimuli leading to more 
 or less conflict between responses. 
 
 Have students report experiences with animals, or from their 
 own past, in which instincts were modified, either through the 
 elimination of elements or through the formation of associations. 
 All sorts of learning and unlearning, breaking and training, in 
 animals and in very young children would furnish illustrations. 
 
 References. For the pupils: DARWIN, Expression of the Emotions; 
 DARWIN, Vegetable Mold and Earthworms ; FABRE, The Wonders of 
 Instinct ; HOLMES, Studies in Animal Behavior, chaps, vi, xi. For the 
 teacher: HOLMES, Evolution of Animal Intelligence, chaps, v, vi ; LOEB, 
 Forced Movements, chap, xviii ; LOEB, Comparative Physiology of the 
 Brain ; LOEB, The Organism as a Whole ; WATSON, Behavior, chaps, iv-v. 
 
 XLIX. HABIT 
 
 The study of habit should culminate in effective resolution. It 
 is well to have clearly in mind the mechanism of habit formation, 
 the association factor and the short-circuiting of impulses out 
 of the cortex into the spinal cord ; but the important thing 
 eventually is the habit of habit-control. 
 
 Have students give striking examples of habit responses (often 
 humorous) and of good and bad habits. Reports on experience 
 in training lower animals ; on forming and breaking habits purpose- 
 fully, from observations as well as from personal experience, 
 from fiction and drama, and from history and biography or other 
 casual reading. 
 
 Get examples of inhibitions from students' experience and 
 observation. 
 
66 MANUAL FOR TEACHERS 
 
 Study the relation of practice to habit formation and the measure- 
 ment of practice effects, for example, the number of repetitions 
 or the time required for mastering a movement (in athletics, in 
 workmanship, in musical performance, etc.) ; the memorizing of 
 poetry or lines in a play ; the mastery of mathematical processes, 
 penmanship, drawing, and so on. Examples of arbitrary associa- 
 tions or habits are found in learning the telegraph instrument and 
 codes, in stenography, in typewriting, in cipher codes, and so on. 
 
 Have students note examples of routineers among young persons, 
 and of older people who are not routineers. Give examples of 
 routine that could be replaced by other equally serviceable routine 
 for the sake of gratuitous practice in changing habits, as shifting 
 keys or money to another pocket, rearranging furniture at home, 
 changing route to school, and so on. 
 
 Consider the utility and the dangers of habits. 
 
 References. JAMES, Psychology (Briefer Course), chap, x; HOLMES, 
 Studies in Animal Behavior, chaps, vii-ix ; HOUGH and SEDGWICK, 
 Human Mechanism, chap, xviii ; STILES, Human Physiology, chap. xii. 
 For the teacher: HOLMES, Evolution of Animal Intelligence, chap, vii ; 
 LOEB, Forced Movements, chap, xix ; WATSON, Behavior, chaps, vi-ix. 
 
 L. CHEMICAL INJURY TO THE NERVOUS SYSTEM 
 
 Have students report on the present status of regulatory laws 
 pertaining to the manufacture, sale, advertising, and labeling of 
 preparations containing alcohol and other habit-forming substances. 
 A comparison of labels from patent medicines, headache cures, etc. is 
 instructive. Have individual reports on special reading assignments. 
 
 The subject of this chapter should not be dismissed without 
 attention being called to the advantages that the race has derived 
 from an understanding of the physiological effects of various 
 alkaloids and synthetic compounds. A report on the contributions 
 of anesthetics and alkaloids to surgery etc. is quite as important as 
 one on the dangers of these substances. 
 
 References. HOUGH and SEDGWICK, Human Mechanism, pp. 376-377 ; 
 LEE, Health and Disease, pp. 128-132. In encyclopedias, articles on 
 anesthetics. 
 
MANUAL FOR TEACHERS 6? 
 
 II. UNITY OF LIFE 
 
 This study should consist of a synthesis of all significant physio- 
 logical ideas. Have students make lists of all the processes or 
 activities that are common to several different organisms specified, 
 the organisms selected representing diverse types and including 
 plants as well as animals. 
 
 For each process or activity, have students describe the behavior 
 of the organism as a whole, and also the behavior of single cells of 
 the organism. 
 
 For each process or activity, have students compare the types of 
 organisms selected ; that is, point out similarities and differences. 
 
 For the organism as a whole, show the interdependence and 
 coordination of processes; no part has meaning except in its 
 relations to all the others. 
 
 References. For the teacher: CANNON, Bodily Changes, chap, xiv; 
 CRILE, Man an Adaptive Mechanism; LOEB, The Organism as a Whole, 
 chaps, i, xii ; MORGAN, Evolution and Adaptation, chaps, i, iii, x. 
 
PART III. THE CONTINUITY OF LIFE 
 LII. GROWTH AND REGENERATION 
 
 The idea of the varying ratio of surface and volume can be 
 made clear to many students by means of suitable diagrams ; but 
 there are very many who find it extremely difficult, or even im- 
 possible, to think in three dimensions from data supplied by figures 
 in one plane ; that is, figures of two dimensions. These can be 
 helped by the use of modeling clay. The clay is first cut into 
 cubes of the same size, say one inch or one centimeter. The 
 cubes are stacked up into a larger mass, and the superficial area 
 determined. The mass is successively broken down, with the 
 resulting increase in exposed surface made obvious. One-inch 
 cubes of wood may be used. 
 
 While the idea of the mathematical limits to the growth of a cell 
 should be clear, it should not be emphasized to the point of excluding 
 the idea of other factors operating in the limitation of growth. Current 
 studies on the relations of internal secretions to the regulation of 
 growth and form are constantly throwing new light on the subject. 
 
 Have regenerated leaves, starfish and Crustacea with regener- 
 ated limbs, specimens of knit chicken bones, etc. on hand for 
 demonstration. In some of the larger cities it is possible to obtain 
 from research laboratories or from museums specimens illustrating 
 regeneration in vertebrates, mollusks, and other forms. 
 
 Have students look out for examples of pollarded and grafted 
 trees, and for newspaper accounts of skin and bone grafting, or trans- 
 plantations of organs. Have specimens of grafts for demonstration. 
 
 References. For the pupils : BERGEN and CALDWELL, Practical Botany, 
 pp. 82-89 ; BERGEN and DAVIS, Principles of Botany, pp. 64-70; COULTER, 
 BARNES, and COWLES, Textbook of Botany, pp. 417-426; DUGGAR, Plant 
 Physiology, chap. xiii. For the teacher: DAVENPORT, Principles of Breed- 
 ing, pp. 316-338 ; LOEB, The Organism as a Whole, chap, vii ; MORGAN, 
 Experimental Zoology, chaps, xv-xxii. 
 
 68 
 
MANUAL FOR TEACHERS 69 
 
 LIII. DEVELOPMENT 
 
 In the spring it is possible to have live frogs' eggs in dishes, 
 and to watch their development under the microscope and 
 magnifying glasses. 
 
 A series of models showing the development of Amphioxus 
 (fifteen to twenty stages) is helpful. In the absence of models, 
 charts may be used. 
 
 Have preparations and models showing the development of 
 different types of insects, a fish, a frog, a bird (chick), and a 
 mammal (sheep or rabbit). Eggs and cocoons of various local 
 insects, also mealworms and other insect larvae, should be examined 
 alive. If possible, the emergence of the animals from the resting 
 stage (egg or pupa) should be observed in the classroom by the 
 students. In some localities it should be possible to visit incubators 
 or henneries, to see the chicks come out of the shell. Along the 
 shore, shedder crabs and the molting of many animals may be 
 observed. Caterpillars in the process of pupation may be studied 
 in the laboratory. From spring to late summer (from April to 
 September for most parts of the country) it is possible to get 
 complete life histories of mosquitoes by exposing tumblers of 
 water on warm evenings ; the female mosquitoes will deposit their 
 eggs, and the development may then be watched in the laboratory, 
 under a reading glass. Cover the tumblers with cheesecloth, to 
 prevent the escape of the adults. 
 
 Under favorable conditions the development of the frog and the 
 early stages of fishes can be followed in the laboratory. If possible, 
 excursions to fisheries and to field should be made for the study 
 of the stages in animal development. 
 
 If goldfish are kept in the laboratory or stock-room, one can 
 manage to get fresh segmentation stages late in the winter and in 
 the early spring. The animals are fed up in the winter; at the 
 beginning of the breeding season the fish are isolated in large 
 battery jars, and then " stripped " into shallow glass vessels. 
 
 Incubators for bacteriological work with thermostats can be 
 used for the incubation of hens' eggs (104 F.). You must make 
 
70 MANUAL FOR TEACHERS 
 
 sure that the eggs are fertilized ; it is best to purchase from poultry 
 specialists, and to examine them by holding up to light after three 
 or four days. 
 
 References. Special reports on life histories of various insects and 
 batrachians; MITCHELL, CHALMERS, The Childhood of Animals, chap. ii. 
 For the teacher : CONKLIN, Heredity and Environment in the Develop- 
 ment of Man, chap, i, pp. 179-187 ; DAVENPORT, Principles of Breeding, 
 chap, vii, pp. 336-344 ; KELLICOTT, General Embryology, chaps, i, ii. 
 
 LIV. CONDITIONS FOR DEVELOPMENT 
 
 It is very difficult for most people to separate in their minds 
 the facts of growth from the facts of development. Call attention 
 to diversities in size among the members of the class ; then have 
 the students decide whether size is always and everywhere directly 
 correlated with maturity ; that is,' whether growth (in size) has 
 always been identical with or even parallel with development. 
 Nevertheless, conditions that are unfavorable to growth are likely 
 to be unfavorable to development ; ordinarily growth furnishes the 
 material basis for development. 
 
 For a comparison of different conditions, concentrations, etc., 
 in relation to growth of yeast, use fermentation tubes (Fig. n). 
 
 Instances of malnutrition reacting upon development are to be 
 found in nearly every community. Malformations and monstrosi- 
 ties of various kinds are referred to in books and in current litera- 
 ture. Consider the effects of early neglect, of foot-binding, etc. 
 
 References. For the teacher : AYRES, Laggards in our Schools, chap, xi ; 
 DAVENPORT, Principles of Breeding, chap, ix ; MANGOLD, Problems of 
 Child Welfare, Part I, chap, iii and Part II, chap, i ; MORGAN, Experimental 
 Zoology, chaps, ii-iii. Publications of the United States Children's Bureau. 
 
 LV. NEW ORGANISMS 
 
 Show yeast cells under the microscope for the buds. Fresh 
 material (in dilute molasses) is necessary. To show the spore 
 formation, use preparations from an older culture ; that is, one 
 from which the food has been exhausted, 
 
MANUAL FOR TEACHERS 
 
 Have students make experiments on the distribution of mold 
 and yeast spores. Thin slices of bread exposed under various 
 conditions or in different localities (or directly inoculated with dust) 
 and placed in moist chambers will serve 
 as media for the molds. For moist chamber 
 a tumbler inverted over a few thicknesses 
 of wet filter-paper or blotter will do. For 
 the yeasts, fruit juices or sirup diluted 
 (a teaspoonful to the pint), or weak cider, 
 exposed in test tubes, which are then 
 closed with plugs of cotton. 
 
 Study spores of molds under the micro- 
 scope. Mildews, rusts, mosses, ferns, and 
 other plants should be drawn upon for 
 specimens of spores. Many kinds of spores, 
 including pollen grains, can be made to 
 germinate by placing them in a drop of 
 dilute sugar solution on a microscopic 
 slide in a moist chamber. Germinate fern 
 and moss spores on moist earth under 
 glass. Sporangia should also be seen. 
 
 References. Special reports on spore for- 
 mation etc. in various plants. HOLMES, Animal 
 Biology, chap, xxvii; OSTERHOUT, Experi- 
 ments with Plants, chap. ix. For the teacher : 
 COULTER, BARNES, and COWLES, Textbook of 
 Botany, pp. 805-816; PARKER and HASWELL, 
 Zoology. 
 
 FIG. n. Fermentation 
 Tube 
 
 Fill the tube completely with 
 the nutritive fluid. Insert the 
 yeast or culture into the low- 
 est part of the bend, using a 
 pipette. Close the mouth with 
 cotton. The accumulation of 
 gas in the highest part of the 
 tube is both an indication and a 
 measure of fermentation. The 
 bulb should be only partially 
 filled, to leave space for the 
 liquid displaced from the tube 
 
 LVI. SEX 
 
 Favorable paramecium cultures show 
 
 conjugation almost constantly ; and if it is at all possible to manage 
 it, the students should see the process under the microscope. 
 
 Conjugating spirogyra can be found late in the summer and in 
 the fall, by collecting very early in the morning. Strings of ladders 
 and zygotes can be preserved in formalin (2 per cent to 3 per cent) 
 or mounted in glycerin for microscopic demonstrations. 
 
72 MANUAL FOR TEACHERS 
 
 Most of the colleges and experiment stations keep cultures 
 of molds that will enable you to obtain zygote formation in the 
 laboratory. 
 
 Gametes of rockweed and other algae are best studied from 
 charts, except at the seacoast, where fresh material is available 
 early in the spring. 
 
 References. For the teacher: COULTER, Evolution of Sex in Plants; 
 COULTER, BARNES, and COWLES, Textbook of Botany, pp. 816-824, 878- 
 904; GALLOWAY, Biology of Sex; GEDDES and THOMSON, Sex; MORGAN, 
 Heredity and Sex, chap. i. 
 
 LVII. FLOWERS 
 
 Where it is possible to have tulips for the first flower, they will 
 be found very useful. Two students can easily work on one flower 
 without mutilating it, and only a few need to be dissected for a 
 whole class. They will keep so that successive classes may use 
 the same material. In many cases it would be no more expensive 
 to have tulips than some other flowers. Whatever flower is taken 
 first should be regular, symmetrical, and perfect. Later other forms 
 may be profitably studied. Flower models are helpful in class dis- 
 cussions, demonstrations, and recitations, as well as for compari- 
 sons of types that blossom at different seasons of the year. There 
 should also be available an abundance of charts. 
 
 For pollen-tube demonstration, put pollen of various flowers in 
 drops of dilute sugar solution on microscope slides ; keep in moist 
 chamber overnight ; examine with microscope under cover glass. 
 
 Slices of larger ovaries may be mounted on glass slides and 
 examined with magnifying glasses ; if they are to be kept for 
 some time, place in glycerin. 
 
 Fertilization in flowers can best be explained with the help of a 
 blackboard diagram that is built up and changed with the progress 
 of the description. 
 
 References. ANDREWS, Practical Course, pp. 196-223 ; BERGEN and 
 CALDWELL, Practical Botany, pp. 20-23 ; BERGEN and DAVIS, Principles 
 of Botany, chap, xiii, pp. 138-145; COULTER, Plant Life and Plant Uses, 
 pp. 258-301 ; OSTERHOUT, Experiments, chap. vi. For the teacher: 
 COULTER, BARNES, and COWLES, Textbook, pp. 825-834. 
 
MANUAL FOR TEACHERS 73 
 
 LVIII. POLLENATION - LIX. ADAPTATIONS OF FLOWERS 
 
 Flowers may be brought to the laboratory for examination as 
 to the mechanism of pollen discharge. Get flowers of grasses, 
 willows, oaks, poplars, maples, etc., as well as those with conspicu- 
 ous corollas. The structure of the bumblebees, honeybees, and 
 other pollenating insects should be studied in this connection. 
 
 Field trips for the study of insect visits to flowers are most 
 interesting and valuable. Have the students find the pollen car- 
 riers for some of the common wild and cultivated plants. What 
 insects visit more than one kind of flower? What flowers are 
 visited by more than one kind of insect ? Are the visits of mutual 
 advantage in all cases ? 
 
 Have students find out what evidence there is that the wind 
 brings pollen over a considerable distance. In regions cultivat- 
 ing pedigreed grains and corn, farmers often have to construct 
 windbreaks to prevent foreign pollen from crossing with their special 
 varieties. Hybrid willows and other species of wind-pollenated 
 trees are evidence of such crossing. 
 
 Study two or three species of zygomorphic flowers that are 
 dependent upon insects, and one or two that are self-pollenating. 
 Visit gardens and greenhouses. 
 
 Assign special readings and reports on extrafloral nectaries, on 
 specific insect-flower relations, on economic aspects of the relation, 
 and on cleistogamous flowers. 
 
 References. ANDREWS, Practical Course, pp. 235-249; BERGEN and 
 DAVIS, Principles, chap, xxxii; COULTER, Plant Life, pp. 301-324; DARWIN, 
 Forms of Flowers. For the teacher: COULTER, BARNES, and COWLES, Text- 
 book, pp. 834-878 ; MORGAN, Evolution and Adaptation, chap. i. 
 
 LX. FRUIT AND SEED DISTRIBUTION 
 
 Dried fruits of many different species are easily kept in boxes 
 and may be used over and over again, although the collection 
 should be constantly supplemented and enlarged by new additions. 
 Present materials in ecological relations ; that is, in accordance 
 with the agency of distribution or the type of seed protection. 
 
74 MANUAL FOR TEACHERS 
 
 Field studies along roadsides, vacant lots, and the woods will fur- 
 nish abundant illustrative material and opportunity for collecting. 
 
 References. ANDREWS, Practical Course, chap, viii ; BERGEN and DAVIS, 
 Principles, chaps, xvi, xxxiii ; COULTER, Plant Life, chap, viii ; OSTERHOUT, 
 Experiments, chap, vii ; Farmers' Bulletins. For the teacher : COULTER, 
 BARNES, and COWLES, pp. 904-929. 
 
 LXI. ALTERNATION OF GENERATIONS 
 
 Use fresh or dried moss plants (the pigeon-wheat moss, Poly- 
 trichum, is good and found almost everywhere) showing both 
 gametophytes and sporophytes. Students should see archegonia 
 and antheridia through the microscope, but good blackboard draw- 
 ings or charts are necessary for satisfactory study. 
 
 Fern prothalli can be grown by sprinkling the spores on moist 
 earth placed in dishes, covered with glass and kept at room tem- 
 perature. Show archegonia and antheridia through microscope. 
 
 Hydromedusae are best studied in small vials with the magnify- 
 ing glasses. Thus preserved, the specimens will keep indefinitely. 
 
 References. BERGEN and DAVIS, Principles, chaps, xxiv-xxix ; COULTER, 
 Plant Life, pp. 401-403. For the teacher: COULTER, Evolution of Sex in 
 Plants ; COULTER, BARNES, and COWLES, pp. 92, 264-268, 805-824. 
 
 LXII. REPRODUCTION IN ANIMALS 
 
 This subject does not lend itself readily to laboratory or field 
 study by young people ; nor is it always feasible to discuss it in 
 class, especially in mixed schools. 
 
 Where it is not feasible to keep live fish (see p. 69), it may 
 be possible to arrange for visits to an aquarium or to a fish station, 
 where the students may see roe and milt, and where they may see 
 a demonstration of " stripping " and artificial fertilization. 
 
 There is a great deal of interesting reading on the breeding 
 habits of common animals, to which students should be referred, 
 even if there is no class discussion of results. 
 
 References. Special reports on habits of birds, fishes, and other 
 animal groups. 
 
MANUAL FOR TEACHERS 75 
 
 LXIII. INFANCY AND PARENTAL CARE 
 
 This is a review study of the whole subject of reproduction, with 
 emphasis upon the relation between parent and offspring, and of 
 the two to the species. This may be correlated with historical and 
 ethnological studies, as well as with social science and community 
 civics. Have students prepare diagrams showing the increasing 
 dependence of spores, gametes, and zygotes upon the parent, in 
 series of plants or of animals. Charts giving a general view of 
 the plant and animal systems are helpful in this connection, even 
 if no attempt has as yet been made to study classification. See 
 Chapters LXXXVI and LXXXVII of the text. 
 
 Guard against the interpretation of phenomena in terms of 
 " purpose." 
 
 References. MITCHELL, The Childhood of Animals, especially chaps, i, 
 Hi, iv; PYCRAFT, The Infancy of Animals; BURBANK, Training of the 
 Human Plant ; FISKE, The Prolongation of Youth. 
 
PART IV. ORGANISMS IN THEIR EXTERNAL 
 RELATIONS 
 
 LXIV. OBSTACLES TO LIFE 
 
 Earlier experiments have already demonstrated the influence of 
 external forces upon growth and upon development. This chapter 
 is in the nature of a summary with a view to a new departure. 
 
 Have students make (in the form of a table) a list of ten 
 familiar plants and ten familiar animals, with a note on the char- 
 acteristic appearance or behavior (a) at high temperatures (sum- 
 mer) and (b) at low temperatures (winter). 
 
 Have students state experiences with frostbite, frozen ear, etc., 
 ,with frozen snakes or fish, and so on. Why is freezing of proto- 
 plasm reversible, whereas the effect of heat is irreversible ? What 
 are the dangers of natural ice? What is the object of cooling 
 milk immediately after taking it from the cow ? What is the 
 object of keeping milk and other food at low temperatures? What 
 is the use of pasteurizing milk, and how is it accomplished? 
 What is the objection to boiling milk ? 
 
 In discussing the effect of water shortage or excess, point out 
 that some of the characteristic summer and winter conditions of 
 plants and animals are due to the water relation. What practical 
 use is made of the fact that protoplasm cannot be active without 
 water ? What practical methods are employed for excluding water 
 from materials that might otherwise be destroyed by bacteria, 
 molds, or yeast ? 
 
 If the influence of light upon growth has not been demonstrated 
 earlier, it should now be shown with bacteria cultures in petri 
 dishes. Cover a portion of each dish with black paper ; or cover 
 the whole dish and cut distinctive holes or letters in the paper, to 
 admit light. After exposing the sterilized medium to infection, the 
 covers are put on and the dishes are exposed to strong sunlight 
 
 76 
 
MANUAL FOR TEACHERS 77 
 
 at room temperature or warmer; later they are examined for 
 bacterial growth, showing different behavior in light and darkness. 
 
 What practical use can be made of the fact that light is injurious 
 to protoplasm (as in bacteria) ? Refer to the use of ultraviolet 
 rays for the sterilization of water supplies and other food materials. 
 Have students make special reports. 
 
 What practical use is made of the fact that many salts (chemi- 
 cals) are injurious to living things ? Refer to the use of salt or 
 ashes on the ground for killing weeds. In the use of salt (and 
 sugar) for preserving food, part of the effect is no doubt due to 
 the drying. Compare the drought characteristics of many swamp 
 plants, such as the mangrove. 
 
 References. For the pupils : COULTER, BARNES, and COWLES, Textbook 
 of Botany, pp. 565-589, 704-718; DARWIN, Origin of Species, chap, iii; 
 JORDAN and KELLOGG, Evolution and Animal Life, chap. iii. For the 
 teacher: MORGAN, Experimental Zoology, chap. ii. 
 
 LXV. THE CONFLICT OF LIFE WITH LIFE 
 
 Most of the ideas in this chapter deal with abstractions that 
 cannot be illustrated or demonstrated directly, as predation, 
 parasitism, competition, or struggle. But these ideas can be easily 
 formed from familiar examples. 
 
 Have specimens of tapeworm and microscopic preparations and 
 pictures of roundworm, hookworm, and other parasites. 
 
 Students can suggest many examples of predatory and parasitic re- 
 lations, and comprehensive lists can be compiled from their reports. 
 
 Selective and nonselective elimination should offer no difficulty ; 
 examples abound on every side, in human affairs as well as in those 
 of the common animals and plants. The important thing is to make 
 clear the metaphorical sense in which the word struggle is used, and 
 to form connotations that avoid the banal element of competition. 
 
 References. BERGEN and CALDWELL, Practical Botany, chap, xxi ; 
 BERGEN and DAVIS, Principles, chap, xxx ; DARWIN, Origin, chap, iv ; 
 EALAND, Insects and Man, chap, vii; HODGE and DAWSON, Civic Biology, 
 chaps, xviii, xx, xxiv; JORDAN and KELLOGG, Evolution and Animal 
 Life, chaps, v, xvii. For the teacher: MORGAN, Evolution and Adaptation, 
 chaps, iv, v ; MORGAN, Experimental Zoology, chap. xiii. 
 
78 MANUAL FOR TEACHERS 
 
 LXVI. PROTECTIVE ARMORS OF ORGANISMS 
 
 It is not worth while to study skin structures of plants and 
 animals in detail. Illustrative specimens should be on hand, and 
 visits to museums, gardens, menageries, aquaria, etc. encouraged. 
 
 The general ideas discussed are simple enough and should not 
 take too much time beyond the reading and summarizing in note- 
 books, with perhaps additional examples. 
 
 References. BERGEN and DAVIS, Principles, chap, xxxi; COULTER, 
 BARNES, and COWLES, Textbook, pp. 741-744. 
 
 LXVII. PROTECTIVE PIGMENTS AND APPEARANCES 
 
 That colors, patterns, etc. may protect is obvious enough. More 
 difficult, and perhaps more important, is the idea that the resem- 
 blances etc. may be quite fortuitous and without practical signifi- 
 cance either in the lives of the organisms or in the evolution of 
 species. Have prepared specimens to illustrate protective colora- 
 tion, warning coloration, and mimicry ; have museum studies and 
 encourage students to bring in specimens found afield. 
 
 What experiences have the students had with sunburn and tan ? 
 Refer to Cunningham's experiment with flatfish. 
 
 What experiences have the students had with the behavior of 
 animals that show dependence upon the coloration etc. ? 
 
 Have cactus and other xerophytic plants to illustrate reduction 
 of surface as an adaptation. Get some students to experiment on 
 whether the drought brings about the reduction of surface, as a 
 modification during development, or whether these plants are 
 incapable of living where there is a relative excess of water. 
 
 References. For the pupils : DAVENPORT, Elements of Zoology, pp. 35-38 ; 
 JORDAN and KELLOGG, Evolution and Animal Life, chap, xix ; KELLOGG, 
 American Insects, chap, xvii; POULTON, The Colors of Animals; WAL- 
 LACE, Natural Selection and Tropical Nature, chap. v. For the teacher: 
 MORGAN, Evolution and Adaptation, pp. 357-360. 
 
MANUAL FOR TEACHERS 79 
 
 LXVIII. PROTECTIVE MOVEMENTS LXIX. PROTECTIVE 
 ACTIVITIES 
 
 Have students handle live animals of various kinds, in the 
 aquarium and in the vivarium at school or wherever they can 
 outside, and report the contracting and flight movements. Many 
 of these movements are already familiar enough, and too much 
 time should not be taken for their consideration in the classroom. 
 " Playing possum " is a widespread reaction ; point out that it 
 is a general reaction that may or may not be useful, and that 
 may or may not be related to the advantage of the species. 
 
 Have specimens of fence lizards and other chameleons, and 
 note color changes in other reptiles, in batrachians, and in fishes. 
 
 Where there is opportunity the students that take an interest 
 in morphology may be encouraged to study homologies and 
 analogies in animal appendages. Individual students might pre- 
 pare mounted series of crustacean or insect appendages and 
 mouth-parts. 
 
 Special reports on bird and fish migrations should include results 
 of field observations as well as of reading. 
 
 Laboratory and field studies of burrowing worms and insect 
 larvae, and of birds' nests. 
 
 Charts and microscopic demonstration of nettling cells. 
 
 Study of leaf-scars to show self-healing surface; microscopic 
 preparation of the scission layer. 
 
 Encourage students to collect insect galls and to find out what 
 insects cause them on common plants. 
 
 Have special reports made on field observations and readings 
 on the homing habits of animals, from the point of view of 
 protection. 
 
 References. COULTER, J. G., Plant Life and Plant Uses, pp. 242-247; 
 COULTER, BARNES, and COWLES, Textbook, pp. 354, 582-588 ; OSTER- 
 HOUT, Experiments, pp. 212-215, 332. For the teacher: MORGAN, Experi- 
 mental Zoology, chap. xvi. 
 
8o 
 
 MANUAL FOR TEACHERS 
 
 LXX. THE FOREST IN RELATION TO MAN 
 
 The forest has for a long time been the favorite hook upon which 
 to hang the sermon of conservation, since it lends itself admirably 
 to the purpose, both for economic reasons and for biological ones. 
 
 FIG. 12 
 
 The slope consists of a wooden frame, supported at an angle of about 45 degrees, 
 inclosing a pane of glass with a trough at the bottom leading to a small drain-hole 
 at the end. The most convenient size is that of the large blotters used on desks or 
 in desk pads. Two beakers, two cylinders, preferably graduated, a florist's spray, and 
 a supply of water complete the equipment. Equal quantities of water are placed in 
 the cylinders or graduates. The water from one of these is drawn into the bulb of 
 the spray and rained first upon the bare glass, representing a deforested mountain 
 side, and then upon the slope covered with two blotters, one representing the forest 
 trees and the other representing the forest floor, or duff. In each case as much 
 water as possible is collected in the beaker and returned to the respective cylinders 
 for comparison. The water can be seen across the schoolroom more easily if it is 
 slightly colored, as with a few drops of red ink. (Apparatus designed for use in the 
 Department of Public Education of the American Museum of Natural History by 
 George H. Sherwood, Curator) 
 
 This subject is perhaps best studied in connection with Arbor 
 Day observance. Special reports on various aspects of the forest 
 in relation to human welfare furnish the best means of arousing 
 interest and impressing the students with the far-reaching contacts 
 
MANUAL FOR TEACHERS 8 1 
 
 between the forest and human affairs. These reports may take 
 the form of statistical reports on such topics as the quantities or 
 values of various forest products ; water supply, navigation, water 
 power ; soil erosion ; harbor maintenance ; Value of improved lum- 
 bering methods; injurious species of insects and fungi, and specific 
 methods of control ; the birds in relation to the forest ; danger of 
 fire and the prevention of fire ; relative values of different kinds of 
 wood ; different rates of growth ; methods of reforesting ; special 
 services of state and federal bureaus ; recent legislation ; etc. 
 
 The effect of clearing upon soil erosion, floods, etc. is often 
 demonstrated by means of the model illustrated in Fig. 12. This 
 demonstration does not, of course, prove that the forest retains 
 water longer than does the nude soil ; it only helps to visualize the 
 relationships between the two kinds of hillside and the run-off. 
 
 References. BERGEN and ' CALDWELL, Practical Botany, chap, xxii ; 
 COULTER, J. G., Plant Life, pp. 195-200; HODGE and DAWSON, Civic 
 Biology, chap, vi ; MOON, The Book of Forestry ; ROGERS, The Tree 
 Book. Yearbooks of the United States Department of Agriculture ; re- 
 ports and bulletins of the United States bureau of Forestry; bulletins 
 and reports of state departments of agriculture ; United States Depart- 
 ment of State, publications on forest reserves and recreation. 
 
 LXXI. BACTERIA AND HEALTH - LXXII. CONTROL AND 
 USE OF BACTERIA 
 
 The subject matter here is largely in the nature of a new 
 synthesis of material that is for the most part already familiar. 
 
 The destruction of bacteria discharged from diseased persons, 
 and the prevention of infections, are the practical problems sug- 
 gested. Various methods, materials, and regulations directed to 
 these ends should be correlated with the data given in the table 
 on page 387. Have specimens of the germicides to be used in 
 various situations ; and perhaps make comparative studies of their 
 effectiveness with petri-dish cultures. An interesting experiment 
 in connection with this study is to obtain cultures from a mouth- 
 rinsing thrown into a petri dish, and then a similar rinsing after 
 the use of a commercial mouth wash. 
 
82 MANUAL FOR TEACHERS 
 
 Special reports on methods and regulations in hospitals and 
 sickrooms are interesting and valuable. 
 
 Typhoid carriers are presented to the public attention from time 
 to time ; local and current references are more interesting than 
 remote cases. 
 
 Special studies may be made of local conditions and current 
 activities in the way of legislation and administrative regulation, 
 with reference to the various items mentioned in the latter part 
 of Chapter LXXI and in section 434 of Chapter LXXII, and with 
 reference to markets, cold-storage plants, etc. 
 
 Analyze city or state health department reports of morbidity 
 and mortality. 
 
 For the economic aspects, reports upon accessible industries men- 
 tioned in the text, or other local activities in which microorganisms play 
 a part, and the collection of commercial products or specimens illus- 
 trating processes, should be encouraged. Have demonstrations of such 
 specimens in class, and, in some cases, of actual processes, as the 
 souring of vinegar and the rotting of flax or of sponges. 
 
 References. BUCHANAN, Household Bacteriology ; CONN, Agricultural 
 Bacteriology ; HODGE and DAWSON, Civic Biology, chaps, xxi-xxiii ; 
 HOLMES, Animal Biology, chap, xxxvi ; JORDAN, Textbook of General 
 Bacteriology, chap, xxxiv ; LIPMAN, Bacteria in Relation to Country Life, 
 chaps, i, xxxvi-xlix ; LOCY, Biology and its Makers, chap. xiii. Bulletins 
 and reports of the local and state departments of health and of the United 
 States Public Health Service. For the teacher: CHAPIN, Sources and 
 Modes of Infection ; JORDAN, Textbook of General Bacteriology, chaps, i, 
 v, xxii, xxxiv. 
 
 LXXIII. INSECTS AS SPREADERS OF DISEASE 
 
 Prepare a number of petri dishes with nutrient agar or gelatin. 
 Have students bring in flies caught in various parts of town and 
 in various situations. Place a fly in each dish, after clipping off 
 the wings, and keep in a warm place for two or three days. Do 
 not omit several control dishes. Have students summarize results 
 in tabular form. 
 
 Have surveys made of various parts of town accessible to the 
 students, to find out the relative prevalence of flies (especially in 
 
MANUAL FOR TEACHERS 83 
 
 relation to food markets) and the distribution of breeding places. 
 Where the flies have not been virtually exterminated through the 
 efforts of the community, it is legitimate to undertake a systematic 
 campaign, in cooperation with official bodies and civic organiza- 
 tions. Where the fly is no longer a pest, this study has only 
 a historical interest ; but the history is so recent that it is worth 
 impressing as an example of man's control of his environment. 
 
 References. CHAPIN, Sources and Modes of Infection, pp. 417-447; 
 EALAND, Insects and Man, pp. 119-136; HODGE and DAWSON, Civic 
 Biology, chap, x ; KELLOGG and DOANE, Economic Zoology, pp. 377-384 ; 
 KELLOGG and DOANE, Insects and Disease; RILEY and JOHANNSEN, 
 Handbook of Medical Entomology, chap. v. Bulletins and reports of local 
 and state departments of health; bulletins of the United States Public 
 Health Service and of the United States Department of Agriculture. 
 
 LXXIV. INSECTS AS INTERMEDIATE HOSTS 
 
 Get first a quantitative idea of the prevalence of malaria (or 
 yellow fever ! ) in the locality. Students should set out to find 
 possible breeding places for mosquitoes, and chart their distribu- 
 tion. Study local operations directed toward the extermination 
 of mosquitoes. 
 
 Have special reports on the sanitary work in the Canal Zone 
 and in Cuba. 
 
 Have special reports on sanitary work in the nearest harbors. 
 
 Draw diagrams illustrating the idea of alternate hosts. Have 
 special reports on the extermination of parasites through attacks 
 upon intermediate hosts. 
 
 References. CHAPIN, Sources and Modes of Infection, pp. 380-417; 
 EALAND, Insects and Man, pp. 88-119, 136-159, chap, iv; HODGE and 
 DAWSON, Civic Biology, chap, xi ; JORDAN, Textbook of General Biology, 
 chap, xxx ; KELLOGG and DOANE, Economic Zoology, pp. 367-377. 
 
 LXXV. INSECTS AND HUMAN WEALTH 
 
 Collect specimens of useful and destructive insects, including 
 the various stages wherever possible ; specimens of commercial 
 products and of stages in industrial processes ; specimens of 
 spoiled materials ; insecticides. 
 
84 MANUAL FOR TEACHERS 
 
 Have special reports on life histories, injuries, and means of 
 fighting destructive insects, and on life histories, value, and means 
 of cultivating useful insects. Study the statistical data. Give special 
 attention to economic insects of local or current interest. 
 
 References. EALAND, Insects and Man, chap, v; HODGE and DAWSON, 
 Civic Biology, chap, xii; KELLOGG, Insect Stories; KELLOGG and DOANE, 
 Economic Zoology, chap. xvii. Bulletins and reports of state and United 
 States departments of agriculture ; farmers' bulletins and yearbooks, 
 United States Department of Biology. 
 
 LXXVI. INSECTS AND OTHER ORGANISMS 
 
 Collect specimens of insects injurious to useful plants (complete 
 life histories if possible), together with specimens of the plants in 
 question. Species of local or current interest should receive special 
 attention. Have special reports on life histories, extent of damage, 
 and means of control. 
 
 Make a similar study of insects related to economic animals. 
 
 Wherever possible, students should be encouraged to mount 
 specimens of economic insects in arrangements showing their 
 relations, for example, a twig with scales and lady-beetle, or life 
 history of gypsy moth, life history of calosoma, and twig of host 
 plant. 
 
 Have special reports on state and federal activities in the culti- 
 vation of insects for the destruction of injurious insects. 
 
 Have reports on spraying and other methods of control ; study 
 a spraying calendar etc. 
 
 New examples of the interrelations of species should be re- 
 corded ; study the fate of introduced species of plants and animals, 
 and the effects of introduced species upon native species. 
 
 References. EALAND, Insects and Man, chaps, ii, viii ; HODGE and 
 DAWSON, Civic Biology, chap, xiv; KELLOGG and DOANE, Economic 
 Zoology, chaps, xxx-xxxvii. Bulletins of the United States Bureau of 
 Entomology ; state bulletins. 
 
MANUAL FOR TEACHERS 85 
 
 LXXVII. BIRDS IN RELATION TO MAN 
 
 Have field observations on resident and migrating birds. En- 
 courage students to become acquainted with the identities and 
 habits of birds, including distinctive songs, notes and calls, and 
 food plants and animals. The " shooting " of birds with cameras, 
 and their " capture" by means of suitable nesting boxes etc., offer 
 worthy substitutes for the expression of primitive gaming instincts, 
 and should be encouraged. Have special reports on life habits and 
 economics of important birds, particularly such as are of local 
 or current interest. Summaries of the various reports should be 
 prepared in tabular form, and should include information about 
 habitats, seasons, and food plants and animals. 
 
 References. BAYNES, Wild Bird Guests ; BEEBE, The Bird ; HODGE and 
 DAWSON, Civic Biology, chaps, iv, v; HOLMES, Animal Biology, chap, xxi; 
 JOB, Domestication of Wild Birds. Reports and farmers' bulletins, United 
 States Department of Agriculture ; annual summaries of game laws, United 
 States Department of Agriculture; publications of the State Department of 
 Agriculture ; publications of the Audubon Society. 
 
 LXXVIII. SOCIAL LIFE OF ORGANISMS 
 
 Have specimens illustrating high points in the evolutionary 
 series, both plant and animal ; or provide suitable charts. The 
 emphasis will be upon the differentiation that follows upon inte- 
 gration, and this should be compared with the parallel process 
 observed in the course of development (Chapter LI 1 1). 
 
 Access to a glass beehive or to an ants' nest under glass is 
 desirable. Have special reports on division of labor in ant and bee 
 colonies. The distinction between the automatic coordinations that 
 obtain in such colonies and the conscious cooperation of various 
 human enterprises should be made clear. 
 
 References. FABRE, Social Life in the Insect World; HODGE and 
 DAWSON, Civic Biology, chap, xiii ; HOLMES, Animal Biology, chap, vii; 
 JORDAN and KELLOGG, Evolution and Animal Life, chap, xviii ; KELLOGG, 
 American Insects, pp. 490-561 ; KROPOTKIN, Mutual Aid; LUBBOCK, Ants, 
 Wasps, and Bees; MAETERLINCK, The Bee; WHEELER, Ants, especially 
 chap, xxiii. 
 
PART V. HEREDITY AND EVOLUTION 
 
 LXXIX. VARIATION 
 
 For the study of variation, use any organic structures available 
 in quantities. Leaves are to be obtained in all regions and are 
 easily preserved for use in all seasons. Fingers of girls and boys, 
 feathers of birds, claws or teeth of mammals, wings of insects, 
 shells of mollusks, pulse beats, ray-flowers, and hundreds of other 
 things are just as good. 
 
 Have a group of specimens matched as to form, for example, 
 maple leaves or finger prints. 
 
 Make a census of careful measurements. Distribute the material 
 in small boxes, envelopes, or bottles, with rulers or scales divided 
 to millimeters. Instruct students to sort the material into classes 
 representing differences of one or two millimeters. A class of 
 ordinary size can obtain several hundred measurements in a short 
 time ; have a committee of students compile the results. If several 
 classes are doing parallel work, it is worth while to consolidate 
 the data for all and illustrate the increased smoothness of the 
 curve obtained from large numbers. Have results presented 
 graphically as well as in tables. Have them posted on blackboard 
 or chart, and if possible have a copy made for each student. 
 
 When the idea of variation is fairly clear, have students bring 
 in examples of variations, physiological as well as meristic etc., that 
 they have themselves observed among human beings and among 
 other organisms. Have them suggest for each variation what the 
 possible advantage or disadvantage of extremes may be to the 
 organism. It is worth while, in connection with this study, to 
 have pupils record their opinions or beliefs as to the causes of the 
 variations observed ; these views are to furnish a basis for further 
 analysis, or hypotheses for further study, leading to a clearing up 
 of the thought. Examples of modifications in which the causes are 
 
 86 
 
MANUAL FOR TEACHERS 8/ 
 
 obvious or inferred with some degree of probability should also 
 be collected. Have noted the modifying effects of disease, exercise, 
 or disuse, nutritional extremes, habit formation, mechanical injuries, 
 injuries caused by insects or other animals, etc. 
 
 Have pictures and charts showing various breeds of domesticated 
 animals and plants and different varieties of cultivated fruits, vege- 
 tables, and flowers ; study seed catalogues, poultry catalogues, etc. 
 Have special reports on new varieties of useful or fancy plants and 
 animals, from the United States Department of Agriculture year- 
 books, from reports of the nearest agricultural experiment station, 
 from the State Department of Agriculture, from the reports of breed- 
 ers' associations, etc. Have a special report on the work of Burbank. 
 
 References. BERGEN and CALDWELL, Practical Botany, pp. 417-421, 
 428-430; JORDAN and KELLOGG, Evolution and Animal Life, chaps, ii, ix. 
 For the teacher : BATESON, Materials for the Study of Evolution ; DAVEN- 
 PORT, Principles of Breeding, chaps, i-v ; MORGAN, Evolution and Adap- 
 tation, pp. 261-270; VERNON, Variation. 
 
 LXXX. HEREDITY 
 
 In having students bring in examples of family resemblances, 
 consider mental .traits that are not likely to be the results of 
 habituation or common experience, as well as physical traits. Simi- 
 larities in voice, pronounced likes or dislikes, the manner of folding 
 the hands, various mannerisms, and physiological idiosyncrasies 
 furnish interesting material for study and comparison. Uncles and 
 cousins and aunts should be considered, as well as parents and 
 grandparents. 
 
 The most valuable outcome of such studies should be a clear 
 realization of the fact that the resemblance to the two houses is 
 a resultant of many complete resemblances to one side and many 
 complete resemblances to the other, rather than a blending of the 
 several characters. 
 
 Have a special report on the alternative characters studied by 
 Mendel. Have specimens and pictures of varieties of cultivated 
 plants and animals, for study of alternative characters, students to 
 find as many pairs as possible in a given set of individuals. 
 
88 MANUA^ -FOR TEACHERS 
 
 Use blackboard and colored crayons for developing the Men- 
 delian principles. Use checkerboard diagram to show the segre- 
 gation of two or more characters. Where possible, show identity 
 of the segregation formula with the algebraic formula for the 
 square of a binomial etc. 
 
 To make clear what is meant by chance in scientific discussions, 
 refer to (or demonstrate in class, or assign for trial and report) 
 the experience of drawing cards from a pack or of throwing a 
 coin or dice. The chances are even that a card drawn at random 
 will be black or red ; that a coin will fall heads up or tails up. A 
 second throw of a coin faces the same chances, and so the third 
 and the millionth. But the chances that all in the series will fall 
 the same way are very small; and the longer the series, the 
 smaller the chances. It is possible for a coin to come heads up 
 six times in succession; but it is more likely to come in some 
 other succession, as there are a great many possible others. Yet, 
 if we took any one of the others, the chances that that one would 
 come up are just the same as the chances that the six heads would 
 come up. Now the larger the number of throws, the greater the 
 possible number of combinations, and the smaller the chances of 
 any particular combination falling out. With three throws there are 
 eight possible combinations (2 3 ), any one of which has one chance 
 in eight of appearing ; with four throws there are sixteen possible 
 successions (2 4 ), and each has one chance in sixteen of appearing ; 
 with five throws there are thirty-two combinations ; and so on, the 
 chances for a special combination diminishing in geometrical ratio. 
 When this idea is applied to the combination of alternative characters 
 derived from the two ancestral lines, we can see that the chances 
 of a particular combination of characters being duplicated are 
 practically one in infinity. 
 
 References. For the pupils : CASTLE, Heredity in Relation to Evolution 
 and Animal Breeding ; DONCASTER, Heredity in the Light of Recent Re- 
 search ; GUYER, Being Well Born, chaps, i, iii, iv ; HOLMES, Animal Biology, 
 chap, xl; JORDAN and KELLOGG, Evolution and Animal Life, chap. x. 
 For the teacher : LOCK, Variation, Heredity, and Evolution, chaps, vii, 
 Viii; MORGAN, Heredity and Sex; PEARSON, The Chances of Death; 
 THOMSON, Heredity. 
 
MANUAL FOR TEACHERS 89 
 
 LXXXI. APPLICATIONS OF THE PRINCIPLES OF HEREDITY 
 
 Have special reports on the economic and esthetic contributions 
 of plant and animal breeding, from recent bulletins and current 
 publications. Have specimens (where possible) and pictures of 
 new combinations brought about through the systematic applica- 
 tion of known facts and principles. Assign readings on eugenics. 
 
 References. BAILEY, Plant Breeding; BERGEN and CALDWELL, Practi- 
 cal Botany, chap, xxiii ; CASTLE, Heredity in Relation to Evolution and 
 Animal Breeding; DAVENPORT, Principles of Breeding, chaps, xix, xx; 
 GUYER, Being Well Born, chaps, v, vii, x ; HARWOOD, New Creations in 
 Plant Life. Yearbooks and bulletins of the United States Department of 
 Agriculture; seedsmen's catalogues. For the teacher: CASTLE, COULTER, 
 and others, Heredity and Eugenics ; DAVENPORT, Heredity in Relation to 
 Eugenics ; GODDARD, The Kallikak Family. 
 
 LXXXII. HEREDITY AND PROTOPLASM 
 
 It should be clear that whatever is inherited is not physically 
 passed on, the red cow is just as red after the calf is bom 
 as she was before ; and the fertilized egg of the leghorn has not 
 white feathers, it has no feathers at all, not even in miniature. 
 
 Get the idea of the immortality of the germ plasm by comparing 
 with the immortality of protozoan protoplasm. 
 
 Show stained cells for karyokinesis. Show stained egg cells, as 
 of Ascaris, for chromosomes and reduction. Explain the suc- 
 cessive steps in reduction and maturation divisions with the help 
 of blackboard diagrams. 
 
 Have students make special reports on sports among animals 
 and plants. 
 
 Discussion of the transmission of modifications will probably 
 arise without special stimulation from the teacher, it always does 
 if there is the slightest occasion. The question of prenatal influ- 
 ence and of the cause of birthmarks should also be given a 
 chance if it presents itself. 
 
 References. CONKLIN, Heredity and Environment in the Development 
 of Man, chap, ii ; GUYER, Being Well Born, chap, ii ; LOCK, Variation, 
 Heredity, and Evolution, chap. x. 
 
QO MANUAL FOR TEACHERS 
 
 LXXXIII. EVOLUTION 
 
 Review the idea of universality of change, and emphasize the 
 practical importance of understanding changes. Have students 
 give examples of the use of knowledge to bring about desirable 
 change, to avoid undesirable change, etc. 
 
 Have examples of continuously progressive changes and of 
 cyclic changes. Does history repeat itself ? Guard against the 
 tendency to assume that we must pin our faith to a yes or a no 
 answer to every question. There are perhaps other possibilities, 
 and both types of change may exist side by side. 
 
 Show fossils peculiar to the region, and geographical varieties 
 of plants and animals. Have museum studies of fossil series and 
 of morphological series. Explain what a reconstruction is, its 
 basis, and the degree of its validity. Present alternative theories 
 or hypotheses to account for fossils. 
 
 Have special readings (with reports) on the various classes of 
 evidence for descent with modification. It is important to avoid 
 the tendency to confuse the evidence for evolution, considered as a 
 purely historical fact, with speculations concerning the mechanism 
 of evolution. 
 
 References. HOLMES, Animal Biology, chap, xxviii ; JORDAN and 
 KELLOGG, Evolution and Animal Life, chaps, iv-ix. For the teacher 1 : 
 LOCK, Variation, Heredity, and Evolution, chaps, i-iii, v ; MORGAN, 
 Critique of the Theory of Evolution, chap, i ; MORGAN, Evolution and 
 Adaptation, chaps, ii, iii. 
 
 LXXXIV. APPLICATIONS AND THEORIES OF EVOLUTION 
 
 The time given by high-school or college students to the study 
 of evolution must justify itself not in a resulting familiarity with 
 theories or with illustrations and statistics ; it must justify itself 
 in a resulting attitude toward life. It may well be that a portion 
 of our population is constitutionally incapable of acquiring a 
 dynamic outlook ; but where there are no constitutional barriers, 
 the failure to acquire this dynamic viewpoint must be charged to 
 the school and specifically to the teachers of biology and history. 
 
MANUAL FOR TEACHERS 91 
 
 The study of this section may well take the form of a free dis- 
 cussion that will ferret out lingering doubts and prejudices, not 
 for the purpose of inculcating sound doctrine on the subject of 
 evolution, but for the purpose of getting the students to feel the 
 majesty of the larger concepts. An academic analysis or a purely 
 intellectual assent is not sufficient. 
 
 Have special reports and summaries on the views of Lamarck, 
 Darwin, De Vries. Have reports on experimental work in evolution. 
 
 References. CONKLIN, Heredity and Environment, chap, v; GUYER, 
 Being Well Born, chap, x; HARWOOD, New Creations in Plant Life. 
 Yearbooks of the United States Department of Agriculture. For the 
 teacher: KELLOGG, Darwinism To-day; LOCK, Variation, Heredity, and 
 Evolution, chap, x; MORGAN, Evolution and Adaptation, chap. iv. 
 
PART VI. MAN AND OTHER ORGANISMS 
 
 LXXXV. THE CLASSIFICATION OF ORGANISMS - LXXXVI. 
 KINDS OF PLANTS LXXXVII. KINDS OF ANIMALS 
 
 It is not to be expected that students will attain to a clear view 
 of the plant and animal series from the study of a chapter or a 
 chart. It is only through prolonged association with many forms, 
 and through constant thought upon similarities and differences and 
 relationships, that this is to be attained. 
 
 As a means of facilitating acquaintance with forms, present 
 constantly new specimens to illustrate the biological principles 
 studied. These new specimens come to the student as laboratory 
 material for direct handling ; as demonstration specimens ; as exhi- 
 bition material in the wall cases etc. of the classroom ; as objects 
 of observation in the field, in museums, in the flower or vegetable 
 show, in the bird store, in the menagerie or at the circus, in pictures 
 found in books and magazines and upon the classroom walls etc., 
 in stereopticon and motion-picture views, and so on. Acquaintance 
 with forms is the beginning ; classification and naming come later. 
 
 But children begin to classify and name almost as soon as they 
 begin to speak. Call attention to the way children name a new 
 object in terms of the familiar one which it most resembles. 
 
 Discuss the difficulty of supplying enough common names, the 
 inadequacy of common names, and the binomial system as applied 
 to proper names. The basis of classification offers opportunity for 
 making students realize both the practical importance of adequate 
 classification and the practical difficulties of establishing a satisfac- 
 tory classification. For the purpose of getting hold of principles of 
 classification, experience with postage stamps, books, pottery, and 
 textiles may be quite as illuminating as experience with flowers or 
 fishes or frogs. The only advantage of experience with the sorting 
 of organisms lies in the suggestion of a natural order. 
 
 92 
 
MANUAL FOR TEACHERS 93 
 
 Where opportunity and interest are present, encourage students to 
 attempt the identification of species with the aid of some manual. 
 
 As a means of facilitating thought about relationships, tables 
 and " trees " similar to those in the text should be constantly be- 
 fore the eyes of the students. It is therefore desirable to have large 
 charts or wall paintings of these fixed points wherever feasible. It 
 is especially recommended that a large portion of the bare wall, 
 above the blackboards, be devoted to outline "trees" with the 
 names of the phyla and chief subdivisions, accompanied by outline 
 sketches of illustrative forms from the more familiar species. As 
 reference is made to one or another species of plant or animal 
 during the course of the year's study, the teacher may lightly 
 indicate the place of the species in the system as a whole, 
 orient without elaborating. More can be achieved by this constant 
 repetition through a long period than by devoting the same amount 
 of time to intensive study of charts and tables and manuals. En- 
 courage students to transcribe portions of the tables for special 
 groups, and to prepare larger diagrams for the classroom wall. 
 
 Apart from the general features of the classification schemes, 
 the significant point of the discussion is the basis for distinguishing 
 between higher and lower plants and animals. This is to be 
 considered with constant regard for .the fact that the lowest are 
 quite as capable of living as the highest, while it is legitimate to 
 bring out the important differentia of human life as the highest. 
 
 References. Manuals for the classification and identification of common 
 flowering plants (including trees), ferns, mosses, common fungi, birds, 
 insects, fishes, reptiles, batrachians, and mammals. Natural-history books. 
 
 LXXXVIII. MAN AND HIS RELATIVES 
 
 This study may serve as a summary of the common facts about 
 animal organization and functions. 
 
 Use pictures, plaster casts, relics of primitive man ; have museum 
 studies. Have special reports on traces of aborigines in the neigh- 
 borhood and on current topics related to man's ancestry. 
 
 The argument is essentially a successive differentiation of man 
 from the invertebrates to the primates. 
 
94 MANUAL FOR TEACHERS 
 
 The common argument that the similarity between man and 
 the lower primates appeals even to the least intelligent must not 
 be pushed too far. The resemblance that appeals may be en- 
 tirely superficial. Young children are quite satisfied to treat dogs 
 and cats exactly as they treat human beings ; that is, there is 
 enough similarity to appeal to their intelligence. Savages attribute 
 to other animals and even to inanimate forces their own type of 
 purpose and thought. This obvious similarity may thus prove too 
 much. It is necessary to consider similarities that indicate rela- 
 tionship in the biological sense. That is, we must separate what 
 men and monkeys have in common with other animals from what 
 they have together that is different from other animals ; and then we 
 must consider the points of difference between man and other pri- 
 mates, with a view to determining whether these differences are 
 so radical in kind or degree as to preclude evolutionary relationship. 
 
 References. CLODD, The Childhood of the World, chaps, i-iv ; DARWIN, 
 Descent of Man, chaps, i, vi, vii ; DUCKWORTH, Morphology and Anthro- 
 pology, chaps, ii, vii, viii; HOLMES, Animal Biology, chap, xxii ; HOLMES, 
 Evolution of Animal Intelligence, chaps, xi-xiii ; HUXLEY, Man's Place in 
 Nature ; JORDAN and KELLOGG, Evolution and Animal Life, chap, xxi ; 
 OSBORN, Man in the Old Stone Age; SPURRELL, Modern Man and his 
 Forerunners, chaps, ii, iii ; TYLOR, Anthropology, chaps, i-iii ; WATSON, 
 Behavior, chap. x. 
 
 LXXXIX. MAN'S BRAIN 
 
 Since the significant part of this study has to do with the results 
 of brain work rather than with the structure and workings of the 
 brain, the latter need not be emphasized unless there is special 
 interest in the subject among the students. Use a model of the 
 human brain, and of such other vertebrate brains as are to be had. 
 A calf's brain from the butcher may be dissected for gross features. 
 
 Have special readings and reports on museum studies on the 
 activities of primitive man, comparing them particularly with the 
 corresponding activities of other animals. 
 
 The question to emphasize is, How does man, despite his struct- 
 ural shortcomings, manage to adjust himself to the inimical aspects 
 of his environment, and how does he manage to supply his needs ? 
 
MANUAL FOR TEACHERS 95 
 
 References. For the pupils : DARWIN, Descent of Man, chaps, iii-v ; 
 TYLOR, Anthropology, chaps, iv-xii. For the teacher : DONALDSON, The 
 Growth of the Brain ; LANKESTER, Nature's Insurgent Son ; LOEB, Com- 
 parative Physiology of the Brain. 
 
 XC. MAN'S CONQUEST OF NATURE - XCI. SCIENCE 
 AND CIVILIZATION 
 
 Man the organic mechanism is gradually replaced by man the 
 designer and creator. The isolated animal supplying his own wants 
 and meeting his personal difficulties is gradually replaced by a 
 member of society. Now he hunts in groups and solves his other 
 problems through interchange of service and experience, and 
 through cooperative effort in many directions. The study of 
 biology merges into the study of psychology and sociology. The 
 study of man is no longer physiology, but anthropology, ethnology, 
 politics, and economics. 
 
 The text should be supplemented by assigned readings along 
 divergent lines, depending upon the interests of the students and 
 upon the available material. Local relics of ancient times and local 
 institutions that embody the highest achievements in the way of 
 organized research are equally significant in the final synthesis. 
 The visit to the museum of natural history may well be supple- 
 mented by a visit to the historical museum or to the art museum ; 
 for here, in the consideration of man's achievements, the study of 
 nature passes into the study of history and art. 
 
 The study of recent statistical material indicating measurable 
 progress in man's conquest of his environment, and the comparison 
 of local conditions in various respects with the general conditions, 
 will help to fix the interest and perhaps to widen the outlook. The 
 emphasis should be finally upon the value of civilization in terms 
 of life more abundant, to which all science must contribute. 
 
 References. CLODD, The Childhood of the World; CONN, Social 
 Heredity and Social Evolution; HODGE and DAWSON, Civic Biology, 
 chaps, xxxi-xxxii ; KELLICOTT, Social Direction of Human Evolution ; 
 LANKESTER, Nature's Insurgent Son; SPURRELL, Modern Man, chaps, iv- 
 vii ; TYLOR, Anthropology, chaps, xiii-xvi. Current reports of progress in 
 applied knowledge. 
 

 SEP 
 
 'OLOGY LIBRARY 
 
 1932 
 
 31 1935 
 
 2 1964 
 
i<2 
 
 JIOLOGY 
 LIBRARY 
 
 ., 
 
 UNIVERSITY OF CALIFORNIA LIBRARY