UC-NRLF 1 SB LABORATORY MANUAL OF A YEAR IN SCIENCE THALMAN AND WE c KEL LABORATORY MANUAL OF A YEAR IN SCIENCE JOSEPH L. THALMAN, A.M. FORMER HEAD OF BIOLOGY DEPARTMENT, OAK PARK AND RIVER FOREST TOWNSHIP HIGH SCHOOL ; PRINCIPAL OF HIGH SCHOOL, NEW CASTLE, PA. AND ADA L. WECKEL, M.S. HEAD OF BIOLOGY DEPARTMENT, OAK PARK AND RIVER FOREST TOWNSHIP HIGH SCHOOL, OAK PARK, ILLINOIS CHICAGO NEW YORK ROW, PETERSON AND COMPANY o COPYRIGHT, 1916 ROW, PETERSON AND COMPANY PREFACE FOR THE LABORATORY MANUAL Laboratory work is an essential part of any course in science. The mental development acquired by pupils performing a series of experiments, interpreting their results, and carefully recording them, is of equal, if not more value, than the mere accumulation of facts. We cannot justify the existence of any course in the high school which has the acquiring of information as its only purpose. The performance of experiments is not a mechanical part of the course in which the use of the intelligence of the pupil plays no part. Too much em- phasis can not be placed upon the fact that the pupil must perform experiments intelligently, using his head as well as his hands. Frequently beginners are inclined to think that laboratory work is merely entertaining. The following outlines for experiments are the result of about fifteen years of experiment and search for inter- esting and fundamental scientific matter adapted to the age and preparation of pupils entering the high school. During this period of experimentation from six to nine- teen classes a year have pursued this course. It has thus been tried on thousands of students under the direction of many teachers. We gratefully acknowledge our indebt- edness to these teachers for their many valuable sugges- tions and criticisms. 35939 ^ MANUAL Since first year pupils have had no training in scientific methods, the experiments must necessarily be short and simple. As far as possible, the following experiments should be performed by the pupils, working individually, or, if necessary, in small groups. We are convinced that the training acquired by pupils in this way is much greater than that obtained when the teacher demonstrates all of the experiments. With the expenditure of a very small amount of money, it is possible to purchase the apparatus necessary for the equipment of a laboratory for individual experimentation. Supplementary or alternative exercises are frequently given. Since both experiments in such cases develop or illustrate the same principle, it is not essential that both be performed. Pupils should also be encouraged to devise experiments of their own. If the laboratory sections are very large, this latter feature is impractical. During the first part of the course it is advisable for the teacher to read carefully the Directions with the pupils. There are always some members of a class who acquire with difficulty the ability to read, interpret, and follow directions intelligently. A note book kept by each pupil should contain records of most of the experiments performed. The record of each experiment should include : 1. An account of the method used in performing the experiment. 2. A simple diagrammatic drawing of the apparatus used. PREFACE FOR THE LABORATORY MANUAL 5 3. A statement of the results. 4. A conclusion drawn from the results, when a con- clusion is possible. It is essential that these notes are clearly and concisely expressed and neatly kept. The development of this laboratory course could not have been made possible except for the encouragement, sympathetic interest, and faith of Mr. J. C. Hanna, to whom we hereby acknowledge our indebtedness. CONTENTS Exercise Page 1. Does Gas Occupy Space? 15 2. Comparison of English and Metric Systems. 16 3. Does Gas Have Weight? 19 4. Diffusion of Liquids 21 5. Diffusion of Liquids through a Membrane . . 22 6. Diffusion of Gases 25 7. Diffusion of Gases (Demonstration) 26 8. Mixing of Alcohol and Water 27 9. Effect of Heat on Solids 28 10. Effect of Heat on Liquids 29 11. Effect of Heat on Gases 31 12. Cohesion, Adhesion, and Gravity 32 13. Thermometers 34 14. Measurement of the Heat of a Flame 35 15. Change from a Solid to a Liquid 38 16. Solution 39 17. Change from Liquid to Solid 40 18. Change from a Liquid to a Gas 41 19. Effect of Pressure on Boiling Point 42 20. How Water is Distilled 43 21. Evaporation 44 22. Physical Change 45 23. Chemical Change 46 24. Mechanical Mixture 47 25. Chemical Synthesis. 48 26. Chemical Analysis ". 49 27. Carbon 50 28. Phosphorus (Demonstration) 51 7 8 CONTENTS Exercise Page 29. Sulphur . 52 30. Iron , 53 31. Oxygen 55 32. Hydrogen 57 33. Nitrogen 59 34. Acids and Bases 60 35. Salts and Neutralization 61 36. A Simple Electric Cell 62 37. Composition of Water (Demonstration) .... 63 38. Composition of Air 64 39. Does Air Exert Pressure? (Demonstration) . 66 40. Barometer (Demonstration) 67 41. Siphon 68 42. Convection 69 43. Moisture in the Atmosphere — Condensation. 70 44. Study of the Weather Map 71 45. Water Capacity of Soils 75 &. Soil Solutions , 76 47. Gross Structure of Leaves 77 48. Chloroplasts 78 49. Making of Food for Plants 79 50. Making of Food for Plants, continued 80 51. By-Products in Food Making 80 52. Transpiration 81 53. Rate of Transpiration 82 54. Is Air Necessary? 83 55. Exchange of Gases in Respiration 84 56. Roots 85 57. Roots as Organs of Absorption 86 58. External Structure of Stems 87 59. Internal Structure of Stems 88 60. Functions of Stems 89 61. A Typical Flower 90 CONTENTS 9 Exercise Page 62. Structure of Seeds 91 63. Seed Dispersal 93 64. Conditions for Germination 93 65. Seedlings 95 66. Bacterial Cultures 97 67. Conditions for Bacterial Growth 100 68. Root Tubercles 101 69. Tests for Foodstuffs 103 70. Foodstuffs in Common Foods 104 71. Study of the Mouth (home study) 105 72. Alimentary Canal and Digestive Glands (Demonstration) 107 73. Digestion in the Mouth 109 74. Digestion in the Stomach 110 75. Digestion in the Intestine 112 76. Absorption 113 77. Study of Beef "Pluck" (Demonstration)... 114 78. Blood 116 79. Respiratory Organs and Mechanics of Res- piration (Demonstration) 118 80. Comparison of Expired and Inspired Air. . . . 120 81. School Ventilation 122 82. The Kidneys 123 83. The Skin 124 84. The Skeleton 125 85. Structure and Composition of Bone 127 86. Levers 128 87. Muscles (Demonstration) 130 88. Nervous System (Demonstration) 131 89. Cutaneous Sensations 133 90. Organs of Taste and Smell 134 91. Organ of Sight 135 92. Organ of Hearing1 137 APPARATUS The following lists contain all the apparatus and sup- plies necessary for a satisfactory presentation of the laboratory exercises given in this manual. Many of the most expensive pieces of apparatus, marked with an asterisk in the following lists, may be eliminated with- out requiring the omission of many exercises. In many cases it is possible to substitute simple improvised appa- ratus for these more expensive pieces. A school equipped for laboratory work in physics and chemistry is equipped, also, for a general science course. The expense of equipping a laboratory for general science will be nominal, if the equipment in the other labora- tories in the school can be used. The following named apparatus can be obtained from dealers in laboratory supplies. The prices given here are only approximate. Any school can secure a discount of from 10 to 25 per cent from these prices. A. PHYSICAL APPARATUS 1. For demonstration work, one set for the whole class. *1 air pump $10.00 3 animal membranes. . . .30 2 balances, spring 1.00 1 bar compound 50 *1 balance and weights. 9.08 1 blow pipe 14 1 ball and ring 1.00 1 brass globe, hollow.. 2.25 1 balloon, rubber 06 2 clamps, burette 16 11 12 APPARATUS 1 cotton roll 3 deflagrating spoons. . . 3 dry cells *1 drying oven (house- hold type may be used) 1 pk. filter paper 15 * 1 Magdeburg hemi- sphere 2 magnets 2 metric sticks 2 mortars and pestles. . 1 pan, dissecting 1 pinch cock The above list does not include several expensive pieces of apparatus wjrich are not used frequently enough to justify placing them in the list. They are : a barometer, a compound microscope, a skeleton, and an anatomical manikin, or models of the principal organs of the body. . 2. For individual work, one set for each pupil, or for each group of pupils. .20 1 porous cup . .14 .30 *1 pneumatic trough . . . .81 1.05 1 ring stand 1.12 1 rubber dam, 1 sq. ft.. .30 1 shears .67 5.50 1 ft. tubing, rubber, Ty .18 .15 1 ft. tubing, rubber, Vs" .12 1 twine . . . . .05 3.00 .45 Total $39 73 .50 Total not essential, .40 marked with an aster- .20 isk . 28.39 .10 Total, essential 11.34 1 asbestos sheet, 8 x 8 x 1 metric rule .03 ,V . . $0.10 2 needles, dissecting 12 1 Bunsen burner (alco- hol lamp may be used) 1 test tube clamp 1 forceps 1 lever holder 22 .07 .10 .18 1 ring stand and rings. . .54 1 scalpel 25 1 test tube rack 38 1 wire gauze 5x5" 05 Total $2.04 B. GLASSWARE 1. Demonstration, one set for the whole class. 2 battery jars $1.00 *1 belljar, closed ground glass stopper. . . . 1.50 *1 burette, 100 c.c 1.80 APPARATUS 13 1 pk. corks 35 ^ oz. round cover glasses 30 fl crystallizing dish, 10" 1.00 2 cylinders, glass, 3 x 15" 1.66 fl electrolysis apparatus 5.00 1 graduate, 100 c.c 56 1 glass plate, 10" 25 2 doz. slides, microscopic 25 5 thistle tubes 40 1 torricellian tube 28 -i Ib. glass tubing, & " 22 Total $14.57 Total, not essential.. 0.30 Total, essential 5.27 2. Individual, one set for each pupil, or for each group of pupils. 2 beakers, 230 c.c $0.30 2 bottles, wide mouth, 8 oz 10 1 evaporating dish 25 2 flasks, 16 oz 36 1 funnel 20 1 petri dish, 100 mm. diam 25 1 plate, 3" 05 1 stirring rod, glass, 5 x 7V' 02 1 set stoppers, rubber 50 No. 3, 1-hole No. 8, solid No. 3, 2-liole No. 8, 1-hole No. 2, 1-hole No. 8, 2-holo 12 test tubes, 6 x %" 25 1 test tube, hard, 6 x %" 10 1 test tube brush 1)5 1 thermometer, 10° to 210° C 1.25 1 tumbler, glass 04 Total . . $2.72 14 APPARATUS C. CHEMICALS The amount of each chemical will vary with the size of the class, but the total cost of chemicals will not exceed $12.00. *Acetic acid Alcohol Ammonium hydroxide (house- hold ammonia) Charcoal Chloroform *Cobalt chloride Copper, sheet Copper sulphate Eosin (red ink may be sub- stituted) *Ether Fehling's solution, No. 1 and No. 2 Flax seed, ground Hydrochloric acid Iodine Iron filings Iron wool Lime water (made by slack- ing lime in water and filter- ing off water) Litmus paper, red and blue Manganese dioxide Marble Mercury *Mercuric chloride Mercuric oxide Molasses Nitric acid Oxalic acid Olive oil Pancreatin Paraffin Pepsin Phosphorus, red Phosphorus, yellow Potassium chlorate Potassium iodide *Potassium oxalate acid *Potassium permanganate Rennet Salt Sodium hydroxide *Sodium hyposulphite Sodium nitrite Starch, corn Sugar, cane Sugar, grape Sulphur, flower Sulphur, roll Sulphuric acid Vaseline Zinc, granulated or scrap Zinc, sheet D. SUMMARY OF COST OF EQUIPMENT 1 complete set of apparatus for demonstration. .$16.61 1 complete set for individual use 4.76 1 set of chemicals, not over 12.00 Total. ..$33.37 LABORATORY MANUAL OF A YEAR IN SCIENCE CHAPTER I MATTER Exercise 1. Does Gas Occupy Space? Object: To determine whether air, which is a gas, occupies space. Apparatus Glass tumbler Large glass jar Wide mouth bottle Two-hole rubber stopper Thistle tube Glass tubing Rubber tubing Clamp Directions: A. Fill the glass jar three- quarters full of water. ~ Push the tumbler, mouth downward, half way under the sur- Fig. i. 15 16 LABORATORY MANUAL face of the water. Does the water rise to fill the tumbler ? Does it rise into the tumbler at all ? Now tilt the tumbler sidewise so that the edge of the mouth of the tumbler comes just above the sur- face of the water. What happens? Without remov- ing the tumbler, push it down into the water again. Does the water rise into the tumbler this time? In the first instance was the tumbler empty ? What did it contain? What do you conclude concerning this substance ? B. Put the stem end of the thistle tube through one of the holes of the rub- ber stopper. Into the other hole, insert the piece of glass tubing. Place the stopper in the mouth of the bottle and close the upper end of the glass tube by means of the rubber tubing and clamp. Now pour water into the bulb of the thistle tube. Does any water run into the bottle ? Keep the bulb full of water. Does the Fig. 2. A YEAR IN SCIENCE 17 water continue to run into the bottle ? Open the clamp. What happened? How do you account for the results? Exercise 2. Comparison of English and Metric Systems.* Object: To compare the English and metric systems. Apparatus Compass English weights Metric rule Quart measure English rule Liter measure Metric weights Centigrade thermometer. Directions: A. Comparison of the English and metric units of length. Use a compass with sharp steel points, a metric rule, and an English rule. Accurately get the space of an inch with the compass. Place the compass on one of the centimeter lines (not the end of the rule) of the metric rule and read as accurately as you can, estimating in tenths of millimeters the distance of the inch. Record in a tabular form. Now get the space of two inches and read the corresponding distance on the metric rule. Do the same for 3, 4, 5, 6, 7, and 8 inches. Average each reading to find the number of centimeters in an inch. Get the general average of all your results. Get the correct value from the instructor or a physics book. "A preliminary exercise for those teachers who wish to acquaint the pupils with the units of measure before undertaking the main work of the course. 18 LABORATORY MANUAL What error did you make? What is the reason for the error? B. Measurements. Accurately measure the length, width, and thickness of the top of the laboratory table, using the metric rule. Calculate the area of the top in square centi- meters and in square meters. Also calculate the number of cubic centimeters in the table top. Change all of these metric readings into English values. Make the same measurements, using the English rule. Find the area of the table top in square inches, square feet and square yards. Compare all of these results with your calculated results. C. Examine a box of metric weights. Study the small or fractional wreights. What relation do these small weights have to a gram weight? Arbitrarily select six different com- binations of small and large weights and express each of these values in grams. Have the instructor verify your readings. D. Comparison of the English and metric units of weight. (a) Weigh a one pound weight as accurately as you can, using metric weights. Record your result. (b) Weigh a two pound weight in the same way. Find the average of both readings. How many grams in a pound? (c) Weigh an ounce to find the number of grams to which it is equivalent. Get the correct values from A YEAR IN SCIENCE 19 the instructor. How much of an error did you make? How do you account for this error? E. Comparison of the English and metric units of volume. Use a liter vessel, a quart measure, and a set of metric weights. (a) Find by measurement, using water, which is larger, a liter or a quart. (b) Weigh a liter of distilled water. First balance the dry liter vessel, then fill with distilled water and weigh. Find the temperature of the water with a centigrade thermometer. (c) Weigh a quart of distilled water. Use the same method as you employed in weighing the liter of water. (d) Find the relation of a quart ^o-a liter from your data of (c). Ask the instructor to verify your results. How accurate has your work been? Does the tem- perature of the water have anything to do with its weight? Can you think of reasons for any errors that you may have made ? Exercise 3. Does Gas Have Weight? Object: To determine whether gases have weight. Apparatus Balance and weights Incandescent lamp bulb Hollow brass globe with (burnt out bulb) stop cock Bunsen burner Air pump Blow pipe Directions : A. On one pan of the balance place the brass globe. Upon the other pan place enough weights 20 LABORATORY MANUAL to balance the globe evenly. Without disturbing the weight pan, remove the globe from the other pan. Fig. 3. With an air pump exhaust the air from the globe and then close the stop cock. Then replace the globe on the pan of the balance from which it was removed. Do the two sides now evenly balance each other ? How do you account for this condition? Does air then have weight? Air is a gas. From the definition of matter, do experiments 1 and 3 prove that gas is matter? Why? B. The bulb of an incandescent lamp is empty save for the filament and a very slight trace of gas which was not exhausted. Weigh the bulb carefully and accurately With the aid of the blow-pipe direct a A YEAE IN SCIENCE 21 tiny flame point of the Bunsen flame upon a small area of the bulb near the top where the diameter is greatest. As the glass softens, the pressure of the air Fig. 4. outside will make a hole. Weigh the bulb after the hole has been made in the glass. Observations : Weight of empty bulb Weight of bulb filled with air Difference equals weight of air in bulb CHAPTER II CONSTITUTION OF MATTER Exercise 4. Diffusion of Liquids. Object: To determine whether liquids will diffuse when in contact. 22 LABOEATORY MANUAL Thistle tube Glass cylinder Metric rule Apparatus Saturated solution of copper sulphate Distilled water Directions: Fill the glass cylinder two-thirds full of distilled water. Into the cylinder place the thistle tube with the bulb upward. When the water is quiet, slowly pour through the thistle tube 50 cubic centi- meters of copper sulphate solution. This must be done as carefully as possible to avoid mixing the liquids. What is now the relative positions of the liquids ? Is there a sharp line of separation between the liquids? Why is the copper sulphate solution placed on the bottom of the glass cylinder? Measure accurately with a metric rule the height of the copper sulphate solution. Record observations and allow the experi- ment to remain undisturbed until the next recitation period. Then repeat the observations made above. 5. What changes? In conclusion, what have you learned from this experiment? Exercise 5. Diffusion of Liquids through a Mem- brane. Object : Will liquids diffuse if separated by an animal membrane? A YEAR IN SCIENCE 23 Apparatus Animal membrane Thistle tube Water Molasses Twine Glass jar Ring stand and clamp Rubber tubing Clamp Card board Egg Glass tubing Sealing wax Hydrochloric acid Glass tumbler Bunsen burner Directions: A. Over the stem end of the thistle tube fit a small piece of rubber tubing. Close this tightly with a clamp. Fill the bulb of the tube with dilute molasses. Over the end of the bulb securely tie an animal membrane, being- careful to exclude all air bubbles. From the ring- stand suspend the tube with the bulb in a jar of Avater. Mark the level of the molasses in the tube. Note the color of the water in the jar. At the end of one hour repeat the same observations. Observe again at the end of twenty-four hours,. Fig. 6. What changes have taken place! Has-any molasses passed into the water? How do you know ? Has any water passed into the molasses ? In which direction has diffusion taken place more rapidly ? How do you know? B. In the cardboard cut a hole large enough so that 24 LABOEATOEY MANUAL the large end of the egg will extend about % of an inch below the cardboard. On the small end of the egg break away the shell to form an opening large enough to insert the glass tube, which should be about 6 inches long. Carefully seal the tube in the egg with the end projecting about half an inch below the shell. Fill the tumbler with hydrochloric acid. Place the cardboard and the egg- over it with the large end of the egg projecting into the acid. The acid gradually dis- solves the shell, ex- posing the thin mem- brane underneath it. When the shell has been removed from the end of the egg, empty the acid and fill the beaker with water. Rinse the acid off the egg and replace the card- board and egg over the tumbler. The water in the tumbler and the contents of the egg are now separated by the egg membrane. Allow the experiment to stand for 24 hours. What change do you note in the tube? How do you account for this change? Fig. 7. A YEAR IN SCIENCE 25 Gas generator Lime water Exercise 6. Diffusion of Gases. Object: Will gases diffuse when in contact? Apparatus Wide mouth bottles Glass covers Directions: From a gas generator fill a bottle with carbon dioxide.* Carbon dioxide is heavier than air and so displaces the air which was in the bottle. Pour lime water into the bottle. By shak- ing the bottle thoroughly, mix the lime water with the carbon dioxide. What change do you note in the lime water ? Such a change in lime water indicates the presence of carbon dioxide. From the generator fill another bottle with carbon dioxide. Cover the bottle with a glass plate and remove it to your desk. Over the mouth of this bottle invert a bottle of air and then remove the glass plate. Allow the bottles to stand in this relation five minutes. Remove the upper bottle and cover it immediately with the glass plate, carbon dioxide in the upper bottle? determine this ? What does this show ? Is there any How do you *To generate carbon dioxide, place a few small pieces of marble in a flask and cover with dilute hydrochloric acid. The flask should be fitted with a delivery tube through which the gas can pass into the wide mouth bottle. 26 LABORATORY MANUAL Exercise 7. Diffusion of Gases. { Demonstration.) Object: Will gases diffuse through a porous wall? Apparatus Porous cup with glass tube Cup of colored liquid inserted Belljar Ring stand Air pump Directions : From the ring stand suspend the porous cup apparatus with the free end of the glass tube projecting into the cup of colored liquid. Place the belljar over the porous cup. Is there any change at the end of the glass tube in the colored liquid ? With an air pump force air into the belljar over the porous cup. Is there any change now at the end of the glass tube in the colored liquid? Thus the air currents have no effect. Fill the belljar with illuminating gas, then quickly lower it over the porous cup. What change of the glass tube in the What change Fig. takes place at colored liquid? the end Remove the belljar. do you now observe? In the first instance what were the bubbles escaping ? Where did they come from ? What must have been the condition in the porous cup A YEAR IN SCIENCE 27 to produce such a result? How do you account for it? What must have been the condition to cause the liquid to rise in the tube when the belljar was removed? What does this exercise teach? Compare the rate of diffusion of gases with that of liquids; of solids. Compare the rate of diffusion of liquids with that of solids. Exercise 8. Mixing of Alcohol and Water. Object: To determine the result of mixing equal volumes of alcohol and water. Apparatus Alcohol 96% Burette, 100 c.c. Distilled water Clamp Directions : Over the small end of the burette place a small rubber tube. Close the tube tightly with the clamp. Into the open end of the burette pour distilled water to the height of the 50 c.c. mark. Then carefully and slowly pour into the tube 50 c.c. of alcohol. Note carefully the height of the two liquids. By means of the thumb close the burette and mix the liquids thor- oughly by repeatedly inverting the tube. Observe again the height to which the liquids rise. What does this condition show? How do you account for it? 28 LABORATOEY MANUAL CHAPTER III EFFECT OF HEAT ON MATTER Exercise 9. Effect of Heat on Solids. Object: To determine the effect of the change of temperature on the volume of a solid. Brass ball Brass ring Bunsen burner Apparatus Compound bar Nail punch Screw nut Directions : A. Try the fit of the ring over the ball. Heat the ball. Will the ball now pass through the ring? Heat the ring. Will the ball now pass through the ring? Cool the ring by running tap water over it. Will the ball pass through the ring now ? In the same manner cool the ball and try the fit again. From these observations what is the effect of an increase of temperature upon the volume of a solid? What is the effect of a decrease of tempera- ture? B. Adjust the nut on Fig. 10. the punch. Mark the point A YEAE IN SCIENCE 29 on the punch to which the nut fits. Then heat the nut and adjust it on the punch once more. Does it pass as far or farther on the punch than it did when cold? Heat the punch and repeat the adjustment. What do you find? What does this show? Have you ever seen a blacksmith fit a tire to a wagon wheel? What is the principle involved? C. Do all solids expand and contract at the same rate? To determine this, use a compound bar. A compound bar consists of two metals tightly welded or riveted together lengthwise. Heat the bar equally on both sides by playing the flame of a Bunsen burner along its edge. Do you observe any change in the direction of the bar? What does this indicate? Cool the bar by running tap wrater over its edge. Does the direction of the bar now change ? How do you explain these results? Exercise 10. Effect of Heat on Liquids. Object: Does the volume of liquids change with a change in temperature ? Apparatus Test tube Bunsen burner One-hole rubber stopper Test tube clamp Glass tube Directions : A. Fill the test tube with cold water. Into the mouth of the tube insert the rubber stopper fitted with a glass tube. Press on the stopper until the water rises about an inch in the glass tube. Marli carefully the level of the water. 30 LABOBATOEY MANUAL Heat the water gently by playing the flame of the Bunsen burner along the side of the test tube. What change do you observe in the water level? Fig, 11. Again mark the level of the water. Cool the water in the test tube by running tap water over it, or by surrounding the test tube with ice. After a few minutes note the level of the water. B. Fill the test tube with water. Tightly cork the filled tube and after thoroughly drying the exterior of the tube, gently heat it over the Bunsen flame. Explain A YEAE IN SCIENCE 31 the result. Did the amount of water increase with the increase of temperature ? Did it decrease with a lower temperature? Then how do you explain the increase and decrease in volume noted upon heating and cooling respectively ? Exercise 11. Effect of Heat on Gases. Object: To determine the effect of a change of temperature upon the volume of gases. Tost tube ( )ne-liole rubber stopper Bunsen burner Apparatus Beaker of colored liquid Test tube clamp Directions: A. Fit the stopper with the glass tube into the test tube as in the preceding exercise. With wliat is the test tube filled? Is this a gas? See Exercise 32 LABORATORY MANUAL 1. Place the projecting end of the glass tube into the beaker of colored liquid. Heat the tube gently with a Bunsen flame. Observe carefully all changes. Without changing the apparatus allow the gas in the test tube to cool. What change do you now observe? How do you account for the change ? B. Tightly cork a test tube filled with air. Gently heat the tube over the Bunsen flame. Explain the result. Does this change indicate an increase in the amount of gas in the test tube or in its volume ? From the last three exercises what is the effect of the increase of temperature upon the intermolecular spaces ? Upon the molecules? The effect of the decrease of tempera- ture upon the intermolecular spaces? Upon the mole- cules ? Exercise 12. Cohesion, Adhesion, and Gravity. Object: A study of forces acting between molecules and between masses. Apparatus Spring balance Battery jar Circular glass plate Sealing wax Directions: By means of sealing wax, attach three strings at equidistant points near the margin of the glass plate. Tie the ends of the strings together and suspend the plate from the hook of the spring balance. (The glass plate must hang horizontally.) Record the weight of the glass plate. Then lower the apparatus over the battery jar filled with water, until the plate touches the water. Slowly lift the balance, at the A YEAR IN SCIENCE 33 same time noting any changes in the reading on the index of the balance. Continue to lift the balance. What happens? Examine the under surface of the plate. What do you find there? Does this indicate that the plate was separated from the water or that the water particles were pulled apart? Thus it will be seen that two forces were acting, the one holding the molecules of water together, called cohesion, the other holding the plate to the water, adhesion. Which in this ex- periment was the greater? With the water still adhering, hold the plate in a vertical position. What happens to the water? This third force causing the water to drop is"" called gravity. Which of these forces acts between Fi§r- 13- molecules of the same kind? Between molecules of different kinds? Between masses? 34 LABORATORY MANUAL CHAPTER IV MEASUREMENT OF TEMPERATURE Exercise 13. Thermometers. Object: A comparative study of thermometers. Apparatus Fahrenheit thermometer Metric rule Centigrade thermometer Directions: Examine a thermometer carefully. How is it made? Note the markings on the scale. What do they indicate? What two points on the thermometer seem of special importance? On this, the centigrade thermometer, zero degree is the freezing point of water and 100 degrees the boiling point. Can you suggest a way of determining these points ? After they are located how would you find the length on the scale of one degree? On your note paper make a drawing of a thermom- eter. On the right side of the line place two points, one for the boiling point, the other for the freezing point. Between these points mark the 10, 20, 30, etc., to 100 degrees. Continue the line representing the thermometer tube below 0 degrees far enough to admit negative 40 degrees. On the left side mark 212 degrees opposite boiling and 32 degrees opposite freezing. How many degrees on this, the Fahrenheit ther- mometer, are there between freezing and boiling? On A YEAB IN SCIENCE 35 the side opposite the 10, 20, 30 (degrees), etc., markings of the centigrade thermometer, fill in the corresponding numbers of the Fahrenheit thermometer. Find the value of one degree centigrade in terms of Fahrenheit degrees. Find the value of one degree Fahrenheit in terms of the centigrade degree. Problems: 1. Fifteen degrees C. are equal to how many degrees F. ? 2. Forty-five degrees F. are equal to how many decrees C. ? 3. The centigrade thermometer registers 21 degrees. What does the Fahrenheit thermometer register at the same time? 4. The Fahrenheit thermometer registers 14 de- grees. What does the centigrade thermometer register at the same time? 5. What is the principle upon • which the construc- tion of the thermometer is based? Exercise 14. Measurement of the Heat of a Flame. It is a well-known fact that if any substance is held in a flame, its temperature is increased. The cause of this increase is called heat. To measure this increase sonic unit of measure is necessary. To this unit the name gram-calorie has been given. A gram-calorie is lh< (unounf of heal, necessary to raise one gram of water <»>< degree ccnliyrade-. Object: To determine the amount of heat given off by a given flame in one minute. 36 LABORATORY MANUAL Apparatus Flask Thermometer Asbestos cover for liask Flame protector Wire gauze Bunsen burner Ring stand Graduate, 100 c.c. Directions: A. Place 100 c.c. of water in the flask and set it aside. From the ring stand suspend the flame protector. Adjust it in such a manner that the lower part of the protector fits over the upper part of the Bunsen burner. Then place the wire gauze upon the ring. Light the Bun- sen burner and regulate the gas and air for a blue flame of moderate size. Place the burner under the protector. Do not change these adjustments until the experiment is 3 completed. Take the temperature of the water in the flask. Cover the flask with an asbestos cover, and place it on the wire gauze, noting the exact time this is done. Note and record the rise in tempera- ture of the water each minute for ten minutes. Then turn off the gas. What is the average number of degrees of rise of temperature per minute ? How many c.c. of water were A YEAR IN SCIENCE 37 increased this number of degrees per minute? Then how many calories of heat was your flame giving off per minute? Tabulate results as follows : Am 't of Water Temp. Time Inc. per min. Ave.Inc. Beginning 1 2 3 4 5 6 7 Q O 9 End 10 B. With the gas adjustment the same throughout, prepare flasks as follows : One containing 100 c.c. water. 200 c.c. " 300 c.c. " 400 c.c. " 500 c.c. " The water in each flask should be the same tempera- ture (room temp.) at the beginning of the experiment. With the bulb of the thermometer in the water in the flask, heat each until the water begins to boil. Note carefully in each instance the length of time necessary 38 LABOEATOEY MANUAL to bring each separate quantity to the boiling point. The product of the quantity of water multiplied by the number of degrees its temperature was raised, divided by the number of minutes required for bringing the water to the boiling point, will give you the approxi- mate amount of heat given off by the name per minute. If you make a number of tests as indicated above, the average of the results will give you a more accurate idea of the available heat given off by your flame per minute. CHAPTER V CHANGES IN THE STATE OF MATTER Exercise 15. Change from a Solid to a Liquid. Object : To determine the heat necessary to convert one gram of ice to water. Apparatus Cracked ice Chemical thermometer Balance and weights Bunsen burner Hot water Tin beaker Ring stand Asbestos cover Directions: Surround the tin beaker with the asbestos cover and ascertain the weight of both. Into the beaker pour 200 c.c. of Avater at 60 degrees C. Now obtain the weight of the beaker and water. Break 75 grams of ice into small pieces. After noting the exact temperature of the water in the beaker, wipe dry the pieces of ice and drop them into the water piece by A YEAR IN SCIENCE 39 piece. When the ice is almost melted, note again the exact temperature of the water. Weigh again the beaker and its contents. Tabulate the data as follows : 1. Weight of beaker and cover. 2. Weight of hot water and beaker. 3. Weight of hot water (calculated). 4. Weight of beaker and water at end of experi- ment . 5. Weight of ice (calculated). 6. Temperature of water before ice was added. 7. Temperature of water after ice was melted. 8. Loss in temperature of water (calculated). 9. Increase in temperature of ice (calculated). Multiply the weight of the hot water by its loss in temperature to obtain the number of calories required to melt the ice and raise it to the final temperature. Multiply the weight of the ice by its increase in tem- perature to obtain the number of calories used in raising its temperature. The difference between these results will give the number of calories used in melting the given amount of ice. How many calories are required to melt one gram of ice? Why is the temperature of the atmosphere near a :dy of freezing water higher than the temperature the atmosphere a little distance away? Exercise 16. Solution. Object: To show the effect of dissolving salt upon the temperature of Avater. 40 LABOEATOEY MANUAL Apparatus Beaker Thermometer Salt Directions : Half fill a beaker with water. Carefully observe and record its temperature. Into the water put several teaspoonfuls of salt. Quickly insert the thermometer into the beaker. Do you note any changes in the temperature? What change is taking place in the salt? What is necessary to produce this change ? For your answer refer to Exercise 15. Then how do you explain the change in temperature which occurs ? Why is salt mixed with the ice in an ice cream freezer? When snow melts, what effect does this have on the surrounding temperature? Does this tend to increase or decrease the rate of melting? Of what advantage is this? Exercise 17. Change from Liquid to Solid. Object: To determine the effect on the temperature of a substance when it changes from a liquid to a solid. Apparatus Hypo Graduate Flask Bunsen burner Thermometer Wire gauze Cotton Ring stand Directions: Into the flask place 10 c.c. of water. To this add 50 g. of hypo. Slowly heat the flask until all of the hypo is dissolved. Close the mouth of the flask with some cotton and very carefully set it aside to cool. Take every precaution not to disturb A YEAE IN SCIENCE 41 the flask while it is cooling. When it feels cool, re- move the cotton, insert the thermometer into the liquid, and note the temperature. Shake the liquid until it begins to crystallize. As it does so, carefully observe the changes in temperature. Explain these results. What effect does a body of water which is freezing have upon the temperature of the surrounding atmosphere ? Why ? Exercise 18. Change from a Liquid to a Gas. Object: To determine the^heat necessary to convert 1 c.c. of water into steam or water vapor. Apparatus Flask Wire gauze Thermometer Bunsen burner Asbestos cover for flask Ring stand Flame protector Graduate, 100 c.c. Directions: Set up apparatus as in Exercise 14. Obtain the heat of the flame as in that exercise. Con- tinue to heat the water, noting the exact instant when it begins to boil. Allow it to boil for ten minutes. Turn off the gas and set the water aside to cool. After cooling, measure the water remaining in the flask. Tabulate data as follows : 1. Amount of water at beginning. 2. Amount of water at end. 3. Loss in water (calculated). 4. Calories given off by flame per minute (calcu- lated). 5. Length of time water boiled. 42 LABOKATOKY MANUAL 6. Number of calories used in boiling away water (calculated). 7. Number of calories required to boil away 1 c.c. of water (calculated). 8. Did the temperature rise during boiling? 9. What became of the heat? Exercise 19. Effect of Pressure on Boiling- Point. Object: To show the effect of lowering the pressure on the boiling point of water. Apparatus Air pump Flask Thermometer Bun sen burner Ring stand Wire gauze Belljar Vaseline Rubber stopper Beaker Fig. 15. Directions : A. Half fill a flask with Avater and place it on a ring stand over the flame of a Bunsen burner. A YEAE IN SCIENCE 43 Heat the water to about 60° C. Then remove the llask and place it on the receiver of the air pump. Rub the edge of the belljar with vaseline and then lower it over the flask. Exhaust the air- from under the belljar. What happens to the water? What is the temperature at which water boils under ordinary conditions? How can you explain the results of this exercise? If the belljar is sufficiently high, the thermometer should be left in the flask. Repeat the experiment several times, each time recording the temperature at which the water boils. B. Again half fill the flask with water and heat it until it boils. After it has boiled about two minutes, insert the rubber stopper. Allow the flask to cool a few minutes and then invert it on the ring of the ring- stand. Pour cold water over the flask. What happens to the water? Why? Will the boiling point of water be above or below 100°C. on top of a mountain? Why? It is impossible to cook potatoes by boiling on top of a very high mountain. Why ? Exercise 20. How Water is Distilled. Object: To determine how substances dissolved in water may be separated from it. Apparatus I' lask Bunseii burner One-bole rubber stopper Ring stand Delivery tube \Yire jjauze Test tube Salt Beaker 44 LABORATORY MANUAL Directions: Into a flask put about 200 c.c. of water and 3 or 4 teaspoonfuls of salt. Stir or shake the mix- ture until all the salt has dissolved. Then insert the delivery tube through the stopper and close the flask. Heat the solution to boiling. Put the free end of the tube into a test tube which is surrounded by cold water. Keep the water cold by adding ice or snoAv. Boil the water in the flask for about 5 minutes. Taste the ^S^--C -^2*^ F[S- 16- liquid that has distilled over into the test tube. Is there any salt present ? Of what commercial value is distillation? Exercise 21. Evaporation. Object: To show a result of evaporation. Thermometer Chloroform Apparatus Absorbent cotton Directions: Wrap a small bit of cotton tightly about the bulb of a thermometer. Record the reading of the thermometer. Saturate the cotton with chloro- form and wave the thermometer in the air to evap- orate the chloroform. -As it evaporates what change A YEAK IN SCIENCE 45 in temperature do you note? How do you account for this change? See Exercise 18. Water, ether, or alcohol may be used in place of the chloroform. Place a drop of chloroform on the back of the hand. What is the sensation produced as the chloroform evaporates? What is the principle used in the manufacture of ice by the use of ammonia? CHAPTER VI PHYSICAL AND CHEMICAL CHANGES Exercise 22. Physical Change. Object: To determine the nature of a physical change. Apparatus Salt Distilled water Evaporating dish Wire gauze Bunsen burner Glass stirring rod Ring stand Directions: Place some salt in an evaporating dish. Cover it with dis- tilled water. Stir it with, the glass rod. What happens to the salt ? Place Fis. n. the evaporating dish with the solution on the wire gauze over the flame. Heat the solution slowly until 46 LABORATORY MANUAL all the liquid has evaporated, being careful not to burn the substance left in the dish. Taste the residue. What is it? Has its form changed? Its nature? Changes which do not involve a change in the composi- tion of substances are called physical changes. Exercise 23. Chemical Change. Object: To determine the nature of a chemical change. Apparatus Sugar Wire gauxe Sulphuric acid Test tube Evaporating dish Potassium iodide crystals Bunsen burner Mercuric chloride crystals Glass stirring rod (poison) Ring stand Mortar and pestle Directions : A. Cover some sugar in the evaporating dish with sulphuric acid. Stir the substance with the glass rod. What happens? Place the solution on the wire gauze and slowly heat it. What happens? Does the resulting substance resemble either the acid or the sugar with which you started? Changes which involve a change in the composition of substances and result in' the formation of new sub- stances are called chemical changes. Classify the following under the head of chemical or physical change respectively : A change from ice to water; water to ice; water to gas; gas to water; action of hydrochloric acid on marble as used in Exercise 6; burning of wood; cider to vinegar. B. The following experiments are to be performed A YEAR IN SCIENCE 47 by instructor only : Rub together in the mortar a few crystals of potassium iodide with a few of mercuric chloride. What evidence appears that a new substance is formed ? Dissolve a few crystals of potassium iodide in water in a test tube. In another dissolve about an equal quantity of mercuric chloride. Warm water will hasten solution. Pour a little of the potassium iodide solu- tion into a third test tube, and gradually add mercuric chloride solution to it. The red precipitate is the same substance as was formed when the different kinds of crystals were rubbed together. CHAPTER VII CHEMICAL PHENOMENA Exercise 24. Mechanical Mixture. Object: To demonstrate a mechanical mixture. Iron filings Wire gauze Salt Ring stand Magnet Glass stirring rod Beaker Mortar and pestle Evaporating dish Funnel Bunsen burner Filter paper Directions: Mix together in a mortar 2 grams of salt and 2 grams of iron filings. By means of a magnet, try to separate the iron from the salt. What is the result? Now pour the contents of the mortar into a beaker. Add 20 c.c. of water to the mixture, and with 48 LABOEATOEY MANUAL a glass stirring rod, stir until the salt is all dissolved. Filter and evaporate the filtrate (the liquid which passed through the filter) to dryness, using the evapo- rating dish. What is the substance left in the evaporating dish? To de- termine this, taste it. With the magnet, test the substance left on the filter paper. What is it ? In mix- ing together iron filings and salt were the prop- erties of either changed? If two or more sub- stances are placed to- Fig- 18- gether, and each retains its original properties, the resulting substance is called a mechanical mixture. Exercise 25. Chemical Synthesis. Object: To determine the formation of compounds. Apparatus Test tube holder Bunsen burner Mortar and pestle Iron filings Flowers of sulphur Test tube Magnet Directions: Note carefully the nature of the ele- ments, iron filings and sulphur. Grind together in a mortar 2 grams of sulphur and 2 grams of iron filings. The grinding is to be done very thoroughly. With a A YEAR IN SCIENCE 49 magnet try to separate the iron from the sulphur. What is the result? Place the mixture in a clean, dry test tube. With the test tube holder, hold the tube over the Bunsen flame until the contents begin to glow. Remove it from the flame until the glow ceases, then heat the tube again very strongly for a few minutes. Remove the tube from the flame. When cool, break the tube. Examine the contents. Test them with the magnet. What changes have the substances under- gone? The new substance is a chemical compound called iron sulphide, resulting from the chemical union of the elements, iron and sulphur. Another experiment to show chemical synthesis is to grind together in a mortar, mercury and iodine crystals. Exercise 26. Chemical Analysis. Object: The decomposition of compounds. Apparatus Mercuric oxide Pine splinter Hard glass test tube Bunsen burner Test tube holder Directions: Such characteristics as hardness, color, form, etc., are known as the physical properties of a substance. Note carefully the physical properties of mercuric oxide. Place a very small amount of it in a test tube and heat it very thoroughly. With the test tube in the flame, insert a glowing pine splinter into the tube. Continue heating the mercuric oxide. What change 50 LABORATORY MANUAL do you note in the ember? Where does the substance come from that causes this change? This same sub- stance is found in the air and is called oxygen. Examine the sides of the tube a little above the mer- curic oxide. What do you find there? From what substance did it come? Scrape it from the sides of the tube and shake it out on to a piece of paper. Thus mercuric oxide has been separated by means of heat into its elements, oxygen and mercury. The process of separating or decomposing a compound into its ele- ments is known as chemical analysis. CHAPTER VIII CHEMICAL ELEMENTS Exercise 27. Carbon. Object: To determine some of the properties of carbon. Apparatus Wood charcoal Pine splinter Lime water Crushed marble Test tube Dilute hydrochloric acid Beaker Directions : One of the forms in which carbon occurs is charcoal. Examine a stick of wood charcoal. What is the color? Is it soluble in water? Light the stick of charcoal. Does it burn freely? Does it give off any odor in burning? Thrust the lighted charcoal into the mouth of a test tube containing some clear lime water. A YEAE IN SCIENCE 51 Allow it to burn in the tube for a minute, then remove it and mix the lime water with the gas in the tube by shaking. What is the effect of the gas on the lime water? Then what must this gas be? (See Exercise 6.) Rinse the test tube with water. Again place some lime water in it. Light the pine splinter and thrust it into the test tube. Remove the splinter and shake the lime water. What change do you note in the lime water? Does wood contain carbon? Place a few pieces of marble in a clean test tube. Pour on it a little dilute hydrochloric acid. What hap- pens? This is a chemical action between the marble and the acid. Over the mouth of this test tube place the mouth of another to collect some of the gas given off. Remove the second test tube, pour into it some lime water and shake. What is the effect on the lime water? What does this indicate? Hydrochloric acid contains no carbon. Does marble? What are the properties of carbon as found in char- coal? In what substances did you find carbon? What other forms of carbon do you know? Exercise 28. Phosphorus. (Demonstration.) Object: To determine some of the properties of phosphorus. Apparatus Yellow phosphorus Forceps Ivcd phosphorus Knife Evaporating dish Filter paper Directions: (('ATTION — Yellow phosphorus must be 52 LABOEATOEY MANUAL kept under water and cut under water. It must not be allowed to come in contact with the bare skin.) With the forceps place a small piece of yellow phos- phorus in the .evaporating dish, which has been filled with water. Cut off a piece with the knife. Does it cut easily? What is the appearance of the new cut sur- face ? What is the consistency of phosphorus ? Pick up a small piece with the forceps and hold it in the air a moment. What takes place? Does phosphorus give off an odor in burning? Why is it kept under water? Rub phosphorus on a piece of filter paper and examine the paper in the dark room. What do you see? Will phosphorus burn at a low temperature? Place a small piece of freshly cut phosphorus in a dish of water exposed to the light. Cover with a bell jar and leave for at least 48 hours. Does any change in color occur ? Examine a small quantity of red phos- phorus. Compare in all details its properties with those of yellow phosphorus. What is the difference between an ordinary and a safety match? Exercise 29. Sulphur. Object: To determine some of the properties of sulphur. Apparatus Flowers of sulphur Beaker Deflagrating spoons Silver spoon Eoll sulphur Bunsen burner Test tube Test tube holder Directions : Examine a little of the flowers of sul- A YEAR IN SCIENCE 53 phur. What is its nature? Color? Has it any odor? Taste? Place some of it in a small beaker and cover with water. Does it dissolve? With a very low flame slowly heat a little sulphur in a test tube. What change takes place ? What is its color? Continue to heat slowly and watch very care- fully the change in consistency and color. When the substance thickens and turns a darker color, continue to heat it until it becomes a thin liquid and then pour part of it into a beaker of cold water. Immediately work the substance in the water with the fingers. What is its nature? Is it elastic? Continue to heat the sulphur in the test tube. What collects on the sides of the tube? What is it? Place a little sulphur in the deflagrating spoon and ignite it. Does it burn easily? What is the color of the flame? Do the fumes have an odor? When sulphur burns it forms a gas called oxide of sulphur, or sulphur dioxide. Examine some roll sulphur. How does it differ from the flowers of sulphur? Place some sulphur in the bowl of a silver spoon or on a silver coin. Heat it slightly. What is the effect of sulphur on silver? The compound formed is called sulphide of silver. Enumerate the properties of sulphur you have learned. Exercise 30. Iron. Object : To determine some of the properties of iron. 54 LABOEATOEY MANUAL Apparatus Iron wool Acid potassium oxalate Iron filings Acetic acid Magnet Ammonium hydroxide Beaker Sulphuric acid Oxalic acid Directions: A. Place some of the iron filings on a piece of paper. Slowly bring the magnet in contact with the filings. Raise the magnet. Are there filings attached to it? Are other things attracted to it in the same way? To answer this question try the magnet on a silver coin, a penny, a pin, a piece of gold, etc. Moisten some iron wool and set it aside in a beaker for forty-eight hours. What is the appearance of the iron wool at the end of that time? Do you know what this reddish deposit is? This is a compound which iron forms with the oxygen of the air in the presence of moisture. From your general observations Avhat other properties of iron could you add to this list? B. Linen, cotton, and other textiles frequently become soiled with such a reddish deposit, and a "rust stain" results. Being insoluble in water and alkalies, such stains are not removed by the ordinary washing processes. However, rust or iron oxide is converted to a soluble salt by the action of suitable acids. Stain several pieces of white cotton cloth with iron rust. This may be done by placing moistened iron filings on the cloth and leaving them for about thirty A YEAR IN SCIENCE 55 minutes. Treat each separately with one of the following : 1. Dilute sulphuric acid. 2. Dilute sulphuric acid, then wash and neutralize with weak ammonium hydroxide. 3. Dilute acetic acid; wash, etc., as in 2. 4. Oxalic acid, dissolved in hot water; wash, etc. 5. Acid potassium oxalate, dissolved in hot water ; wash, etc. Which is the most rapid and effective in action? Examine specimens number one and number two after several days have elapsed. Has the acid attacked the cotton as well as dissolved the stain? Why should the cloth always be thoroughly washed after treatment? What is the added advantage of using ammonia water ? Exercise 31. Oxygen. Object: To determine some of the properties of oxygen. Apparatus Potassium chlorate Bunsen burner Manganese dioxide Large mouth bottles Florence flask Glass plates Rubber stopper (one-hole) Deflagrating spoon Pneumatic trough Charcoal Delivery tube Sulphur Ring stand Pine splinter Wire gauze Lime water Directions: Place in the flask a mixture of four parts of potassium chlorate and one part of manganese dioxide. Insert into the mouth of the flask the rubber 56 LABORATORY MANUAL stopper carrying the delivery tube. Place the free end of the tube in the pneumatic trough. Place the flask on the wire gauze over the flame of a Bunsen Fig. 19. burner and heat gently. By heating the mixture a gas, called oxygen, is given off. Allow the first gas from the flask to escape. Why? Then place the delivery tube under the mouth of an inverted bottle filled with water. When the bottle is filled with oxygen, cover it with a glass plate and set it aside. Fill five other bottles with oxygen in the same manner. 1. Examine the gas in one bottle. Has it any color? Any odor? 2. Place a piece of charcoal in the deflagrating spoon and heat it until it glows. Quickly thrust it into a bottle of oxygen. Note the result. What property does this show oxygen to possess? What are the A YEAE IN SCIENCE 57 fumes given off from the burning charcoal ? To deter- mine this pour some lime water into the bottle and shake. 3. Into the deflagrating spoon place some powdered sulphur. Light the sulphur and lower it into a bottle of oxygen. What is the result? After the sulphur has burned, smell the fumes in the bottle. What are they? How were they formed? 4. Burn a pine splinter until a good ember is formed. Extinguish the flame and thrust the glowing ember into a bottle of oxygen. What happens? Does oxygen burn? Does it support combustion? Is it found in the air? Why do you think it is or is not found in the air? Summarize the properties of oxygen you have learned from this exercise. Exercise 32. Hydrog'en. Object: To determine some of the properties of hydrogen. Apparatus Granulated zinc Delivery tube Dilute hydrochloric acid Pneumatic trough Flask Pine splinter Test tubes Large mouth bottles Thistle tube Directions: Place a handful of zinc in the flask. Into the mouth of the flask insert a rubber stopper, fitted with the thistle tube and the delivery tube. Pour enough hydrochloric acid through the thistle tube into 58 LABORATORY MANUAL the flask to cover the zinc. What action is observed? This is a chemical action between the zinc and the Fig. 20. acid. The gas given off is hydrogen. Allow the gas to escape from the delivery tube for a few seconds. Why? Fill a number of bottles with hydrogen by the downward displacement of water. Keep the bottles inverted. 1. Examine the hydrogen in one of the bottles. Has it any color ? Odor ? 2. With the mouth downward, thrust into a second bottle of hydrogen a lighted splinter. What is the result? Docs the splinter continue to burn? Does the hydrogen burn? If so, what is the color of the flame? Examine the sides of the bottle? What do you find there ? Where did it come from ? What is the oxide of hydrogen? 3. Allow a third bottle of hydrogen to stand mouth upward for three minutes. Then insert a lighted splin- ter. Is the hydrogen still there? Is hydrogen lighter or heavier than air? A YEAR IN SCIENCE 59 Exercise 33. Nitrogen. Object: To determine some of the properties of nitrogen. Apparatus Ammonium chloride Bunsen burner Sodium nitrite Wire gauze Flask Wide mouth bottles Rubber stopper Glass plates Delivery tube Pine splinter Pneumatic trough Thistle tube Ring stand Directions : Place 8 grams of sodium nitrite, 3 grams of ammonium chloride, and 15 c.c. of water in the flask. Into the mouth of the flask insert a rubber stopper, fitted with a thistle tube and a delivery tube. Place the flask on the wire gauze over the Bunsen flame. Heat gently and allow the first gas to escape. Fill several bottles with water, and invert them in the water in the pneumatic trough. Fill the bottles with the gas from the flask by doAvnward displacement of water. The gas given off is nitrogen. Examine a bottle of nitro- gen. Has it color? Odor? Into a second bottle of nitrogen insert a lighted splinter. Does the splinter continue to burn? Does the nitrogen burn? What are the properties of nitrogen? 60 LABORATORY MANUAL CHAPTER IX ACIDS, BASES, AND NEUTRAL SUBSTANCES Exercise 34. Acids and Bases. Object: To determine the properties of acids and bases. Apparatus Hydrochloric acid (dilute) Red litmus paper Nitric acid (dilute) Blue litmus paper .Sodium hydroxide Glass rod Ammonium hydroxide Beaker Directions: Examine some of the dilute hydro- chloric acid. Describe its odor. Dip the glass rod into the acid and touch it to the tip of the tongue. What is its taste ? Rub some acid between the fingers. Describe its "feel." Dip a piece of red litmus paper into the acid. What is the effect of the acid on the paper? Dip a piece of the blue litmus into the acid. What effect does the acid have on the blue paper? Apply the above tests to the nitric acid. Are the results the same as those obtained with the hydro- chloric acid? These are methods commonly used to detect any acid. Examine some sodium hydroxide. Describe its odor, taste, "feel," using the methods given in the study of acids. Test this substance with both red and blue litmus paper. What are the results? Examine ammo- nium hydroxide in the same manner. How do the results compare with those obtained with sodium A YEAR IN SCIENCE 61 hydroxide? These substances are called bases. All bases react similarly to these tests. Exercise 35. Salts and Neutralization. Object: A study of neutralization and its results. Apparatus Hydrochoric acid (10%) Blue litmus paper Sodium hydroxide (10%) Glass rod Evaporating dish Bunsen burner Red litmus paper Directions: Pour one cubic centimeter of hydro- chloric acid into the evaporating dish. To this add, drop by drop, some sodium hydroxide. Stir constantly to mix the liquids. Test the solution frequently with both kinds of litmus paper. If too much sodium hydroxide is added, the solution will turn the red litmus paper blue ; if too much acid is present, the blue litmus will turn red. Balance the solution by alternately adding a few drops of acid and base until neither litmus paper is affected. When a solution has no effect on either red or blue litmus paper, it is said to be neutral. The process of mixing an acid and base to produce a neutral substance is called neutralization. Over a flame evaporate the solution. Examine the residue. What is its appearance? Does it taste like any substance with which you are familiar? This product is called a neutral salt. Dissolve some of it in water. Does the solution have any effect on litmus paper? What was the substance evaporated? What, then, are the products of neutralization? 62 LABORATORY MANUAL CHAPTER X WATER AND AIR Exercise 36. A Simple Electric Cell.* Object: To show how a current of electricity is produced. Apparatus Strip of amalgamated zinc, 4x1 (Strip of copper 4x1) Two pieces of copper wire, each 12 in. long A block of wood about 4x1x1 Dilute sulphuric acid, about 5C/C. A compass or magnetic needle Note : On one side, at the mid-point of the long axis of the block of wood, tack the strip of zinc perpen- dicularly with one inch of the zinc projecting above the wood and two inches extending below. On the opposite side of the wood, similarly fasten the strip of copper. To the upper- ends of the metallic strips attach the copper wires. Directions : Fill the Flg 21 glass about f full of the *This exercise is given here for those teachers who wish to present to their classes some preliminary facts about electricity before performing Exercise 37. A YEAE IN SCIENCE 63 sulphuric acid solution. Put the block of wood across the tumbler with the free ends of the metals dipping into the acid. Eecord what happens. Are there any bub- bles of gas given off? From where do they come? Touch the free ends of the copper wires to your tongue. What effect do you notice ? What is the evidence that an electric current is passing through the wires ? Twist the free ends of the wires together and hold them over the compass. How is the compass affected? Is there evidence of an electric current? Eecord all of your observations. Find out from some source what is the origin of the electric current. Exercise 37. Composition of Water. (Demonstra- tion.) Object: To determine the composition of water. Apparatus Electrolysis apparatus Pine splinters Sulphuric acid (5%) Belljar Electric current Directions: Fill the apparatus with water con- taining 5% sulphuric acid. When the apparatus is almost filled, into each arm insert the burette, at the same time opening the cock to drive out the air. After the burettes are completely filled, connect the positive and negative poles of the series with the city current. Note what happens. From what place do, the bub- bles arise ? In which tube do they form more rapidly ? What is the ratio by volume of .the , gases int the 64 LABOKATORY MANUAL two tubes ? This may be accurately obtained by taking the readings on the burettes. When the tube contain- ing the most gas is three-fourths full, disconnect the current. Remove the entire apparatus into a trough of water, so that the open ends of the arms are submerged. Then remove each burette separately, the one of less volume first. Cover the mouth of the burette with the finger and invert. Remove the finger and quickly insert a lighted splinter into this gas. What happens? What is this gas? Remove the other burette in the same manner as the first. Hold the mouth downward and insert a lighted splinter. What happens? What is this gas? (See Exercise 32.) Of what elements is water composed ? What proportion by volume? Exercise 38. Composition of Air. Object: To determine the composi- tion of air. Fig. 22. Pneumatic trough Belljar Evaporating dish Phosphorus Lime water Apparatus Beaker Glass plate Pine splinter Test tube Iron filings Directions: A. Fill the beaker with lime water and A YEAR IN SCIENCE 65 leave it exposed to the air for 48 hours. At the end of that time examine the appearance of the surface of the water. What does this indicate? What then forms a part of the air? Does wood burn in the air? What element does this indicate to be present ? How does the burning of a pine splinter in the air compare with the burning in Exercise 31. part 4? What does this indicate ? Pour water, of room temperature, into the pneumatic trough. On the surface of the water float the evaporating dish con- taining a piece of phosphorus, the size of a small pea. Ignite the phorphorus and cover quickly with the bell jar. What is the result? With what does the phos- phorus unite in burning? When does it stop burning in the jar? What are the white fumes? Leave the experiment until these fumes have been dissolved ii? the water. Does the water rise in the jar? What part by volume does it occupy? This represents the approximate proportion of oxygen in the air. Slip a glass plate over the mouth of the belljar and invert it. Examine the gas. Has it color? Odor? Will it support combustion? Does it burn? What is this gas? (See Exercise 33.) Air is a mixture of gases of Fig. 23. 66 LABORATORY MANUAL which the above are the chief ones. If this experiment- is performed at home, a small candle may be lighted under the belljar instead of phosphorus. B. In a test tube place about a half teaspoonful of iron filings. Cover them with water. Then invert the test tube and allow the water to run out slowly so that the filings will adhere to the sides of the tube. Place the mouth of the tube in a beaker filled with water and allow the apparatus to stand for twenty-four hours. At the end of that time measure the height to which the water has risen in the tube. What part of the air by volume did the oxygen occupy? What change has' taken place in the iron filings? How do the results in this experiment compare with those in the one above? CHAPTER XI ATMOSPHERE Exercise 39. Does Air Exert Pressure? (Demon- stration.) Object: To demonstrate air pressure. Apparatus Oil can with screw top Bunsen burner Magdeburg hemispheres \Yater Air pump Directions : A. Screw the Magdeburg hemispheres on to the plate of the air pump and open the stop-cock. 'Exhaust the air from the hemispheres and close the A YEAE IN SCIENCE 67 stop-cock. Try to separate the hemispheres. What do you find? Open the stop-cock and try to separate the hemispheres. How does this result compare with the result obtained in the first instance? How do you explain these r.esults? B. Fill the tin can with water to a depth of two inches. With the aperture open, place the apparatus over the Bunseii flame and heat until the water boils. Tightly close the aperture and remove the apparatus. Let it cool and note what happens. How do you explain the result? Exercise 40. Barometer. (Demonstration.) Object: To study a means of measuring atmospheric pressure. Apparatus If! Mercury Glass dish Torricellian tube Barometer Meter stick Directions: Fill the Torricellian tube with mercury. Carefully close the open end with the thumb and invert the tube into a basin of mer- cury. Remove the thumb from the open end of the tube under the mercury in the .basin. Measure the height of the column of mercury in the tube above the surface of the mercury in the basin. What keeps the mercury in the tube? Would the same results be obtained if both ends of the tube \\cre open? Fig. 24. 68 LABORATORY MANUAL Examine the standard barometer. How does the height of the column of mercury in the tube compare with that of the barometer ? The principle upon which each is constructed is essentially the same. The barom- eter is an instrument used for measuring atmospheric pressure. Exercise 41. Siphon. Object: To demonstrate the action of a siphon. Apparatus Rubber tubing Battery jars Directions: Fill a battery jar with water and place it on top of the desk. Immerse a piece of rubber tubing about 3 feet long into the jar of water. When the tube is filled with water, close one end of the tube by pinching between the fingers. Place a second battery jar on a chair or on the floor below, but near, the first jar. Quickly remove the closed end of the rubber tube and put it into the lower vessel. Release the tube. What happens ? What caused the water to run ? How long does the water run? What causes the water to rise in the first part of the tube ? What pulls it down into the longer arm? Instead of immersing the rubber tube in water to fill it, place one end in the jar of water. Then suck the air out of the tube until it is filled with water. Then remove the mouth and note the result. Can you suggest any uses for the siphon? A YEAE IN SCIENCE 69 Fig. 25. Exercise 42. Convection. Object: To show a method of producing currents in air and water. Bunsen burner Wire gauze Cotton, dandelion, or milk- weed fruits King stand Apparatus Test tube Water Test tube holder Fine sawdust 70 LABORATORY MANUAL Directions: A. Convection of Gases. Place the wire gauze on the ring stand and adjust a low flame under the gauze. Over the wire gauze drop very small bits of cotton or the fruits of dande- lion or milk-weed. Make a drawing indicating with arrows the path taken by the moving particles. How do you explain this action? B. Convection of Liquids. Place a small amount of fine sawdust in the bottom of the test tube. Fill the test tube three-quarters full of water. Adjust the Bunsen burner for a low flame. Hold the test tube at a small angle over the flame and heat it gently at one point at the base. Note very carefully the movements of the sawdust particles as the water becomes heated. Make a drawing, indicat- ing with arrows the direction taken by the particles in the water. How do you explain these movements? How does this result compare with that obtained with gas? Convection is the process by means of which heat is carried from a hotter to a colder substance by a moving fluid. Crystals of potassium permanganate may be used effectively in place of sawdust to show convection cur- rents in liquids. Exercise 43. Moisture in the Atmosphere — Con- densation. Object: To show the presence of water- vapor in the atmosphere. A YEAE IN SCIENCE 71 Apparatus Beaker Glass plate Ice Bunsen burner Flask Directions : A. Fill the beaker with small pieces of ice and water. Dry the surface of the beaker thor- oughly and set it aside, for about five minutes. At the end of that time what do you find on the surface of the beaker ? How do you account for it ? B. Fill the flask half full of water and place it over the Bunsen flame. Heat the water until it boils. Hold a dry glass plate over the mouth of the flask. What do you find on the plate? What is its source? Why did you use the glass plate ?. What happens, when the temperature of the atmosphere is suddenly lowered? Exercise 44. Study of the Weather Map. Object: To study the causes of weather changes. Apparatus Several weather maps for each pupil. These maps should include some with well developed low regions and some with well developed high areas. Directions: At the lower left corner of the map are "Explanatory notes." Kead them. At the lower right corner of the map is the " Wind-barometer indication. ' r Study this. Locate the isothermal and isobaric lines. What does each mean? All barometric readings have been reduced to what they wrould be if the place were at sea level. 72 LABOEATOEY MANUAL A YEAK IN SCIENCE 73 74 LABORATORY MANUAL Select a map with a well developed low region. This low region is called a cyclone or cyclonic area. Using the scale of miles indicated on the map, find the approx- imate width of this low region. How many states does it cover? Can you tell in what direction it is moving? What is the air pressure (barometric reading) at the center of the low area ? ' How much would the barom- eter rise in being carried from the center of the low to the outer isobar of the area? What is the weather condition over the low region? Study the direction of the wind over the whole low area. To what conclusion do you come as regards the direction of the wind in the low region? About what is the average wind velocity of this area? Select another map with a well developed high area, having a number of isobars curving around the word high. This region is called an anticyclone or anti- cyclonic area. What is the air pressure at the center of this high area? How much would a barometer fall in being taken from the center of this high to the center of an adjacent low area ? What is the weather condition over the high area? Study the direction of the wind over the high region. What is the difference between the general direction of the wind over the high and low regions? What is the general direction of the movement of the high and low areas? Find out from some source how rapidly they move. Study the isothermal lines. What is their general direction? What is the lowest and Loi „ A YEAE IN SCIENCE 75 highest temperature recorded on the map? What rela- tion does temperature have to the high and low area regions ? Choose a map, give its date, and record for your locality, the temperature, direction of the wind, veloc- ity of the wind, barometer reading, state of the sky, and kind of precipitation, if any. CHAPTER XII SOILS Exercise 45. Water Capacity of Soils. Object: To determine the capacity for water of different soils. Apparatus Sand Leaf-mold Clay Tin cans Loam Balance and weights Directions: Expose the different soils used in this ercise to the room air for a period of two days. At the end of that time find the weight of the can. The can should have a number of holes in the bottom. Fill the can two thirds full of the air dried sand, and find the weight of both the can and the sand. Then compute the weight of the sand. Thoroughly saturate the sand with water and set it aside for about two hours. Again weigh the can with its contents. From this result subtract the weight of the can and dry soil. The difference represents the amount of water, 76 LABORATORY MANUAL by weight, which the sand is capable of holding. What per cent of the weight of the sand is the weight of the water ? Eepeat the above experiment for each of the soils: clay, loam, and leaf -mold, or any combination of soils suggested by the instructor. Is the water capacity the same for all soils?' Which holds the most? Which the least? Record results as follows : Sand Clay Loam Leaf- mold Sand and Leaf- mold Clay and Leaf- mold Weight of can Weight of can and dried soil Weight of dry soil ( calculated ) Weight of both with water Weight of water ( calculated ) Water capacity in per cent. Exercise 46. Soil Solutions. Object: To determine whether water in passing through the soil dissolves mineral substances. Apparatus Slips of Wandering Jew Evaporating dishes Bunsen burner Well water Rain water Flasks Ring stand Directions: A. Place 50 c.c. of well water in one evaporating dish and the same amount of rain water, A YEAE IN SCIENCE 77 or distilled water, in another. Evaporate the water in each dish over the Bunsen flame. What is left in each case ? How do you account for the difference ? B. In which kind of water do plants grow best? Fill one flask with well water and another with rain, or distilled water. In each flask place "slips" of Wandering Jew of about the same size. Change the water in the flasks two or three times a week for about a month. In which do the plants grow best? What is the explanation? CHAPTER XIII PLANTS DEPENDENT UPON AIR AND MOISTURE Exercise 47. Gross Structure of Leaves. Object: To study the parts of a leaf. Apparatus Lilac leaves Lily-of-the-valley leaves Directions : A. Parts. Carefully examine a lilac leaf. Make a drawing of the leaf. Label the broad expanded portion, the Made, and the stem by which it was attached, the petiole. Compare the lengths of the petioles on a num- ber of leaves on a lilac branch. From this observation what is one of the functions of the petiole? The sur- face of the leaf is provided with small openings or pores, called stomates, through which the leaf respires. 78 LABORATORY MANUAL At the discretion of the instructor these may be shown under the microscope. B. Venation. Examine the lilac leaf again. Note the continuation of the petiole through the blade. This is called the mid-rib, and its branches, the veins. Compare the arrangement of the veins in the leaves of any lily with that of the lilac leaf. How do they differ? These are examples of the two kinds of venation. Make a draw- ing of each and. label the lilac leaf, netted veined, and the lily leaf, parallel veined. Exercise 48. Chloroplasts. Object: To study the organs which contain the green coloring matter of plants. Apparatus Moss or Elodea leaves Scalpel Glass slides Compound microscope Cover glasses Directions: Place a drop of water on the center of a glass slide. In this put a leaf of elodea or moss and cover it with the thin glass cover. Examine this very carefully under the low power of the microscope. Note the oblong parts of which the leaf is composed. Each of these parts is a cell. Examine one of these carefully. What is its shape? What is the appearance of the wall, cell wall, surrounding it? Within the cell note the many small bodies, green in color. What is their shape ? How many are there in a A YEAE IN SCIENCE 79 cell? What is their arrangement? These small bodies contain a green substance known as chlorophyll and for that reason they are called chloroplasts (chloro menus green; plattein, to form). Within the cell there is an almost colorless, jelly-like substance known as protoplasm. This is the living part of the cell. It is somewhat granular in appearance. Upon careful exam- ination you may be able to see it. Exercise 49. Making of Food for Plants. Object: The relation of chlorophyll to starch forma- tion. Apparatus Variegated ^cranium Iodine Alcohol Beaker Bunsen burner Evaporating dish Corn starch Directions: Place a small amount of corn starch in an evaporating dish and pour a drop of iodine over it. What color does the starch turn? If, when iodine is placed on a substance, its color turns to a blue-black, starch is present. Place a geranium with variegated colored leaves in the bright sunlight for the greater portion of a day. Select a few leaves on the plant and sketch the blades to show the color patterns on them. Remove these leaves and immerse them immediately into boiling water to kill them. After five minutes boiling, place the leaves in a vessel of 96% alcohol to extract the chlorophyll. When the leaves become white, spread 80 LABOEATOKY MANUAL them on a white surface and cover them with a weak solution of iodine. In what part of the leaf is starch found? Has chlorophyll anything to do with starch formation ? Exercise 50. Making of Food for Plants, continued. Object: To determine the relation of sunlight to starch formation. Apparatus Nasturtium Iodine Alcohol Beaker Bunsen burner Evaporating dish Corn starch Directions: Place a nasturtium plant in the bright sunlight and another in a dark room. On the after- noon of the second day remove several leaves from each plant, being careful to keep the two sets of leaves separate. Kill them and extract the chlorophyll in the same manner as directed in the preceding exercise. Place the leaves on a white surface and test each for the presence of starch. Is starch found in both sets of leaves? What does this indicate concerning the rela- tion of sunlight to starch making ? Exercise 51. By-Products in Food Making. Object: To determine the gas given off when plants make starch. Apparatus Green water plants Funnel Mushrooms Test tube Glass jar Pine splinter A YEAE IN SCIENCE 81 Directions: Place some green water plants under a funnel in clear water, as in Figure 28. Place the jar in sunlight for several days, and allow any escaping gas to collect in a test tube placed over the stem end of the funnel. When there is an inch or more of gas in the test tube, remove the tube from over the fun- nel, being careful not to take it out of the water in the jar. After closing the mouth of the tube with the thumb, remove it from the jar of water. Invert the tube, then remove Fis"- 28< the thumb and quickly thrust a glowing pine splinter into the gas in the tube. What is the result? What gas does this indicate is present? Repeat the same experiment, using mushrooms in place of the green plants. What result do you obtain this time? How do you account for the difference between this result and the one obtained with the green plants? Exercise 52. Transpiration. Object: To show that the excess water in plants is given off by the leaves. Glass tumblers Card board Apparatus Paraffin Geranium Directions: Cut off a small branch of geranium. Place the cut end of it through a hole in a piece of 82 LABORATORY MANUAL cardboard. Fill one tumbler with water and place the cardboard over it, with the cut end of the geranium extending into the water. Paraffin the entire upper surface of the cardboard to prevent any evaporation of water through it or around the stem of the geranium. Over the leaves of the geranium invert the second tumbler and set the experiment aside for a few hours. Then examine the inside of the upper tumbler. How do you account for the condition found ? Fig. 29. Exercise 53. Rate of Transpiration. Object: To determine the difference in the rates of loss of water in different plants. Cobalt paper Rubber plant Nasturtium Apparatus Scissors Paper clips Directions: Cobalt paper is prepared by saturating filter paper in a solution of cobalt chloride. The paper is then thoroughly dried in an oven. What is the color of the paper? On a small piece of paper place a drop of water. What happens ? Cut several pieces of paper, each about one inch square. With a clip fasten one piece on the upper, and another piece on the under surface of a leaf of a rubber plant. Note the exact time that this is done. Watch the paper. What change do you observe? How long did it take to produce this A YEAR IN SCIENCE 33 change ? What causes it ? Do the papers on the upper and lower surfaces change at the same time? What does this indicate? Repeat this experiment on leaves of the nasturtium and of several other plants. At what rate do you find water is given off from their leaves? Do all plants transpire at the same rate? Exercise 54. Is Air Necessary? Object: To determine whether air is necessary for the growth of plants. Apparatus Wide mouth bottles Paraffin Kubber stoppers Glass plate Seeds (well soaked) Bell jar Geranium plant Blotting paper Directions: A. Place blotting paper to the depth of an inch in the bottom of each of two wide mouth bottles. Saturate the paper thoroughly with water. Fill each bottle three-fourths full of soaked pea seeds. Close one bottle tightly with a rubber stopper to exclude the air and leave the second bottle open to the air. Place the two bottles under the same condi- tions of temperature and light. Make and record daily observations for one week on the growth of the seeds in the bottles. What do you conclude from the results? B. Do other forms of plant life require air? To determine this select two potted plants of equal size. Water both plants thoroughly and place one under a belljar. Make this air-tight by sealing the open end of the belljar to a glass plate. Now place the 84 LABORATORY MANUAL two plants under the same conditions of light, moisture, and temperature. Do not change these conditions until the experiment is completed. Note and record results as you did with the seeds. At the end of a week do you notice any differences in the two plants? What does this indicate? Exercise 55. Exchange of Gases in Respiration. Object: To determine the gases exchanged in res- piration of plants. Apparatus Wide mouth bottles Pine splinter Green plants Stoppers Lime water Directions: Fill three bottles to the depth of one- half inch with water. Into two of the bottles place a few shoots of green plants. Close the three bottles tightly with rubber stoppers and place them in a dark room until the next recitation. What gas was in the bottles when the experiment was set up? Is this same gas present in the bottles containing the green plants at the end of the experiment? In the bottle without plants? To determine this, insert into one of the bottles with plants a lighted splinter. What is the result? In the same manner insert a lighted splinter into the bottle having no plants. What is the result? What do these results indicate? Test the gas in the third bottle with lime water. What is the effect ? From these results what gases are exchanged in respiration of plants? A YEAB IN SCIENCE §5 Exercise 56. Roots. Object: A study of the kinds and functions of roots. Apparatus Lupine seedlings Carrot Wheat seedlings Dahlia roots Directions: Examine the root of a lupine. Is there a single branch, or are there several of equal size arising from the same point? These are called the primary roots. The roots growing from the primary are called the secondary roots. Have they any definite arrange- ment on the single primary root of the lupine? At what angle do they grow from the main root? What function of the root does this suggest? With the lupine compare a carrot, radish, beet, or dandelion root. How do the latter differ from the lupine? What other function does this suggest for some roots ? Examine the roots of some grain seedlings. Do they have a single primary root or many fibrous roots? Make observations similar to those made on the lupine root. What difference do you observe? Compare the dahlia root with those of any grain. There are two principal kinds of underground roots. Those growing with a single main branch are called primary tap roots, while those with several main branches are called mul- tiple primary or fibrous roots. An example of the tap root is the lupine ; of the fibrous roots, the grains. When the tap root is used for food storage as in the radish, it is called a fleshy tap root. When the fibrous §6 LABOEATOEY MANUAL roots store food, as in the dahlia, we have the fleshy fibrous or fascicled roots. Sketch one of each of the above kinds of roots. Exercise 57. Roots as Orguns of Absorption. Object : To study root hairs and the path of liquids through the root. Apparatus Petri dishes Carrot Blotting paper Eosin solution Eadish seeds Directions : A. Line the bottom of a petri dish with blotting paper. Moisten it thoroughly and scatter over it a half dozen radish seeds. Cover and set aside for forty-eight hours. At the end of that time examine the roots which have been formed. The fine hair-like growths found along the surface are called root hairs. Are they found on all parts of the root? What is the condition of the tip of the root ? The little yellow portion over the tip of the root is the root cap which protects the delicate portion of the root tip. Make an accurate drawing showing root hairs and root cap. The mineral foods for plants are dissolved in the soil water. These substances enter the roots by diffusion through the root hairs. B. Make a longitudinal section of a carrot or any other good tap root. How many different regions do you distinguish? The central portion is the woody part, outside of which is the cortex. Surrounding the whole A YEAE IN SCIENCE 87 is a thin skin, the epidermis, one layer of cells thick. Make a cross section of the carrot and identify the parts. Make a drawing of both the cross and the longitudinal sections. To determine the paths of liquids through roots, place the cut end of a carrot in eosin solution for a number of hours. Make a cross section and examine. Indicate in the drawing of the cross section the region through which the liquid passed. Exercise 58. External Structure of Stems. Object: ,To study the external characteristics of stems. Apparatus Box elder twi«;s Dissecting microscope Scalpel Directions: Procure a twig of box elder about two feet in length. Examine it carefully, noting the gen- eral characteristics of the bark. At intervals on the twig notice the small blister-like elevations, the lenti- cels. These are openings through the bark of young stems for the interchange of gases. On a twig of this season's growth, how are the leaves arranged? On the older portions of the stem note the leaf scars. Do you find any buds on the stem ? What relation do they bear to the leaves or to the leaf scars? Do you find rings of narrow scars on the stem? What difference in the appearance of the stem above and below these rings? Prom what were these rings of scars caused? 88 LABOKATORY MANUAL How would you determine the age of the branch from the external markings? From the external structure, how would you distinguish a stem from a root ? Draw a twig to show the above mentioned parts. Exercise 59. Internal Structure of Stems. Object: To study the internal structure of stems. Apparatus Box elder twigs Scalpel Corn stems Dissecting microscope Directions : A. Corn Stem : Take an internode of an old corn stalk. Note on the cut end the outer rind surrounding the pith. Throughout the pith note the small dots of woody substance. Break the stalk into two parts. What do you find the small dots to be? Cut a longitudinal section and follow a few of the small fibres. Do they pass the length of the internode ? Through the node into the next internode? These thread-like fibres are called fibro-vascular bundles. Make a drawing showing these points. Under the lens of the dissecting microscope examine a cross section of the corn stem. Are the bundles regularly arranged ? Where are they most numerous, near the margin or toward the center? Can you determine of what the rind is composed? Make a drawing to show these points. B. Box Elder Stem : Make a longitudinal section of a small piece of box elder stem. How many parts do you distinguish? Where is the wood in this stem in refer- A YEAR IN SCIENCE 89 once to the pith? In a cross section of the stem, locate the parts seen in the longitudinal section. Note the lines running through the wood from the pith to the hark. These lines of pith are called medullary rays. How does the arrangement of the wood in the box elder stem differ from that in the corn stem? Make a drawing of both the longitudinal and cross section of the box elder, and label the parts. These stems are examples each of the two classes of stems of flowering plants. The corn stalk is an example of the monocoty- ledenous type, and the box elder of the dicotyledenous type. Exercise 60. Functions of Stems. Object : To determine one of the functions of stems. Apparatus Impatiens stem Beaker Eosin solution Scalpel Potato Directions: Cut off a number of branches of the Impatiens, of the Coleus, or of any other plant with a thin epidermis, and immediately place the cut end in a beaker of eosin solution. Similarly, cut off the end of a potato and place the cut end in the eosin solution. Set them aside for several hours. Then examine the stems to determine the paths taken by the red solu- tion. To see this more clearly, make a longitudinal section of the stem. What part of the stem is stained, the pith, wood, or epidermis? Does this stain extend into the leaves ? What is its course through the leaves ? 90 LABOKATOEY MANUAL Break off a leaf from the stem. Examine the end of the leaf stalk. What do the red dots on the end indi- cate ? Through Avhat part of the stem do liquids pass ? Make a drawing of a cross section of a stem to show the path of liquids. From general observations can you suggest other functions of stems? CHAPTER XIV FLOWERS AND SEEDS Exercise 61. A Typical Flower. Object: To learn the parts of a typical flower. Apparatus Trillium Forceps Dissecting microscope Needles Scalpel Directions: Carefully examine the flower of the trillium. Note the outer circle or whorl of leaf-like parts. How many are there? What is their size and shape ? Each of these parts is called a sepal; together they form the calyx. The second whorl of parts forms the corolla, each separate part being a petal. How many petals are there ? How are they arranged on the flower stalk in reference to the sepals? How do they compare in size and number to the sepals? What is the nature of the parts of the third cycle of floral parts just inside of the corolla? These are the stamens. How many are there? How are they arranged? Remove a stamen and note the slender A YEAR IN SCIENCE 91 stalk, the filament, with the enlarged end, the anther. On a mature anther note the powdery substance, the lH)lh-n. Make a drawing of a stamen showing these parts. In the center of the flower is the pistil. The large bulbous base is the ovary and the three parted pro- jection above is the stigma. Examine the stigma care- fully. Is its upper surface smooth or rough? Make a drawing of the pistil and label the parts. Make a cross section of the ovary. How many compartments do you find in the ovary? How many rows of seeds in each compartment? Where are they attached? Draw a cross section of the ovary. Make a diagram of the flower showing its parts and their relation to each other. Examine a number of other flowers to acquaint yourself with the floral parts. Exercise 62. Structure of Seeds. Object: To study the structure and parts of seeds. Apparatus Scalpel Lima beans (soaked) Needles Castor beans (soaked) Dissecting microscope Corn (soaked) Directions : A. Lima Bean. (a) External structure. Examine a lima bean. What is its color, size, shape? What are the charac- teristics of the outer coating, the testa of the seed? Note the scar, the Jiilum, on the concave side of the seed. How was this formed? At one end of the 92 LABORATORY MANUAL hilum, locate a small opening, the micropyle. Draw the bean from the side, and from the edge. Label the parts. (b) Internal structure. With the scalpel carefully open the seed by cutting through the testa along the convex side. Again examine the testa. Within, the testa notice the embryo plant consisting of : (1) the cotyledons, two large seed leaves. Are these joined? Where? (2) the plumule, the small rudimentary leaves be- tween the cotyledons ; (3) the hypocotyl, the rudimentary stem and root. Draw one of the cotyledons showing the plumule and the hypocotyl in position, labeling parts. B. Corn. In the bean, the entire contents of the seed consist of the embryo ; but this is not always the case. Often, as in corn, food is stored in a part called the endosperm. (a) External structure. Examine a kernel of corn. Note the outer covering ; also notice the groove where the embryo lies. The hilum and micropyle are at the small end of the kernel. Draw the flat side of the kernel showing the position of the embryo. (b) Internal structure. Remove the skin. Cut the kernel lengthwise, perpendicular to the flat surface. Most of the outside of the kernel consists of a white flowery substance, the endosperm. Of what use is this? Find the embryo. Locate the plumule, radicle, or root, and the cotyledon. Compare each of these parts with A YEAR IN SCIENCE 93 corresponding parts in the bean. Draw a longitudinal section of the corn, showing and labeling the coty- ledon, plumule, radicle, and endosperm. C. Castor bean. Compare the parts of the castor bean with those of the lima bean and corn. Exercise 63. Seed Dispersal. Object: To see how seeds are adapted for the pur- pose of distribution. Apparatus The available seeds and fruits of your locality Directions: Seeds are scattered in various ways by wind, water, animals, and by some contrivance for forcibly expelling the seeds. Examine the seeds and fruits supplied you, and classify each according to its means of distribution as follows : Seed or Fruit Wind W7ater Animal Other Methods How Adapted Dandelion Stick-tights Burdock Wild-cherry Mi Ik wood Wild geranium Morning-glory Impatiens Exercise 64. Conditions for Germination. Object: To determine the best conditions of tem- perature, moisture, and air supply for the germination of seeds. 94 LABORATORY MANUAL Apparatus Wide mouth bottles Rubber stoppers Blotting paper Thermometer Soaked seeds, peas, corn, etc. Refrigerator Oven Directions: A. Relation of temperature to germi- nation. In the bottom of each of the four wide mouth bot- tles, place several layers of thoroughly moistened blotting paper. In each bottle put twelve soaked pea seeds. With the conditions of moisture, light, and air- supply the same for all bottles, place them in different but fairly constant temperatures. Place : 1. the first bottle on the ice in the refrigerator ; 2. the second bottle on the shelf in the refrigerator ; 3. the third bottle in the room ; 4. the fourth in an oven at a temperature of 100° F. With a thermometer obtain and record the exact temperature in each instance. Make daily observa- tions for a week, tabulating your results as follows : Bottle Temp. 24 hrs. 48 hrs. 72 hrs. 96 hrs. 120 hrs. A, A2 A:t A4 What do you conclude from the above experiment is the best temperature for the germination of peas? B. Relation of moisture to germination. Place seeds in four wide mouth bottles as follows: A YEAR IN SCIENCE 95 1. twelve dry seeds in a bottle in which there are several layers of barely moistened blotting paper; 2. twelve soaked seeds in a bottle with barely moistened paper ; 3. twelve soaked seeds in a bottle with thoroughly wet paper ; 4. twelve soaked seeds in a bottle and almost cover them with water. Place these bottles aside under similar conditions of temperature, light, and air supply. Make daily obser- vations for a week and tabulate results as above. What do you conclude from this experiment? C. Relation of air supply to growth. Place several layers of blotting paper in each of two bottles. Moisten the paper thoroughly. Fill each bottle one-third full of soaked seeds. Cork one of the bottles tightly making it air tight, and leave the other open. With all other conditions the same, set the bottles aside. At the end of 48 hours examine the seeds in each bottle and record results. Is air neces- sary for the germination of seeds? Exercise 65. Seedlings. * Object: A general study of seedlings. Apparatus Wide mouth bottle Seedlings, peas, corn, etc. Mosquito netting Scalpel Directions: A. Make observations on a number 96 LABORATORY MANUAL of seeds just beginning to sprout. Review the parts of the embryo in Exercise 62. What part of the embryo emerges first from the seed coat? At what point does it come through? Into what part of the mature plant does it develop? Make a sketch to show these points. B. To determine one of the functions of a cotyledon, set up the following experiment : Fill a wide mouth bottle with water. Cover the mouth of the bottle with mosquito netting. Choose four young seedlings of about the same size each of corn, pea, and lupine. From two of each kind care- fully remove the cotyledons. Then suspend all the seedlings from the netting with the roots projecting into the water. After a week make observations on the growth of the seedlings with cotyledons, and com- pare with the growth of those from which the coty- ledons were removed. C. Methods of emerging from the soil. In a pot of germinating seeds of the castor bean, squash or lima bean, and corn, or any other grain, make observations on various stages of the growth of the seedlings. In the castor bean, squash, or lima bean, what part of the seedling emerges from the soil first? In what manner does it come above the surface? Of what advantage is this method to the seedling? Does the arch persist after the cotyledons and plumule are above the surface ? Sketch at least three stages in the above develop- A YEAE IN SCIENCE 97 ment. Make similar observations on the corn. In what manner does it send its shoot through the soil ? Sketch. Examine a number of other seedlings and place them under the proper one of the above classes. D. The growth above the ground is called the shoot (stem and leaves), while that below is the root. The points on the stem from which the leaves grow are called nodes. The portion of the stem between two nodes is the internode. Sketch a pea seedling to show nodes and internodes. Examine well grown seedlings of peas and beans. In each instance where are the cotyledons, above or below the surface of the soil? What is their present condition? What does this indicate as to the function of the cotyledons? What change has the plumule undergone? Is there a new plumule? Sketch to show the above points. CHAPTER XV FRIENDS AND ENEMIES OF LIVING ORGANISMS Exercise 66. Bacterial Cultures. Object: To show the prevalence of bacteria and something of their nature. Apparatus Petri dishes Steam sterilizer Culture media (gelatine, agar, Inoculating tubes and potato)* Dissecting needles *Culture media ready for use may be obtained from dealers in laboratory supplies. 98 LABORATORY MANUAL Directions: Thoroughly wash all dishes and other apparatus to be used in this exercise. Follow this by dipping each article separately into alcohol. Then place the dishes in the steam sterilizer and heat at a temperature of 150° C. for a period of twenty minutes. If gelatin culture medium is used, mix together the following : 200 c.c. of water. 1 gram extract of beef. 2 grams of peptone. 20 grams of gelatin. Place the mixture in the dish in which it is to be boiled, heat until the gelatin is thoroughly melted, and then boil briskly for a few minutes. Test with litmus paper. The solution should be slightly alkaline. If it is not, add to it, drop by drop, a solution of sodium hydroxide until it is slightly alkaline to litmus paper. Filter the solution through absorbent cotton and collect the clear liquid in a sterilized flask. Into the sterilized petri dishes pour enough of the medium to cover the bottom of the dish. Cover the dishes immediately, place them in the sterilizer, and heat at a temperature of 150° C. for fifteen minutes. When cooled sufficiently to handle, set aside for twenty-four hours, then heat again at 150° C. for fifteen minutes. After another twenty-four hours repeat the steriliza- tion process. The medium is now thoroughly sterilized A YEAR IN SCIENCE 99 (if properly done) and is ready for inoculation. The agar medium is prepared in the same way, except that instead of using 20 grams of gelatin, use 2/5 of a gram of agar. In all other respects the culture is made pre- cisely as the gelatin culture medium. Potato may be used by paring and placing thin cut slices in the sterilized dishes. Sterilize as indicated above. 1. After the medium has hardened, expose the medium of one dish to the air of the laboratory for three minutes. Cover the dish, label it No. 1, and set aside until the next recitation period. 2. At the same time expose the medium of another dish to the air out of doors for three minutes. Cover and label No. 2, and set aside. 3. Touch the surface of the medium of a third dish with the fingers in several places. Cover, label No. 3, and set aside. 4. Over the surface of the medium of a fourth dish, roll the end of your lead pencil (which you so fre- quently place in your mouth). Cover, label No. 4, and set aside. 5. If a fly is obtainable, capture it, and place it inside another dish, permitting it to walk over the surface of the medium. Free the fly, cover the dish and label No. 5. Set aside until next recitation. (>. Set one dish aside unopened as a check, and label No. 6. Place all vessels under similar conditions of light, heat, etc. Make daily observations for the appearance 100 LABOBATOBY MANUAL of colonies of bacteria. Describe and sketch the appearance of the growths. What do these experi- ments show as to the prevalence of bacteria ? Exercise 67. Conditions for Bacterial Growth. Object: To determine conditions for bacterial growth. Apparatus Hay . Test tubes Milk Absorbent cotton Meat Directions : A. Prepare three test tubes as follows : Put in one some pieces of chopped hay and cover with water; in the second some milk; and in the third a small piece of meat covered with water. Set these aside, uncovered, for a few days and note the changes in appearance and odor of the contents. Mount some of the scum on a slide and cover with a cover glass. The instructor will find the bacteria for you under the high power of the microscope. Determine the shape of some of these bodies and sketch. B. Prepare three test tubes as follows: Fill each tube half full with milk. Place one in a beaker and pack ice around it. Leave the top open. Set the entire apparatus on ice in the refrigerator. Boil the contents of the second tube for a few minutes and stopper with sterilized absorbent cotton. Set aside in a warm place. Place the third tube, uncorked, in a A YEAR IN -SCIENCE 101 warm place. Make daily observations and 'record results. What is the effect of heat on bacteria? Of cold? C. Prepare two test tubes as follows : Boil two test tubes in water and fill each half full of boiled milk. Into one tube introduce some of the scum from the tube of hay infusion. Close the tube with absorbent cotton and set in a warm place. Take some scum from the hay infusion and mix it with a teaspoonful of a 2% solution of corrosive sub- limate, or of formalin, and let it stand ten minutes. Then pour this mixture into the second tube. Close with absorbent cotton and place beside the first tube in a warm place. After a day examine the contents of the two tubes. Is the milk still fresh in either tube? How do you account for the condition found? From this experiment what conditions are favorable to bacterial growth? What conditions are unfavor- able? What are some of the methods of killing bacteria? Exercise 68. Root tubercles. Object: To show a use of bacteria. Apparatus Compound microscope Roots of legumes Slides, etc. Directions: Bring to the laboratory the roots of any leguminous plants (pea, bean, vetch, etc.) Exam- ine the roots carefully for nodules. Sketch to show 102 LABORATORY MANUAL their distribution. Crush a portion of a nodule on a glass slide and mount a portion of the material in a drop of water. Cover with a cover glass. With the aid of the instructor, find the mass of moving bacteria under the high power microscope. Sketch to show the form of some of the bacteria. These bacteria are very helpful to the plants of the pulse family, enabling them to obtain and utilize the nitrogen from the air as food. CHAPTER XVI CLASSIFICATION OF FOODS Substances which are taken into the body as nourish- ment are known as foods. Foods contain many elements, chief of which are carbon, hydrogen, oxygen, nitrogen, sulphur, phos- phorus, and iron. These elements do not occur in living matter as elements, but in various combinations or compounds. These compounds in foods are known as foodstuffs. There are five such foodstuffs. Proteins, or nitrogenous compounds. Carbohydrates, or starches and sugars. Hydrocarbons, or fats and oils. Mineral salts. Water. A YEAR IN SCIENCE 103 Each foodstuff shows certain definite qualities by which its presence may be detected. Exercise 69. Tests for Foodstuffs. Object: To determine a test for protein, starch, sugar, fat and oil. Apparatus Cornstarch Grape sugar Ammonia Egg-white Benzine and ether Mutton tallow Vnglazed paper Ground flax seed Test tubes Iodine Evaporating dish Fehling's solution Filter paper Nitric acid Bunsen burner Hydrochloric acid Stirring rod Directions: A. Test for starch: Place a small amount of cornstarch in a test tube. Add water and shake the mixture. Does the starch dissolve? (To answer this question compare this mixture with a solution of salt and water.) Boil the mixture. What hange do you note? Dip the end of a glass stirring rod into the paste. Over the paste on the glass rod pour a few drops of iodine. What is the result? B. Test for grape sugar : Place a small amount of grape sugar in a test tube and add enough water to dissolve it. What is the difference in the effect of at(M- on sugar and starch? Add a few drops of Fehling's solution and boil. What change do you To a solution of cane sugar add Fehling's 104 LABOEATOEY MANUAL solution and boil. Do you obtain the same result? Take a fresh solution of cane sugar, add a few drops of hydrochloric acid, then Fehling's solution and boil. How does this result compare with the two preceding? Thus cane sugar is converted into grape sugar by the acid. C. Tests for protein : Into a test tube half full of water, place some rav/ egg-white. Heat this over the Bunsen flame. What is the effect of heat on the egg- white ? Pour off the water. Cover the egg-white with dilute nitric acid and boil. What is the color of the egg? Pour off the acid. Add enough ammonia to cover the egg. What is the color produced? D. Tests for oil and fat : To four teaspoonfuls of ground flax seed, add an equal volume of benzine or ether. Thoroughly stir the mixture and let it stand for about ten minutes. Filter and place the nitrate aside in a strong draught of air until the benzine or ether has entirely evaporated. What is the substance left? What is the odor? Why are benzine and ether used to remove grease spots from clothing? Rub some mutton tallow on the surface of a piece of unglazed paper. Hold the paper over a Bunsen flame to melt the fat. Then hold it to the light. What is the effect of fat or oil on paper? Summarize the tests you have learned for protein, starch, sugar, fat. Exercise 70. Foodstuffs in Common Foods. Object: To determine the foodstuffs found in some foods. .A YEAR IN SCIENCE 105 Egg-white Milk Potato Apple Beans ( soaked ) English walnuts Flour Apparatus Iodine Nitric acid Fehling's solution Ammonia Unglazed paper Bunsen burner Directions: Apply the four tests, which you have learned in Exercise 69, to each of the following foods and tabulate your results as follows : Foods Egg-white Milk Starch Grape Sugar Protein Oil and Fat Potato Apple Beans English- walnuts Flour CHAPTER XVII DIGESTIVE SYSTEM Exercise 71. Study of the Mouth (home study). Object: To study the parts and structure of the mouth. Apparatus Hand mirror Directions: Take a position with your back toward a strong light, and study your mouth cavity with the aid of a hand mirror. 106 LABORATORY MANUAL A. Walls of the mouth cavity. 1. How do the walls enclosing the mouth cavity differ from each other ? Note the hard portion or roof of the mouth. How far back does it extend? This is called the hard palate. The softer portion at the back of the mouth is called the soft palate; hanging down from its free border is a conical projection, the uvula. What is its function? 2. What difference do you observe between the outer and inner covering of the cheeks? What are the characteristics of the inner covering, or mucous membrane? B. Salivary glands. 1. Pull aside with the fingers one corner of the mouth. Find the small elevation on the inside of the cheek. The duct from one of the salivary glands (parotid gland, lying close in front of the ear) opens on this elevation. 2. Lift the tongue and note the glands (sub-lingual) lying just beneath. The ducts from these glands open in the front of the mouth beneath the tongue. Feel them with the tip of the tongue. 3. Find the third pair of salivary glands (sub- maxillary) lying beneath the floor of the mouth just behind the sub-lingual near the angle of the jaw. C. The tongue. What kind of covering has the tongue? Describe the difference between the upper and under surfaces. Can you see any difference in the size, shape, number, A YEAR IN SCIENCE 107 and arrangement of the minute elevations (papillae) on the upper surface? D. The teeth. 1. Teeth differ in minor points from one another, but in all, three parts are found : one, seen in the mouth and called the crown of the tooth ; a second, imbedded in the jawbone and called the root; and between the two surrounded by the edge of the gum, the neck of the tooth. 2. Count the teeth in the upper and lower jaws. How many in all? Describe the edges of the front teeth (incisors). How many teeth have this sharp cutting edge? How does the tooth (canine) next to the incisors differ from the other teeth? What is its function? How many teeth have two points to the crown? These are known as bicuspids. What is the character of the last three teeth? What is their func- tion? These are the molars. Do you have all the molars? Why not? E. Tonsils. The opening from the back of the mouth leads into the throat. Press the tongue down and note the almond shaped elevations at the sides of the throat. These are called tonsils. Exercise 72. Alimentary Canal and Digestive Glands. (Demonstration.) Object: A study of digestive organs. Apparatus Models of digestive organs Charts 108 LABOKATOBY MANUAL Directions: On the models and charts locate the parts of the alimentary canal. A. Alimentary Canal. At the back of the mouth note the funnel-shaped cavity, the pharynx or throat. What other openings are there into this cavity? What openings lead from this cavity? Note the gullet or esophagus, a small tube leading from the pharynx to the stomach. What is the position of the stomach in the body? Its approximate size and shape? Following the stomach is a long, very much coiled tube, the small intestine. This tube connects with a larger tube known as the large intestine. B. Glands. The salivary glands of the mouth, the parotid, the sub-maxillary, and the sub-lingual were studied in Exercise 71. In the internal walls of the stomach are small glands known &s gastric glands. These discharge their secre- tion into the stomach. Intestinal glands are located in the walls of the first part of the small intestine. Other glands which pour their secretions into the small intestine are the pancreas and the liver. The pancreas is a long, lobulated gland lying beneath the stomach. The liver, the largest gland in the body, lies just beneath the diaphragm above and to the right of the stomach. From the chart make a drawing of the alimentary canal and glands, labeling parts. A YEAE IN SCIENCE 109 CHAPTER XVTII DIGESTION AND ABSORPTION Exercise 73. Digestion in the Mouth. Object: To determine the foodstuffs acted upon by saliva. Apparatus Litmus paper Iodine Corn starch Test tube Egg-white Test tube rack Olive oil Test tube clamp Hydrochloric acid Bunsen burner Fehling's solution Directions: Food is first acted upon by a fluid, saliva, which is secreted by glands discharging into the mouth. Test saliva by placing a piece each of red and blue litmus paper upon the tongue. Is saliva acid or base? Dry the mouth as much as possible by swal- lowing and then place on the top of the tongue a pinch of salt. Can you taste the salt? Keep the salt on the tongue for a minute. What happens to the salt? Can you now taste it? To determine the chemical action of saliva on the foodstuffs, prepare test tubes as follows : In the first, place a small amount of thin starch paste, to which add a few c.c. of saliva. Label No. 1. In the second, place some starch paste and saliva, to which add a few drops of hydrochloric acid. Label No. 2. J10 LABORATORY MANUAL In the third, place a few small bits of egg-white and cover with saliva. Label No. 3. In the fourth, place a few c.c. of olive oil and saliva. Label No. 4. Shake the tubes and set them in a basin of water having a temperature of 36° C., or about body tem- perature. Leave them for half an hour and then test the contents of the tubes. Tube No. 1 — Test part of the contents for starch and the remainder for sugar. Tube No. 2 — Repeat the test applied to tube No. 1. Tube No. 3 — Has the egg-white begun to dissolve? Tube No. 4 — Has any change taken place in the oil? Upon which of the foodstuffs does saliva act? Does it act in an acid or base solution? Exercise 74. Digestion in the Stomach. Object: To determine the foodstuffs acted upon in the stomach. Apparatus Corn starch Test tube clamp Egg-white Iodine Olive oil Sodium hydroxide (dilute) Milk Pepsin Hydrochloric acid (dilute) Rennet Fehling's solution Bunsen burner Test tubes and racks Directions: In the stomach the food comes in con- tact with the gastric juice. This contains two active substances, pepsin and rennin. A YEAE IN SCIENCE HI A. Pepsin. Make a weak solution of pepsin by dissolving a few grams of pepsin in 50 c.c. of water. Prepare five test tubes as follows : In the first, place a small amount of starch paste, 10 c.c. of pepsin, and a few drops of very dilute hydro- chloric acid. Label tube No. 1. In the second, place a few pieces of egg-white,- 10 c.c. of pepsin, and dilute hydrochloric acid. Label No. 2. In the third, place a few pieces of egg-white, 10 c.c. of pepsin, and a few drops of very dilute sodium hydroxide solution (0.2%). Label No. 3. In the fourth, place 5 c.c. of olive oil, 10 c.c. of pep- sin, and a few c.c. of dilute hydrochloric acid. Label No. 4. Shake the tubes and keep them at a temperature of 36° C. for 24 hours. At the end of that time test the contents of the tubes. Test No. 1 for starch and sugar. In No. 2, has the egg-white dissolved? In No. 3, has the egg-white dissolved? In No. 4, is there any change in the olive oil ? Upon which foodstuffs does pepsin act? In comparing tubes No. 2 and No. 3 does pepsin act in a base or acid solution? B. Rennin. In the fifth tube place 10 c.c. of milk and 5 c.c. of rennet (which contains rennin). Set aside for 30 112 LABORATORY MANUAL minutes at a temperature of 36° C. At the end of that time what change do you observe in the milk? Exercise 75. Digestion in the Intestine. Object: To determine the foods acted upon by the pancreatic juice. Apparatus Corn starch Pancreatin Egg-white Bunsen burner Olive oil Test tubes and racks Hydrochloric acid (dilute) Test tube clamps Sodium hydroxide (dilute) Directions: In the small intestine the food is acted upon by three digestive juices : intestinal, which is secreted by the glands in the walls of the small intestine; bile, secreted by the liver; pancreatic, secreted by the pancreas. Prepare a weak solution of pancreatin by dissolving a few grains of pancreatin in 50 c.c. of water. Prepare four test tubes as follows : In No. 1 place starch paste, 10 c.c. of pancreatin solution, and a few drops of very dilute sodium hydroxide. In No. 2 place starch paste, 10 c.c. pancreatin solu- tion, and a few c.c. of hydrochloric acid. In No. 3 place a few bits of egg-white, pancreatin solution, and sodium hydroxide. In No. 4 place 10 c.c. olive oil, pancreatin solution, and sodium hydroxide. A YEAR IN SCIENCE 113 Shake the tubes and set them aside in a temperature of 36° C. for 24 hours. At the end of that time examine : No. 1 for starch and sugar. No. 2 for starch and sugar. No. 3. Has the egg-white dissolved? No. 4. Has the olive oil changed? Upon which foodstuffs does pancreatin act? Does it act in an acid or base solution? From the last three exercises complete the following table : Digestive Fluid Acid or Base Region of Alimentary Foodstuffs Digested Canal Acted Upon Product Saliva Gastric Pepsin Rennin Pancreatin Exercise 76. Absorption. Object: To determine which foodstuffs will diffuse through an animal membrane. Corn starch Olive oil Egg-white (raw) Iodine Ammonia Nitric acid Apparatus Thistle tube Animal membrane Glass jar Ring stand Twine Directions: For the method of setting up the apparatus for this exercise, see Exercise 5 on "Diffu- sion of Liquids through a Membrane. ' ' Set up similar experiments, using in place of the molasses : LABORATORY MANUAL a. starch paste, b. olive oil, c. raw egg-white. After 48 hours note any change in the level of the liquids in the thistle tubes. At the same time test the water in which the bulbs of the thistle tubes were suspended : a. for starch, b. for oil, c. for protein. Has diffusion taken place in any of the foregoing? In Exercise 5 did molasses diffuse through the animal membrane? Why is it necessary to have foods digested? CHAPTER XIX CIRCULATORY SYSTEM Exercise 77. Study of Beef "Pluck." (Demon- stration.) Object: A study of the relation of the heart and lungs and their structure. Apparatus Beef "pluck," to consist of the Plaster model trachea, lungs, heart, and its Scissors covering, and the main blood- Scalpel vessels leading to and from Large glass tube the heart Directions: A. In what part of the body are these A YEAR IN SCIENCE 115 organs located? What is their position to each other? Notice the trachea with its circular rings of cartilage. Are the rings entire? These are necessary to prevent collapse of the tube. HOAV far down do these rings continue? With a scalpel follow a branch of the trachea into the lungs. How do these branches end? This large amount of branching allows the air to be brought in contact with very small blood vessels, through the walls of which oxygen is absorbed into the blood. B. Lungs. How many lobes has each lung? What are their relative sizes ? Note the texture of the lungs. By inserting a glass tube into a branch of one of the bronchi, force air into the lung. What happens? The lungs are the organs chiefly concerned in breathing. C. Heart. What is the general shape? The cover- ing about the heart is the pericardium. The heart has four compartments: the upper two, the auricles (right and left) ; the lower two, ventricles (right and left). Which parts have the thickest walls? The Avails are made of muscle with the thick-walled parts doing the pumping. Find the blood vessels, superior and inferior vena cava, leading into the right auricle. Open the veins, also the walls of the auricle, and observe the path of the blood into the right ventricle. Note the tricuspid valve that closes this entrance between auricle and ventricle. Also notice the cords bv which this valve 114 LABORATORY MANUAL a. starch paste, b. olive oil, c. raw egg-white. After 48 hours note any change in the level of the liquids in the thistle tubes. At the same time test the water in which the bulbs of the thistle tubes were suspended : a. for starch, b. for oil, c. for protein. Has diffusion taken place in any of the foregoing? In Exercise 5 did molasses diffuse through the animal membrane? Why is it necessary to have foods digested? CHAPTER XTX CIRCULATORY SYSTEM Exercise 77. Study of Beef ''Pluck." (Demon- stration.) Object: A study of the relation of the heart and lungs and their structure. Apparatus Beef "pluck," to consist of the Plaster model trachea, lungs, heart, and its Scissors covering, and the main blood- Scalpel vessels leading to and from Large glass tube the heart Directions: A. In what part of the body are these A YEAR IN SCIENCE H5 organs located? What is their position to each other? Notice the trachea with its circular rings of cartilage. Are the rings entire? These are necessary to prevent collapse of the tube. How far down do these rings continue? With a scalpel follow a branch of the trachea into the lungs. How do these branches end? This large amount of branching allows the air to be brought in contact with very small blood vessels, through the walls of which oxygen is absorbed into the blood. B. Lungs. How many lobes has each lung? What are their relative sizes ? Note the texture of the lungs. By inserting a glass tube into a branch of one of the bronchi, force air into the lung. What happens? The lungs are the organs chiefly concerned in breathing. C. Heart. What is the general shape? The cover- ing about the heart is the pericardium. The heart has four compartments: the upper two, the auricles (right and left) ; the lower two, ventricles (right and left). Which parts have the thickest walls? The walls are made of muscle with the thick-walled parts doing the pumping. Find the blood vessels, superior and inferior vena cava, leading into the right auricle. Open the veins, also the walls of the auricle, and observe the path of the blood into the right ventricle. Note the tricuspid valve that closes this entrance between auricle and ventricle. Also notice the cords bv which this valve 118 LABORATORY MANUAL number? In size? The smaller are called red cor- puscles. How are they arranged? Can you make out their shape? Make two drawings of a red corpuscle, one as seen on end, the other from the side. The larger bodies are the white corpuscles. Describe them. CHAPTER XX RESPIRATORY SYSTEM Exercise 79. Respiratory Organs and Mechanics of Respiration. (Demonstration.) Object: To study the organs and mechanics of respiration. . Apparatus Chart or plaster model Sheet rubber Skeleton Rubber balloon Mechanical device for rib action Glass tube Belljar with stopper Directions: A. The lungs are the chief organs of respiration. The structure of the lungs was studied in Exercise 77, in the study of the beef "pluck." Note on the chart or plaster model their position in the body. The cavity in which the lungs and heart are found is the thorax. On the skeleton note the bones forming the frame work of this cavity. The floor of the thorax is a muscular sheet called the diaphragm. Note on the skeleton the attachment of the ribs to the sternum by means of cartilage. This permits the A YEAK IN SCIENCE 119 movement of the ribs by the action of the muscles between the ribs called the intercostals. To demonstrate this movement use the mechanical device. in The vertical bar AB represents the spinal column, DF the sternum, CD and EF two ribs. Letter c repre- sents the muscular attachment from the spine and collar bone to the ribs. Letters a and b represent inter- costal muscles. Note on the skeleton that the ribs slant downward toward the sternum. On the device place the bar DF lower than points CE. Measure the perpendicular dis- tance between CE and DF. Then lift the ribs CD and EF to a position perpendicular to AB (in the body this movement is brought about by the contraction of the intercostal muscles). Again measure the perpendicular distance between CE and DF. How does it compare with the first measurement? How has the position of DF been affected? How does this movement affect the size of the thoracic cavity? B. The thoracic cavity is enlarged vertically by the 120 LABOEATOEY MANUAL movements of the diaphragm. This action is demon- strated by the following experiment : Fasten a toy balloon to one end of a glass tube. Insert the tube into a rubber stopper and fit this into the bell jar with the balloon suspended inside. Over the other end of the belljar, securely fasten the rubber sheet to the center of which a handle has been attached. The belljar represents the chest walls, the tube the trachea, and the bal- loon a lung. The rubber sheet represents the diaphragm. Pull the rubber sheet downward. What happens to the balloon? Then let the rubber sheet return to its normal position. What is the effect on the balloon? The action of the balloon represents the action of the lungs in response to the movements of the diaphragm. Exercise 80. Comparison of Expired and Inspired Air. Object: To determine the changes which take place in the air while in the lungs. Apparatus Thermometer Glass plate Wide mouth bottles Two-holed rubber stopper Glass tubing Lime water Pine splinter Pneumatic trough A YEAR IN SCIENCE 121 Directions: A. Temperature. Expose the ther- mometer to the room temperature for five minutes and record the temperature. Then breathe on the bulb of the thermometer for a few minutes and record the temperature of expired air. What change has taken place in the temperature of the air while in the lungs ? B. Composition. For the composition of inspired air see Exercise 38. a. Breathe on the glass plate. What collects on the surface? Does expired air contain more or less mois- ture than inspired air ? b. Into a wide mouth bottle pour lime water to the depth of an inch. Fit the mouth of the bottle with a rubber stopper fitted with a long and short glass tube. Adjust the long tube so that the end is below the level of the lime water. Draw air from the room through the lime water by suction applied to the free end of the short tube. Continue this for two minutes. Insert the stopper with the tubes into a second bottle containing lime water. Pass expired air through the lime water by blowing into the free end of the long Fig- 32- tube. Continue this for. two minutes. How does the lime water in the two bottles compare? Which contains the greater amount of carbon dioxide, inspired or expired air? c, Fill a bottle Avith expired air by downward displacement of water. Turn the bottle mouth upward 122 LABOEATOKY MANUAL and introduce into it a burning splinter. Does the splinter continue to burn as brightly as in the air? What does this indicate? Air expired in ordinary breathing has lost about one-fourth of the oxygen contained in inspired air. Exercise 81. School Ventilation. Object: To determine the efficiency of the room ventilation. Apparatus Tape measure Directions: For a sufficient air supply most author- ities agree that an individual requires 300 cu. ft. of space with 1,800 cu. ft. of air per hour. With the tape measure determine the dimensions of the laboratory. From the dimensions what is the volume of the laboratory in cubic feet? Divide the cubic contents of the laboratory by the number of people in the room. How does the quotient compare with the number of cubic feet of space each individual should have? What is the method of ventilation in the school building? Learn from those in authority the number of times per hour the air is changed in the room. Compute from this data the number of cubic feet of air each person receives per hour. Is this sufficient for the individual? Follow the same directions in computing the volume of your session room. Divide the cubic contents by A YEAK IN SCIENCE 123 the number of students in the room. Determine the number of cubic feet of air each individual receives per hour. Has each individual the requisite amount of air? If not, what change would you suggest to meet the requirements? For your own information compute the volume of your sleeping room in cubic feet. How long would the air in the room suffice without change? What means are there for changing the air in the room? Are these sufficient? From what you have learned above, correct the fault. CHAPTER XXI EXCRETORY SYSTEM Exercise 82. The Kidneys. Object: To study the structure of a kidney. Apparatus Sheep kidney Scalpel Dissecting pan Scissors Directions: Describe the capsule surrounding the kidney. Where is it attached to the kidney? Slit the capsule on the convex side enough to allow the kidney to be removed. Cut the kidney longitudinally from the convex border toward the hilum sufficiently to open the cavity within. What is the shape of the kidney ? Size ? Color ? How many tubes do you find connected with this organ? In the longitudinal section of the kidney notice two 124 LABORATORY MANUAL parts: the outer solid part, the cortex; the inner striated part, the medulla. The slight elevations are called pyramids of Malpiglii, between which small tubes may be seen leading into the sinus. The tube leading from the sinus is the ureter which carries the excretion into the bladder. Notice the enlarged end of the ureter in the sinus. Note also the entrance of the renal artery and the renal vein into the kidney just above the ureter. The artery brings in the blood which gives up its waste in the kidney. This waste is collected by the tubules and emptied from the sinus into the ureter. The capillaries collect the blood which has been cleared of waste and return it to the vein. Exercise 83. The Skin. Object: To study the structure and functions of the skin. Apparatus Plaster model of skin Directions : A. External structure : The outer layer of the skin is called the cuticle, .or the epidermis. What is its color ? Thickness ? Where is it thickest on the hand? What markings do you find on it? Can you find the pores, openings of the sweat glands ? Does the epidermis contain blood vessels? Does it contain nerves ? B. Internal structure : From the plaster model, or a prepared slide of the skin, note the two layers comprising it. Note the epidermis again. What is its A YEAE IN SCIENCE 125 structure? The inner layer is the derm-is. How does it compare with the epidermis in thickness? Note that its surface is ridged. These ridges are made up of a number of papillae. Each papilla marks- the end of a nerve of touch. Is the skin sensitive to other stimuli than touch? If so, what are they? In the dermis locate the fat cells, the roots of the hair, the oil or sebaceous glands, and the sic eat glands. Where do the ducts from the sweat glands open ? What effect does the evaporation of sweat from the surface of the skin have on the temperature of the skin? To answer this question refer to Exercise 21. Make a drawing to show the parts of the skin. From this exercise what are some of the functions of the skin? Hair and nails are modifications of the skin. CHAPTER XXII SKELETAL SYSTEM Exercise 84. The Skeleton. Object: To study the general plan of the skeleton. Apparatus Skeleton Directions: The skeleton may be divided into three parts : the head, trunk, and limbs with the bones to which they are attached, hip and shoulder. A. Head. Notice that the head is divided into the LABOEATOEY MANUAL face and the cranium. The face is composed of a num- ber of irregular bones. The cranium consists of a number of flat bones, sutured together to form a strong covering for the brain. B. Trunk. The trunk consists of the spinal column, breast-bone, and ribs. The spinal column is composed of a number of irregular bones called vertebrae. The upper seven are the neck, or cervical vertebrae. The next twelve to which the ribs are attached are the dorsal vertebrae. The five following are the lumbar vertebrae. The next five in the adult are grown together, forming the sacrum. This is followed by four small vertebrae united to form the coccyx. How do the lower vertebrae compare in size with the upper? What are the advantages of this arrange- ment ? Note the pads of cartilage between the vertebrae. What is their purpose? Through the center of this chain of bones is a canal which contains the spinal cord. How many curves in the backbone ? Of what advantage are the curves? Note the flat breast-bone. Of how many bones is it composed? What bones are attached to it? How many ribs are there ? Where are they attached ? How many have one end free? What is their general shape ? C. Limbs. The shoulder consists of the shoulder blade and collar bone. Locate these. Note the socket A YEAE IN SCIENCE 127 formed by their union for the upper limb. The upper limb consists of the upper arm bone, the humerus; two bones in the forearm, the ulna and radius; eight irregu- lar wrist bones, the carpals; five bones in the palm of the hand, the metacarpals; and fourteen bones in the fingers, the phalanges. The hip consists of one large bone on each side. Notice the size and strength of the hip as compared with the shoulder. Why this difference ? The lower limb consists of the upper leg bone, the femur; the two lower leg bones, the tibia and fibula; the knee cap or patella; seven ankle or tar sal bones; five metatarsals; and fourteen toe bones or phalanges. Compare each of these parts with the corresponding parts in the arm. Exercise 85. Structure and Composition of Bone. Object: To study the structure and chemical com- position of bone. Apparatus Section of a long bone Hydrochloric acid 20% (femur) Glass cylinder Beef rib Directions: A. Structure. Examine a long bone. Note the long central shaft with enlarged ends. Of what advantage are the enlarged ends ? Note the pink- ish colored covering surrounding the bone. What is its function? This covering is the periosteum. Make a longitudinal section through the bone. Beneath the periosteum note the hard bone; inside of this the spongy 128 LABORATORY MANUAL bone and central canal. The spongy bone contains in its cavities red marrow, while the central canal contains yellow marrow. B. Composition. To determine the chemical compo- sition of bone, place a rib in a twenty per cent solu- tion of hydrochloric acid. Leave the bone in the solu- tion for at least four days. At the end of that time examine the bone. Has it changed in shape? Can it be cut ? Is it elastic ? The acid has dissolved from the bone the mineral matter leaving only the animal mat- ter, cartilage. The animal matter may be extracted by burning the bone. Again the shape remains the same but the substance left is hard and brittle. This mineral matter is chiefly lime. CHAPTER XXIII MUSCULAR SYSTEM. Exercise 86. Levers. Object: To determine the action and advantages of levers. Apparatus Yard stick Ring stand Weight (500 gms.) Lever holders Spring balance Directions: A lever is an inflexible bar moving about a fixed point, called a fulcrum, and having two other points, called power and weight. Weight is the A YEAE IN SCIENCE 129 mass moved. Power is the force used to move the mass. Weight arm (W. A.) is the distance from the fulcrum to the point of application of the weight. Fig. 33. Power arm (P. A.) is the distance from the fulcrum to the point of application of the power. Levers are divided into three classes based upon the relative positions of the three points : fulcrum, power, and weight. In the first class lever, the fulcrum is in the middle, the weight at one end, and the power at the other. The second class lever has the fulcrum at one end, the power at the other end, and the weight in the middle. The third class lever has the fulcrum at one end, the weight at the other end, and the power in the middle. Fasten one end of the yard stick to the ring stand. From the second ring stand suspend the spring bal- ance. Wire the free end of the yard stick to the hook of the spring balance. Take the reading of the indicator on the scale. Suspend the 500 gm. weight from the zero point on the yard stick. 130 LABOKATORY MANUAL Locate on the apparatus the fulcrum, the power, weight, power-arm, and weight arm. Shift the weight on the bar, and record the readings on the balance with the weight at 0, 6, 12, 18, 24, 30, and 36 inches from the fulcrum. Tabulate your readings as follows : Power X Power-arm = Product Weight X Power-arm = Product How do the two product columns compare? What class of lever is used in this exercise? Of what mechanical advantage is the lever in lifting the 500 gm. weight as shown by the reading at the 6-inch point? How would you convert this apparatus into a third class lever? Into a first class lever? From the results of this exercise what law can you deduce for levers? Exercise 87. Muscles. (Demonstration.) Object: To determine the structure and action of muscles. Frog Dissecting pan Scalpel Apparatus Scissors Needles A YEAR IN SCIENCE 131 Directions; Dissect away the skin of a frog's leg. Note the muscles on the leg. What is the general shape of the muscle? Note the tendon attachment of the muscles to the bone. Of Avhat advantage is the tendon attachment? Note that the body of the muscle is sur- rounded by a thin sheet of connective tissue. Find the large muscle on the calf of the leg. Where are its two ends attached? What effect does the contraction of this muscle have upon the lower leg? Upon the foot? The bones of the skeleton serve as places for muscle attachment and as levers for their action. CHAPTER XXIV NERVOUS SYSTEM Exercise 88. Nervous System. (Demonstration.) Object: To study the brain, spinal cord, and nerves. Apparatus Perch Scalpel Dissecting pan Model of human brain Scissors Directions: Carefully dissect away the roof of the cranium and the dorsal part of the spinal column of the fish to expose the brain and the spinal cord. Note that the brain is divided into a number of regions : the small anterior lobes, the olfactory lobes; the larger cerebral hemispheres; the rounded optic lobes; the single lobed cerebellum; and behind this, tapering grad- ually into the spinal cord, the medulla oblongata. 132 LABORATORY MANUAL From these centers branches lead to all parts of the head and to some of the internal organs. Examine the spinal cord in the fish. Is it of the same dimensions throughout its length? Note the numerous lateral branches. Are they single or in pairs? These are distributed to the remaining parts of the body. Examine the model of the human brain. Observing the upper surface of the brain, note the two large con- voluted (folded) hemispheres of the fore-brain, or cerebrum. At the base of the cerebrum note the smaller lobes of the cerebellum. How do the convolu- tions on the cerebellum compare in size with those of the cerebrum ? What is the color of each ? On the under surface of the brain, note again the cerebral hemispheres and the cerebellum. How do they compare in size? At the forward end of the cerebrum note the two small white olfactory lobes. Back of these note the two nerves which cross. These are the optic nerv&s. The third portion of the brain is the medulla oblongata. On the model it is the white portion lying just beneath and in front of the cere- bellum. Extending downward from the medulla is the spinal cord which continues through the spinal column. Nerves are given off in pairs from the brain and spwwl cord which continues through the spinal column. On the model of the longitudinal section of the brain, locate the parts mentioned above. A YEAR IN SCIENCE 133 CHAPTER XXV ORGANS OF SPECIAL SENSES Exercise 89, Cutaneous Sensations. Object: A study of the sensations of touch and temperature. Apparatus Metal compasses Cold water Hot water Directions: A. One pupil should operate, another acting as subject. The subject should be blindfolded. What is the least distance apart at which the two points of the compass may be held and felt as two points, when applied to the tips of the fingers ? The tip of the tongue? Back of the hand? Back of the neck? Record results. Are all parts of the body equally sensitive to touch? Which parts are most sensitive? B. Dip a point of the compass in cold water and move it lightly over the back of the hand. Does it feel equally cold to all parts of the hand? Mark with an ink dot those spots where the sensation is most acute. Now dip the compass point in hot water, and repeat the experiment. Locate as before, the points where the sensation is most .acute. Do the hot and cold spots coincide? Test other areas of the body in the same way. Are all parts of the body equally sensitive to temperature ? Which parts are most sensi- 134 LABOEATOEY MANUAL tive? Least sensitive? Where are the hot spots most numerous? Where are the cold spots most numerous? C. Do we derive any sensations other than touch and temperature through the skin? If so, what are they? Exercise 90. Organs of Taste and Smell. Object: A study of the tongue and the sensations of taste and smell. Apparatus Sugar Quinine Salt Onion Vinegar Directions: A. With the aid of a mirror examine the upper and lower surfaces of the tongue. What differences do you note? The raised points on the upper surface are called papillae. Observe that they are of three forms : long and slender, filiform; small, red, mushroom shaped spots, fungi form; far back on the tongue the large circumvallate papillae. How many of them can you see? Draw an outline of the tongue, and locate on it the regions where these dif- ferent forms are to be found. B. Place some sugar on the tip of the tongue. Let it dissolve. Has it any taste? Repeat, placing the sugar at the back of the tongue. Is its sweetness more or less prominent? Repeat again, using quinine, vinegar, and salt successively. Where are the sensa- tions of bitterness, sourness, sweetness, and saltiness most prominent? C. The sense organs of smell are located in the A YEAR IN SCIENCE 135 mucous membrane lining the upper part of the cavity of the nose. Particles of matter in the form of a gas striking this membrane stimulate the nerves of smell, olfactory nerves. To determine which of the sub- stances named under "Apparatus" have taste and Avhich have odor, perform the following experiment. Place each of these substances 011 the tongue of a pupil who has been previously blindfolded, and who is holding his nose tightly. Record the substance recog- nized by taste alone. Repeat, leaving the nose free. Record the substances recognized by smell alone; by taste and smell combined. Exercise 91. Organ of Sight. Object: To study the structure and action of the eye. Apparatus Model of human eye Lenses Directions: A. With the aid of a mirror examine the eye. Feel the upper eyelid; fold it. In what part of it is there a stiff, thick strip of connective tissue? Compare with this the corresponding strip in the lower lid. At the angle of the lower lid, about one- eighth of an inch from the inner corner, look for a little papilla in which is the opening of the tear duct. Can you find a similar opening in the upper lid? Notice the eyeball. What do you find in the inner corner which is different from the outer? The eye 136 LABORATORY MANUAL is covered with a firm white coat, the sclerotic, except in front wrhere there is a clear layer, the cornea. Look at your neighbor's eye from the side. Does the cornea curve more or less than the remainder of the eye? Directly back of the cornea is the colored part of the eye, called the iris. In the center of the iris is a hole, the pupil. Compare the size of the pupil when in a bright light with its size in a dim light. From this, what do you conclude is the function of the iris? Is its action voluntary or involuntary? Now examine the model. Locate the parts mentioned above. The wall of the eyeball consists of three layers : the outer, composed of the sclerotic and the cornea; the middle, the black choroid, and in front the colored iris; and the inner, the retina. Note where the optic nerve enters the two outer coats and spreads out to form the retina. Just back of the pupil note the convex crystalline lens. The space between the lens and the cornea is filled with a liquid, the aqueous humor; and the larger space back of the lens is filled with a jelly-like mass, the vitreous humor. Draw a section of the eye, showing parts given above. On the outside of the model locate the six muscles used in moving the eyeball. From the position of each determine what motions it gives to the eyeball. B. Hold your pencil point at several different dis- tances from your eye. At what distance can you see it most comfortably and most clearly? From this distance move the pencil toward the eye. At what A YEAE IN SCIENCE 137 distance from the eye does it become indistinct, or fringed with a haze? Hold a book with the edge placed directly toward you. Close the left eye and look at the book. Then close the right eye and look at it again. Then look at it with both eyes open. What differences do you note ? How do you account for these differences ? In front of a lens, both of whose faces are convex, place a lighted candle or a gas flame. Back of the lens place a piece of paper to form a screen. Move the paper back and forth until a distinct image of the flame is seen upon the paper. What effect does it have upon the image formed to move the flame nearer, or farther away from the lens? Adjust the apparatus again so that a distinct image is formed on the screen. Remove the lens and put in its place one which is more convex. Which way must the screen be moved to secure a distinct image? Repeat this experiment, using a lens which is less con- vex than the first one used; also use one which is concave. Exercise 92. Organ of Hearing. Object: A study of the ear. Apparatus Model of the ear Directions: The ear is made up of an external ear, a middle ear, and an inner ear. On the model examine the external ear. Note the pinna, the oval, expanded, 138 LABORATORY MANUAL funnel-shaped portion. Leading from this is a canal. Across the inner end of this canal, or tube, is stretched a thin membrane, known as the ear drum or tympanic membrane. Examine the middle ear. What is its size? How is it connected with the pharynx? What is the name of this tube? What is its function? On the inner surface of the cavity of the middle ear and separating it from the inner ear are two small open- ings covered with membrane. Across the cavity of the middle ear is a chain of three smaH bones, called from their shape the hammer (malleus), the anvil (incus), and the stirrup (stapes) bones. How are they placed with reference to each other? With reference to the outer and inner ears? Can you suggest any functions for them? The inner ear is formed by an irregular cavity in the temporal bone, and is called the bony labyrinth. It is lined with a membrane which secretes a fluid. It is divided into three parts. The middle part is the vestibule. The part back of this consists of three tubes, the semi-circular canals. The part in front of the vestibule is a single tube coiled like a snail shell and called the cochlea. The branches of the auditory nerve enter this bony labyrinth. Locate the parts of the inner ear on the model. Draw a diagram showing the relation of the parts in the ear. h. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. 4 1937 LD 21-100m-8,'34 YB 17585 359397 UNIVERSITY OF CALIFORNIA LIBRARY