F/J'-'I^^* ^n '/■/'' I \[\ n H a y .jy^. :C'. // o- y/ C^ - ^ ^ O- /. „ / i 'i >' /^^'-,' FIRST COURSE IN BIOLOGY BY L. H. BAILEY PART I. PLANT BIOLOGY WALTER M. COLEMAN PART 11. ANIMAL BIOLOGY PART ILL HUMAN BIOLOGY TORONTO THE MACMILLAN CO. OF CANADA, Ltd, 1910 Copyright, 1908, By the MACMILLAN COMPANY. Set up and electrctyped. Published July, 1908. Reprinted October, 1908; February, September, 1909 ; January, 1910. XorfaootJ litfS3 J. S. Cashing Co. — IJerwick & Smith Co. Norwood, Mass., U.S.A. PREFACE The present tendency in secondary education is away from the formal technical completion of separate subjects and toward the developing of a workable training in the activities that relate the pupil to his own life. In the natural science field, the tendency is to attach less im- portance to botany and zoology and physiology as such, and to lay greater stress on the processes and adaptations of life as expressed in plants and animals and men. This tendency is a revolt against the laboratory method and research method of the college as it has been impressed into the common schools, for it is not uncommon for the pupil to study botany without really knowing plants, or physiology without knowing himself. Education that is not applicable, that does not put the pupil into touch with the living knowledge and the affairs of his time, may be of less educative value than the learning of a trade in a shop. We are coming to learn that the ideals and the abilities should be developed out of the common surround- ings and affairs of Hfe rather than imposed on the pupil as a matter of abstract, unrelated theory. One of the marks of this new tendency in education is the introduction of unit courses in biology in the sec- ondary schools, in the place of the formal and often dry and nearly meaningless isolated courses in botany, zoology, and physiology. This result is one of the outcomes of the recent nature-study discussions. The present volume is an effort to meet the need for Vi PREFACE a simple and untechnical text to cover this secondary biology in its elementary phases. The book stands be- tween the unorganized nature-study of the intermediate grades and the formal science of the more advanced courses. It is a difficult space to bridge, partly because the subjects are so diverse, and partly because some teachers do not yet understand the importance of im- parting to beginners a general rather than a special view point. Still another difficulty is the lack of uniformity in the practice of different schools. It is not urged that it is desirable to have uniformity in all respects, but the lack of it makes it difficult to prepare a book that shall equally meet all needs. It is hoped, however, that the present book is fairly adaptable to a variety of conditions, and with this thought in mind the following suggestions are made as to its use : Being in three separate parts, the teacher may begin with plants, or with animals, or with human physiology. If a one-year course is desired, the topics that are printed in large type in Parts II and III may be used, and a choice from the chapters in Part I. For three half-year courses, all the parts may be cov- ered in full. If the course in biology begins in the fall (with the school year), it may be well to study plant biology two days in the week and animal biology three days until midwinter; when outdoor material becomes scarce, human biology may be followed five days in the week ; in spring, plants may be studied three days and animals two days. If the use of the book is begun at midyear, it will prob- ably be better to follow the order in the book consecu- tively. PREFACE vil If it is desired to take only a part of the plant biology, Chapters VI, XIV, XX, XXIII, XXIV may be omitted, and also perhaps parts of other chapters (as of X, XII, XIII) if the time is very short. The important point is to give the pupil a rational conception of what plants are and of their main activities ; therefore, the parts that deal with the underlying life processes and the relation of the plant to its surroundings should not be omitted. If more work is wanted it is best to provide the extra work by means of the study of a greater abundance of specimens rather than by the addition of more texts; but the teacher must be careful not to introduce too much detail until the general subject has first been covered. The value of biology study lies in the work with the actual things themselves. It is not possible to provide specimens for every point in the work, nor is it always desirable to do so ; for the beginning pupil may not be able to interest himself in the objects, and he may become immersed in details before he has arrived at any general view or reason of the subject. Great care must be exer- cised that the pupil is not swamped. Mere book work or memory stuffing is useless, and it may dwarf or divert the sympathies of active young minds. Every effort should be made to apply the lessons to daily life. The very reason for knowing plants and ani- mals is that one may live with them, and the reason for knowing oneself is that he may live his daily life with' some degree of intelligence. The teacher should not be afraid to make all teaching useful and practical. In many cases a state syllabus designates just what subjects shall be covered ; the topics may be chosen easily from the text, and the order of them is usually left largely to the discretion of the teacher. Vlii PREFACE Finally, let it be repeated that it is much better for the beginning pupil to acquire a real conception of a few central principles and points of view respecting common forms that will enable him to tie his knowledge together and organize it and apply it, than to familiarize himself with any number of mere facts about the lower forms of life which, at the best, he can know only indirectly and remotely. If the pupil wishes to go farther in later years, he may then take up special groups and phases. CONTENTS General Introduction PART I. PLANT BIOLOGY CHAPTER I. No Two Plants or Parts are Alike II. The Struggle to Live III. Survival of the Fit IV. Plant Societies V. The Plant Body VI. Seeds and Germination VII. The Root — The Forms of Roots VIII. The Root — Function and Structure IX. The Stem — Kinds and Forms — Pruning X. The Stem — Its General Structure XI. Leaves — Form and Position . XII. Leaves — Structure and Anatomy XIII. Leaves — Function or Work XIV. Dependent Plants . XV. Winter and Dormant Buds XVI. Bud Propagation XVII. How Plants Climb . XVIII. The Flower — Its Parts and Forms XIX. The Flower — Fertilization and Pollination XX. Flower-clusters XXI. Fruits .... XXII. Dispersal of Seeds . XXIII. Phenogams and Cryptogams XXIV. Studies in Cryptogams PAGE xi X CONTENTS PART II. ANIMAL BIOLOGY CHAPTER PAGE I. Introduction i II. Protozoans lo III, Sponges 17 IV. Polyps 22 V. Echinoderms 34 VI. Worms 42 VII. Crustaceans 51 VIII. Insects 63 IX. MOLLUSKS 97 X. Fishes 109 XL Batrachians 126 XII. Reptiles 139 XIII. Birds 150 XIV. Mammals 184 PART III. HUMAN BIOLOGY I. Introduction i II. The Skin and Kidneys 16 III. The Skeleton 29 IV. The Muscles 39 V. The Circulation 51 VI. The Respiration 70 VII. Food and Digestion 89 VIII. The Nervous System 117 IX. The Senses . . 142 X. Bacteria and Sanitation 158 General Index i GENERAL INTRODUCTION PRELIMINARY EXPERIMENTS These experiments are inserted for those pupils who have not had instruction in chemistry and physics, to give them a point of view on the subjects that follow. At least a general understanding of some of these subjects is necessary to a satisfactory elementary study of biology. Elements and Compounds. — The material world is made up of elements and compounds. An element is a sub- stance that cannot be separated into two or more sub- stances. A compound is formed by the union of two or more elements. All the material or substance of which the earth and its inhabitants is composed is formed of the chemical elements ; this substance taken all together is known as matter. Carbon and iron are examples of elements. Compare a bit of charcoal, which is one form of carbon, with a new iron nail. Which is brighter } Heavier for its size } Tougher .'' More brittle } Harder .-* More readily com- bustible .-* Resistant to change when left exposed to air and dampness .-' There are two other forms of carbon : graphite or black lead (used in pencils and stove polish); and diamond, which occurs in crystals and is the hardest known substance. Iron does not have varied forms like carbon. Sulfur is another element. What is its color .-' Has it odor.-* Taste.'* Will it dissolve in water .-* Is it heavy or light .'' Will it burn 1 What is the color of the flame } Of the fumes .'' Phosphorus, another element, xii GENERAL INTRODUCTION burns so readily that it ignites by friction and is used in matches. Rub the tip of a match with the finger. What is the odor of phosphorus.-' Phosphorus exists in nature only in combination with other elements. Lead, tin, silver, gold, copper, zinc, nickel, platinum, are elements. There are less than eighty known elements ; but the com- pounds formed of them are innumerable. Carbon is found in all substances formed by the growth of living things. That there is carbon in sugar, for example, can easily be shown by charring it on a hot shovel or a stove until its water is driven off and only charcoal is left. Part of the starch in a biscuit remains as charcoal when it has been half burned. Favorable and Unfavorable Conditions for Evaporation. — Pour the same quantity of water (half a glassful) into three saucers and two bottles. Place one saucer near a hot stove ; place the other two in a cool place, having first covered one of them with a dish. Place one of the bottles by the stove and the other by the remaining saucers. After some hours, examine the saucers and bottles and compare and record the results. Explain. State three conditions that are favorable to evaporation. State three ways in which evaporation may be prevented or decreased. Tests for Acid, Alkaline, and Neutral Substances. — For acid tests, use sour buttermilk (which contains lactic acid), or hydrocJiloric acid diluted in ten parts water, or strong vinegar (which contains acetic acid). Has the acid a char- acteristic (" sour") odor and taste (test it only when very dilute)? Rub dilute acid between the fingers; how does it feel.-* Is there any effect on the fingers } Obtain Htmus paper at a druggist's. Dip a strip of red Htmus and of blue litmus paper into the acid. What result .-* For alkaline tests, dissolve in a glass of water a spoonful PRELIMINARY EXPERIMENTS xiii of baking soda or some laundry soap ; or dissolve an inch stick of caustic soda in a glass of water. Test odor and " feel " of last solution as with the acid ; likewise test effect of alkaline solution on red and blue litmus paper. Record results. Alkalies are strong examples of a more general class of substances called bases, which have the opposite effect from acids. Test pure water. Has it odor .-' A taste } Test it with red and blue litmus paper. Water is a neiitral substance ; that is, it is neither an acid nor an alkali (or base). After making appropriate tests, write ac, al, or neti after each name in the following list (or write in three columns): vinegar, soda, saliva, sugar, juice of apple, lemon, and other fruits, milk, baking powder, buttermilk, ammonia, salt water. Pour some of the alkaline solution into a dish, gradually add dilute acid (or sour buttermilk), stirring with glass rod and testing with litmus until the mixture does not turn red litmus blue nor blue litmus red. The acid and alkali are then said to have neutralized each other, and the resulting substance is called a salt. The salt may be obtained by evaporating the water of the solution. Most common minerals are salts. If the last experiment is tried with soda and sour buttermilk, the demonstration will show some of the facts involved in bread making with the use of these substances. Tests for Starch. — Starch turns blue with iodine. The color may be driven away by heat, but will return again as the temperature lowers. Produce a few cents' worth of tinc- ture of iodine and dilute it. Get a half dozen pieces of paper and cardboard, all different, and test each for starch by placing it over mouth of bottle and tipping the bottle up. If much starch is present, the spot will be blue-black xiv GENERAL INTRODUCTION or dark blue ; if little starch, pale blue ; if no starch, brown or yellowish. Make pastes with wheat flour, potato starch, and corn starch. Treat a little of each with a solution of rather dilute tincture of iodine. Try grains from crushed rice with the same solution. Are they the same color? Cut a thin section from a potato, treat with iodine and examine under the microscope. To study Starch Grains. — Mount in cold water a few grains of starch from each of the following : potato, wheat, arrowroot (buy at drug store), rice, oats, corn. Study under microscope the sizes, forms, layers, fissures, and location of nuclei, and make a drawing of a few grains of each. Test for Grape Sugar. — Make a thick section of a bit of the edible part of a pear and place it in a bath of Fehling's solution. After a few moments boil the liquid containing the section for one or two minutes. It will turn to an orange color, showing a deposit of an oxid of copper and perhaps a little copper in the metallic form. A thin sec- tion treated in like manner may be examined under the microscope, and the line particles, precipitated from the sugar of the pear, may be clearly seen. {Fehling's solution is made by taking one part each of these three solutions and two parts of water: (i) Copper sulfate, 9 grams in 250 cubic centimeters of water; (2) sodium hydroxid, 30 grams in 250 c.c. water; (3) Rochelle salts, 43 grams in 250 c.c. water.) Test for Nitrogenous Substances, or Proteids. — Put a little white of Qgg into a test tube and heat slowly. What change takes place in the Qgg'f Put another part of the white of egg into a test tube and add dilute nitric acid. Compare the results of the two experiments. White of tgg is an ex- ample of a proteid ; that is, it is the form of nitrogen most PRELIMINARY EXPERIMENTS XV commonly found in plant and animal tissue, and it can be formed only by life processes. Do acid and heat harden or soften most substances ? Either of the above tests reveals proteid, if present. Does cooking tend to soften or toughen lean meat .'' Another test for proteid is nitric acid, which t7irns pro- teid (and hardly anything else) yellow. Proteid when burned has a characteristic odor ; this will be noticed if lean meat or cheese is charred in a spoon. The offensive odor from decomposing proteid is also characteristic, whether it comes from stale beans, meat, mushrooms, or other things containing proteid. Test for Fats and Oils. — Place a little tallow from a candle on unglazed paper and warm. Hold the paper up to the light and examine it. What effect has the fat had on the paper .-• Place a little starch, sugar, powdered chalk, or white of tgg on paper and repeat the experiment ; is the effect the same } Place some of the tallow in a spoon, and heat. Compare the effect of heat on fat and proteid. Water also makes paper semi-transparent, but it soon evaporates : fat does not evaporate. Another test for fats is to mount a thin section of the endosperm of castor-oil seed in water and examine with high power. Small drops of oil will be quite abundant. Treat the mount with alcanin (henna root in alcohol). The drops of oil will stain red. This is a standard test for fats and oils. To make or liberate Oxygen. — If there is a chemistry class in school, one of its members will doubtless be glad to prepare some of the gas called oxygen, and furnish several glass jars filled with it to the biology class. If it is desired to make oxygen, the following method may be employed : Provide a dry glass flask of three to four XVI GENERAL INTRODUCTION ounces capacity. It should have a glass delivery tube, inserted through a one-holed rubber stopper, and so bent as to pass under the surface of water contained in a deep dish. Fill several pint fruit-jars with water, cover with pieces of stiff pasteboard, and turn mouth down- wards in the dish of water. From one half to two thirds ounce of an equal mixture of potassium chlorate and manganese dioxid (procured at drug store) is put in the flask and heated by means of a gas or alcohol lamp. When the oxygen begins to form, collect some in jars by inserting the end of delivery tube under the jars as they stand in water. Caution : Remove delivery tube from water before cooling the flask, to prevent any water being drawn back. Oxygen and the Air. — The great activity of pure oxygen in attacking other substances can be shown by passing into a fruit-jar a Hghted splinter, a piece of light :d mag- nesium ribbon, an old watch spring (or a bit or picture wire), the end of which has been dipped in suifur and lighted. About one fifth of the air is oxygen and about four fifths is nitrogen and other inactive gases. Pure nitrogen will quickly extinguish a lighted splinter thrust into it. It is the oxygen in the air that supports all forms of burning. Less than one half of one per cent of the air is an inactive gas called carbon dioxid, a compound of carbon and oxygen. It is formed not only when wood or coal is burned, but also by the life processes of animals and plants. Oxidation. — That something besides wood or coal is necessary to a fire can be shown by shutting off entirely the draught of a stove. Fire and other forms of combus- tion depend on a process called oxidation. This consists in the uniting of oxygen with other substances. When PRELIMINARY EXPERIMENTS XVU wood decays, the carbon in it oxidizes (unites with oxygen) and carbon dioxid gas is formed. When wood burns, the oxidation is more rapid. When iron oxidizes, iron rust is formed. When hydrogen is oxidized, water is formed. Kerosene oil contains hydrogen, and water is formed when it is burned. Almost every one has noticed the cloud of moisture which collects on the chimney when the lamp is first lighted. By using a chimney which has been kept in a cold place, the moisture becomes apparent ; soon the chimney becomes hot and the water no longer collects, but it continues to pass into the room as long as the lamp burns. Fats also contain hydrogen. Hold a piece of cold glass or an inverted tumbler above the flame of a tallow candle. Does water collect on it .■' Oxidation may be said to be the basis of all life processes for this reason : oxidation gives rise to heat and sets free energy, and all living things need heat and energy in order to grow and live. The heat of animals is very noticeable. The oxidation in plants also forms a slight amount of heat. In both animals and plants oxidation is much slower than in ordinary fires. That heat is formed even in slow oxida- tion is shown by fires which arise spontaneously in masses of decaying material. The rotting of wood is not only accompanied by heat but sometimes by light, as when " fox fire " is emitted. Rub the end of a match on your finger in the dark. Explain the result. Strike a match and notice the white fumes which rise for an instant. These fumes are not ordinary smoke (particles of carbon), but they are oxid of phosphorus. Why will water (oxid of hydrogen) not burn .? Sand is oxid of silicon. Explain how throwing sand on a fire puts it out. [See also experi- ments with candle and breath, in Introduction to Human Biology.] xviii GENERAL INTRODUCTION Inorganic and Organic Matter. — Test for Minerals. — The earth was once in a molten condition, which would have destroyed any combustible material if any had then existed. Before plants and animals existed, the earth con- sisted mostly of incombustible minerals, known as ijiorganic matter. Substances formed by animals and plants are organic juatter, so called because built up by organized or organ-bearing or living things; starch is an example, being formed in plants. Organic substances are composed chiefly of carbon, oxygen, hydrogen, and nitrogen. (See page i of "Animal Biology.") Coal-oil, and all combustible ma- terials have their origin in life. Hence, burning to find whether there is an incombustible residue is also a test for minerals. Meat, bread, oatmeal, bone, wood, may be tested for mineral matter by burning in a spoon held over a hot fire, or flame of gas or lamp. The substance being tested should be burned until all black material (which is organic carbon and not a mineral) has disappeared. Any residue will be mineral matter. Protoplasm. — Inside the cells of plants and animals is the living substance, known as protoplasm. It is a struc- tureless, nearly or quite colorless, transparent jelly-like substance of very complex and unstable composition. Eighty per cent or more is water ; the remainder is pro- teid, fats, oils, sugars, and salts. Protoplasm has the power of groivtJi and reproduction ; it can make living sub- stattce from dead or lifeless substances. It has the power of m-ovement within the cell, and it is influenced (or is irrita- ble) by heat, light, touch, and other stimuli. When proto- plasm dies the organism dies. Physics is the science that treats of the properties and phenomena (or behavior) of matter or of objects; as of such properties or phenomena or agencies as heat, light, PRELIMINARY EXPERIMENTS xix force, electricity, sound, friction, density, weight, and the like. Chemistry is the science that treats of the composition of matter. All matter is made up, as we have seen, of ele- ments. Very few elements exist in nature in a free or uncombined form. The nitrogen and oxygen of the air are the leading uncombined elements. In order to express the chemical combinations clearly, symbols are used to represent each element, and these symbols are then combined to represent the proportions of each in the compound. If C stands for carbon and O for oxygen, the carbon dioxid might be represented by the formula COO. In order to avoid the repetition of any letter, however, a number is used to denote how many times the element is taken : thus the formula always used for carbon dioxid is CO2. The formula for hydrogen oxid, or water, is HgO ; that for starch is CgHj^jOj. N stands for nitrogen ; P, for phosphorus ; K, potassium ; Fe, iron ; S, sulfur. Biology is the science that treats of life ; that is, of all knowledge of plants and animals of all kinds. (See page I, "Animal Biology.") How A Candle Burns Some of the foregoing suggestions may be readily explained and illustrated by simple experiments with a burning candle. The following directions for such experiments are by G. W. Cavanaugh. The materials needed for this exercise are : a piece of candle about two inches long, a lamp chimney (one with a plain top is best), a piece of white crockery or window glass, a piece of fine wire about six inches long, a bit of quicklime about half the size of an egg, and some matches. All of these, with the possible exception of the quicklime, can be obtained in any household. XX GENERAL INTRODUCTION If you perform the experiment requiring the hme, be sure that you start with a fresh piece of quick or stone Ume, which can be had of any Hme or cement dealer. During the performance of the following simple experiments, the pupil should describe what he sees at each step. The questions inserted in the text are offered merely as suggestions in the development of the desired ideas. The answers are those which it is desired the pupils shall reach or confirm by their own observation. I. Oxygen Light the candle and place it on a piece of blotting paper (yA). What do you see burning } Is anything burn- ing besides the candle ? The answer will probably be " no." Let us see. Place the lamp chimney over the lighted candle, and partly cover the top by a piece of stiff paper, as in Fig. A. Ask the pupils to observe and describe how the flame goes out ; i.e. that it is gradually extinguished and does not go out instantly. Why did the flame go out ? The probable thought will be, A. — The Hf'-.inmng of THE Candle Ex- periment. " Because there was no air." (If there was no air within the chimney, some could have entered at the top.) Place two pencils beside the re- lighted candle and on them the chim- ney {E). What is the difference be- tween the way in which the candle burns now and before the chimney was placed over it.' It flickers, or dances about more. W^hat makes i). — Supplying Air un- derneath the Chim- ney. PRELlMlN-ARy EXPERIMENTS XXI boys and girls feel like dancing about when they go out from a warm schoolroom ? What makes the flame dance or flicker when the chimney is raised by the pencils ? Because it gets fresh air under the chimney. Repeat the first experiment, in which the flame grows gradually smaller till it is extinguished. Why does the flame die out now } Is it really necessary to have fresh air in order to keep a flame burning.'* To prove this further, let the candle be relighted. Place the chimney over it, now having the top completely closed by a piece of paper. Have ready a lighted splinter or match, and just as soon as the candle is extinguished remove the paper from the chimney top and thrust in the lighted splinter. Why does the light on the splinter go out } What became of the freshness that was in the air .-' It was destroyed by the burning candle. - Evidently there is some decided difference between un- burned air and burned air, since a flame can continue to burn only in air that has the quality known as freshness. This quality of fresh air is due to oxygen, represented by O. Why was the splinter put out instantly, while the candle flame died out gradually .'* When the splinter was thrust in, the air had no freshness or oxygen at all, while when the candle was placed under the chimney, it had whatever oxygen was originally in the air within the chimney. Endeavor to have this point clearly understood : that the candle did not go out as long as the air had any oxygen and that the splinter was extinguished immediately because there was no oxygen left. Rehght the candle. A former question may now be repeated : Is anything else burning besides the candle.'' When the subject of the necessity of fresh air and con- sequently of oxygen for the burning of the candle seems Xxu GENERAL INTR OD UC TION to be understood, the following questions, together with any others which suggest themselves, may be asked: What is the reason that draughts are opened in stoves ? Why is the bottom of a "burner" on a lamp always full of holes? II. Carbon Let us now observe the blackened end of a burned match or splinter. This black substance is usually known by the name of charcoal. If handled, it will blacken the fingers. Try this. The same substance is found on the bottoms of kettles which have been used over a wood fire, but it is there a fine powder. Let us see what was burning when the candle was lighted, besides the oxygen in the air. Relight the candle and hold the porcelain or glass about an inch above the bright part of the flame. What happens to it there } Next, lower it directly into the flame {C). What is the black stuff that gets on the glass .-^ Look closely and see whether it is not deposited here also as a fine powder. Will this de- posit from the candle blacken the fingers } Instead of using the name cJiarcoal for this black sub- stance, let us call it carbon, the better name, because there are several kinds of carbon, and charcoal is only that kind which is rather light and easily blackens the hands. The carbon from the candle flame came mostly from the wax or tallow ; only a very small part came from the wick. It cannot be seen in the tallow, neither can it be seen in C. — The Carbon (ok Soot) is deposited ON THE Glass. PRELIMINARY EXPERIMENTS xxiii unburned wood, and yet it can be found when the wood is partly burned. Why, now, is the glass blackened when held in the flame and not when held directly above it ? It is because the carbon from the candle has not been completely burned at the middle of the flame ; but it is burned beyond the bright part of the flame. When the glass is held in the flame, the carbon that is not yet completely burned is de- posited on it, because it is cooler than that in the surround- ing flame. A fine deposit of carbon can be had from any of the luminous parts of the flame; and it is these thousands of little particles of carbon, getting white hot, which glow like coals in the stove and make the light. Just as soon as they are completely burned, there is no more light, as coals cease to glow when burned to ashes. III. Carbon dioxid Let us now inquire what becomes of the carbon that we find in the bright part of the flame and of the oxygen that was in the air in the lamp chimney. When the candle was extinguished within the chimney, there was no oxygen left, as shown by the lighted splinter, which was put out immedi- ately. Neither could any of the particles of carbon be found except on the wick. Yet they both still exist within the chimney, but in an entirely different condition. While the candle was burning, the little particles of carbon that we find ascending in the flame are joining with the oxygen of the air and making an entirely new substance. This new substance is a gas and cannot be seen in the air. Of what two substances is this new substance made .-' It is COo. XXIV GENERAL INTRODUCTION Z?. — The Test WITH THE Sus- pended Film OF Limewater. Place a bit of quicklime in about half a glass of water on the day previous to the experiment. When ready for use there will be a white sediment at the bottom and a thin white scum on the top of the clear lime- water. The pupils should see this white scum, as a question about it will follow. Make a loop in the end of the piece of wire by turning it around the point of a lead pencil. Remove the scum from the limewater with a piece of paper and insert the loop into the clear water. When withdrawn, the loop ought to hold a film of clear water. Pass the wire through a piece of cardboard or stiff paper, and arrange as shown in D. Place the chimney over the lighted candle. Lower thfe loop into the chimney and cover the top of the chimney with the paper. Withdraw the wire two minutes after the candle goes out. Note the cloudy appearance of the film of water on the wire. The cloudiness was caused by the carbon dioxid formed while the candle was burning. Omitting the candle, hang the freshly wetted wire in the empty chimney. Let the film of limewater remain within the chimney for the same length of time as when the can- dle was used. It does not become cloudy now. The cloudiness in clear limewater is a test or indication that carbon dio.xid is present. What caused the white scum on the limewater which stood overnight .'' How does the COg get into the air } It is formed when- ever wood, coal, oil, or gas is burned. The amount of COg in ordinary air is very small, being only three parts in ten thousand. If the limewater in the PRELIMINARY EXPERIMENTS XXV loop be left long enough in the air, it will become cloudy. The reason it clouds so quickly when the candle is being burned is that a large amount of CO2 is formed. Besides being made by real flames, CO3 is formed every time we breathe out air. Renew the film of water in the loop and breathe against it gently for two or three minutes. The presence of CO2 in the breath may be shown better by pouring off some of the clear limewater into a clean glass and blowing into it through a straw. Why does water put out a fire.-* The answer is, not alone because it wets and shuts off the supply of free oxygen, but because it cools the carbon, which must be hot in order to unite with the oxygen, and prevents the oxygen of the air from getting as near the carbon as before. PLANT BIOLOGY CHAPTER I NO TWO PLANTS OR PARTS ARE ALIKE compj same rVRE Alike. plants of \ it will be found that they dijfer from each other. The difference is apparent in size, form, color, mode of branching, number of leaves, number of flowers, vigor, season of maturity, and the like ; or, in other words, all plants and animals vary from an assumed or standard type. If one compares any two branches or twigs on a tree, it will be found that they differ in size, age, form, vigor, and in other ways (Fig. i). If one compares any two leaves, it will be found that they are unlike in size, shape, color, veining, hairiness, markings, cut of the margins, or other sm.all features. In some cases (as in Fig. 2) the differences are so great as to be readily seen in a small black-and-white drawing. PLAXT BIOLOGY If the pupil extends his observation to animals, he will still find the same truth ; for probably no two living objects arc exact duplicates. If any person finds two objects that he thinks to be exactly alike, let him set to work to Fig. 2. — No Two Leaves are Alike. discover the differences, remembering that notJiing ifi jiatiire is so small or apparently trivial as to be overlooked. Variation, or differences between organs and also be- tween organisms, is one of the most significant facts in nature. Suggestions. — The first fact that the pupil should acquire about plants is that no two are alike. The way to apprehend this great fact is to see a plant accurately and then to compare it with NO TWO PLANTS OR PARTS ARE ALIKE 3 another plant of the same species or kind. In order to direct and concentrate the observation, it is well to set a certain number of attributes or marks or qualities to be looked for. 1. Suppose any two or more plants of corn are compared in the following points, the pupil endeavoring to determine whether the parts exactly agree. See that the observation is close and accurate. Allow no guesswork. Instruct the pupil to measure the parts when size is involved : (i) Height of the plant. (2) Does it branch? How many secondary stems or "suck- ers" from one root? (3) Shade or color. (4) How many leaves ? (5) Arrangement of leaves on stem. (6) Measure length and breadth of six main leaves. (7) Number and position of ears ; color of silks. (8) Size of tassel, and number and size of its branches. (9) Stage of maturity or ripeness of plant. (10) Has the plant grown symmetrically, or has it been crowded by other plants or been obliged to struggle for hght or room ? (11) Note all unusual or interesting marks or features. (12) Always make note of comparative vigor of the plants. Note to Teacher. — The teacher should always insist on per- sonal work by the pupil. Every pupil should handle and stuay the object by himself. Books and pictures are merely guides and helps. So far as possible, study the plant or animal just whe^-e it grows naturally. Notebooks. — Insist that the pupils make full notes and preserve these notes in suitable books. Note-taking is a powerful aid in organizing the mental processes, and in insuring accuracy of obser- vation and record. The pupil should draw what he sees, even though he is not expert with the pencil. The drawing should not be made for looks, but to aid the pupil in his orderly study of the object; it should be a means of self-expression. Laboratory. — Every school, however small, should have a laboratory or work-room. This work-room may be nothing more than a table at one side of the room where the light is good. Here the specimens may be ranged and studied. Often an aquarium and terrarium may be added. A cabinet or set of shelves should be provided for a museum and collection. The laboratory may be in part out of doors, as a school garden ; or the garden may be at the pupil's home, and yet be under the general direction of the teacher. CHAPTER II THE STRUGGLE TO LIVE Every plant and animal is exposed to unfavorable con- ditions. It is obliged to contend with these conditions in order to live. No two plants or parts of plants are identically exposed to the conditions in which they live. The large branches Fig. 3. — a Battle for Life. in Fig. I probably had more room and a better exposure to light than the smaller ones. Probably no two of the leaves in Fig. 2 are equally exposed to light, or enjoy identical advantages in relation to the food that they re- ceive from the tree. Examine any tree to determine under what advantages or disadvantages any of the limbs may live. Examine similarly the different plants in a garden row (Fig. 3); or the different bushes in a thicket ; or the different trees in a wood. 4 / THE STRUGGLE TO LIVE 5 The plant meets its conditions by siicannbing to them (that is, by dying), or by adapting itself to them. The tree vieets the cold by ceasing its active growth, hardening its tissues, dropping its leaves. Many her- baceous or soft-stemmed plants meet the cold by dying to the ground and withdrawing all life into the root parts. Some plants meet the cold by dying outright and provid- ing abundance of seeds to perpetuate the kind next season. Fig. -The Reach for Light of a Tree on the Edge of a Wood. Plants adapt themselves to light by growing toward it (Fig. 4); or by hanging their leaves in such position that they catch the light ; or, in less sunny places, by expand- ing their leaf surface, or by greatly lengthening their stems so as to overtop their fellows, as do trees and vines. The adaptations of plants will afford a fertile field of study as we proceed. 6 PLANT BIOLOGY Struggle for existence and adaptation to conditions are among the most significant facts in nature. Tlio sum of all the conditions in which a plant or an ani- mal is placed is called its environment, that is, its surround- ings. The environment comprises the conditions of climate, soil, moisture, exposure to light, relation to food supply, contention with other ])lants or animals. The orgaiiisui adapts itself to its ctivifoiimcnt, or else it zveakctis or dies. Every weak branch or plant has undergone some hardship that it was not wholly able to withstand. Suggestions. — The pupil should study any plant, or l)ranch of a plant, with reference to the position or condition under which it grows, and compare one plant or branch with another. With animals, it is common knowledge that every animal is alert to avoid or to escape danger, or to protect itself. 2. It is well to begin with a branch of a tree, as in Fig. i. Note that no two parts are alike (Chap. I). Note that some are large and strong and that these stand farthest towards Jight and room. Some are very small and weak, barely able to live under the competition. Some have died. The pupil can easily determine which ones of the dead branches perished first. He should take note of the position or place of the branch on the tree, and determine whether the greater part of the dead twigs are toward the center of the tree top or toward the outside of it. Determine whether acci- dent has overtaken any of the jjarts. 3. Let the pupil examine the top of any thick old apple tree, to see whether there is any struggle for existence and whether any limbs have j)erished. 4. If the pupil has access to a forest, let him determine why there are no branches on the trunks of the old trees. Examine a tree of the same kind growing in an open field. 5. A row of lettuce or other plants sown thick will soon show the competition between plants. Any fence row or weedy place will also show it. Why does the farmer destroy the weeds among the corn or potatoes? How does the florist reduce competition to its lowest terms? what is the result? CHAPTER III THE SURVIVAL OF THE FIT The plants that most perfectly meet their conditions are able to persist. They perpetuate themselves. Their off- spring are likely to inherit some of the attributes that enabled them successfully to meet the battle of life. The Jit (those best adapted to their conditions) tend to survive. Adaptation to conditions depends on the fact of varia- tion; that is, if plants were perfectly rigid or invariable (all exactly alike) they could not meet new conditions. Conditions are necessarily new for every organism. // is impossible to picture a perfectly ijiflexible and stable succes- sion of plants or animals. Breeding. — • Maji is able to modify plants atid animals. All our common domestic animals are very unlike their original ancestors. So all our common and long-culti- vated plants have varied from their ancestors. Even in some plants that have been in cultivation less than a century the change is marked : coiiipare the com- mon black-cap raspberry with its common wild ances- tor, or the cultivated black- fig. 5. — desirable and undesirable berry with the wild form. "^^'^^ of Cotton plants, why? By choosing seeds from a plant that pleases him, the breeder may be able, under given conditions, to produce PLANT BIOLOGY numbers of plants with more or less of the desired quali- ties ; from the best of these, he may again choose ; and so on until the race becomes greatly improved (F'igs. 5, 6, 7). This process of continu- ously choosing the most suita- ble plants is known as selec- tion. A some- what similar process pro- ceeds in wild nature, and it is then known as natural se- lection. \ Fig. 6. — Flax Breeding. /J is a plant grown for seed production; B, for fiber production. Why ? Suggestions. — 6. Every pu- pil should un- dertake at least one simple ex- periment in se- lection of seed. He may select kernels from the best plant of corn in the field, and also from the poorest plant, — having reference not so much to mere incidental size and vigor of the plants that may be due to accidental conditions in the field, as to the apparendy constitutional strength and size, number of ears, size of ears, perfectness of ears and kernels, habit of the plant as to sucker- ing, and the like. The seeds may be saved and sown the next year. P'.very crop can no doubt be very gready improved by a careful process of selection extending over a series of years. Crops are increased in yield or efficiency in three ways : better general care ; enriching the land in which they grow; attention to breeding. Fig. 7. — Breed- ing. A, effect from breed- ing from smallest grains (after four years), average head; B, result from breeding from the plumpest and heaviest grains (after four years), average head. CHAPTER IV PLANT SOCIETIES In the long course of time in which plants have been accommodating themselves to the varying conditions in which they are obliged to grow, tJiey have become adapted to every different environment. Certain plants, therefore, may live together or near each other, all enjoying the same general conditions and surroundings. These aggre- gations of plants that are adapted to similar general con- ditions are known as plant societies. Moisture and temperature are the leading factors in determining plant societies. The great geographical societies or aggregations of the plant world may con- veniently be associated chiefly with the moisture supply, as : wet-region societies, comprising aquatic and bog vegetation (Fig. 8); arid-region societies, comprising desert and most sand-region vegetation ; mid-region societies, comprising the mixed vegetation in intermediate regions (Fig. 9), this being the commonest type. Much of the characteristic scenery of any place is due to its plant societies. Arid-region plants usually have small and hard leaves, apparently preventing too rapid loss of water. Usually, also, they are characterized by stiff growth, hairy covering, spines, or a much-contracted plant-body, and often by large underground parts for the storage of water. Plant societies may also be distinguished with reference to latitude and temperature. There are tropical societies, temperate-region societies, boreal or cold-region societies, 9 lO PLANT BIOLOGY With reference to altitude, societies might be classified as loivland (which are chiefly wet-region), intermediate (chiefly mid-region), subnlpinc or inid-uioinitain (which are chiefly boreal), alpine or higJi-viountain. The above classifications have reference chiefly to great geographical floras or societies. But there are societies ivithiti societies. There are small societies coming within the experience of every person who has ever seen plants Fk;. 8. — A \\ET-KKi;ioN Society. growing in natural conditions. There are roadside, fence- row, lawn, thicket, pasture, dune, woods, cliff, barn-yard societies. Every different place has its cha^'actcristic vegeta- tion. Note the smaller societies in Figs. 8 and 9. In the former is a water-lily society and a cat-tail society. In the latter there are grass and bush and woods societies. Some Details of Plant Societies. — Societies may be com- posed of scattered and i)itermijigled plants, or of dense chimps or groups of plants. Dense clumps or groups are usually made up of one kind of plant, and they are then PLANT SOCIETIES II called colonies. Colonies of most plants are transient : after a short time other plants gain a foothold amongst them, and an intermingled society is the outcome. Marked exceptions to this are grass colonies and forest colonies, in which one kind of plant may hold its own for years and centuries. In a large newly cleared area, plants usually yfri-^ estab- lish themselves m dense colonies. Note the great patches Fig. 9. — A Mid-region Society. of nettles, jewel-weeds, smart-weeds, clot-burs, fire-weeds in recently cleared but neglected swales, also the fire-weeds in recently burned areas, the rank weeds in the neglected garden, and the ragweeds and May-weeds along the re- cently worked highway. The competition amongst them- selves and with their neighbors finally breaks up the colonies, and a mixed and intermingled flora is generally the result. In many parts of the world the general tendency of neg- lected areas is to run into forest. All plants rush for the 12 PLANT BIOLOGY cleared area. Here and there bushes gain a foothold. Young trees come up ; in time these shade the bushes and gain the mastery. Sometimes the area grows to poplars or birches, and people wonder why the original forest trees do not return ; but these forest trees may be growing unob- served here and there in the tangle, and in the slow pro- cesses of time the poplars perish — for they are short-lived — and the original forest may be replaced. Whether one kind of forest or another returns will depend partly on the kinds that are most seedful in that vicinity and which, therefore, have sown themselves most profusely. Much depends, also, on the kind of undergrowth that first springs up, for some young trees can endure more or less shade than others. Some plants associate. They grow together. This is possible largely because they diverge or differ in charac- ter. Plants asso- ciate in two ways : by grozving side by side ; by growing above or beneath. In sparsely popu- lated societies, plants may grow alongside each other. In most cases, however, there is overgrowth and itndergrowth : one kind grows beneath another. Plants that have be- come adapted to shade are usually undergrowths. In a cat- tail swamp, grasses and other narrow-leaved plants grow in the bottom, but they are usually unseen by the casual Fig. io. — Overgrowth and Undergrowth in Three Serifs, — trees, bushes, grass. PLANT SOCIETIES 1 3 observer. Note the undergrowth in woods or under trees (Fig. 10). Observe that in pine and spruce forests there is almost no undergrowth, partly because there is very little light. On the same area the societies may differ at different times of the year. There are spring, summer, and fall soci- eties. The knoll which is cool with grass and strawber- ries in June may be aglow with goldenrod in September. If the bank is examined in May, look for the young plants that are to cover it in July and October; if in Septem- ber, find the dead stalks of the flora of May. What suc- ceeds the skunk cabbage, hepaticas, trilliums, phlox, violets, buttercups of spring .'' What precedes the wild sunflowers, ragweed, asters, and goldenrod of fall } The Landscape. — To a large extent the color of the land- scape is determined by the character of the plant societies. Evergreen societies remain green, but the shade of green varies from season to season ; it is bright and soft in spring, becomes dull in midsummer and fall, and assumes a dull yellow-green or a black-green in winter. Deciduous societies vary remarkably in color — from the dull browns and grays of winter to the brown greens and olive-greens of spring, the staid greens of summer, and the brilliant colors of autumn. The aiitnmn colors are due to intermingled shades of green, yellow, and red. The coloration varies with the kind of plant, the special location, and the season. Even in the same species or kind, individual plants differ in color ; and this individuality usually distinguishes the plant year by year. That is, an oak which is maroon red this autumn is likely to exhibit that range of color every year. The au- tumn color is associated with the natural maturity and death of the leaf, but it is most brilliant in long and open 14 PLANT BIOLOGY falls — largely because the foliage ripens more gradually and persists longer in such seasons. It is probable that the autumn tints are of no utility to the plant. Autumn colors arc not cuiiscd by frost. Because of the long, dry falls and the great variety of plants, the autumnal color of the American landscape is phenomenal. Ecology. — The study of the relationships of plants and animals to each other and to seasons and environments is known as ecology (still written (ecology in the dictionaries). It considers the habits, habitats, and modes of life of liv- ing things — the places in which they grow, how they migrate or are disseminated, means of collecting food, their times and seasons of flowering, producing young, and the like. Suggestions. — One of the best of all subjects for school instruc- tion in botany is the study of plant societies. It adds definiteness and zest to excursions. 7. Let each excursion be confined to one or two societies. Visit one day a swamp, another day a forest, another a pasture or meadow, another a roadside, another a weedy field, another a cliff or ravine. Visit shores whenever possible. Each pupil should be assigned a bit of ground — say lo or 20 ft. square — for special study. He should make a list showing (i) how many kinds of plants it contains, (2) the relative abundance of each. The lists secured in different regions should be com- pared. It does not matter greatly if the pupil does not know all the plants. He may count the kinds without knowing the names. It is a good plan for the pupil to make a dried specimen of each kind for reference. The pupil should endeavor to discover why the plants grow as they do. Note what kinds of plants grow next each other; and which are undergrowth and which overgrowth; and which are erect and which wide-spreading. Challenge every plant society. THE PLANT BODY The Parts of a Plant. — Our familiar plants are made up of several distinct parts. The most prominent of these parts are root, stem, leaf, flower, fruit, and seed. Familiar plants differ ivonderfnlly m size and shape, — from fragile mushrooms, delicate waterweeds and pond-scums, to float- ing leaves, soft grasses, coarse weeds, tall bushes, slender climbers, gigantic trees, and hanging moss. The Stem Part. — In most plants there is a maifi central part or shaft on which the other or secondary parts are borne. This main part is the plant axis. Above ground, in most plants, the main plant axis bears the bra^icJies, leaves, and fozuers ; below ground, it bears the roots. The rigid part of the plant, which persists over winter and which is left after leaves and flowers are fallen, is the framework of the plant. The framework is composed of both root and stem. When the plant is dead, the frame- work remains for a time, but it slowly decays. The dry winter stems of weeds are the framework, or skeleton of the plant (Figs, ii and 12). The framework of trees is the most conspicuous part of the plant. The Root Part. — ■ The root bears the stem at its apex, but otherwise it normally deaths only root-branches. The stem, however, bears leaves, flozvers, and frnits. Those living surfaces of the plant which are most exposed to light are green or highly colored. The root tends to grow downward, but the stem tends to grow upward toward light 15 i6 PLANT BIOLOGY -J^m and air. The plant is anchored or fixed in the soil by the roots. Plants have been called " earth parasites." The Foliage Part. — The leaves precede the flowers in point of time or life of the plant. TJic floivers always precede the fruits and seeds. Many plants die when the seeds have matured. The whole mass of leaves of any plant or any branch is known as its foliage. In some cases, as in crocuses, the flowers seem to precede the leaves ; but the leaves that made the food for these flowers grew the preceding year. The Plant Generation. — The course of a plant's life, with all the events through which the plant naturally passes, is known as the plant's life-history. The life-history em- braces various stages, or epochs, as dormant seed, germittation, growth, flozveriug, fruiting. Some plants run their course in a few weeks or months, and some live for centuries. The entire life-period of a plant is called a generation. It is the whole period from birth to normal death, without reference to the various stages or events through which it passes. A generation begins with the yoimg seed, not with germi- FiR. II. — Plant of a Wild Sunflower. Fig. 12. — Frame- work OF Fig. II. THE PLANT BODY 1/ nation. // ends with death — that is, when no life is left in any part of the plant, and only the seed or spore remains to perpetuate the kind. In a bulbous plant, as a lily or an onion, the generation does not end until the bulb dies, even though the top is dead. When the generation is of only one season's duration, the plant is said to be annual. When it is of two seasons, it is biennial. Biennials usually bloom the second year. When of three or more seasons, the plant is perennial. Examples of annuals are pigweed, bean, pea, garden sun- flower; of biennials, evening primrose, mullein, teasel ; of perennials, dock, most meadow grasses, cat-tail, and all shrubs and trees. Duration of the Plant Body. — Plant structures which are more or less soft and which die at the close of the season are said to be herbaceous, in contradistinction to being ligneous or woody. A plant which is herbaceous to the ground is called an herb ; but an herb may have a woody or perennial root, in which case it is called an herbaceous perennial. Annual plants are classed as herbs. Examples of herbaceous perennials are buttercups, bleed- ing heart, violet, water lily, Bermuda grass, horse-radish, dock, dandelion, golden rod, asparagus, rhubarb, many wild sunflowers (Figs, ii, 12), Many herbaceous perennials have short generations. They become weak with one or two seasons of flowering and gradually die out. Thus, red clover usually begins to fail after the second year. Gardeners know that the best bloom of hollyhock, larkspur, pink, and many other plants, is secured when the plants are only two or three years old. Herbaceous perennials which die away each season to bulbs or tubers, are sometim-^s called pseud-annuals (that i8 FLA XT BIOLOGY is, false annuals). Of such are lily, crocus, onion, potato, bull nettle, and false indigo of the Southern states. True annuals reach old age the first year. Plants which are normally perennial may become annual i?i a shorter- season elimatc by being killed by frost, rather than by dying naturally at the end of a season of growth. They are cli- matic annuals. Such plants are called plur-annuals in the short-season region. Many tropical perennials are plur- •*--^?,m: Fig. 13. — A Shrub or Bush. Dogwood osier, annuals when grown in the north, but they are treated as true annuals because they ripen sufficient of their crop the same season in which the seeds are sown to make them worth cultivating, as tomato, red pepper, castor bean, cotton. Name several vegetables that are planted in gardens with the expectation that they will bear till frost comes. Woody or ligneous plants are usually longer lived than herbs. Those that remain low and produce several or THE PLANT BODY 19 many similar shoots from the base are called shrubs, as lilac, rose, elder, osier(Fig. 13). Low and thick shrubs are bushes. Plants that produce one main trunk and a more or less elevated head are trees (Fig. 14). All shrubs and trees are perennial. Every plant makes an effort to propagate, or to perpetuate its kind ; and, as far as we can see, this is the end for which the plant itself lives. TJie seed or spore is the final product of the plant. \U Fig. 14. —A Tree. The weeping birch. Suggestions. — 8. The teacher may assign each pupil to one plant in the school yard, or field, or in a pot, and ask him to bring out the points in the lesson. 9. The teacher may put on the board the names of many common plants and ask the pupils to classify into annuals, pseud- annuals, plur-annuals (or climatic annuals), biennials, perennials, herbaceous perennials, ligneous perennials, herbs, bushes, trees. Every plant grown on the farm should be so classified : wheat, oats, corn, buckwheat, timothy, strawberry, raspberry, currant, tobacco, alfalfa, flax, crimson clover, hops, cowpea, field bean, sweet potato, peanut, radish, sugar-cane, barley, cabbage, and others. Name all the kinds of trees you know. CHAPTER VI SEEDS AND GERMINATION The seed contains a miniature plant, or embryo. The embryo usually has three parts that have received names : the stemlet, or caulicle ; the seed-leaf, or cotyledon (usually I or 2); the bud, or plumule, lying between or above the cotyledons. These parts are well seen in the common bean (Fig. 15), particu- larly when the seed has been soaked for a few hours. One of the large cotyledons — FlO. 15. — Pa R TS . . 1 ir r ^1 1- • i OF THE Bean. comprismg halt 01 the bean — is shown at R, cotyledon; o, R. The cauUclc is at O. The plumule is cauiicieM.piu- j^own at A. The cotyledons are attached mule; F, first -' node. to the caulicle at F : this point may be taken as tJie first node or joint. The Number of Seed-leaves. — All plants having two seed-leaves belong to the group called dicotyledons. Such seeds in many cases split readily in halves, e.g. a bean. Some plants have only one seed-leaf in a seed. They form a group of plants called monocotyledons. Indian corn is an example of a plant with only one seed-leaf : a grain of corn does not split into halves as a bean does. Seeds of the pine family contain more than two cotyledons, but for our purposes they may be associated with the dicoty- ledons, although really forming a different group. These two groups — the dicotyledons and the mono- cotyledons — represent two great natural divisions of the vegetable kingdom. The dicotyledons contain the woody SEEDS AND GERMINATION 21 bark-bearing trees and bushes (except conifers), and most of the herbs of temperate cHmates except the grasses, sedges, rushes, lily tribes, and orchids. The flower-parts are usually in fives or multiples of five, the leaves mostly netted-veined, the bark or rind distinct, and the stem often bearing a pith at the center. The monocotyledons usually have the flower-parts in threes or multiples of three, the leaves long and parallel-veined, the bark not separable, and the stem without a central pith. Every seed is, provided with food \.o support the germinat- ing plant. Commonly this food is starch. The food may be stored i?t the cotyledons, as in bean, pea, squash ; or out- side the cotyledons, as in castor bean, pine, Indian corn. When the food is outside or around the embryo, it is usually called endosperm. Seed-coats ; Markings on Seed. — The embryo and en- dosperm are inclosed within a covering made of two or more layers and known as the seed-coats. Over the point of the caulicle is a minute hole or a thin place in the coats known as the micropyle. This is the point at which fig. i6.— exter- the pollen-tube entered the forming ovule ^^^ parts of Bean. and through which the caulicle breaks in germination. The micropyle is shown at M in Fig. i6. The scar where the seed broke from its funiculus (or stalk that attached it to its pod) is named the hilum. It occu- pies a third of the length of the bean in Fig. i6. The hilum and micropyle are always present in seeds, but they are not always close together. In many cases it is difficult to identify the micropyle in the dormant seed, but its loca- tion is at once shown by the protruding caulicle as germi- nation begins. Opposite the micropyle in the bean (at the other end of the hilum) is an elevation known as the raphe. 22 PLANT BIOLOGY This is formed by a union of the funiculus, or seed-stalk, with the seed-coats, and through it food was transferred for the development of the seed, but it is now functionless. Seeds differ wonderfully in size, shape, color, and other characteristics. They also vary in longevity. These characteristics are peculiar to the species or kind. Some seeds maintain life only a few weeks or even days, whereas others will " keep " for ten or twenty years. In special cases, seeds have retained vitality longer than this limit, but the stories that live seeds, several thousand years old, have been taken from the wrappings of mummies are un- founded. Germination. — The embryo is not dead ; it is only dor- mant. When supplied with moisture, ivarmth, and oxygen {air), it awakes and groivs : this growth is germination. The embryo lives for a time on the stored food, but gradu- ally the plantlet secures a foothold in the soil and gathers food for itself. When the plantlet is finally able to shift for itself, gcrniination is eoniplete. Early Stages of Seedling. — The germinating seed first absorbs water, a?id siuells. The starchy matters gradually become soluble. The seed-coats are ruptured, the caulicle and plumule emerge. During this process the seed respires freely, tlirozuing off carbon dioxid (COj). The caulicle usually elongates, and from its lower end roots are emitted. The elongating caulicle is known as the hypocotyl ("below the cotyledons"). That is, the hypocotyl is that part of the stem of the plantlet lying between the roots and the cotyledon. TJie general direc- tion of the you Jig hypocotyl, or emerging caulicle, is down- wards. As soon as roots form, it becomes fixed and its subsequent growth tends to raise the cotyledons above the ground, as in the bean. When cotyledons rise into the SEEDS AND GERMINATION 23 Fig. 17. — Pea. Grotesque forms assumed when the roots cannot gain entrance to the soil. air, germination is said to be epigeal (" above the earth "). Bean and pumpkin are examples. When the hypocotyl does not elongate greatly ,^^^. and the cotyledons remain under ground, the germi- nation is hypogeal ("be- neath the earth"). Pea and scarlet runner bean are examples (Fig. 48). When the germinating seed lies on a hard sur- face, as on closely com- pacted soil, the hypocotyl and rootlets may not be able to secure a foothold and they assume grotesque forms. (Fig. 17.) Try this with peas and beans. The first internode ("between nodes ") above the coty- ledons is the epicotyl. It elevates the plumule into the air, and tJie phimiile-leaves expand into the first true leaves of the pla7it. These first true leaves, however, may be very unlike the later leaves in shape. Germination of Bean. — The common bean, as we have seen (Fig. 15), has cotyledons that occupy all the space inside the seed-coats. When the hy- pocotyl, or elongated caulicle, emerges, the plumule-leaves have begun to en- large, and to unfold (Fig. 18). The hypocotyl elongates rapidly. One end of it is held by the roots. The other is held by the seed-coats in the soil. It therefore takes the form of a loop, and the central part of the loop " comes up " first {a. Fig. 19). Presently the cotyledons come out of the seed-coats. Fig. 18. — Cotyledons OF Germinating Bean spread apart TO SHOW Elongat- ing Caulicle and Plumule. 24 PLANT BIOLOGY and the plant straightens and the cotyledons expand. These coty- ledons, or " halves of the bean," persist for some time {b, Fig. 19). They often become green and probably perform some function of foliage. Because of its large size, the Lima bean shows all these parts well. Germination of Castor Bean. — In the castor bean the hilum and micropyle are at the smaller end (Fig. 20). The bean " comes up" with a loop, which indicates that the hypocotyl greatly elongates. On examining germi- nating seed, however, it will be found that the cotyledons are contained inside a fleshy body, or sac {a, Fig. 21). This sac is the endosperm. Against its inner surface the thin, veiny coty- ledons are very closely pressed, ab- FlG. 19. -Germination of Bean. Fig. 20. — Sprout- ing OF Castor Bean. Fig. 21.— Germina- tion OF Castor Bean. Endosperm at a. Fig. 22. — Castor Bean. Endosperm at a, a: coty- ledons at b. ^*. Fig. 23. — GtK.MiN.vTioy Complete in Casi\>r Bean. sorbing its substance (Fig. 22). The cotyledons increase in size as they reach the air (Fig. 23), and become func- tional leaves. SEEDS AND GERMINATION 25 Germination of Monocotyledons. — Thus far we have stud- ied dicotyledonous seeds ; we may now consider the mono- cotyledonous group. Soak kernels of corn. Note that the micropyle and hilum are at the smaller end (Fig. 24). Make a longitudinal section through the Ji narrow diameter; Fig. 25 shows it. The Fig. 24. — Sprout- ing Indian Corn. Hilum at h ; micro- pyle at d. Fig. 25. — Kernel OF Indian Corn. Caulicle at b; cotyle- don at a; plumule at /. Fig. 26.— Indian Corn. Caulicle at c; roots emerging at »r, plumule at/. single cotyledon is at a, the caulicle at b, the plumule at/. The cotyledon remains in the seed. The food is stored both in the cotyledon and as endosperm, chiefly the latter. The emerging shoot is the plumule; with a sheath- ing leaf (/, Fig. 26). The root is emitted from the tip of the caulicle, c. The caulicle is held in a sheath (formed mostly from the seed-coats), and some of the roots escape through the upper end of this sheath {m, Fig. 26). The epicotyl elongates, particularly if the seed is planted deep or if it is kept for a time confined. In Fig. 27 the epicotyl has elongated from n to p. The true plumule-leaf is at o, but other leaves grow from its sheath. In Fig. 28 the roots are seen emerging from the two ends of the caulicle- Fig. 27. — Indian Corn. o, plumule: « to/, epicotyl. 26 PLANT BIOLOGY sheath, i\ ;// ; the cpicotyl has grown to / ; the first plu- mule-leaf is at 0. In studying corn or other fruits or seeds, the pupil should note how the seeds are arranged, as on the cob. Count the rows on a corn cob. Odd or even in number ? Always the same number ? The silk, is the style : find where it was attached to the kernel. Did the ear have any coverings .'' Explain. Describe colors and markings of kernels of corn ; and of peas, beans, castor bean. Gymnosperms. — The seeds in the pine cone, not being inclosed in a seed-vessel, readily fall out when the cone dries and the scales separate- Hence it is difficult to find cones with seeds in them after autumn has passed (Fig, 29). The cedar is also a gymno- sperm. Remove a scale from a pine cone and draw it and the seeds as they lie in place on the upper side of the scale. Examine the seed, preferably with a magnifying glass. Is there a hilum ? The micropyle is at the bottom or little end of the seed. Toss a seed upward into the air. Why does it fall so slowly } Can you explain the peculiar whirl- ing motion by the shape of the wing ? Repeat the ex- FiG. 28. — Germination is Com ri.KTE. /, top of epicotyl; o, plumule-leaf; m, roots; c, lower roots. SEEDS AND GERMINATION' 27 periment in the wind. Remove the wing from a seed and toss it and an uninjured seed into the air together. What do you infer from these ex- periments ? Suggestions. — Few subjects con- nected with the study of plant-life are so useful in schoolroom demonstrations as germination. The pupil should prepare the soil, plant the seeds, water them, and care for the plants. 10. Plant seeds in pots or shallow boxes. The box should not be very wide or long, and not over four inches deep. Holes may be bored in the bottom so it will not hold water. Plant a number of sqjash, bean, corn, pine, or other seeds about an inch deep in damp sand or pine sawdust in this box. The depth of planting should be two to four times the diameter of the seeds. Keep the sand or sawdust moist but not wet. If the class is large, use several boxes, that the supply of speci- mens may be ample. Cigar boxes and chalk boxes are excellent for individual pupils. It is well to begin the planting of seeds at least ten days in advance of the lesson, and to make four or five differ- ent plantings at intervals. A day or two before the study is taken up, put seeds to soak in moss or cloth. The pupil then has a series from swollen seeds to complete germination, and all the steps can be made out. Dry seeds should be had for comparison. If there is no special room for laboratory, nor duplicate ^nparatus for every pupil, each ex- periment may be assigned to a committee of two pupils to watch in the schoolroom. 11. Good seeds for study are those detailed in the lesson, and buckwheat, pumpkin, cotton, morning glory, radish, four o'clock, oats, wheat. It is best to use familiar seeds of farm and garden. Make drawings and notes of all the events in the germination. Note the effects of unusual conditions, as planting too deep and too shallow and different sides up. For hypogeal germination, use the garden pea, scarlet runner or Dutch Fig. 29. — Cones of Hem- lock (above), White Pine, Pitch Pine. 28 PLANT BIOLOGY case-knife bean, acorn, horse-chestnut. Squash seeds are excellent for germination studies, because the cotyledons become green and leafy and germination is rapid. Its germination, as also that of the scarlet runner bean, is explained in "Lessons with Plants." Onioa is excellent, except that it germinates too slowly. In order to study the root develoi)ment of germinating plantlets, it is well to pro- vide a deeper box with a glass side against which the seeds are planted. 12. Observe the germination of any common seed about the house premises. When elms, oaks, pines, or maples are abundant, the germination of their seeds may be studied in lawns and along fences. 13, When studying germination, the pupil should note the differences in shaj^e and size between cotyledons and plumule-leaves, and between plumule-leaves and the normal leaves (Fig. 30). Make drawings. 14. Make the tests described in the introductory experi- ments with bean, corn, the castor bean, and other seed for starch and proteids. Test flour, oatmeal, rice, sunflower, four o'clock, various nuts, and any other seeds obtainable. Record your results by ar- ranging the seeds in three classes, i. Much starch (color blackish or purple), 2. Little starch (pale blue or greenish), 3. No starch (brown or yellow). 15. Rate of gnnoth of seedlings as affected by differences in tempera- ture. Pack soft wet paper to the depth of an inch in the bottom of four glass bottles or tumblers. Put ten soaked peas or beans into each. Cover each securely and set them in places having different temperatures that vary little. (A furnace room, a room with a stove, a room without stove but reached by sunshine, an unheated room not reached by the sun.) Take the temperatures occasion- ally with a thermometer to find difference in temperature. The tumblers in warm places should be covered very tightly to prevent the germination from being retarded l)y drying out. Record the number of seeds which sprout in each tumbler within i day ; 2 days ; 3 days ; 4 days, etc. 16. Is air necessary for the germination and groiidh of seedlings 1 Place damp blotting paper in the bottom of a bottle and fill it three fourths fiill of soaked seeds, and close it tightly with a rubber stopper or oiled cork. Prepare a " check experiment" by having another bottle with all conditions the same except that it is covered loosely that air may have access to it, and set the bottles side by side (why keep the bottles together?). Record results as in the preceding exj)eriment. 17. What is the Fig. 30. — MusKMEi.oN Seedlings, with the unlike seed-leaves and true leaves. SEEDS AND GERMINATION 29 nature of the gas given off by germinating seeds ? Fill a tin box or large-necked bottle with dry beans or peas, then add water ; note how much they swell. Secure two fruit-jars. Fill one of them a third full of beans and keep them moist. Allow the other to remain empty. In a day or two insert a lighted splinter or taper into each. In the empty jar the taper burns : 'it contains oxygen. In the seed jar the taper goes out : the air has been replaced by carbon dioxid. The air in the bottle may be tested for carbon dioxid by removing some of it with a rubber bulb attached to a glass tube (or a fountain-pen filler) and bubbling it through lime water. 18. Temperature. Usually there is a perceptible rise in temperature in a mass of germinating seeds. This rise may be tested with a thermometer. 19. Interior of seeds. Soak seeds for twenty- four hours and remove the coat. Distinguish the embryo from the endosperm. Test with iodine. 20. Of what utility is the food in seeds ? Soak some grains of corn overnight and remove the endosperm, being careful not to injure the fleshy cotyledon. Plant the incomplete and also some complete grains in moist sawdust and measure their growth at intervals. (Boiling the sawdust will destroy molds and bacteria which might interfere with experiment.) Peas or beans may be sprouted on damp blotting paper ; the cotyledons of one may be removed, and this with a normal seed equally advanced in germi- nation may be placed on a perforated cork floating in water in a jar so that the roots extend into the water. Their growth may be observed for several weeks. 21. Effect of darkness on seeds and seedlings. A box may be placed mouth downward over a smaller box in which seedlings are growing. The empty box should rest on half-inch blocks to allow air to reach the seedlings. Note any effects on the seedlings of this cutting off of the light. Another box of seedUngs not so covered may be used for a check. Lay a plank on green grass and after a week note the change that takes place beneath it. 22. Seedling of pine. Plant pine seeds. Notice how they emerge. Do the cotyledons stay in the ground ? How many cotyledons have they ? When do the cotyledons get free from the seed-coat ? What is the last part of the cotyledon to become free ? Where is the growing point or plumule ? How many leaves appear at once ? Does the new pine cone grow on old wood or on wood formed the same spring with the cone? Can you always find partly grown cones on pine trees in winter? Are pine cones when mature on two-year-old wood ? How long do cones stay on a tree after the seeds have fallen out ? What is the advantage of the seeds falling before the cones? 23. Home experiments. If desired, nearly all of the foregoing experiments may be 30 PLANT BIOLOGY Fig. 31. — a Homk-madk Seed-ti:si KR. tried at home. The pupil can thus make the drawinn;s for the notebook at home. A daily record of measurements of the change in size of the various parts of the seedhng should also be made. 24. Seed-testing. — It is important that one know before planting whether seeds are good, or able to grow. A simple seed-tester may be made of two plates, one inverted over the other (Fig. 31). The lower plate is nearly filled with clean sand, which is covered with cheese cloth or blotting paper on which the seeds are placed. Canton flannel is sometimes used in place of sand and blotting paper. The seeds are then covered with another blotter or piece of cloth, and water is applied until the sand and papers are saturated. Cover with the second plate. Set the plates where they will have about the temperature that the given seeds would require out of doors, or perhaps a slightly higher temperature. Place 100 or more grains of clover, corn, wheat, oats, rye, rice, buckwheat, or other seeds in the tester, and keep record of the number that sprout. The result will give a percentage measure of the ability of the seeds to grow. Note whether all the seeils sprout with equal vigor and rapidity. Most seeds will sprout in a week or less. Usually such a tester must have fresh sand and paper after every test, for mold fungi are likely to breed in it. If canton flannel is used, it may be boiled. If possible, the seeds should not touch each other. Note to Tkacher. — With the study of germination, the pupil will need to begin dissecting. For dissecting, one needs a lens for the examination of the smaller parts of plants and animals. It is best to have the lens mounted on a frame, so that the pupil has both hands free for pulling the part in pieces. An ordinary pocket lens may be mounted on a wire in a block, as in Fig. A. A cork is slipped on the top of the wire to avoid injury to the face. The pupil should be provided with two dissecting needles (Fig. B), made by securing an ordinary needle in a pencil-like stick. Another con- venient arrangement is shown in Fig. C. A small tin dish is used for the base. Into this a stiff wire standard is soldered. The dish is filled with solder, to make it heavy and firm. Into a cork slipped on the standard, a cross wire is inserted, holding on the end a jeweler's glass. The lens can be moved up and down and sidewise. This outfit can be made for about seventy-five cents. Fig. D shows a convenient hand-rest or dissecting-stand to be SEEDS AND GERMINATION 31 used under this lens. It may be 16 in. long, 4 in. high, and 4 or 5 in. broad. Various kinds of dissecting microscopes are on the market, and these are to be recommended when they can be afforded. 5. — Dis- secting Needle V2 natural size. D. — Dissecting Stand. C — Dissecting Glass. /i. — Improvised Stand for Lens. Instructions for the use of the compound microscope, with which some schools may be equipped, cannot be given in a brief space ; the technique requires careful training. Such microscopes are not needed unless the pupil studies cells and tissues. CHAPTER VII THE ROOT — THE FORMS OF ROOTS The Root System. — The offices of the root are to hold the plant in place, ?iW^ to gather food. Not all the food materials, however, are gathered by the roots. Fig. 32. — Tap-root System of Alfalfa. Fig. 33. — Tap-root of the Dandelion. The entire mass of roots of any plant is called its root system. The root system may be annual, biennial or peren- nial, herbaceous or woody, deep or shallow, large or small. Kinds of Roots. — A strong leading central root, which runs directly downwards, is a tap-root. The tap-root forms 32 THE ROOT— THE FORMS OF ROOTS 33 an axis from which the side roots may branch. The side or spreading roots are usually smaller. Plants that have such a root system are said to be tap-rooted. Examples are red clover, alfalfa, beet, turnip, radish, burdock, dandelion, hickory (Figs. 32, 33). A fibrous root system is one that is composed of many nearly equal slender branches. The greater number of plants have fibrous roots. Examples are many common grasses, wheat, oats, corn. The . buttercup in Fig. 34 has a fibrous root system. Many trees have a strong tap-root when very young, but after a while it ceases to ex- tend strongly and the side roots develop until finally the tap-root character disappears. Shape and Extent of the Root Sys- tem. — The depth to which roots extend depends on the kind of plant, and the nature of the soil. Of most plants the roots extend far /;/ all directions and lie comparatively 7iear tlif surface. The roots usually radiate from a common point just beneath the surface of the ground. The roots grozv Jiere and there in search of food, often extending much farther in all directions than the spread of the top of the plant. Roots tend to spread farther in poor soil than in rich soil, for the same size of plant. The root has no such definite form as the stem has. Roots are usually very crooked, because they are constantly turned aside by obstacles. Examine roots in stony soil. Fig. 34. — A Buttercup Plant, with fibrous roots. 34 PLANT BIOLOGY Tltf extent of root surfaee is usuaUy very large, for the feeding roots are fine and very numerous. An ordinary plant of Indian corn may have a total length of root (measured as if the roots were placed end to end) of several hundred feet. The fine feeding roots are most abundant in the richest part of the soil. They are attracted by the food materials. Roots often will completely surround a bone or other morsel. When roots of trees are exposed, observe that most of them are horizontal and lie near the top of the ground. Some roots, as of willows, extend far iti search of -water. They often run into wells and drains, and into the margins of creeks and ponds. Grow plants in a long narrow box, in one end of which the soil is kept very dry and in the other moist : observe where the roots grow. Buttresses. — With the increase in diameter, the upper roots often protrude above the ground and become bracing buttresses. These buttresses are usually largest in trees which always have been exposed to strong winds (Fig- 35)- Because of growth and thickening, the roots elevate part of their diameter, and the washing away of the soil makes them to appear as if having risen out of the ground. Aerial Roots. — Although roots usually grow underground, tJiere are some that naturally grow above ground. These usually occur on climbing plants, the roots becoming sup- ports or fulfilling the office of tendrils. These aerial roots usually turn aiuay from the light, and therefore enter the O.^^- Fig. 35. — Tjif. Bracing Base of a Field Pine. THE ROOT— THE FORMS OF ROOTS 35 crevices and dark places of the wall or tree over which the plant ,3,^ climbs. The trumpet creeper (Fig. 36), true or . ; English ivy, and poison ivy climb by ' means of roots. mmf^. Fig. 37. — Aerial Roots of an Orchid. In some plants all the roots are aerial ; that is, the plant grozvs above ground, and the roots gather food from the air. Such plants usually grow on trees. They are known as epiphytes or air-plants. The most fa- FiG. 36. — Akrial Roots OF Trumpet Creeper miliar examples are some of the tropi- OR tecoma. ^2\ orchids, which are grown in glass- hou.ses (Fig. 37). RootUke organs of dodder and other parasites are discussed in a future chapter. 36 PLAXT BIOLOGY Some plants bear aerial roots, that may propagate the plant or may act as braces. They are often called prop-roots. The roots of Indian corn are familiar (Fig. 38). Many ficus trees, as the banyan of India, send out roots from their branches ; when these roots reach the ground they take hold and become great trunks, thus spreading the top of the parent tree over large areas. The muscadine grape of the Southern states often sends down roots from its stems. The man- grove tree of the tropics grows along seashores and sends down roots from the overhanging branches (and from the fruits) into the shal- low water, and thereby gradually marches into the sea. The tangled mass behind catches the drift, and soil is formed. Adventitious Roots. — Sometimes roots grow from the stem or other unusual places as the result of some accident to the plant, being located without known method or law. ^'"showiii^ ^^^^hlcTrlo^ They are called adventitious (chance) atroto/>las?fi); and the protoplasmic lining membrane of the wall governs the entrance of luater and substances in solu- tion. Being long and tube- like, these root-hairs are especially adapted for tak- ing in the largest quantity of solutions ; and they are the principal means by which plant-food is absorbed from the soil, although the sur- faces of the rootlets them- selves do their part. Water plants do not produce an abundant system of root-hairs, and such plants depend largely on their rootlets. The root-hairs are very small, often invisible. They, with the young roots, are usually broken off when the plant is pulled up. They arc \o s , c best seen when seeds are germi- nated between layers of dark blotting paper or flannel. On the young roots, they will be seen as a mold-like or gossamer- like covering. Root-hairs soon die : they do not grow into roots, pj^, ^5 _ root-iiair, much en- New ones form as the root grows. i-T-ged, in contact with the soil . . particles (.f). Air-spaces at rt ; Osmosis. The water with its water-films on the particles, as nourishment goes through the a'"*- thin walls of the root-hairs and rootlets by the process of osmosis. If there arc two liquids of different density THE ROOT— FUNCTION AND STRUCTURE 43 on the inside and outside of an organic (either vegetable or animal) membrane, the liquids tend to mix through the membrane. The laiv of osmosis is that tJic most rapid floiv is toivard the denser solution. The protoplasmic lin- ing of the cell wall is such a membrane. The soil water being a weaker solution than the sap in the roots, the flow is into the root. A strong fertilizer sometimes causes a plant to wither, or " burns it." Explain. Structure of Roots. — The root that grows from the lower end of the caulicle is the first or primary root. Secondary- roots branch from the primary root. Branches of second- ary roots are sometimes called tertiary roots. Do the sec- ondary roots grow from the cortex, or from the central cylinder of the primary root.-" Trim or peel the cortex from a root and its branches and determine whether the branches still hold to the central cylinder of the main root. Internal Structure of Roots. — A section of a root shows that it consists of a central cylinder (see Fig. 45) sur- rounded by a layer. This layer is called the cortex. The outer layer of cells in the cortex is called the epidermis, and some of the cells of the epidermis are prolonged and form the delicate root-hairs. The cortex resembles the bark of the stem in its nature. The central cylinder contains many tube-like canals, or " vessels " that convey water and food (Fig. 45). Cut a sweet potato across (also a radish and a turnip) and distinguish the central cylin- der, cortex and epidermis. Notice the hard cap on the tip of roots. Roots differ from stems in having no real pith. Microscopic Structure of Roots. — Near the end of any young root or shoot the cells are found to differ from each other more or less, according to the distance from the point. This differentiation takes place in the region Just back of the groiving point. To study growing points, use \ 44 PLANT BIOLOGY the hypocotyl of Indian corn which has grown about one half inch. Make a longitudinal section. Note these points (Fig. 47): {a) the tapering root-cap beyond the growing point ; {b^ the blunt end of the root proper and the rec- tangular shape of the cells found there ; (r) the group of cells in the middle of the first layers beneath the root- cap, — this group is the growing point ; {d) study the slight differ- ences in the tissues a short dis- tance back of the growing point. There are four regions : the central cylinder, made up of several rows of cells in the center (//); the en- dodermis, {e) composed of a single layer on each side which separates the central cylinder from the bark ; the cortex, or inner bark, (r) of sev- eral layers outside the endodermis ; and the epidermis, or outer layer of bark on the outer edges {d). Make a drawing of the section. If a series of the cross-sections of the hypocotyl should be made and stud- ied, beginning near the growing point and going upward, it would be found that these four tissues become more distinctly marked, for at the tip the tissues have not yet assumed their characteristic form. The central cylinder contains the ducts and vessels which convey the sap. The Root-cap. — Note the form of the root-cap shown in the microscopic section drawn in Fig. 47. Growing cells, and especially those which are forming tissue by sub- dividing, are very deUcate and are easily injured. The Fig. 47. — Growing Point OK Root of Indian Cor.n. d, d, cells which will form the epidermis; /, p, cells that will form bark; e, e, endoder- mis; //.cells which will form the axis cylinder; /, initial group of cells, or growing point proper; c, root-cap. THE ROOT— FUNCTION AND STRUCTURE 45 cells forming the root-cap are older and tougher and are suited for pushing aside the soil that the root may pene- trate it. Region of most Rapid Growth. — The roots of a seedling bean may be marked at equal distances by waterproof ink or by bits of black thread tied moderately tight. The seedling is then replanted and left undisturbed for two days. When it is dug up, the region of most rapid growth in the F1G.48.— -The Mark- ing OF THE Stem AND Root. Fig. 49. — The Result root can be deter- mined. Give a reason why a root cannot elongate tJirotigJiont its length, — whether there is anything to pre- vent a young root from doing so. In Fig. 48 is shown a germinating scarlet rujiner bean with a short root upon which are marks made with waterproof ink ; and the same root (Fig. 49) is shown after it has grown longer. Which part of it -^ did not lengthen at all .'' Which part lengthened slightly .-* Where is the region of most rapid growth.'' Geotropism. — Roots turn to- ward the earth, even if the seed is planted with the micropyle up. This phenomenon is called posi- tive geotropism. Stems grow away from the earth. This is negative geotropism. 46 PLANT BIOLOGY SUGOKSTIONS (Chaps. VII and VIII). — 25. Tests for food. Ex- amine a number of roots, including several fleshy roots, for the presence of food material, making the tests used on seeds. 26. Study of root-hairs. Carefully germinate radish, turnip, cabbage, or other seed, so that no delicate parts of the root will be injured. For this purpose, place a few seeds in packing-moss or in the folds of thick cloth or of blotting paper, being careful to keep them moist and warm. In a few days the seed has germinated, and the root has grown an inch or two long. Notice that, except at a dis- tance of about a quarter of an inch behind the tip, the root is covered with minute hairs (Fig. 44). They are actually hairs ; that is, root-hairs. Touch them and they collapse, they are so delicate. Dip one of the plants in water, and when removed the hairs are not to be seen. The water mats them together along the root and they are no longer evident. Root-hairs are usually destroyed when a plant is pulled out of the soil, be it done ever so carefully. They cling to the minute particles of soil (Fig. 46). The hairs show best against a dark background. 27. On some of the blotting papers, sprinkle sand ; observe how the root-hairs cling to the grains. Observe how they are flat- tened when they come in contact with grains of sand, 28. Root hold of phxnt. The pupil should also study the root hold. Let him carefully pull up a plant. If a plant grow alongside a fence or other rigid object, he may test the root hold by se- curing a string to the plant, letting the string hang over the fence, and then add- ing weights to the string. Will a stake of similar size to the plant and extending no deeper in the ground have such firm hold on the soil ? What holds the ball of earth in Fig. 50? 29. Roots exert pressure. Place a strong bulb of hyacinth or daffodil on firm-packed earth in a pot ; cover the bulb nearly to the top with loose earth ; place in a cool cellar ; after some days Fig. 50.— Ihf. Grasp of a Pi. ant on thf. Parti- cles OF Earth. A grass plant pulled in a garden. THE ROOT— FUNCTION AND STRUCTURE 47 Fig. 51.— Plant grow- ing IN In- verted Pot. or weeks, note Ihat the bulb has been raised out of the earth by the forming roots. All roots exert pressure on the soil as they grow. Explain. 30. Response of roots and stems to the force of gravity^ or geotropism. Plant a fast-growing seedling in a pot so that the plumule extends through the drain hole and suspend the pot with mouth up {i.e. in the usual position). Or use a pot in which a plant is already growing, cover with cloth or wire gauze to prevent the soil from falling, and suspend the pot in an inverted position (Fig. 51). Notice the behavior of the stem, and after a few days remove the soil and observe the position of the root. 31. If a pot is laid on one side, and changed every two days and laid on its opposite side, the effect on the root and stem will be interesting. 32. If a fleshy root is planted wrong end up, what is the result ? Try it with pieces of horse-radish root. 33. By planting radishes on a slowly revolving wheel the effect of gravity may be neutralized. 34. Region of root most sensitive to gravity. Lay on its side a pot containing a growing plant. After it has grown a few days, wash away the earth surrounding the roots. Which turned downward most decidedly, the tip of root or the upper part? 35. Soil texture. Carefully turn up soil in a rich garden or field so that you have unbroken lumps as large as a hen's egg. Then break these lumps apart carefully with the fingers and determine whether there are any traces or remains of roots (Fig. 52). Are there any pores, holes, or channels made by roots ? Are the roots in them still living? 36. Compare an- other lump from a clay bank or pile where no plants have been growing. Is there any differ- ence in texture? 37. Grind up this clay lump very fine, put it in a saucer, cover with water, and set in the sun. After a time it will have the appearance shown in the lower saucer in Fig. 43. Compare this with mellow garden soil. In which will plants grow best, even if the plant-food were the same in both? Why? 38. To test the effect of moisture on the plant, let a plant in a pot or box dry Fig. 52. -Holes in Soil made by Roots, now- decayed. Somewhat magnified. 48 PLANT BIOLOGY out till it wilts ; then add water and note the rapidity with which it recovers. Vary the e.\])eriinent in ^fe?^ at the base of the petiole. A leaf that has all three of these parts is said to be complete (Figs. 91, 106). The stipules are often green and leaflike and per- form the function of foliage, as in the pea and Japanese quince (the latter common in yards). Leaves and leaflets that have no stalks are said to be sessile (Figs. 98, 103), i.e. sitting. Find several examples. ovate Sessile Leaves of Tea. LEAVES— FORM AND POSITION 77 Fig. 99.— Clasp- ing Leaf of a Wild Aster. The same is said of flowers and fruits. The blade of a sessile leaf may partly or wholly surround the stem, when it is said to be clasping. Examples: aster (Fig. 99), corn. In some cases the leaf runs down the stem, forming a wing ; such leaves are said to be decurrent (Fig. 100). When opposite sessile leaves are joined by their bases, they are said to be connate (Fig. loi). Leaflets may have one or all of these three parts, but the stalks of leaflets are called petiolules and the stipules of leaflets are called stipels. The leaf of the garden bean has leaflets, peti- olules, and stipels. The blade is usually attached to the petiole by its lower edge. In pinnate-veined leaves, the petiole seems to continue through the leaf as a midrib (Fig. 91). In some plants, however, the petiole joins the blade inside or beyond the margin (Fig. 92). Such leaves are said to be pel- tate or shield-shaped. This mode of attachment is par- ticularly common in float- ing leaves {e.g. the water lilies). Peltate leaves are usually digitate-veined. How to Tell a Leaf. —It is often difficult to distin- guishcompound leaves from ^ ^ „ * ^ Fig. ioi.— Two Pairs of Connate leafy branches, and leaflets leaves of honeysuckle. Fig. 100. — De- current Leaves of Mullein. 78 PLANT BIOLOGY from leaves. As a rule leaves can be distinguished by the following tests: (i ) Leaves are toiiporary structures, sooner or later falling. (2) Usually buds are borne in their axi/s. (3) Leaves are usually borne at joints or nodes. (4) They arise on wood of the current years groivth. (5) They have a more or less definite arrangement. When leaves fall, the twig that bore them remains ; when leaflets fall, the main petiole or stalk that bore them also falls. Shapes. — Leaves and leaflets are infinitely variable in shape. Names have been given to some of the more definite or regular shapes. These names are a part of the language of bot- any. The names represent ideal or «^ typical shapes; there are no two ^ leaves alike and very > few that perfectly con- tf) form to the definitions, ^xn?-*;',' / The shapes are likened C*^ to those of familiar ob- jects or of geometrical figures. Some of the commoner shapes are as Fii;. 102. — Linear- acuminate ^ ,, . • • 1 LEAF OF follows (name original fig. 103. - short-oblong Grass. examples in each class): Leaves of Box. Linear, several times longer than broad, with the sides \ nearly or quite parallel. Spruces and most grasses are examples (Fig. 102). In linear leaves, the main veins are usually parallel to the midrib. Oblong, twice or thrice as long as broad, with the sides \ parallel for most of their length. Fig. 103 shows the short-oblong leaves of the box, a plant that is used for permanent edgings in gardens. LEAVES— FORM AND POSITION 79 Elliptic differs from the oblong in having the sides gradu- ally tapering to either end from the middle. The ^ European beech (Fig. 104) has elHptic leaves. (This tree is often planted in this country.) Lanceolate, four to six times longer than broad, widest below the middle, and \ tapering to either end. Some of the narrow-leaved willows are, examples. Most of the willows and the peach have oblong-lanceolate leaves. Spatulate, a narrow leaf that is broadest toward the apex. The top is usually 104. — Elliptic Leaf OF Purple Beech. Fig. 105. — Ovate Serrate Leaf of Hibiscus. Fig. 106. ■ •Leaf of Apple, showing blade, petiole, and small narrow stipules. Ovate, shaped somewhat like the longitudinal section of an ^ egg: about twice as long as broad, tapering from near ^k the base to the apex. This is one of the commonest ^ leaf forms (Figs. 105, 106). 8o PLANT BIOLOGY Obovate, ovate inverted, — the wide part towards the apex. Leaves of mullein and leaflets of horse-chestnut and ^^ false indigo are obovate. This form is commonest in leaflets of digitate leaves : why .-' Reniform, kidney-shaped. This form is sometimes seen in ^^ wild plants, particularly in root-leaves. Leaves of ^* wild ginger are nearly reniform. Orbicular, circular in general outline. Very few leaves are ^^ perfectly circular, but there are many that are ^^ nearer circular than any other shape (Fig. 107). Fig. 107. — Orbicular LoBED Leaves. Fig. 108. —Truncate Leaf of Tulip Tree. The shape of many leaves is described in combinations of these terms : as ovate-lanceolate, lanceolate-oblong. The shape of the base and apex of the leaf or leaflet is often characteristic. The base may be rounded (Fig. 104), tapering (Fig. 93), cordate or heart-shaped (Fig. 105), truncate or squared as if cut off. The apex may be blunt or obtuse, acute or sharp, acuminate or long-pointed, trun- cate (Fig. 108). Name examples. The shape of the margin is also characteristic of each kind of leaf. The margin is entire when it is not in- dented or cut in any way (Figs. 99, 103). When not LEAVES — FORM AND POSITION entire, it may be undulate or wavy (Fig. 92), serrate or saw-toothed (Fig. 105), dentate or more coarsely notched (Fig. 95), crenate or round-toothed, lobed, and the Hke. Give examples. Leaves often differ greatly in form on the same plant. Observe the different shapes of leaves on the young growths of mulberries (Fig. 2) and wild grapes ; also on vigorous squash and pumpkin vines. In some cases there may be simple and compound leaves on the same plant. This is marked in the so-called Boston ivy or ampelop- sis (Fig. 109), a vine that is used to cover brick and stone build- ings. Different degrees of compounding, even in the same leaf, may often be found in honey locust and Kentucky coffee tree. Remarka- ble differences in forms are seen by comparing seed-leaves with mature leaves of any plant (Fig. 30). The Leaf and its Environment. — The form and shape of the leaf often have direct relation to the place in which the leaf grozvs. Floating leaves are usually expanded and flat, and the petiole varies in length with the depth of the water. Submerged leaves are usually linear or thread- like, or are cut into very narrow divisions: thereby more surface is exposed, and possibly the leaves are less injured by moving water. Compare the sizes of the leaves on the ends of branches with those at the base of the Fig, log. — Different Forms of Leaves FROM ONE Plant of Ampelopsis. 82 PLANT BIOLOGY branches or in the interior of the tree top. In dense foUage masses, the petioles of the lowermost or under- most leaves tend to elongate — to push the leaf to the light. On the approach of winter the leaf usually ceases to work, and dies. It may drop, when it is said to be decidu- ous ; or it may remain on the plant, when it is said to be persistent. If persistent leaves remain green during the winter, the plant is said to be evergreen. Give examples in each class. Most leaves fall by breaking off at the lower end of the petiole with a distinct joint or articula- tion. There are many leaves, however, that wither and hang on the plant until torn off by the wind ; of such are the leaves of grasses, sedges, lilies, orchids, and other plants of the monocotyledons. Most leaves of this char- acter are parallel-veined. Leaves also die and fall from lack of light. Observe the yellow and weak leaves in a dense tree top or in any thicket. Why do the lower leaves die on house plants .-' Note the carpet of needles under the pines. All ever- greens shed their leaves after a time. Counting back from the tip of a pine or spruce shoot, determine how many years the leaves persist. In some spruces a few leaves may be found on branches ten or more years old. Arrangement of Leaves. — Most leaves have a regular position or arra?igenient on the stem. This position or direction is determined largely by exposure to sunlight. In temperate climates they usually hang in such a way that they receive the greatest amount of light. One leaf shades the other to the least possible degree. If the plant were placed in a new position with reference to light, the leaves would make an effort to turn their blades. When leaves are opposite the pairs usually alternate. That is, if one pair stands north and south, the next pair LEAVES— FORM AND POSITION 83 Stands east and west. See the box-elder shoot, on the left in Fig. 1 10. One pair does not shade the pair beneath. The leaves are in four vertical ranks. There are several kinds of alternate arrangement . In the elm shoot, in Fig. no, the third bud is vertically above the first. This is true no matter which bud is taken as the starting point. Draw a thread around the stem until the two buds are joined. Set a pin at each bud. Ob- serve that two buds are passed (not counting the last) and that the thread makes one circuit of the stem. Representing the number of buds by a de- nominator, and the num- ber of circuits by a numerator, we have the fraction \, ivhich expresses the part of the circle that lies betzueen any two buds. That is, the buds are one half of 360 degrees apart, or 180 degrees. Looking endwise at the stem, the leaves are seen to be 2-ranked, Note that in the apple shoot (Fig. no, right) the thread makes two circuits and five buds are passed : two-fiftJis represents the divergence between the buds. The leaves are 5-ranked. Every plant has its own arrangement of leaves. For opposite leaves, see maple, box elder, ash, lilac, honey- suckle, mint, fuchsia. For 2-ranked arrangement, see all grasses, Indian corn, basswood, elm. For 3-ranked Fig. iio. — Phyllotaxy of Box Elder, Elm, Apple. 84 PLANT BIOLOGY arrangement, see all sedges. For 5-ranked (which is one of the commonest), see apple, cherry, pear, peach, plum, poplar, willow. For 8-ranked, see holly, osage orange, some willows. More complicated arrangements occur in bulbs, house leeks, and other condensed parts. The buds or "eyes'" on a potato tuber, which is an underground stem (why .'), show a spiral arrangement (Fig. 1 1 1). The airangement of leaves on the stem is ktioivn as phyllotaxy (literally, "leaf arrange- ment"). Make out the phyllota.xy on six different plants nearest the schoolhouse door. In some plants, several leaves occur at one level, being arranged in a circle around the stem. Such leaves are said to be verticillate, or whorled. Leaves arranged in this way are usually narrow: why .•' Although a definite arrangement of leaves is the rule in most plants, // is subject to viodification. On shoots that receive the light only from one side or that grow in dif- ficult positions, the arrangement may not be definite. Examine shoots that grow on the under side of dense tree tops or in other par- tially lighted positions. Fig. III. — Phyllotaxy OF THE Po- T.\TO TLBER Work it out on a fresh long tuber. Suggestions. — 55. The pupil should match leaves to determine whether any two are alike. Why ? Compare leaves from the same plant in size, shape, color, form of margin, length of petiole, venation, texture (as to thickness or thinness), stage of maturity, smoothness or hairiness. 56. Let the pupil take an average leaf from each of the first ten different kinds of plants that he meets and compare them as to the above points (in Exer- cise 55), and also name the shapes. Determine how the various leaves resemble and differ. 57. Describe the stipules of rose, apple, fig, willow, violet, pea, or others. 58. In what part of the world are parallel-veined leaves the more common ? 59. Do LEAVES— FORM AND POSITION 85 and spruce trees ? decorations. Why vicinity are most you know of parallel-veined leaves that have lobed or dentate mar- gins ? 60. What becomes of dead leaves ? 61. Why is there no grass or other undergrowth under pine 62. Name several leaves that are useful for are they useful ? 63. What trees in your esteemed as shade trees ? What is the character of their foliage ? 64. Why are the internodes so long in water-sprouts and suckers ? 65. How do foliage characters in corn or sorghum differ when the plants are grown in rows or broadcast ? Why ? 66. Why may removal of half the plants increase the yield of cotton or sugar- beets or lettuce ? 67. How do leaves curl when they wither ? Do different leaves behave differently in this respect? 68. What kinds of leaves do you know to be eaten by insects ? By cattle ? By horses ? What kinds are used for human food ? 69. How- would you describe the shape of leaf of peach? apple? elm? hackberry? maple? sweet-gum? corn? wheat? cotton? hickory? cowpea? strawberry? chrysanthemum ? rose? carnation? 70. Are any of the foregoing leaves compound? How do you describe the shape of a compound leaf? 71. How many sizes of leaves do you find on the bush or tree nearest the schoolroom door? 72. How many colors or shades? 73. How many lengths of petioles? 74. Bring in all the shapes of leaves that you can find. '^ Fig. 112. — Cow'- PEA. Describe the leaves. For what is the plant used? CHAPTER XII LEAVES — STRUCTURE OR ANATOMY Besides the framework, or system of veins found in blades of all leaves, there is a soft cellular tissue called mesophyll, or leaf parenchyma, and an epidermis or skin that covers the entire outside part. Mesophyll. — The mesophyll is not all alike or homoge- neous. The upper layer is composed of elongated cells placed perpendicular to the surface of the leaf. These are called palisade cells. These cells are usually filled with green bod- ies called chlo- rophyll grains. The grain con- tains a great number of chlo- rophyll drops imbedded in the protoplasm. Below the pali- sade cells is the Fig. 113. — S?:cTioN ok a Leaf, showing the airspaces. Breathing-pore or stoma at a. The palisade cells which chiefly contain the chlorophyll are at b. Epidermal cells at c. spongy parenchyma, composed of cells more or less spher- cal in shape, irregularly arranged, and provided with many intercellular air cavities (Fig. 113). In leaves of some plants exposed to strong light there may be more than one layer of palisade cells, as in the India-rubber plant and oleander. Ivy when grown in bright light will develop two such layers of cells, but in shaded places it may be 86 { LEAVES— STRUCTURE OR ANATOMY 8/ found with only one. Such plants as iris and compass plant, which have both surfaces of the leaf equally exposed to sunlight, } usually have a palisade layer beneath each epidermis. Epidermis. — The outer or epidermal cells of leaves do not bear chlorophyll, but are usually so transparent that the green mesophyll can be seen through them. They often become very thick-walled, and are in most plants devoid of all protoplasm except a thin layer lining the walls, the cavities being filled with cell sap. This sap is sometimes colored, as in the under epidermis of begonia leaves. It is not common to find more than one layer of epidermal cells forming each surface of a leaf. The epi- dermis serves to retain moisture in the leaf and as a general protective covering. In desert plants the epidermis, as a rule, is very thick and has a dense cuticle, thereby pre- venting loss of water. There are various outgrowths of the epidermis. Hairs are the chief of these. They may be (i) simple, as on primula, geranium, naegelia; (2) once branched, as on wall- flower; (3) compound, as on verbascum or mullein; (4) disk-like, as on shepherdia ; (5) stellate, or star-shaped, as in certain crucifers. In some cases the hairs are glandular, as in Chinese primrose of the greenhouses (^Primula Sinensis) and certain hairs of pumpkin flowers. The hairs often protect the breathing pores, or stomates, from dust and water. Stomates (sometimes called breathing-pores) are small openings or pores in the epidermis of leaves and soft stems that allow the passage of air and other gases and vapors {stomate or stoma, singular ; stomates or stomata, plural). They are placed near the large intercellular spaces of the mesophyll, usually in positions least affected by direct 88 PLANT BIOLOGY sunlight. Fig. 114 shows the structure. There are two guard-cells at the mouth of each stomate, which may in most cases open or close the passage as the conditions of the atmosphere may require. The guard-cells contain .^^^\\ Fig. 114. — Diagram OF Stomate Fk.. 115. — Sio.mate of Ivy, OF IKIS (Osterhout). showing compound guard-cells. chlorophyll. In Fig. 115 is shown a case in which there are compound guard-cells, that of ivy. On the margins of certain leaves, as of fuchsia, impatiens, cabbage, are openings known as water-pores. Stoviatcs are very ninnerous, as will be seen from the num- bers showing the pores to each square inch of leaf surface : Lower surface Upper surface Peony i3«79o None Holly 63,600 None Lilac 160.000 None Mistletoe 200 200 Tradescantia 2.000 2,000 Garden Flag (iris) ii<572 iii572 The arrangement of stomates on the leaf differs with each kind of plant. Fig. 116 shows stomates and also the outlines of contiguous epidermal cells. mK^ I The function or work of the stomates is to reo-u/ate the f(^ssage qf_gases_ jnto and out of the plant. The directly active organs or parts are guard-cells, on either side the opening. One Fig. 116. — Stomates _ ' " OF Geranium Leaf. method of opening is as follows: The LEAVES— STRUCTURE OR ANATOMY 89 «■ thicker walls of the guard-cells (Fig. 114) absorb water from adjacent cells, these thick walls buckle or bend and part from each other at their middles on either side the opening, causing the stomate to open, when the air gases may be taken in and the leaf gases may pass out. When moisture is reduced in the leaf tissue, the guard cells part with some of their contents, the thick walls straighten, and the faces of the two opposite ones come together, thus closing the stomate and preventing any water vapor from pass- ing out. WJi£7i a leaf is actively at work making nezu organic compounds, the stomates are nsually open; when unfavorable condi- tions arise, they are usually closed. They also commonly close at night, when growth (or the utilizing of the new materials) is most likely to be active. It is sometimes safer to fumigate greenhouses and window gardens at night, for the noxious vapors are less likely to enter the leaf. Dust may clog or cover the stomates. Rains benefit plants by washing the leaves as well as by provid- ing moisture to the roots. Lenticels. — On the young woody twigs of many plants (marked in osiers, cherry, birch) there are small corky spots or eleva- tions known as lenticels (Fig. 117). They mark the loca- tion of some loose cork cells that function as stomates, for green shoots, as well as leaves, take in and discharge gases; that is, soft green twigs function as leaves. Under some of these twig stomates, corky material may form and the opening is torn and enlarged: the lenticels are successors to the stomates. The stomates He in the epi- Fig. 117. — Len- t i c e l s on Young Shoot OF Red Osier (CORNUS). 90 PLANT BIOLOGY tk-nnis, but as the tuii; ages the ei>iclernii.s perishes and the bark becomes the external layer. Gases continue to pass in and out through the /entieels, until the branch be- comes heavily covered with thick, corky bark. With the growth of the twii;, the Icnticcl scars enlarge lengthwise or crosswise or assume other shapes, often becoming char- acteristic markings. Fibro-vascular Bundles. — W'c have studied the fibro- vascular bundles of stems (Chaj). X). These stem bun- dles continue into the /eaves, ramifying' into the veins, carrying the soil water inwards and bringing, by diffusion, the elaborated food out through the sieve-cells. Cut across a petiole and notice the hard spots or areas in it; strip these parts lengthwise of the petiole: what are they.^ Fall of the Leaf. — In most common deciduous plants, when the season's work for the leaf is ended, the nutritious matter may be withilrawn, ami a /aver of corky ce//s is com- p/eted over the surface of the stem where the /eaf is attached. The leaf soon fa//s. It often falls even before it is killed by frost. Deciduous leaves begin to show the surface line of articulation in the early growing season. This articula- tion may be observed at any time during the summer. The area of the twig once covered by the petioles is called the leaf-scar after the leaf has fallen. In Chap. XV are shown a number of leaf-scars. In the jijane tree (sycamore or button wood), the leaf-scar is in the form of a ring surround- ing the bud, for the bud is covered by the hollowed end of the petiole; the leaf of sumac is similar. Ivxaminc with a hand lens leaf-scars of several woody plants. Note the number of bundle-scars in each leaf-scar. Sections may be cut through a leaf-scar and e.xamined with the micro- scope. Note the character of cells that cover the leaf- scar surface. LEAVES— STRUCTURE OR AXATOJfY 9! ScGGEsnoxs. — To study ffidrrmal hairs : 75. For this study, use the leaves of any hairy or woolly planL A good hand lens wiH reveal the identity of many of the coarser hairs. A dissecting micro- scope wili show them still better. For the smdy of the cell srnictnre, a compound microscope is necessary. Cross-sections may be made so as to bring hairs on the edge of the sections : or in some cases the hairs may be peeled or scraped from the epidermis and placed in water on a slide. Make sketches of the different kinds of hairs. 76. It is good pracnce tor the pupil to describe leaves in respect to their covering : Are they smooth on both surfaces ? Or hairy? Woolly? Thickly or thinly hairy? Hairs long or ^ort? Standing straight out or lying close to the sitrfece of the leaf ? Simple or branched ? Attached to the veins or the plane suitace ? Color? Most abundant on young leaves or old? 77. Place a hairy or woolly leaf under water. Does the hairy snrfece appear silvery? Why? Oikir questions : 78. \Miy is it good practice to wash the leaves of house plants? 79. Describe the leal- scars on sis kinds of plants : size, shape, color, position with reference to the bud, bundie-scars. 80. Do you find leaf-scars on naono- cot\-ledonous plants — com. cereal grains, lilies, canna. banana, palin, bamboo, green brier? 81. Note the table on page 88. Can vou suggest a reason why there are equal numbers of stomates on both surfaces of leaves of tradescantia and flag, and none on upper surtice of other leaves ? Suppose you pick a leaf of IQac (^or some larger leaT). seal the periole with wax and then rub the under surface with vaseline : on another leaf apply the vaseline to the upper surface : which leaf withers first, and why? Make a similar experiment with iris or tdue flag. 82. Why do leaves and shoots of house plants turn towards the light? What happens when the plants are turned around? 83. Note position of leaves of beans, clover, oxalis, alfalfa, locust, at night. CHAPTER XIII LEAVES — FUNCTION OR WORK We have discussed (in Chap. VIII) the work or function of roots and also (in Chap. X) the function of stems. We are now ready to complete the view of the main vital activities of plants by considering the function of the green parts (leaves and young shoots). Sources of Food. — The ordinary green plant has but two sources from wJiich to secure food, — the air and the soil. When a plant is thoroughly dried in an oven, the water passes off ; this water came from the soil. The remaining part is called the dry substance or dry matter. If the dry matter is burned in an ordinary fire, only the ash remains; tJiis ash came frovi the soil. The part that passed off as gas in the burning cojitaiued the elements that came from the air ; it also contained some of those that came from the soil — all those (as nitrogen, hydrogen, chlorine) that are transformed into gases by the heat of a common fire. The part that comes from the soil (the ash) is small in amount, being considerably less than lo per cent and sometimes less than i per cent. Water is the most abundant single constituent or substance of plants. In a corn plant of the roasting-ear stage, about 80 per cent of the substance is water. A fresh turnip is over 90 per cent water. Fresh wood of the apple tree contains about 45 per cent of water. Carbon. — Carbon enters abundantly into the composition of all plants. Note what happens when a plant is burned 92 LEAVES— FUNCTION OR WORK 93 without free access of air, or smothered, as in a charcoal pit. A tnass of charcoal remains, almost as large as the body of the plant. Charcoal is almost pure carbon, the ash present being so small in proportion to the large amount of carbon that we look on the ash as an impurity. Nearly half of the dry substance of a tree is carbon. Carbon goes off as a gas when the plant is bm'ned in air. It does not go off alone, but in combination with oxygen in the form of carboji dioxid gas, CO2. The green plant secures its carbon from the air. In other words, much of the solid matter of the plant comes from one of the gases of the air. By volume, carbon dioxid forms only a very small fraction of i per cent of the air. It would be very disastrous to animal life, however, if this percentage were much increased, for it excludes the life- giving oxygen. Carbon dioxid is often called "foul gas." It may accumulate in old wells, and an experienced person will not descend into such wells until they have been tested with a torch. If the air in the well will not support com- bustion,— that is, if the torch is extinguished, — it usually means that carbon dioxid has drained into the place. The air of a closed schoolroom often contains far too much of this gas, along with little solid particles of waste matters. Carbon dioxid is often known as carbonic acid gas. Appropriation of the Carbon. — TJie carbon dioxid of tJie air readily diffuses itself into the leaves and other green parts of tJie plant. The leaf is delicate in texture, and when very young the air can diffuse directly into the tissues. The stomates, however, are the special inlets adapted for the admission of gases into the leaves and other green parts. Through these stomates, or diffusion-pores, the out- side air enters into the air-spaces of the plant, and is finally absorbed by the Uttle cells containing the hving matter. 94 riAXT BIOLOGY Chlorophyll ("leaf green") is the agent that secures the energy by means of which carbon clioxid is utilized. This material is contained in the leaf cells in the form of grains (p. ^6>)\ the grains themselves are protoplasm, only the coloring matter being chlorophyll. The chloropliyll bodies or grains are often most abundant fiear the upper surface of the leaf, where they can secure the greatest amount of light. Without this green coloring matter, there would be no reason for the large flat surfaces which the leaves possess, and no reason for the fact that the leaves are borne most abundantly at the ends of branches, where the light is most available. Plants with colored leaves, as coleus, have chlorophyll, but it is masked by other coloring matter. This other coloring matter is usually soluble in hot water : boil a coleus leaf and notice that it becomes green and the water becomes colored. Plants groivn in darkness are yelloiv and slender, and do not reach maturity. Compare the potato sprouts that have grown from a tuber lying in the dark cellar with those that have grown normally in the bright light. The shoots have become slender and are devoid of chloro- phyll ; and when the food that is stored in the tuber is exhausted, these shoots will have lived useless lives. A plant that has been grown in darkness from the seed will soon die, although for a time the little seedling will grow very tall and slender: why.? Light favors the production of chlorophyll, and the chlorophyll is the agent in the mak- ing of the organic carbon compounds. Sometimes chloro- phyll is found in buds and seeds, but in most cases these places are not perfectly dark. Notice how potato tubers de- velop chlorophyll, or become green, when exposed to light. Photosynthesis. — Carbon dioxid diffuses into the leaf ; during sunlight it is used, and oxygen is given off. How the LEAVES — FUNCTION OR WORK 95 carbon dioxid which is thus absorbed may be used in mak- ing an organic food is a complex question, and need not be studied here; but it may be stated that carbon dioxid and water are the constituents. Complex compounds are built up out of simpler ones. Chlorophyll absorbs ccrtaiji light rays, a7id the energy thus directly or indirectly obtained is used by the living matter in uniting the carbon dioxid absorbed fi'om the air with some of the zuater brought up front the roots. The ultimate result usually is starch. The process is obscure, but sugar is generally one step ; and our first definite knowledge of the product begins when starch is deposited in the leaves. The process of using the carbon dioxid of the air has been known as carbon assimilation, but the term now most used is photosynthesis (from two Greek words, meaning light and to put together). Starch and Sugar. — All stare Ji is composed of carbon, hydrogen, and oxygen (CgHjoO^),,. The sugars and the substance of cell walls are very similar to it in composition. All these substances are called carbohydrates. In making fruit sugar from the carbon and oxygen of carbon dioxid and from the hydrogen and oxygen of the water, there is a surplus of oxygen (6 parts CO2 + 6 parts H2O = CgHj.20g + 6 O2). It is this oxygen that is given off into the air during sunlight. Digestion. — Starch is in the form of insoluble granules. When such food material is carried from one part of the plant to another for purposes of growth or storage, it is made soluble before it can be transported. When this starchy material is transferred from place to place, it is usually changed into sugar by the action of a diastase. This is a process ^digestion. It is much like the change of starchy foodstuffs to sugary foods by the saliva. 96 PI.AXT BIOLOGY Distribution of the Digested Food. —After being changed to the soluble form, t/iis material is ready to be used in c^roii'th, either in the leaf, in the stem, or in the roots. With other more comple.x products it is then distributed tJmntghout all of the growing parts of the plant ; and when passing down to the root, it seems to pass more readily through the iivier bark, in plants which have a defi- nite bark. This gradual down- ward diffusion through the inner bark of materials suitable for growth is the process referred to when the " descent of sap " is men- tioned. Starch and other products are often stored in one groiving season to be used in the next sea- son. If a tree is constricted or strangled by a wire around its trunk (Fig. ii8), the digested food cannot readily pass down and it is stored above the girdle, causing an enlargement. Assimilation. — The food from the air and that from the soil ujiite in the living tissues. The "sap" that passes upwards from the roots in the growing season is made up largely of the soil water and the salts which have been absorbed in the diluted solutions (p. 67). This upward- moving water is conducted largely through certain tubular canals of the young wood. These cells are never continu- ous tubes from root to leaf ; but the water passes readily from one cell or canal to another in its upward course. The upward-moving water gradually passes to the grow- ing parts, and everywhere in the living tissues, it is of } Fig. 118. — Trunk Girdled BY A Wire. See Fig. 85. LEA VES — FUNCTION OR WORK 97 course in the most intimate contact with the soluble carbo- hydrates and products of photosynthesis. In the build- ing up or reconstructive and other processes it is therefore available. We may properly conceive of certain of the simpler organic molecules as passing through a series of changes, gradually increasing in complexity. There will be formed substances containing nitrogen in addition to carbon, hydrogen, and oxygen. Others will contain also sulfur and phosphorus, and the various processes may be thought of as culminating in protoplasm. Protoplasm is the living matter in plants. It is in the cells, and is usually semifluid. Starch is not living matter. The -complex process of building up the protoplasm is called assimilation. Respiration. — Plants need oxygen for respiration, as ajiimals do. We have seen that plants need the carbon dioxid of the air. To most plants the nitrogen of the air is inert, and serves only to dilute the other elements ; but the oxygen is necessary for all life. We know that all animals need this oxygen in order to breathe or respire. In fact, they have become accustomed to it in just the proportions found in the air ; and this is now best for them. When animals breathe the air once, they make it foul, because they use some of the oxygen and give off carbon dioxid. Likewise, all living parts of tJie plant must have a constant supply of oxygen. Roots also need it, for they respire. Air goes in and out of the soil by diffusion, and as the soil is heated and cooled, causing the air to expand and contract. The oxygen passes into the air-spaces and is absorbed by the moist cell membranes. In the living cells it makes possible the formation of simpler compounds by which energy is released. This energy enables the plant to 98 PLANT BIOLOGY work and grow, and the final products of this action are carbon dioxid and ivater. As a result of the use of this oxygen by night and by day, plants give off carbon dioxid. Plants respire ; but since they arc stationary, and more or less inactive, they do not need as much oxygen as animals, and they do not give off so much carbon dioxid. A few plants in a sleeping room need not disturb one more than a family of mice. It should be noted, however, that germinating seeds respire vigorously, hence they consume much oxy- gen ; and opening buds and flowers are likewise active. Transpiration. — Much more water is absorbed by the roots than is used in growth, aiid this surplus water passes from the leaves into the atmosphere by an evaporation process known as transpiration. Transpiration takes place more abundantly from the under surfaces of leaves, and through the pores or stomates. A sunflower plant of the height of a man, during an active period of growth, gives off a quart of water per day. A large oak tree may transpire 150 gallons per day during the summer. For every ounce of dry matter produced, it is estimated that 15 to 25 pounds of water usually passes through the plant. When the roots fail to supply to the plant sufficient water to equalize that transpi7'ed by the leaves, the plant wilts. Transpiration from the leaves and delicate shoots is in- creased by all of the conditions which increase evapora- tion, such as higher temperature, dry air, or wind. The stomata open and close, tending to regulate, transpiration as the varying conditions of the atmosphere affect the moisture content of the plant. However, in periods of drought or of very hot. weather, and especially during a hot wind, the closing of these stomates cannot sufficiently prevent evaporation. The roots may be very active and yet fail to absorb sufficient moisture to equalize that given LEAVES — FUNCTION OR WORK 99 off by the leaves. The plant shows the effect (how ?). On a hot dry day, note how the leaves of corn " roll " tow- ards afternoon. Note how fresh and vigorous the same leaves appear early the following morning. Any injury to the roots, such as a bruise, or exposure to heat, drought, or cold may cause the plant to wilt. Water is forced up by root pressure or sap pressure. (Exercise 99.) Some of the dew on the grass in the morn- ing may be the water forced up by the roots ; some of it is the condensed vapor of the air. The wiltijig of a plant is diie to the loss of water from the cells. The cell walls are soft, and collapse. A toy "balloon will not stand alone until it is inflated with air or liquid. In the woody parts of the plant the cell walls may be stiff enough to support themselves, even though the cell is empty. Measure the contraction due to wilt- ing and drying by tracing a fresh leaf on page of note- book, and then tracing the same leaf after it has been dried between papers. The softer the leaf, the greater will be the contraction. Storage. — We have said that starch may be stored in twigs to be used the following year. The very early flowers on fruit trees, especially those that come before the leaves, and those that come from bulbs, as crocuses and tulips, are supported by the starch or other food that was organ- ized the year before. Some plants have very special stor- age reservoirs, as the potato, in this case being a thickened stem although growing underground. (Why a thickened stem.? p. 84.) It is well to make the starch test on winter twigs and on all kinds of thickened parts, as tubers and bulbs. Carnivorous Plants. — Cei"tain plants capture insects and other very small animals and utilize them to some extent as food. Such are the sundew, that has on the leaves lOO PLANT BIOLOGY Fig. 119. — The Common Sticky hairs that close over the insect ; the Venus's flytrap of the Southern states, in which the halves of the leaves close over the prey hke the jaws of a steel trap ; and the various kinds of pitcher plants that col- lect insects and other organic matter in deep, water-filled, flask- like leaf pouches (Fig. 1 19). The sundew and Venus's fly- trap are sensitive to contact. Other plants are sensitive to the touch without being insectivo- rous. The common cultivated sensitive plant is an example. This is readily grown from seeds PITCHER PLANT (5arra..«/ -J 00 Pear-buij. 142. In P'ig. 143 it is opening. In Fig. 145 Fig. 143. — The opening of THE Pear Fruit-bud. Fig. 144. — Open- iN(; Pear Leaf-bud. WINTER AND DORMANT BUDS 115 it is more advanced, and the woolly unformed flowers are appearing. In Fig. 146 the growth is more advanced. Fig. 146. — a sin- gle Flower IN THE Pear CLUSTER, as seen at 7 a.m. on the day of its opening. At 10 o'clock it will be fully ex- panded. Fig. 147. — The opening of THE FLOWER- BUD OF Apricot. Fig. 148. — Apricot Flower-bud, enlarged. Buds that contain or produce only leaves are leaf-buds. Those which contain only flowers are flower buds or fruit-buds. The latter occur on peach, almond, apricot, and many very early spring-flowering plants. The single flower is emerging from the apricot bud in Fig. 147. A longi- tudinal section of this bud, enlarged, is shown in Fig. 148. Those that contain both leaves and flowers are mixed buds, as in pear, apple, and most late spring- flowering plants. Fruit buds arc usually thicker or stouter than leaf-buds. They are borne in differcjit positions on different plants. In some plants (apple, pear) they are on the ends of short branches or spurs; in others (peach, red maple) they are along the sides of the last year's ■' Fig. 149. — Fruit-buds growths. In Fig. 149 are shown and leaf-buds of pear. ii6 PLANT BIOLOGY three fruit-buds and one leaf-bud on /•", and leaf-buds on A. See also Fi^s. 150, 151, 152, 153, and explain. Fk;. 150. — FRi'iT-Buns of Apple ON Spurs : a dormant bud at the top. Fig. 151. — Clus- ter OK Fruit- buds OF SWEET Cherry, with one pointed leaf-bud in cen- ter. Fl<;. 152. —Two Fruit-buds OF Peach with a leaf- bud between. Fig. 153. — ui'K.MiNG (ji- Llai-i;uds and 1-'luwkr-1!UD.s of Apple. " Tlic burst of spring'' means in large part the opening of the buds. Everything was made ready the fall before. The embryo shoots and flo^ocrs ivere tucked aivay, and the food was stored. The warm rain falls, and the shutters open and the sleepers wake : the frogs peep and the birds come. Arrangement of Buds. — We have found that leaves are usually arranged in a definite order ; buds are borne in the axils of leaves : therefore buds must exhibit pJiyllotaxy. WINTER AND DORMANT BUDS 117 Moreover, branches grow from buds: branches, therefore, should show a definite arrangement; usually, however, they do not show this arrangement because not all the buds grow and not all the branches live. (See Chaps. II and III.) It is apparent, however, that the mode of arrangement of buds determines to some extent the form of the tree: com- pare bud arrangement in pine or fir with that in maple or apple Fig. 154. — Oak Spray. How are the leaves borne with reference to the annual growths ? The uppermost buds on any twig, if they are well matured, are usually the larger and stronger and they are the most likely to grow the next spring; therefore, branches tend to be arranged in tiers (particularly well marked in spruces and firs). See Fig. 154 and explain it. Winter Buds show what has been the Effect of Sunlight. — Buds are borne in the axils of the leaves, and tJie sise or vigor of the leaf determines to a large extent the size of tJie bud. Notice that, in most instances, the largest buds are nearest the tip (Fig. 157). If the largest ones are not near the tip, there is some special reason for it. Can you state it ^ Examine the shoots on trees and bushes. Il8 PLANT BIOLOGY Suggestions. — Some of the best of all observation lessons are those made on dormant twigs. There are many things to be learned, the eyes are trained, and the specimens are everywhere accessible. 123. .At whatever time of year the pupil takes up the study of branches, he should look for three things : the ages of the various jiarts, the relative positions of the buds and leaves, the different sizes of similar or comparable buds. If it is late in spring or early- in summer, he should watch the development of the buds in the axils, and he should determine whether the strength or size of the bud is in any way related to the size and vigor of the subtending (or supporting) leaf The sizes of buds should also be noted on leafless twigs, and the sizes of the former leaves may be inferred from the size of the leaf-scar below the bud. The pupil should keep in mind the fact of the struggle for food and light, and its effects on the developing buds. 124. The hud and the branch. A twig cut from an apple tree in early spring is shown in Fig. 155. The most hasty obser- vation shows that it has various parts, or members. It seems to be divided at the point / into two parts. It is evident that the part from/ to h grew last year, and that the part below/ grew two years ago. The buds on the two parts are very unlike, and these differences challenge investigation. — In order to under- stand this seemingly lifeless twig, it will be necessary to see it as it looked late last summer (and this condition is shown in Fig. 156). The part from / to h, — which has just completed its growth, — is seen to have its leaves growing singly. In every axil (or angle which the leaf makes when it joins the shoot) is a bud. The leaf starts first, and as the season advances the bud forms in its axil. When the leaves have fallen, at the approach of winter, the buds remain, as seen in Fig. 155. Every bud on the last year's growth of a winter twig, therefore, marks the position occupied by a leaf when the shoot was growing. — The i)art below / in Fig. 156, shows a wholly different arrangement. The leaves are two or more together {aaaa), and there are buds without leaves {bbbb). A year ago this part looked like the present shoot from / to //, — that is, the leaves were single, with a bud in the axil of each. It is now seen that some of these bud-like parts are longer than others, and that the longest ones are those which have leaves. It must be because of the leaves that they have increased in length. The body c has lost its leaves through some accident, and its growth has ceased. In other words, the parts at aaaa are like the shoot ///, except that they are shorter, and they are of the same age. One grew from the end or terminal bud of the main branch, and the others from the side or lateral buds. Parts or bodies that bear leaves are, therefore, branches. — The buds at bbbb have no leaves, and they remain the same WINTER AND DORMANT BUDS 119 size that they were a year ago. They are dormant. The only way for a mature bud to grow is by making leaves for itself, for a leaf f)/ i a, Fig. 155. — An Apple Twig. Fig. 156. — Same twig before leaves fell. will never stand below it again. The twig, therefore, has buds of two ages, — those at bbbb are two seasons old, and those on the 120 PLAXT BIOLOGY tips, of all the branches (aaaa, //), and in the axil of every leaf, are one season old. It is only the terminal buds that are not axillary. When the bud begins to grow and to put forth leaves, it gives rise to a branch, which, in its turn, hears buds. — It will now be interesting to determine why certain buds gave rise to branches and why others remained dormant. The strongest shoot or branch of the year is the terminal one (///). The next in strength is the uppermost later.d one, and the weakest shoot is at the base of the twig. The dormant buds are on the under side (for the twig grew in a hori/onlal jiosition). All this suggests that those buds grew which had tlie best chance, — the most sunlight and room. 'Fhere were too many buds for the space, and in the struggle for existence those that had the best oppor- tunities made the largest growths. This struggle for existence began a year ago, however, when the buds on the shoot below/ were forming in the axils of the leaves, for the buds near the tip of the shoot grew larger and stronger than those near its base. The growth of one year, tlierefore, is very largely determined by the conditions under which the buds were formed the previous year. Other bud characters. 125. It is easy to see the swelling of the buds in a room in winter. Secure branches of trees and shrubs, two to three feet long, and stand them in vases or jars, as you would flowers. Renew the water frequently and cut off the lower ends of the shoots occasionally. In a week or two the buds will begin to swell. Of red maple,' peach, apricot, and other very early-flowering things, flowers may be obtained in ten to twenty days. 126. The shape, size, and color of the winter buds are different in every kind of plant. By the buds alone botanists are often able to distinguish the kinds of plants. Even such similar plants as the different kinds of willows have good bud characters. 127. Distinguish and draw fruit-buds of apple, pear, peach, yjlum, and other trees. If different kinds of maples grow in the vicinity, secure twigs of the red or swamp maple, and the soft or silver maple, and compare the buds with those of the sugar maple and Norway maple : What do you learn? Fig. 157. —Buns of the Hickorv. CHAPTER XVI BUD PROPAGATION We have learned (in Chap. VI) that plants propagate by means of seeds. TJicy also propagate by means of bud parts, — as rootstoeks {rhicoiues), roots, ruuners, layers, bulbs. The pupil should determine how any plant in which he is interested naturally propagates itself (or spreads its kind). Determine this for raspberry, blackberry, strawberry, June- grass or other grass, nut-grass, water lily, May apple or mandrake, burdock, Irish potato, sweet potato, buckwheat, cotton, pea, corn, sugar-cane, wheat, rice. Plants may be artificially propagated by similar means, as by layers, cuttings, and grafts. The last two we may discuss here. Cuttings in General. — A bit of a plant stuck into the ground stands a chance of groiuing; and this bit is a cutting. Plants have preferences, however, as to the kind of a bit which shall be used, but there is no ivay of tellijig udiat this preference is except by trying. In some instances this prefer- ence has not been discovered, and we say that the plant cannot be propagated by cuttings. Most plants prefer that the cutting be made of the soft or growing parts (called "wood" by gardeners), of which the "slips" of geranium and coleus are examples. Others grow equally well from cuttings of the hard or mature parts or wood, as currant and grape; and in some instances this mature wood may be of roots, as in the blackberry. In some cases cuttings are made of tubers, as in the Irish 121 ri.A.\T BIOLOGY potato (Fig. 60). Pupils should make cuttings now and then. If they can do nothing more, they can make cut- tings of potato, as the farmer docs; and they can plant them in a box in the window. The Softwood Cutting.— The softwood cutting is made from tissue that is still growing, or at least from that which is not dormant. // comprises one or two joints^ with Fig. 158. — GiRANn.M Cutting. Fig. 159. —Rose Cutting. a leaf attached {¥\gs. 158, 159). It must not be allowed to wilt. Therefore, it must be protected front direct sun- light and dry air until it is ivell established ; and if it has many leaves, some of them should be removed, or at least cut in two, ill order to reduce the evaporating surface. The soil should be uniformly moist. The pictures show the depth to which the cuttings are planted. For most plants, the proper age or maturity of wood for the making of cuttings may be determined by giving the twig a quick bend: if it snaps and hangs by the bark, it is in proper cotiditioti ; if it bends without breaking, it is too young and soft or too old ; if it splinters, it is too old and woody. The tips of strong upright shoots usually make the best cuttings. Preferably, each cutting should have a joint or node near its base; and if the internodes are very short it may comprise two or three joints. BUD PROPAGATION 123 Fig. 160. — CuttinG-box. TJie stem of the eiitting is inserted one third or more its length iji clean sand or gravel, and the earth is pressed firmly about it. A newspaper may be laid over the bed to ex- clude the light — if the sun strikes it — and to prevent too rapid evaporation. The soil should be moist clear through, not on top only. Loose sandy or gravelly soil is used. Sand used by masons is good material in which to start most cuttings; or fine gravel — sifted of most of its earthy matter — may be used. Soils are avoided which contain much decay- ing organic matter, for these soils are breeding places of fungi, which attack the soft cutting and cause it to " damp off," or to die at or near the surface of the ground. If the cuttings are to be grown in a window, put three or four inches of the earth in a shallow box or a pan. A soap box cut in two lengthwise, so that it makes a box four or five inches deep — as a gardener's fiat — is excellent (Fig. 160). Cuttings of common plants, as geranium, coleus, fuchsia, carnation, are kept at a living-room temperature. As long as the cuttings look bright and green, they are in good condition. It may be a month before roots form. When roots have formed, the plants begin to make new leaves at the tip. Then they may be transplanted into other boxes or into pots. The verbena in Fig. 161 is just ready for transplanting. Fig. 161. — Verkf.xa Cutting ready for transplanting. 124 iPLAXT BIOLOGY Fig, 102. — Old Geranium Plant cut back to make it throw out Shoots from which Cuttings can be made. dovv plants are those which old. The gcraniH))i and fuchsia ciit- tuigs which are made i?i January, February, or MaJxJi zuill give compact blooniitig plants for the next tvinter ; and thereafter nezo ones should take their places ( Fig. 163). The Hardwood Cutting. — Best re- sults with cuttings It is not always easy to find growing shoots from which to make the cut- tings. The best practice, in that case, is to cut back an old plant, then keep it zuarvi a)id well watered, and tJiereby force it to throw out tieiv shoots. The old geranium plant from the window garden, or the one taken up from the lawn bed, may be treated this way (see Fig. 162). The best plants of geranium and coleus and most win- are not more than one year of mature wood are Fig. 163.- Earlv Winter Geranium, from a spring cutting. BUD PROPAGATION 125 secured when the cuttings are made in tJie fall attd then buried until spring in sand in the cellar. These cuttings are usually six to ten inches long. They are not idle while they rest. The lower end calluses or heals, and the roots form more readily when the cutting is planted in the spring. But if the proper season has passed, take cuttings at any time in winter, plant them in a deep box in the window, and watch. They will \\ need no shading or special care. Grape, currant, gooseberry, willow, and poplar readily take root from the hardwood. Fig. 164 shows a currant cutting. It has only one bud above the ground. The Graft. — When the cutting is inserted in a plant rather than- in the soil, it is a graft ; and the graft may grow. In this case the cutting grows fast to the other plant, and the two become one. When the cutting is inserted in a plant, it is no longer called a cutting, but a cion; and the plant in which it is inserted is called the stock. Fruit trees are grafted /;/ order that a certain variety or kind may be per- petuated, as a Baldwin or Ben Davis vari- ety of apple, Seckel or Bartlett pear. Navel or St. Michael orange. Plants have preferences as to the stocks on zvhich they ivill grozv ; but zve can find out zvhat their choice is only by jnakiug the experiment. The pear grows well on the quince, but the quince does not thrive on the pear. The pear grows on some of the hawthorns, but it is an unwilling subject on the apple. Tomato plants will grow on potato plants and potato plants on tomato plants. Fig. 164. — Cur- rant Cutting. 126 PLANT BIOLOGY When the potato is the root, both tomatoes and potatoes may be produced, although the crop will be very small; when the tomato is the root, neither potatoes nor tomatoes will be produced. Chestnut will grow on some kinds of oak. In general, one species or kind is grafted on the same species, as apple on apple, pear on pear, orange on orange. Tlic fonniug, grozving tissue of the stem (on the plants we have been discussing) is tlic cambium (Chap. X), lying on the outside of the woody ey Under beneath the bark. In order that union may take place, the cambium of the cion and of the stock must come together. Therefore the cion is set in the side of the stock. There are many ways of shaping the cion and of preparing the stock to receive it. These ways are dictated largely by the relative sizes of cion and stock, although many of them are matters of personal preference. The underlying principles are two : securing close contact between the cambiums of cion and stock ; covering the wounded surfaces to prevent evapora- tion and to protect the parts from disease. On large stocks the commonest form of grafting \t> the cleft-graft. The stock is cut off and split ; and in one or both sides a wedge-shaped cion is firmly inserted. Fig. 165 shows the cion ; Fig. 166, the cions set in the stock; Fig. 167, the stock wa.xed. It will be seen that the lower bud — that lying in the wedge — is covered by the wax; but being nearest the food supply and least exposed to weather, it is the most likely to grow : it will push through the wax. Cleft-grafting is practiced in spring, as groivth begins. The cions are cut previously, when perfectly dormant, and from the tree which it is desired to propagate. The cions are kept in sand or moss in the cellar. Limbs of various BUD PROPAGATION 127 sizes may be cleft-grafted, — from one half inch up to four inches in diameter ; but a diameter of one to one and one half inches is the most convenient size. All the leading or main branches of a tree top may be grafted. If the remaining parts of the top are gradually cut away and the cions grow well, the entire top will be changed over to the new variety. Fig. 165.— ClON OF Apple. Fig. 166.— The CioN Inserted. Fig. 167. — The Parts Waxed. Another form of grafting is known as budding. In this case a single bud is used, and it is sHpped underneath the bark of the stock and securely tied (not waxed) with soft material, as bass bark, corn shuck, yarn, or raffia (the last a commercial palm fiber). Budding is performed when tJie bark of the stock will slip or peel (so that the bud can be inserted), and wJien the bud is mature enotigJi to groiv. Usually budding is performed in late summer or early fall, when the winter buds are well formed ; or it may be practiced in spring with buds cut in winter. In ordinary summer budding (which is the usual mode) the "bud" or cion forms a union with the stock, and then lies dormant till the following spring, as if it were still on its own twig. 128 PLANT BIOLOGY Budding is mostly restricted to young trees in the nursery. In tiie spring following the budding, the stock is cut off just above the bud, so that only the shoot from the bud grows to make the future tree. This prevailing form of budding (shield-budding) is shown in Fig. i68. SuGGKSTioNs. — 128. Name the plants that the gardener propagates by means of cuttings. 129. Ry means of grafts. 130. The cutting-box may be set in the window. If the box does not receive direct sunlight, it may be covered with a pane of glass to prevent evaporation. Take care that the air is not kept too close, else the damping- off fimgi may attack the cuttings, and they will rot at the surface of the ground. See that the pane is raised a little at one end to afford ventila- tion ; and if the water collects in drops on the under side of the glass, remove the pane for a time. 131. Grafting wax is made of beeswax, resin, and tallow. A good recipe is one part (as one pound) of rendered tallow, two parts of bees- wax, four parts of rosin ; melt together in a kettle ; pour the liquid into a pail or tub of water to so- lidify it ; work with the hands until it has the color and "grain" of taffy candy, the hands being greased when necessary. The wax will keep any length of time. For the little grafting that any pupil would do, it is better to buy the wax of a seedsman. 132. Grafting is hardly to be recom- mended as a general school diversion, as the mak- ing of cuttings is ; and the account of it in this chapter is inserted chiefly to satisfy the general curiosity on the subject. 133. In Chap. V we had a definition of a plant generation : what is "one generation" of a grafted fruit tree, as Le Conte pear, Baldwin, or Ben Davis apple? 134. The Elbcrta peach originated about i88o : what is meant by " originated " ? 135. How is the grape, propagated so as to come true to name (explain what is meant by "coming true")? currant? strawberry? raspberry? blackberry? peach? pear? orange? fig? plum? cherry? apple? chest- nut? pecan? Fio. i68. — Bud- ding. The "bud"; the opening to re- ceive it ; the bud tied. CHAPTER XVII HOW PLANTS CLIMB We have found that plants struggle or contend for a place in which to live. Some of them become adapted to grow in the forest shade, others to grow on other plants, as epiphytes, others to climb to the light. Observe how woods grapes, and other forest climbers, spread their foli- age on the very top of the forest tree, while their long flexile trunks may be bare. There are several ways by which plants climb, but most climbers may be classified into four groups : ( i ) scramblers, (2) root climbers, (3) tendril climbers, (4) twiners. Scramblers. — Some plants rise to light and air by rest- ing their long and iveak stems on the tops of bushes and quick-growing herbs. Their stems may be elevated in part by the growing twigs of the plants on which they recline. Such plants are scramblers. Usually they are provided with prickles or bristles. In most weedy swamp thickets, scrambling plants may be found. Briers, some roses, bed- straw or galium, bittersweet {Solatium Dulcamara, not the Celastrus\ the tear-thumb polygonums, and other plants are familiar examples of scramblers. Root Climbers. — Some plants climb by means of true roots. These roots seek the dark places and therefore enter the chinks in walls and bark. The trumpet creeper is a familiar example (Fig. 36). The true or English ivy, which is often grown to cover buildings, is another instance. Still another is the poison ivy. Roots are K 129 I30 PLANT BIOLOGY Fig. 169. — Tendril, to show where the coil is changed. distinguished from stem tendrils by their irregular or indifuiitc position :is well as by their mode of growth. Tendril climbers. — A slender coiling part that serves to hold a climbing plant to a support, is known as a tendril. The free end swings or curves until it strikes some object, when it attaches itself and then coils and t/razc's tJic plant close to the support. The spring of the coil also allows the plant to move in the tvind, thereby enabling the plant to maintain its hold. Slowly pull a well-matured tendril from its support, and note how strongly it holds on. Watch the tendrils m a wind-storm. Usually the tendril attaches to the support by coiling about it, but the Virginia creeper and Boston ivy (Fig. 170) attach to walls by means of disks _ ... on the ends of the tendrils. Since both ends of the tendril are fixed, when it finds a support, the coil- ing would tend to twist it in two. It will be found, how- ever, that the tendril coils in different di- rections in different parts of its length. In Fig. 169, show- ing an old and stretched-out tendril, the change of direction in the coil occurred at a. In long tendrils of cucumbers and melons there may be several changes of direction. Tendrils may represent either branches or leaves. In the Fig. 170.— Tendril OF Boston Ivy, HOW PLANTS CLIMB 131 Virginia creeper and grape they are branches ; they stand opposite the leaves in the position of fruit clusters, and sometimes one branch of a fruit cluster is a tendril. These tendrils are therefore homologous with fruit-clusters, and fruit-clusters are branches. In some plants tendrils are leaflets (Chap. XI). Ex- amples are the sweet pea and common garden pea. In Fig. 171, observe the leaf with its two great stipules, petiole, six normal leaflets, and two or three pairs of leaflet tendrils and a termi- nal leaflet tendril. The cobea, a common garden cHmber, has a similar arrangement. In some cases tendrils are stipules, as prob- ably in the green briers Fig. 171. — Leaves of Pea, — very large stipules, op- posite leaflets, and leaflets represented by tendrils. (smilax). The petiole or midrib may act as a tetidril, as in various kinds of clem- atis. In Fig. 172, the common wild clematis or " old man vine," this mode is seen. Twiners. — The entire plant or shoot may wind about a support. Such a plant is a twiner. Examples are bean, hop, morning-glory, moon- flower, false bittersweet or waxwork {Celastrus), some honeysuckles, wistaria, Dutchman's pipe, dodder. The free" tip of the twining branch sweeps about in curves, much as the tendril does, until it finds support or becomes old and rigid. Each kind of plant usually coils /;/ only one direction. Most plants coil against the sun, or from the observer's left across his front to his right as he faces the plant. 132 PLANT BIOLOGY Examples are bean, morning-glory. The hop twines from the observer's ri^ht to his A left, or with the sun. Fig. 172. —Clematis climbing bv Lf..-\f-tf,ndril. Suggestions. — 136. Set the pupil to watch the behavior of any plant that has tendrils at different stages of maturity. A vigorous cucumber plant is one of the best. Just i)eyon(l the point of a young straight tendril set a stake to compare the y)osition of it. Note whether the tendril changes position from hour to hour or day to day. 137. Is the tip of the tendril perfectly straight? Why? Set a small stake at the end of a strong straight tendril, so the tendril will just reach it. Watch, and make drawing. 138. If a tendril does not find a support, what does it do? 139. To test the movement of a free tendril, draw an ink line lengthwise of it, and note whether the line remains always on the concave side or the convex side. 140. Name the tendril-bearing plants that you know. 141. Make similar observations and experiments on the tips of twining stems. 142. A\'hat twining plants do you know, and which way do they twine? 143. How docs any plant that you know get up in the world ? 144. Does the stem of a climbing plant con- tain more or less substance (weight) than an erect self-supporting stem of the same height ? Explain. CHAPTER XVIII THE FLOWER— ITS PARTS AND FORMS The function of the flower is to produce seed. It is probable that all its varied forms and colors contribute to this supreme end. These forms and colors please the human fancy and add to the joy of living, but the flower exists for the good of the plant, not for the good of man. The parts of the flower are of two general kinds — those that are directly concerned in the production of seeds, and those that act as covering and protectitig o'gans. The former parts are known as the essential organs; the latter as the floral envelopes. Envelopes. — The floral envelopes usually bear a close resemblance to leaves. These envelopes are very com- monly of two series or kinds — the outer and the ituier. The outer series, known as the calyx, is usually smaller and green. It usually comprises the outer cover of the flower bud. The calyx is the lowest whorl in Fig. 173. p,^^ 173. -flower of The inner series, known as the a buttercup in sec- coroUa, is usually colored and more special or irregular in shape than the calyx. It is the showy part of the flower, as a rule. The corolla is the second or large whorl in Fig. 173. The calyx may be composed of several leaves. Each leaf is a sepal. If it is of one piece, it may be lobed or divided, in which case the divisions are called calyx -lobes. m 134 FLAiXr BIOLOGY In like manner, the corolla may be composed of petals, or it may bo of one piece and variously lobed. A calvx of one piece, no matter how deeply lobed, is gamosepalous. A corolla of one piece is gamopetalous. When these series are of separate j^ieces, as in Fig. 173, the flower is said to be polysepalous and polypetalous. Sometimes both series are of separate parts, and sometimes only one of them is so formed. Tlw floral envelopes are ho- mologous with leaves. Sepals and petals, at least when more than three or five, are in more than one whorl, and one whorl stands below another so that the parts overlap. They are borne on the expanded or thickened end of the flower stalk ; this end is the torus. In Fig. 173 all the parts are seen as attached to the torus. This part is sometimes called .the re- ceptacle, but this word is a common-language term of several meanings, whereas torus has no other meaning. Sometimes one part is attached to another part, as in the fuchsia (Fig. 174), in which the petals are borne on the calyx-tube. Subtending Parts. — Sometimes there are leaf-like parts just belozu the calyx, looking like a second calyx. Such parts accompany the carnation flower. These parts are bracts (bracts are small specialized leaves); and they form an involucre. We must be careful that we do not mistake them for true flower parts. Sometimes the bracts are large and petal-like, as in the great white blooms of the Fig. 174. — Flower of Fuchsia in Section. THE FLOWER — ITS PARTS AND FORMS 135 flowering dogwood : here the real flowers are several, small and greenish, forming a small cluster in the center. Essential Organs. — ■ The essential organs are of two series. The outer series is composed of the stamens. The inner series is composed of the pistils. Stamens bear the pollen, which is made up of grains or spores, each spore usually being a single plant cell. The stamen is of two parts, as is readily seen in Figs. 173, 174, — the enlarged terminal part or anther, and the stalk or filament. The filament is often so short as to seem to be absent, and the anther is then said to be sessile. The anther bears the pollen spores. It is made up of two or four parts (known as sporangia or spore-cases), which burst and discharge the pollen. WJien the pollen is shed, the stamen dies. The pistil has three parts : the lowest, or seed- bearing part, which is the ovary ; the stigma at the upper extremity, which is a flattened or expanded surface, and usually rough- ened or sticky ; the stalk- like part or style, connect- ing the ovary and stigma. Sometimes the style is apparently wanting, and the stigma is said to be sessile on the ovary. These parts are shown in the fuchsia (Fig. 174). The ovary or seed vessel is at a. A long style, bearing a large stigma, projects from the flower. See also Figs. 175 and 176. Stamens and pistils probably are homologous with leaves. A pistil is sometimes conceived to represent anciently a Fig. 175. — The Structure of a Plum Blossom. se, sepals; p, petals; sia, stamens; o, ovary; J, style; x/, stigma. The pistil consists of the ovary, style, and stigma. It contains the seed part. The stamens are tipped with anthers, in which the pollen is borne. The ovary, o, ripens into the fruit. 136 r/..l.\r BIOLOGY FKI. 176. — Sl.Ml'I.E Pis rii.s of But- tercup, one in leaf as if rolled into a tube ; and an anther, a leaf of which the edges may have been turned in on the midrib. The pistil may be of one part or com- pnrt}i!iut, or of many parts. The different units or parts of which it is composed are carpels. Each carpel is homologous with a leaf. Each carpel bears one or more seeds. A pistil of one carpel is simple ; longitudinal sec- of two or morc carpels, compound. Usu- "°"' ally the structure of the pistil may be de- termined by cutting horizontally across the lower or seed- bearing part, as Eigs. 177, 178 explain. A flower may contain a simple pistil (one carpel), as the pea (Fig. 177); several simple pis- tils (several separate carpels), as the buttercup (Fig. 176); or a eompoiuul pistil with carpels united, as the Saint cA John's wort (Fig. 1 78) and apple. How F'f^- 177- - Pistil of . 1 ■> A 11 G.XRIJEN Pea, the many carpels m an apple i A peach ? ,,^,„^„^ ^eing puiied down in order to dis- close it ; also a section showing the single compartment (com- pare Fig. 188). ..^^sQy An okra pod ? A bean pod .-* The seed cavity in each carpel is called a locule (Latin locus, a place). In these locules t/ie seeds are Iwnic. Conformation of Fig. 178. —Compound Pistil of a St. John's Wort. It has 5 carpels. the Flower. — A flower that has calyx, corolla, stamens, and pistils is said to be complete (Fig. 173); all others are incomplete. In some flowers both the floral envelopes are wanting : such are naked. When one of the floral envelope series is wanting, the remaining series is said to be calyx, and the flower is therefore apetalous (without petals). The knot- THE FLOWER — ITS PARTS AND FORMS 137 weed (Fig. 179), smartweed, buckwheat, elm are examples. Some flowers lack the pistils : these are stami- nate, whether the envelopes are missing or not. Others lack the stamens : these are pistillate. Others have neither stamens nor pistils: these are sterile (snowball and hydrangea). Those that have both stamens and pistils are per- fect, whether or not the envelopes are missing. Those that lack eitherstamensor pistils are imper- fect or diclinous. Staminate and pistillate flowers are imperfect or diclinous. When staminate and pistillate flowers are borne on the same plant, e.g. oak (Fig. 180), corn, beech, chestnut, hazel, walnut, hickory, pine, begonia (Fig. 18O. watermelon, Fig. 179. — Knotweed, a very common but inconspicu- ous plant along hard walks and roads. Two flowers, enlarged, are shown at the right. These flowers are very small and borne in the axils of the leaves. Fig. 180. — Staminate Catkins of Oak. The pistillate flowers are in the leaf axils, and not shown in this pic- ture. Fig. 181. — Begonia Flowers.. Staminate at A ; pistil- late below, with the winged ovary at B. 138 PLANT BIOLOGY gourd, pumpkin, the plant is monoecious ("in one house"). When they are on different plants, e.g. poplar, cottonvvood, bois d'arc, willow (Fig. 182), the j)lant is dioecious (" in two houses "). Some varieties of strawberry, grape, and mul- berry are partly dioecious. Is the rose either monoecious or ditecious .-' Flowers in which the parts of each series are alike are said to be regular (as in Fig.s. 173, 174, 175). Those in which some parts are unlike other parts of the same series are irregular. Their regularity may be in calyx, as in nasturtium (Fig. 183); in corolla (Figs. 184, 185); in the stamens (compare nasturtium, catnip. Fig. 185, sage); in the pistils. Irregu- larity is most frequent in the corolla. Fig. 182. — Catkins of a Willow. A staminate flower is shown at s, and a pistillate flower at /. The staminate and pistillate are on different plants. Fig. 183. — Flower of Garden Nasturtium. Separate petal at a. The calyx is produced into a spur. Fig. 185. — Flower of Catnip. Fig. 184. — The F'ive Petai^ OF THE Pansy, detached to show the form. THE FLOWER — ITS PARTS AND FORMS 1 39 Various Forms of Corolla. — The corolla often assumes very definite or distinct forms, especially when gamopet- alous. It may have a long tube with a wide-flaring limb, when it is said to be funnelforin, as in morning-glory and pumpkin. If the tube is very narrow and the limb stands at right angles to it, the corolla is salverform, as in phlox. If the tube is very short and the limb wide- spreading and nearly circular in outline, the corolla is rotate or wheel-shaped, as in potato. A gamopetalous corolla or gamosepalous calyx is often cleft in such way as to make two prominent parts. Such parts are said to be lipped or labiate. Each of the lips or lobes may be notched or toothed. In 5-membered flowers, the lower Hp is usually 3-lobed and the upper one 2-lobed. Labiate flowers are characteristic of the mint family (Fig. 185), and the family therefore is called the Labiatae. (Lit- erally, labiate means merely "lipped," without specifying the number of lips or lobes ; but it is commonly used to desig- nate 2-lipped flowers.) Strongly 2-parted polypetalous flowers may be said to be labiate ; but the term is often- est used for gamopetalous co- rollas. Labiate gamopetalous flowers that are closed in the throat (or entrance to the tube) are said to be grinning or personate (per- „ 4.^^^ u J ^ J. Fig. 186. — Personate Flower sonate means masked, or person- ^ ' ^ OF Toadflax. like\ Snap-dragon is a typical example; also toadflax or butter-and-eggs (Fig. 186), and many related plants. Personate flowers usually have definite relations to insect pollination. Observe how an insect forces his head into the closed throat of the toad- flax. I40 PLANT BIOLOGY The peculiar flowers of the j3ea tribes are explained in Figs. 187, 188. Spathe Flowers. — In many plants, very simple (often naked) flowers are borne in dense, more or less fleshy spikes, and the spike is inclosed in or attended by a leaf, sometimes corolla-like, known as a spathe. The spike of flowers is technically known as a spadix. This type of flower is characteristic of the great arum family, which is Fig. 187. — Flowkrs of the Common Bean, with one flower opened (a) to show the structure. Diagram of Ai.fai.fa Flower IN Section : C, calyx, Z>, standard; Jf^, wing; K, keel; T, sta- men-tube: F, filament of tenth stamen; X, stigma; }', style; <9, ovary; the dotted lines at E show position of stamen- tube, when pushed upward by insects. Enlarged. chiefly tropical. The commonest wild representatives in the North are Jack-in-the-pulpit, or Indian turnip, and skunk cabbage. In the former the flowers are all diclin- ous and naked. In the skunk cabbage all the flowers are perfect and have four sepals. The common calla is a good example of this type of inflorescence. Compositous Flowers. — The head (anthodium) or so- called "flower" of sunflower (Fig. 189), thistle, aster, dandelion, daisy, chrysanthemum, goldenrod, is com- posed of several or viany little flowcis, or florets. These THE FLOWER — ITS PARTS AND FORMS 141 Fig. i8q. — Head of Sunflower. florets are inclosed in a more or less dense and usually green involucre. In the thistle (Fig. 190) this involucre is prickly. A longitudinal section discloses the flo- rets, all attached at bot- tom to a common torus, and densely packed in the involucre. The pink tips of these florets con- stitute the showy part of the head. Each floret of the this- tle (Fig. 190) is a com- plete flower. At a is the ovary. At /' is a much-divided plumy calyx, known as the pappus. The corolla is long- tubed, rising above the pappus, and is enlarged and 5-lobed at the top, c. The style pro- jects at c. The five anthers are united about the st}^le in a ring at d. Such anthers are said to be syngenesious. These are the various parts of the florets of the Com- positae. In some cases the pappus is in the form of barbs, bristles, or scales, and sometimes it is wanting. The pappus, as we shall see later, assists in distributing the seed. Often the florets are not all alike. The corolla of those in the outer circles may be developed into a long, straplike, or tubular part, and the head then has the ap- FiG. 190. — Longitudinal Section OF Thistle Head; also a Floret OF Thistle. 142 PLANT BIOLOGY pearance of being one flower with a border of petals. Of such is the sunflower (Fig. 189), aster, bachelor's button or cornflower, and field daisy (Fig. 21 1 ). These long corolla- limbs are called rays. In some cultivated composites, all the florets may develop rays, as in the dahlia and chrysan- themum. In some species, as dandelion, all the florets naturally have rays. Syngenesious arrangement of an- thers is the most characteristic single feature of the composites. Double Flowers. — Under the stimulus of cultivation and increased food supply, flowers tend to become double. True doubling arises in two ways, mor- phologically : ( I )sta- inctis or pistils may produce petals (Fig. 191 ) ; (2) adventi- tious or accessory petals may arise in the circle of petals. Both of these cate- gories may be pres- ent in the same flower. In the full double hollyhock the petals derived from the staminal col- umn are shorter and make a rosette in the center of the flower. In P'ig. 192 is shown the doubling of a daffodil by the modification of stamens. Other modifications of flowers are sometimes known as doubling. For example, double dahlias, chrysanthemums, and sunflowers are forms in which the disk flowers have developed rays. The snow- ball is another case. In the wild snowball the external flowers of the cluster are large and sterile. In the culti- FiG. 191. — Petai^ arising from the Stami- nal Column of Hollyhock, and accessory petals in the corolla-whorl. THE FLOWER — ITS PARTS AND FORMS 1 43 vated plant all the flowers have become large and sterile. Hydrangea is a similar case. Fig. 192. — Narcissus or Daffodil. Single flower at the right. Suggestions. — 145. If the pupil has been skillfully conducted through this chapter by means of careful study of specimetis rather than as a mere memorizing process, he will be in mood to chal- lenge any flower that he sees and to make an effort to understand it. Flowers are endlessly modified in form ; but they can be understood if the pupil looks first for the anthers and ovaries. How may anthers and ovaries always be distinguished? 146. It is excellent practice to find the flowers in plants that are commonly known by name, and to determine the main points in their struc- ture. What are the flowers in Indian corn? pumpkin or squash? celery? cabbage? potato? pea? tomato? okra? cotton? rhubarb? chestnut? wheat? oats? 147. Do all forest trees have flowers? Explain. 148. Name all the monoecious plants you know. Dioecious. 149. What plants do you know that bloom before the leaves appear? Do any bloom after the leaves fall? 150. Ex- plain the flowers of marigold, hyacinth, lettuce, clover, asparagus, garden calla, aster, locust, onion, burdock, lily-of-the-valley, crocus, Golden Glow rudbeckia, cowpea. 151. Define a flower. Note to the Teacher. — It cannot be urged too often that the specimens themselves be studied. If this chapter becomes a mere recitation on names and definitions, the exercise will be worse than useless. Properly taught by means of the flowers themselves, the names become merely incidental and a part of the pupil's language, and the subject has living interest. CHAPTER XIX THE FLOWER — FERTILIZATION AND POLLINATION Fertilization. — SiT(/s result from the union of tzvo ele- ments or parts. One of these elements is a cell-nucleus of the pollen-grain. The other ele- ment is the cell-nucleus of an egg- cell, borne in the ovary. The pollen-grain falls on the stigma (Fig. 193). It absorbs the juices exuded by the stigma, and grows by sending out a tube (Fig, 194). This tube grows downward through the style, absorbing food as it goes, and finally reaches the egg-cell in the interior of an ovule in the ovary (Fig. 195), and fertilization, or union of a nucleus of the pollen and the nucleus of the egg-cell in the ovule, takes place. The ovule and ejnbryo within then develops into a seed. The growth of the pollen-tube is often spoken of as germination of the pollen, but it is not germination in the sense in which the word is used when speaking of seeds. Better seeds — that is, those that produce stronger and more fruitful plants — often re- sult when \)c\Q, pollen comes from another floiaer. F'ertili/.ation effected between different flowers is cross-fertilization ; that resulting from the 144 Fig. 193". — D, Pollen escap- ing from anther; A, pollen germinating on a stigma. Enlarged. P'lc. 194. — A POLLKN- ORAIN AND THE Grow- iNG Tube. 7 HE FL O WER — PER TILIZA TION AND POLLINA TION 1 4 5 e-K application of pollen to pistils in the same flower is close- fertilization or self-fertilization. It will be seen that the cross-fertilization relationship may be of many degrees — between two flowers in the same cluster, between those in different clusters on the same branch, between those on different plants. Usually fertilization takes place only between plants of the same species or kind. In many cases there is, in effect, an apparent selection of pollen when pollen from two or more sources is applied to the stigma. Sometimes the foreign pollen, if from the same kind of plant, grows, and fertiliza- tion results, while pollen from the same flower is less promptly effec- tive. If, however, no foreign pol- len is present, the pollen from the same flower may finally serve the same purpose. In order that the pollen may grow, the stigma viiist be ripe. At this stage the stigma is usually moist and some- times sticky. A ripe stigma is said to be receptive. The stigma may remain receptive for several hours or even days, depending on the kind of plant, the weather, and how soon pollen is received. Watch a certain flower every day to see the anther locules open and the stigma ripen. When fertilization takes place, the stigma dies. Observe, also, how soon the petals wither after the stigma has received pollen. Pollination. — The transfer of the pollen from anther to stigma is known as pollination. The pollen may m Fig. 195. — Diagram to represent fertiliza- TION. i, stigma; j/, style; (7r', ovary; o, ovule; /, pollen-grain; pt, pollen-tube; e, egg-cell; tn, micropyle. 146 PL A. XT BIOLOGY fall of its own weight on the adjacent stigma, or it may be carried from flower to flower by wind, insects, or other agents. There may be self-pollination or cross-pol- lination, and of course it must always precede fertilization. a Usually the pollen is discharged by the burst- ing of the anthers. The commonest method of discharge is through a slit on either side of the anther (Fig. 193). Sometimes it discharges through a pore at the ape.x, as in azalea ( Fig. Fig. 196. — Anther of 196), rhododendron, huckleberry, wintergreen. Azalea, j,-^ gorne plants a part of the anther wall raises opening by terminal or falls as a lid, as in barberry (Fig. 197), blue pores. cohosh, May apple. The opening of an anther (as also of a seed-pod) is known as dehiscence (^r, from; hisco, to gape). When an anther or seed pod opens, it is said to dehisce. Most floii'crs are so eonstnicted as to increase the chances of cross-pollination. We have seen that the stigma may have the power of choosing foreign pollen. The commonest means of necessitating cross-pollina- tion is the different times of viatnrijig of stamens and pistils in the same flower. In most cases the stamens mature first : the flower is then proterandrous. When the pistils mature first, the flower is proterogynous. (Aner, andr, is a Greek root often used, in combinations, for sta- barberry men, and gj'ne for pistil.) The difference in stamen, with anther time of ripening may be an hour or two, or it opening by may be a day. The ripening of the stamens '"^s- and pistils at different times is known as dichogamy, and flowers of such character are said to be dichogamous. There is little chance for dichogamous flowers to pollinate themselves. Many flowers are imperfectly dichogamous — THE FL O WER — FER T I LIZ A TION AND POLLINA TION 1 47 some of the anthers mature simultaneously with the pistils, so that there is chance for self-poUination in case for- eign pollen does not arrive. Even when the stigma receives pollen from its own flower, cross-fer- tilization may result. The hol- lyhock is proter- androus. Fig. 198 shows a flower rerentlv ^'*^* ^9^" — Flower of Hollyhock; proterandrous. expanded. The center is occupied by the column of sta- mens. In Fig. 199, showing an older flower, the long styles are conspicuous. Some floivers arc so constructed as to proJiibit self-polli- nation. Very irregular flowers are usually of this kind. With some of them, the petals form a sac to inclose the anthers and the pol- len cannot be shed on the stigma but is retained until a bee forces the sac open ; the pollen is rubbed on the hairs of the bee and transported. Regular flowers usu- ally depend mostly on dichogamy and the selective power of the pistil to insure crossing. Flowers that are very Fig. 199. — Older Flower of Hollyhock. 148 PLANT BIOI.OGY irregular and provided tvitJi nectar and strong perfume are nsnal/y pollinated by insects. Gaudy colors probably attract insects in many cases, but perfume appears to be a greater attraction. The insect visits tJie flower for the nectar {iox the making of honey) and may nnknounngly carry the pollen. Spurs and sacs in the flower are necta- ries (Fig. 200 ), but in spurless flowers the nectar is usually secreted /// the bottom of the flower cup. This compels the insect to pass by the anther and Fig. 200.— Fi.owER of rub against the pollen before it reaches AKKbi'UR. ^^ nectar. Sometimes the anther is a long lever poised on the middle point and the insect bumps against one end and lifts it, thus bringing the other end of the lever with the pollen sacs down on its back. Flowers that are pollinated by insects are said to be entomophilous ( " insect lov- ing"). Fig. 200 shows a larkspur. The envelopes are separated in Fig. 201. The long spur at once suggests insect pollination. The spur is a sepal. Two hollow petals project into this spur, ap- parently serving to guide the bee's tongue. The two smaller petals, in front, are peculiarly colored and perhaps serve the bee in locating the nectary. The stamens ensheath the pistils (Fig. 202). As the insect stands on the flower and thrusts its head into the center, Fig. 201. — Envelopes of .k Larkspur. There are five wide sepals, the upper one be- ing spurred. There are four small petals. THE FL O WER — PER TILIZA TION AND POLLINA TION 149 the envelopes are pushed downward and outward and the pistil and stamens come in contact with its abdomen. Since the flower is proterandrous, the pollen that the pistils receive from the \u "^^^^^M'^fJ^ '7 bee's abdomen must come from another flower. Note a somewhat similar ar- rangement in the toadflax or butter-and- eggs. In some cases (Fig. 203) the stamens are longer than the pistil in one flower and shorter in another. If the insect visits such flowers, it gets pollen on its head from the long-stamen flower, and deposits this pollen on the stigma in the long-pistil flower. Such flowers are di- morphous (of two forms). If pollen from its own flower and from another flower both fall on the stigma, the proba- bilities are that the stigma will choose the foreign pollen. Fig. 202. — Stamens OF Larkspur, sur- rounding the pistils. Fig. 203.— Dimorphic Flowers ok Primrose. Many flowers are pollinated by the wind. They are said to be anemophilous (" wind loving "). Such flowers pro- 150 PLANT BIOLOGY duce great quantities of pollen, for much of it is wasted. They usually have broad stigmas, which expose large surfaces to the wind. They are usually lacking in gaudy colors and in perfume. Grasses and pine trees are typical examples of anemophilous plants. In many cases cross-pollination is insured because the stamens and pistils are in different flowers (diclinous). Monoecious and ^ , , ^^ ^ dioecious plants may be polli- nated by wind or insects, or other agents(Fig. 204). They are usually wind - pollinated, although willows are often, if not mostly, insect- pollinated. The Indian corn is a monoecious plant. The staminate flowers are in a terminal panicle (tassel). The pistillate flowers are in a dense spike (ear), inclosed in a sheath or husk. Each " silk " is a style. Each pistillate flower produces a kernel of corn. Some- times a few pistillate flowers are borne in the tassel and a few staminate flowers on the tip of the ear. Is self-fertili- zation possible with the corn.'' Why does a "volunteer" stalk standing alone in a garden have only a few grains on the ear .' What is the direction of the prevailing wind in summer? If only two or three rows of corn are Fig. 204. — Flowers of Black Walnut: two pis- tillate flowers at A, and staminate catkins at B. THE FL O WER — FER T I LIZA TION AND POLLINA TION I 5 I planted in a garden where prevailing winds occur, in which direction would they better run ? Although most flowers are of such character as to insure or increase the chances of cross-pollination, there are some that absolutely forbid crossing. These flowers are usually borne beneath or on the ground, and they lack showy colors and per- fumes. They are known as cleistogamous flowers (meaning " hidden flow- ers"). The plant has normal showy flowers that may be insect-pol- linated, and in addition is provided with these simplified flowers. Only a few plants bear cleis- togamous flowers. Hog- peanut, common blue violet, fringed winter- green, and dahbarda are Fig. 205. -Common Blue Violet. The , , . . , familiar flowers are shown, natural size. the best subjects in the The corolla is spurred. Late in the season, Northern states. Fio*. cleistogamous flowers are often borne on . the surface of the ground. A small one is 205 snows a CieiSlOga- shown at (j. A nearly mature pod is shown moUS flower of the blue at b. Both a and b are one third natural violet at a. Above the true roots, slender stems bear these flowers, that are provided with a calyx, and a curving corolla which does not open. Inside are the stamens and pistils. Late in the season the cleistogamous flowers may be found just underneath the mold. They never rise above ground. The following summer one may find a seedling plant, in 152 PLA.XT BIOLOGY some kinds of plants, with the remains of the old cleistog- amous flower still adhering to the root. Cleistogamous flowers usually appear after the showy flowers have Fig. 206. — Pods of Peanuts ripening underground. passed. They seem to insure a crop of seed by a method that expends little of the plant's energy. The pupil will be interested to work out the fruiting of the pea- nut (Fig. 206). Unbaked fresh peanuts grow readily and can easily be raised in the North in a warm sandy garden. Suggestions. — 152. Not all the flowers pioduce seeds. Note that an apple tree may bloom very full, but that only rela- tively few apples may result (Fig. 207). More pollen is produced than is needed to fertilize the flowers ; this increases the chances that sufficient Fig. 207. ■ SiKrGGi.E i-oR Existence among the Apple Flowers. THE FL O WER — FER TILIZA TION AND POLLINA TION I 5 3 stigmas will receive acceptable pollen to enable the plant to perpetuate its kind. At any time iii summer, or even in fall, examine the apple trees carefully to determine whether any dead flowers or flower stalks still remain about the apple ; or, examine any full-blooming plant to see whether any of the flowers fail. 153. Keep watch on any plant to see whether insects visit it. What kind? When? What for? 154. Determine whether the calyx serves any purpose in protecting the flower. Very carefully remove the calyx from a bud that is normally exposed to heat and sun and rain, and see'\vhether the flower*then fares as well as others. 155. Cover a single flower on its plant with a tiny paper or muslin bag so tightly that no insect can get in. If the flower sets fruit, what do you conclude? 156. Remove carefully the corolla from a flower nearly ready to open, preferably one that has no other flowers very close to it. Watch for insects. 157. Find the nectar in any flower that you study. 158. Remove the stigma. What happens? 159. Which of the following plants have perfect flowers : pea, bean, pumpkin, cotton, clover, buckwheat, potato, Indian corn, peach, chestnut, hickory, watermelon, sunflower, cab- bage, rose, begonia, geranium, cucumber, calla, willow, cotton- wood, cantaloupe ? What have the others ? 160. On wind- pollinated plants, are either anthers or stigmas more numerous ? 161. Are very small colored flowers usually borne singly or in clusters ? 162. Why do rains at blooming time often lessen the fruit crop ? 163. Of what value are bees in orchards ? 164. The crossing of plants to improve varieties or to obtain new varieties. — It may be desired to perform the operation of polli- nation by hand. In order to insure the most definite results, every effort should l)e made rightly to apply the pollen which it is desired shall be used, and rigidly to exclude all other pollen. {a) The first requisite is to remove the anthers from the flower which it is proposed to cross, and they must he removed before the pollen has been shed. The flower-bud is therefore opened and the anthers taken out. Cut off the floral envelopes with small, sharp- pointed scissors, then cut out or pull out the anthers, leaving only the pistil untouched ; or merely open the corolla at the end and pull out the anthers with a hook or tweezers ; and this method is often the best one. It is best to delay the operation as long as possible and yet not allow the bud to open (and thereby expose the flower to foreign pollen) nor the anthers to discharge the pollen, {b) The ?io\vtr must 7iext be covered iinth a paper bag to prevent the access of pollen (Figs. 208, 209). If the stigma is not receptive at the time (as it usually is not), the desired pollen is not applied at once. The bag may be removed from time to time to allow of examination of the pistil, and when the stigma is mature, which is told by its glutinous or roughened appearance, 154 PLANT BIOLOGY the time for pollination has come. If the bag is slightly moist- ened, it can be i)iickere(l more tightly about the stem of the plant. The time required for the stigma to mature varies from several hours to a few days, (r) When the stigma is ready, an unopened anther from the desired flower is crushed on the finger nail or a knife blade, and the pollen is nibbed on the stigma by means of a tiny brush, the point of a knife blade, or a sliver of wood. The Fig. 208. — A Paper Bag, with string inserted. Fig. 209. — The Bag tied OVKR A Fl.OWER. flower is again covered with the bag, which is allowed to remain for several days until all (ianger of other pollination is past. Care must be taken completely to cover the stigmatic surface with pollen, if possible. The seeds produced by a crossed flower pro- duce hybrids, or plants having parents belonging to diff"erent varieties or species. 165. One of the means of securing new forms of plants is by making hybrids, ^\'hy ? Fig. 210. — Fig. The fig is a hollow torus with flowers borne on the inside, and pollinated by insects that enter at the apex. CHAPTER XX FLOWER-CLUSTERS Origin of the Flower-cluster. — We have seen that branches arise from the axils of leaves. Sometimes the leaves may be reduced to bracts and yet branches are borne in their axils. Some of the branches grow into long limbs ; others be- come short spurs ; otJiers bear flowers. In fact, a flower is it- self a specialized branch. Flowers are usually borne near the top of the plant. Often they are produced in great num- bers. It results, therefore, that flower branches usually stand close together, forming a clus- ter. The shape and arrange- ment of the flower-cluster differ with the kind of plant, since each plant has its own mode of branching. Certain definite or well-marked types of flower-clusters have re- ceived names. Some of these names we shall discuss, but the flower-clusters that perfectly match the definitions are the exception rather than the rule. The determining of the 155 Fig. 211. —Terminal Flowers OF THE Whiteweed (in some places called ox-eye daisy). 156 PLANT BIOLOGY kinds of flower-clusters is one of the most perplexing sub- jects in descriptive botany. We may classify the subject around three ideas : solitary flowers, centrifugal or deter- minate clusters, centripetal or indeterminate clusters. Solitary Flowers. — In many cases flowers are borne singly ; they are separated from other flowers by leaves. They are then said to be solitary. The solitary flower may be either at the end of the main shoot or axis (Fig. 211), when it is said to be terminal ; or from the side of the shoot (Fig. 212), when it is said to be lateral or axillary. Centripetal Clusters. — If the flower-bearing axils were rather close together, an open or leafy flower-cluster might result. If the plant continues to grow from the tip, the older flowers are left farther and farther behind. If the cluster were so short as to be flat or convex on top, the out- ermost flowers would be the older. A flower-cluster in which the lower or outer flowers open first is said to be a centripetal cluster. It is some- times said to be an indeterminate cluster, since it is the result of a type of growth which may go on more or less continuously from the apex. The simplest form of a definite centripetal cluster is a raceme, which is an open elongated cluster in which the jloivcrs are borne singly on very short bratiehes and open from below (that is, from the older part of the shoot) Fig. 212. — Lateral Flower of AN Abutilon. a greenhouse plant. FL O WER- CL US TERS 157 upwards (Fig. 213). The raceme may be terminal to the main branch; or it may be lateral to it, as in Fig. 214. Racemes often bear the flowers on one side of the stem, thus form- ing a single row. When a cen- tripetal flower- cluster is long and dense and the flowers are sessile or nearly so, it is called a spike (Fig. 215). Common .MmJL^ examples of spikes are plantain, migno- nette, mullein. A very s/iort and dense spike is a head. Clover (Fig. 216) is a good example. The sunflower and related plants bear many small flowers in a very dense and often flat head. Note that in the sunflower (Fig. 189) the outside or exterior flowers Fig. 213.— Raceme of Currant. Terminal or lateral ? Fig. 214. — Lateral Racemes (in huit) of Barberry. Fig. 215.— Spike of Plantain. I5S ri.AXT BIOLOGY open first. Another special form of spike is the catkin, which usually has scaly bracts, the whole cluster being deciduous after flowering or fruiting, and the flowers (in typical cases) having only stamens or pistils. Examples arc the "pussies" of willows (Fig. ^J^^^j^Ms/)/^ 182 ) and flower-clusters of oak (Fig. 180), walnuts (Fig. 204), poplars. ';„„/i';i„ Fig. 216. — Head of Clo- ver Blossoms. Fig. 217. — Corv.mh of Candy- TUFr. When a loose, elongated centripetal flower-cluster has some primary branches simple, and others irregularly branched, it is called a panicle. It is a branching raceme. Because of the earlier growth of the lower branches, the panicle is usually broadest at the base or conical in outline. True panicles are not very common. When an indeterminate flower-cluster is short, so that FL O WER- CL US TERS 159 the top is convex or flat, it is a corymb (Fig. 217). The outermost flowers open first. Centripetal flower-clusters are sometimes said to be corymbose in mode. When the branches of an indeterminate cluster arise from a common point, like the frame of an umbrella, the cluster is an umbel (Fig. 218). Typical umbels occur in carrot, parsnip, caraway and other plants of the parsley family : the family is known as the Umbelliferae, or umbel-bearing Fig. 218. —Remains of a Last Year's Umbel of Wild Carrot. family. In the carrot and many other Umbelliferae, there are small or secondary umbels, called umbellets, at the end of each of the main branches. (In the center of the wild carrot umbel one often finds a single, blackish, often aborted flower, comprising a i-flowered umbellet.) Centrifugal or Determinate Clusters. — When the ter- minal or central flower opens first, the cluster is said to be centrifugal. The growth of the shoot or cluster is deter- minate, since the length is definitely determined or stopped by the terminal flower. Fig. 219 shows a determinate or centrifugal mode of flower bearing. i6o PLANT BIOLOGY Dense centrifugal clusters are usually flattish on top because of the cessation of growth in the main or central axis. These com- pact flower-clusters are known as cymes. Centrifugal clusters are sometimes said to be cymose in mode. Apples, pears (Fig. 220), and elders bear flowers in cymes. Some cyme-forms are like umbels in general appear- ance. A head-like cymose clus- ter is a glomerule ; it blooms from the top downwards rather than from the base upwards. Mixed Clusters. — Often the cluster is mixed, being determi- nate in one part and indeterminate in another part of the same clus- ter. The main cluster may be indeterminate, but the branches determinate. The cluster has the appearance of a panicle, and is usually so called, but it is really a thyrse. Lilac is a familiar example of a thyrse. In some cases the main cluster is determinate and the branches are indeterminate, as in hydrangea and elder. Inflorescence. — The viodc or vuiliod of flower arrangement is known as the inflorescence. That is, the inflorescence is cymose, co- rymbose, paniculate, spicate, solitary, determinate, inde- terminate. By custom, however, the word "inflorescence " Fig. 219. — Determinate or CvMosE Arrangement,— Wild geraiiiuni. Fig. 220. — Cyme of Pear. Often imperfect. FL O WER- CL US TERS l6l 3 ^ 3 5 5 ■A i -^ .3.i\^Jii^^2,,A r 1 . ;. 221. — Forms of Centripetal Flower-clusters. I, raceme; 2, spike; 3, umbel; 4, head or anthodium; 5, corymb. ¥^\^ Fig. 222. — Centripetal Inflorescence, co«//««^rf. 6, spadix; 7, compound umbel; 8, catkin. Fig. 223. — Centrifugal Inflorescence. I, cyme; 2, scirpioid raceme (or half cyme). l62 PLANT BIOLOGY has come to be used for the flinver-ilustcr itself in works on descriptive botany. Thus a cyme or a panicle may be called an inflorescence. It will be seen that even solitary flowers follow either indeterminate or determinate methods of branchini;. The flower-stem. — • The stem of a solitary flower is known as a peduncle; also the general stem of a flower- clustcr. The stem of the individual flower in a cluster is a pedicel. In the so-called stemless plants the peduncle may arise directly from the ground, or crown of the plant, as in dandelion, hyacinth, garden daisy ; this kind of peduncle is called a scape. A scape may bear one or many flowers. It has no foliage leaves, but it may have bracts. Suggestions. — 166. Name six columns in your notebook as follows : spike, raceme, corymb, umbel, cyme, solitary. Write each of the following in its appropriate column : larkspur, grape, rose, wistaria, onion, bridal wreath, banana, hydrangea, phlox, China berry, lily-of-the-valley, Spanish dagger (or yucca), sorghum, tuberose, hyacinth, niustani, goldenrod, peach, hollyhock, mul- lein, crepe myrtle, locust, narcissus, snapdragon, peppergrass, shepherd's purse, coxcomb, wheat, hawthorn, geranium, carrot, elder, millet, dogwood, castor bean : substitute others for plants that do not grow in your region. 167. In the study of flower- clusters, it is well to choose first those that are fairly typical of the various classes discussed in the preceding paragraphs. As soon as the main types are well fixed in the mind, random clusters should be examined, for the pupil must never receive the impres- sion that all tlower-clusters follow the definitions in books. Clus- ters of some of the commonest plants are very puzzling, but the pupil should at least be able to discover whether the inflorescence is determinate or indeterminate. Figures 221 to 223 (from the German) illustrate the theoretical modes of inflorescence. The numerals indicate the order of opening. CHAPTER XXI FRUITS The ripened ovary, with its attachments, is known as the fruit. It contains the seeds. If the pistil is simple, or of one carpel, the fruit also will have one com- partment. If the pistil is compound, or of more than one carpel, the fruit usually has an equal number of com- partments. The com- partments in pistil and fruit are known as lo- cules (from Latin locus, meaning "a place"). The simplest kind of fruit is a ripened \-loculed ovary. The first stage in complex- ity is a ripened 2- or many-loculed ovary. Very complex forms may arise by the attachment of otJier parts to the ovary. Sometimes the style persists and becomes a beak (mustard pods, dentaria. Fig. 224), or a tail as in clematis ; or the calyx may be attached to the ovary ; or the ovary may be embedded in the receptacle, and ovary and receptacle together consti- tute the fruit : or an involucre may become a part of the 163 Fig. 224. — Dentaria, or Tooth-wort, in fruit. 164 PL A XT BIOLOGY fruit, as possibly in the walnut and hickory (Fig. 225), and cup of the acorn (Fig. 226). The chestnut and the beech bear a prickly involucre, but the nuts, ) Fig. 225. — Hickory-nut. The nut is the fruit, con- tained in a husk. Fig. 226. — Live-oak Acorn. The fruit is the " seed " part ; the involucre is the " cup." or true fruits, are not grown fast to it, and the involucre can scarcely be called a part of the fruit. A ripened ovary is a pericarp. A pericarp to which other parts adhere has been called an accessory or reenforced fruit. (Page 169.) Some fruits are dehiscent, or split open at maturity and liberate the seeds ; others are indehiscent, or do not open. A dehiscent pericarp is called a The parts into which such a pod breaks or splits are known as valves. In inde- hiscent fruits the seed is liberated by the decay of the envelope, or by the rupturing of the envelope by the germinating seed. Indehiscent winged peri- carps are known as samaras or key fruits. Fig. 227. — Key of Sugar Maple. Fig. 228. — Key of Common American Elm. Maple (Fig. 227), elm (Fig. 228), and ash (Fig. 93) are examples. FRUITS 165 Fig. 229 — Akenes of Buttercup. Fig. 230. — Akenes OF Buttercup, one in longitudi- nal section. Pericarps. — The simplest pericarp is a dry, one- seeded, indehiscent body. It is known as an akene. A head of akenes is shown in Fig. 229, and the structure is explained in Fig. 230. Akenes may be seen in buttercup, hepatica, anemone, smartweed, buckwheat. A i-loculed pericarp which dehisces along the front edge (that is, the inner edge, next the center of the flower) is a follicle. The fruit of the larkspur (Fig. 231) is a follicle. There are usually five of these fruits (sometimes three or four) in each larkspur flower, each pistil ripening into a follicle. If these pistils were united, a single compound pistil would be formed. Columbine, peony, ninebark, milk- weed, also have follicles. A i-loculed pericarp that de- hisces on both edges is a legume. Peas and beans are typical exam- ples (Fig. 232); in fact, this character gives name to the pea family, — Leguminosas. Often the valves of the legume twist forcibly and expel the seeds, throwing them some distance. The word " pod " is sometimes restricted to legumes, but it is better to use it generi- cally for all dehiscent pericarps. A compound pod — dehiscing peri- carp of two or more carpels — is a capsule (Figs. 233, 234, Fig. 232. — A^ Bean Pod. Fig. 233. — Capsule of Castor -OIL Bean after Dehiscence. 1 66 PLANT BIOLOGY Fig. 234. — Cap- SL'LE OF Morn- ing Glory. 236, 237). Some capsules are of one locLile, but they may have been compound when young (in the ovary stage) and the partitions may have vanished. Sometimes one or more «of the carpels are uniformly crowded out by the exclusive growth of other carpels (Fig. 235). The seeds or parts which are crowded out are said to be aborted. There are several ways in which cap- sules dehisce or open. When they break along the partitions (or septa), the mode is known as septi- cidal dehiscence ( Fig. 236) ; In septicidal dehiscence the fruit separates into parts representing the original carpels. These carpels may still be entire, and they then dehisce individu- ally, usually along the inner edge as if they were follicles. When the compartments split in the middle, between the partitions, the mode is loculicidal dehiscence (Fig. 237). In some cases the dehiscence is at the top, when it is said to be apical (al- though several modes of dehis- cence are here included). When the ivhole top comes off, as in purs- lane and garden portulaca (Fig. 238), the pod is known as a pyxis. In some cases apical dehiscence is by means of a hole or clefts. The peculiar capsule of the mustard family, or Cruci Fio. 235. — Three-carpeled Fruit OF Horse-chestnut. Two locules are closing by abortion of the ovules. Fig. 236. — St. John's Wort. Sep- ticidal. Fig. 237.— Loculici- dal FoiJ of Day-lily. FRUITS 167 ferge, is known as a silique when it is distinctly longer than broad (Fig. 224), and a silicle when its breadth nearly Fig. 238. — Pyxis of Portu- LACA OR Rose-moss. Fig. 239. — Berries of Goose- berry. Remains of caly.\ at c. equals or exceeds its length. A cruciferous capsule is 2-carpeled, with a thin partition, each locule containing seeds in two rows. The two valves detach from below upwards. Cabbage, turnip, mustard, water-cress, radish, rape, shepherd's purse, sweet alyssum, wall- flower, honesty, are examples. Fig. 240. — Berry of the Ground Cherry or Husk Tomato, contained in the inflated calyx. The pericarp may ho. fleshy and indehiscent. A pulpy pericarp with several or many seeds is a berry (Figs. 239, 240, 241). To the horticulturist a berry is a small, soft, edible fruit, without Fig. 241. — Orange; example of a berry. 1 68 PLAXr BIOLOGY particular reference to its structure. The botanical and horticultural conccjitions of a berry are, therefore, unlike. In the botanical sense, gooseberries, currants, grapes, to- matoes, i)otato-balls, and even eggplant fruits and oranges (Fig. 241) are berries; strawlDcrrics, raspberries, black- berries are not. A fleshy pericarp containing one relatively large seed or stone is a drupe. l{\ami)les arc plum (Fig. 242), peach, (cherry, apricot, olive. The walls of the pit in the plum, peach, and cherry are formed from the inner coats of the ovary, and the flesh from the outer coats. Drupes are also known as stonc-fniits. Fruits that are formed by the sub- sequent union of sej')arate pistils are aggregate fruits. The carpels in aggregate fruits are usually more or less fleshy. In the raspberry and blackberry flower, the pistils are essentially distinct, but as the pistils ripen they co- here and form one body (Figs. 243, 244). Fig. 242. — Pl.UM ; exam- ple of a drupe. Fig. 243— FRt'iT of Rasp- HKKKY. Fig. 244. — Ag(;kkgaik Fkiht ok Mui.hkrry; and a separate fruit. Each of the carpels or pistils in the raspberry and blackberry is a little drupe, or drupelet. In the rasp- berry the entire fruit .separates from the torus, leaving the torus on the plant. In the blackberry and dew- FRUITS 169 berry the fruit adheres to the torus, and the two are re- moved together when the fruit is picked. Accessory Fruits. — When the pericarp and some other part grow together, the fruit is said to be accessory or reenforced. An example is the straw- berry (Fig. 245). The edible part is a greatly enlarged torus, and the pericarps are akenes embedded in it. These akenes are commonly called seeds. Various kinds of reenforced fruits have received special names. One of these is the hip, characteristic of roses. In this V ^^^' ~ a TRAw- (,g^gg ^j-,g torus is deep and hollow, like an BERRY ; fleshy ' ^ torus in which akenes urn, and the Separate akenes are borne are embedded. • .j -, t-i 4.1. r ii ^ 1 inside It. ihe mouth of the receptacle may close, and the walls sometimes become fleshy ; the fruit may then be mistaken for a berry. The fruit of the pear, apple, and quince is known as a Fig. 246. — Section of AN Apple. Fig. 247. — Cross-section OF AN Apple. pome. In this case the five united carpels are completely buried in the hollow torus, and the torus makes most of the edible part of the ripe fruit, while the pistils are repre- sented by the core (Fig. 246). Observe the sepals on the top of the torus (apex of the fruit) in Fig. 246. Note the outlines of the embedded pericarp in Fig. 247. I/O PLANT BIOLOGY Gymnospermous Fruits. — In pine, spruces, and their kin, there is no fruit in the sense in which the word is used in the preceding pages, because there is no ovary. The ovules are naked or uncovered, in the axils of the scales of the young cone, and they have neither style nor stigma. The pollen falls directly on the mouth of the ovule. The ovule ripens into a seed, which is usually winged. Because the ovule is not borne in a sac or ovary, these plants are called gymnosperms (Greek for "naked seeds"). All the true cone-bearing plants are of this class ; also certain other plants, as red cedar, juniper, yew. The plants are monoecious or sometimes dioecious. The staminate flowers are mere naked stamens borne beneath scales, in small yellow catkins which soon fall. The pistillate flowers are naked ovules beneath scales on cones that persist (Fig. 29). Gymnospermous seeds may have several cotyledons. Suggestions. — 168. Study the following fruits, or any five fruits chosen, by the teacher, and answer the questions for each : Apple, peach, bean, tomato, pumpkin. What is its form ? Locate the scar left by the stem. By what kind of a stem was it attached ? Is there any remains of the blossom at the blossom end ? De- scribe texture and color of surface. Divide the fruit into the seed vessel and the surrounding part. Has the fruit any pulp or flesh? Is it within or without the seed vessel? Is the seed vessel simple or subdivided? What is the number of seeds? Are the seeds free, attached to the wall of the vessel, or to a support in the center? Are they arranged in any order? What kind of wall has the seed vessel? What is the difference between a peach stone and a peach seed? 169. The nut fruits are always available for study. Note the points suggested above. Determine what the meat or edible part represents, whether cotyledons or not. Figure 248 is suggestive. 170. Mention all the fleshy fruits you know, tell where they come from, and refer them to their proper groups. 171. What kinds of fruits can you buy in the market, and to what groups or classes do they belong? Of which ones are the seeds only, and not tiie pericarps, eaten ? 172. An ear of corn is always available for study. What is it — a fruit or a collection of fruits ? How are the grains arranged on the cob ? How many rows do you count on each of several ears ? Are all the rows on an ear FRUITS 171 equally close together ? Do you find an ear with an odd number of rows ? How do the parts of the husk overlap ? Does the husk serve. as protection from rain ? Can birds pick out the grains? How do insect enemies enter the ear ? How and when do weevils lay eggs on corn ? 173. Study a grain of corn. Is it a seed ? Describe the shape of a grain. Color. Size. Does its surface show any projections or depressions ? Is the seed-coat thin or thick ? Transparent or opaque ? Locate the hilum. Where is the silk scar ? What is the silk ? Sketch the grain from the two points of view that show it best. Where is the embryo ? Does the grain have endosperm ? What is dent corn ? Flint corn ? How many kinds of corn do you know ? For what are they used ? Fig. 248. — Pecan Fruit. Note to Teacher. — There are few more interesting subjects to beginning pupils than fruits, — the pods of many kinds, forms, and colors, the berries, and nuts. This interest may well be utilized to make the teaching alive. All common edible fruits of orchard and vegetable garden should be brought into this dis- cussion (some of the kinds are explained in " Lessons with Plants"). Of dry fruits, as pods, burs, nuts, collections may be made for the school museum. Fully mature fruits are best for study, particularly if it is desired to see dehiscence. For com- parison, pistils and partially grown fruits should be had at the same time. If the fruits are not ripe enough to dehisce, they may be placed in the sun to dry. In the school it is well to have a collection of fruits for study. The specimens may be kept in glass jars. Ahvays note exte7-ior of fruit and its parts : interior of fruit with arrangement and attachment of contents. CHAPTER XXII DISPERSAL OF SEEDS It is to the plant's advantage to have its seeds distributed as widely as possible. // //as a better eJiance of surviving in the struggle for cxistetice. It gets away from competi- tion. Many seeds and fruits are of such character as to increase their chances of wide dispersal. The commonest means of dissemination may be classed under four heads: explosive fruits ; transportation by.ivind ; transportation by birds; burs. Fig. 249. — Exi'i.osioN ok THK Balsam Fod. Fig. 250. — Explosive Fruits ok Oxalis. An exploding pod is shown at c. The dehiscence is shown at b. 'rhe structure Fig. 265. — Strand OF Spirogyra, showing the chlo- rophyll bands. There is a nu- cleus at a. How many cells, or parts of cells, are shown in this fig- ure ? STUDIES IN CRYPTOGAMS 185 plant often forms the greater part of the floating green mass (or " frog spittle ") on ponds. The threadlike character of the thallus can be seen with the naked eye or with a hand lens, but to study it carefully a microscope magnifying two hundred diameters or more must be used. ThejhreadJs-jiividfid-iiLto-Jang cells by cross walls_which, according to the species, are^either straight or curiously folded (Fig. 266). The ^chlorophyll is -arranged-in beaiitiftil spira^_ba7id^jc\s:3x~x!ae^^ii^sXux^ each cgH. From the character of these bands the plant takes its name. Each cell is jrovided^witli a nucleus _ax\d other protoplawL^ The nucleus is suspended near the center of the cell {a, Fig. 265) by delicate strands of protoplasm radiat- ing toward the wall and terminating at certain points in the chlorophyll band. The remainder of the protoplasm forms a thin layer lining the wall. The interior oj^_th^_celLis__fi]led_with cell-sap. The protoplasm and nucleus cannot Se~easily seen, but if the plant is stained with a dilute alcoholic solution of eosin they become clear. Spirogyra is propagated vegetatively by the breaking off of parts^ of the threads, which con- tinue to grow as new plants. R^sting-spores, which may remain dormant for a time, are formed by_a process known as conjugation. Two threads lying side by side send out short projections, usually from all the cells of a long series (Fig. 266). The projections or processes from opposite cells grow toward each other, meet, and fuse, form- ing a connecting tube between the cells. The protoplasm, nucleus, and chlorophyll band of one cell now pass through this tube, and unite with the contents of the other cell. The en- tire mass then becomes surrounded by a thick cellulose wall, thus completing the resting- spore, or zygospore (z, Fig. 266). Zygnema is an alga closely related to spiro- gyra and found in similar places. Its life history is practically the same, but it differs from spirogyra in having two star-shaped chlo7'ophyll bodies (Fig. 267) in each cell, in- stead of a chlorophyll-bearing spiral band. Fig. 266. —Con- jugation OF Spirogyra. Ripe zygospores on the left; a, connecting tubes. Fig. 267. — strand, OR Filament of Zygnema, freed from its gelatinous covering. 1 86 PLANT BIOLOGY Vaucheria is another alga common in shallow water and on damp soil. The thallus is much branched, but the threads are not divided by cross walls as in spirogyra. The plants are attached by means of colorless root-like organs which are much like the root hairs of the higher plants : these are rhizoids. The chloro- phyll is in the form oi grains scattered through the thread. Vaucheria has a special mode of asexual reproduction by means of swimming spores or sivartn -spores. These are formed singly in a short enlarged lateral branch known as the sporangium. When the sporangium bursts, the entire contents escape, forming a single large swarm-spore, which swims about by means of numerous lashes or cilia on its surface. The swarm spores are so large that they can be seen with the naked eye. After swimming about for some time they come to rest and germinate, producing a new plant. The formation of resting-spores of vaucheria is acomplished by means of special organs, odgonia {p, Fig. 268) and antheridia {a, Fig. 268). Both of these are specially devel- oped branches from the thallus. The antheridia are nearly cylindrical, and curved toward the oogonia. ^ ^„ .^ ,, The upper part of an an- FiG. 268. — Thread of Vaucheria with , . ,.' '^ ^ rr ^ ObGONiA AND ANTHERmiA. thcridium IS cut off by a cross wall, and withm it numerous ciliated sperm-cells are formed. These escape by the ruptured apex of the antheridium. The oogonia are more en- larged than the antheridia, and have a beak-like projection turned a little to one side of the apex. They are separated from the thallus thread by a cross wall, and contain a single large green cell, the egg-cell. The apex of the oogonium is dissolved, and through the opening the sperm-cells enter. Fertilization is thus accomplished. After fertilization the egg-cell becomes invested with a thick wall and is thus converted into a resting-spore, the oospore. Fucus. — These are rather large specialized algse belonging to the group known as brown seaweeds and found attached by a disk to the rocks of the seashore just below high tide (Fig. 269). They are firm and strong to resist wave action and are so attached as to avoid being washed ashore. They are very abundant alga. In shape the plants are long, branched, and multicellular, with either flat or terete branches. They are olive-brown. Propagation is by the breaking off of the branches. No zoospores are produced, as in many other seaweeds ; and reproduction is wholly sexual. STUDIES IN CRYPTOGAMS 1^7 The antheridia, bearing sperm-cells, and the odgonia, each bearing eight e^g-cells, are sunken in pits or concepiacles. These pits are aggregated in the swollen Hghter colored tips of some of the branches {s, s, Fig. 269). The egg-cells and sperm-cells escape from the pits and fertilization takes place in the water. The matured eggs, or spores, reproduce the fucus plant directly. Fio. 269. — Fucus. Fruiting branches at s, s. On the stem are two air-bladders. Fig. 270. — NiTELLA. Nitella. — This is a large branched and specialized fresh-water alga found in tufts attached to the bottom in shallow ponds (Fig. 2 70) . Between the whorls of branches are long internodes consisting of a single cylindrical cell, which is one of the largest cells known in vegetable tissue. Under the microscope the walls of this cell are found to be lined with a layer of small stationary chloroplastids, within which layer the protoplasm, under favorable circumstances, will be found in motion, moving up one side and down the other (in rotation). Note the clear streak up the side of the cell and its relation to the moving current. Fungi Some forms of fungi are familiar to every one. Mushrooms and toadstools, with their varied forms and colors, are common in fields, woods, and pastures. In every household the common molds are famihar intruders, appearing on old bread, vegetables, and even within tightly sealed fruit jars, where they form a felt- like layer dusted over with blue, yellow, or black powder. The strange occurrence of these plants long mystified people, who i88 PLANT BIOLOGY thought they were productions of the dead matter upon which they grew, but now we know that a mold, as any other plant,^ cannot originate spontaneously ; it must start from something which is analogous to a seed. The "seed " in this case is a spore. A spore may be produced by a vegetative proeess (growing out from the ordinary plant tissues), or it may be the result of d. fertilization process. Favorable conditions for the grorvth of fungi. — Place a piece of bread under a moist bell jar and another in an uncovered place near by. Sow mold on each. Note the result from day to day. Moisten a third piece of bread with weak copper sulfate (blue vitriol) or mercuric chlorid solution, sow mold, cover with bell jar, note results, and explain. Expose pieces of different kinds of food in a damp atmosphere and observe the variety of organisms appearing. Fungi are saproi)hytes or parasites, and must be provided with organic matter on which to grow. They are usually most abundant in moist places and wet seasons. Fig. 271. — MucoR MUCEDO, showing habit. Mold. — One of these molds {Alucor mu- cedo), which is very common on all decay- ing fruits and vegetables, is shown in Fig. 271, somewhat magnified. When fruiting, this mold appears as a dense mass of long white hairs, often over an inch high, standing erect from the fruit or vegetable on which it is growing. The life of this mucor begins with a minute rounded spore {a, Fig. 272), which lodges on the decaying material. When the spore germinates, it sends out a delicate thread that grows rapidly in length and forms very many branches that soon permeate every part" of the substance on which the plant grows {]>, Fig. 272). One of these threads is termed a hypha. All the threads together form the mycelium of the fungus. The mycelium disorganizes the ma- terial in which it grows, and thus the mucor plant (Fig. 271) is nourished. It corresponds physiologically to the roots and stems of other plants. When the mycelium is about two days old, it begins to form the long fruiting stalks which we first noticed. To study them, use a compound microscope magnifying about two hundred diameters. One of the stalks, magnified, is shown in a, Fig. 274. It consists of a rounded head, the sporangium, sp, supported on a long, ^b\l Fig. 272. — Spores OF Mucor, some germinating. STUDIES IN CRYPTOGAMS 189 Fig. 274. — MucoR. sporangium; bursting; c b, sporangium , columella. delicate stalk, the sporangiophore. The stalk is separated from the sporangium by a wall which is formed at the base of the spo- rangium. This wall, however, does not extend straight across the thread, but it arches up into the sporangium like an inverted pear. It is known as the col- U77iella, c. When the sporangium is placed in water, the wall immediately dissolves and allows hundreds of spores, which were formed in the cavity within the sporangium, to escape, b. All that is left of the fruit is the stalk, with the pear-shaped columella at its summit, c. The spores that have been set free by the breaking of the sporangium wall are now scattered by the wind and other agents. Those that lodge in favorable places be- gin to grow immediately and reproduce ■the fungus. The others soon perish. The mucor may continue to reproduce itself in this way indefi- nitely, but these spores are very delicate and usually die if they do not fall on favorable ground, so that the fungus is provided with another means of carrying itself over unfavora- ble seasons, as winter. This is accomplished by means of curious thick-tvalled resting-spo7'es or zygospores. The zygospores are formed on the mycelium buried within the substance on which the plant grows. They originate in the following way : Two threads that lie near to- gether send out short branches, which grow toward each other and finally meet (Fig. 273). The walls at the ends, a, then disappear, allow- ing the contents to flow together. At the same time, however, two other walls are formed at points farther back, b, b, separating the short section, c, from the remainder of the thread. This section now increases in size and becomes covered with a thick, dark brown wall orna- mented with thickened tubercles. The zygo- spore is now mature and, after a period of rest, it germinates, either producing a sporan- gium directly or growing out as mycelium. The zygospores of the mucors form one of the most interesting and instructive objects among the lower plants. They are, how- ever, very difficult to obtain. One of the mucors \Sporodinia Fig. 273. — MucoR, showing formation of zygospore on the right; germi- nating zygospore on the left. I90 PI.AXT BIOLOGY grandis) may be frequently found in summer growing on toad- stools. This i)lant usually produces zygospores that are formed on the aerial mycelium. The zygospores are large enough to be recognized with a hand lens. The material may be dried and kept for winter study, or the zygospores may be prepared for permanent microscopic mounts in the ordinary way. Yeast. — This is a very much reduced and simple fungus, con- sisting normally of isolated spherical or elliptical cells (Fig. 275) containing abundant protoplasm and prob- ably a nucleus, although the latter is not easily observed. It propagates rapidly by budding, which consists of the gradual extru- sion of a wart-like swelling that is sooner or later cut off at the base by constriction, thus forming a separate organism. Although sim- „"'"^ .,^ ^^ pie in structure, the veast is found to be Fig. 275.— \ east , , , , v 1 1 • 1 r Pi ants closely related to some of the higher groups of fungi as shown by the method of spore forma- tion. When grown on special substances like potato or carrot, the contents of the cell may form spores inside of the sac-like mother cell, thus resembling the sac-fungi to which blue mold and mildews belong. The yeast plant is remarkable on account of its power to induce alcoholic fermentation in the media in which it grows. There are many kinds of yeasts. One of them is found in the common yeast cakes. In the process of manufacture of these cakes, the yeast cells grow to a certain stage, and the material is then dried and fashioned into small cakes, each cake containing great numbers of the yeast cells. When the yeast cake is added to dough, and proper conditions of warmth and moisture are pro- vided, the yeast grows rapidly and breaks up the sugar of the dough into carbon dioxid and alcohol. This is fermentation. The gases escape and puff up the dough, causing the bread to rise. In this loosened condition the dough is baked ; if it is not baked quickly enough, the bread ''falls'' Shake up a bit of yeast cake in slightly sweetened water : the water soon becomes cloudy from the growing yeasts. Parasitic fungi. — Most of the molds are saprophytes. Many other fungi are parasitic on living plants and animals (Fig. 285). Some of them have complicated life histories, undergoing many changes before the original sj)ore is again produced. The 7villow mildew and the common rust of ivheat yi\\\ serve to illustrate the habits of parasitic fungi. The willo7v mildeiv (Uncinula salicis). — This is one of the sac fungi. It forms white downy patches on the leaves of willows STUDIES IN CRYPTOGAMS 191 Fig. 276. — Colonies of Willow Mildew. (Fig, 276). These patches consist of numerous interwoven threads that may be recognized under the microscope as the mycehum of the fungus. The myceUum in this case hves on the surface of the leaf and nour- ishes itself by sending short branches into the cells of the leaf to ab- sorb food materials from them. Numerous summcr-sporcs are formed of short, erect branches all over the white surface. One of these branches is shown in Fig. 277. When it has grown to a cer- tain length, the upper part begins to segment or divide into spores which fall and are scattered by the wind. Those falling on other wil- lows reproduce the fungus there. This process continues all summer, but in the later part of the season provision is made to maintain the mildew through the winter. If some of the white patches are closely ex- amined in July or August, a number of little black bodies will be seen among the threads. These little bodies are cdi\\e.d perithecia, shown in Fig. 278. To the naked eye they appear as minute specks, but when seen under a magnifi- cation of 200 diameters they present a very interesting appear- ance. They are hollow spheri- cal bodies decorated around the outside with a fringe of crook-like hairs. The res ting-spores of the willow mildew are produced in sacs or crn' in- closed with- in the leath- ery perithecia. Figure 279 shows a cross-section of a perithecium with the asci arising from the bottom. The spores remain securely Fig. 277. — Summer-spores of Willow Mildew. Fig. 278. — Perithecium of Wil- low Mildew. Fig. 279. — Section THROUGH Peri- thecium OF Wil- low Mildew. 193 PLAXr BIOLOGY packed in the perithecia. They do not ripen in the autumn, but fall to the ground with the leaf, and there remain securely pro- tected among tlie dead foliage. The following spring they mature and are liberated by the decay of the perithecia. They are then ready to attack the unfolding leaves of the willow and repeat the work of the summer before. l-u;. 2S0. — SORI CON- TAINING Tkleuto- spoRES OF Wheat Rust. The "d'heat rust. — The development of some of the rusts, as the common 7<.'/u-iif n/sf i^Piiccinia p-aminis), is even more interesting and complicated than that of the mildews. Wheat rust is also a true parasite, affecting wheat and a few other grasses. The mycelium here cannot be seen by the unaided eye, for it consists of threads which are present within the host plant, mostly in the intercellular spaces. These threads also send short branches, or hausioria (Fig. 132), into the neigh- boring cells to absorb nutriment. The resting-spores of wheat rust are produced in late summer, when they may be found in black lines breaking through the epidermis of the wheat stalk (black-rust stage). They are formed in masses, called sori (Fig. 280), from the ends of numerous crowded mycelial strands just beneath the epidermis of the host. The individual spores are very small and can be well studied only with a microscope of high power (X about 400). They are brown two-celled bod- ies with a thick wall (Fig. 281). Since they are the resting or winter-spores, they are termed teleu- tospores ("comijleted spores"). Usually they do not fall, but remain in the sori during winter. The following spring each cell of the teleutospore puts forth a ratiier stout thread, which does not grow more than several times the length of the spore and terminates in a blunt extremity. This germ tube, promxcelium, now becomes divided into four cells by cross walls, which are formed from the top downwards. Each cell gives rise to a short, pointed branch whicb, in the course of a few hours, forms at its summit a single spore called a sporidiinn. This in turn germinates and produces a mycelium. In Fig. 282 a germinating teleutospore is drawn to show the promycelium, /, divided into four cells, Fig. 281. — Te- leutospore OF Wheat Rust. STUDIES IN CRYPTOGAMS 193 each producing a short branch with a httle spo- ridiiim, s. A most remarkable circumstance in the Hfe history of the wheat rust is the fact that the my- ceUum produced by the sporidium can live only in barberry leaves, and it follows that if no bar- berry bushes are in the neighborhood the sporidia finally perish. Those which happen to lodge on a barberry bush germinate immediately, produc- ing a mycelium that enters the barberry leaf and grows within its tissues. Very soon the fungus produces a new kind of spores on the barberry leaves. These are called cscidiospores. They are formed in long chains in little fringed cups, or cBcidia, which appear in groups on the lower side of the leaf (Fig. 283). These orange or yellow secidia are termed cluster-cups. In Fig. 284 is shown a cross-section of one of the cups, outlin- ing the long chains of spores, and the mycelium in the tissues. The fecidiospores are formed in the spring, and after they have been set free, some of them lodge on wheat or other grasses, where they germinate immediately. The germ-tube enters the Fig. 282. — Ger- minating Te- leutospore OF Wheat Rust. Fig. 283. — Leaf OF Barberry with Clus- ter-cups. Fig. 284. —Section through a Cluster-cup on Barberry Leaf. leaf through a stomate, whence it spreads among the cells of the wheat plant. In summer one-celled reddish uredospores ("blight spores," red-rust stage) are produced in a manner similar to the teleutospores. These are capable of germinating immediately, o 194 PLANT BIOLOGY and serve to disseminate the fungus during the summer on other wheat plants or grasses. I^ate in the season, teleutospores are again produced, completing the life cycle of the plant. Many rusts besides Puicinia graminis produce different spore forms on different plants. The phenomenon is called heteroecism, and was first shown to exist in the wheat rust. Curiously enough, the peasants of Europe had observed and asserted that barberry bushes cause wheat to blight long before science exjjlained the relation between the cluster-cups on barberry and the rust on wheat. The true relation was actually demonstrated, as has since been done for many other rusts on their respective hosts, by sow- ing the aicidiospores on healthy wheat plants and thus producing Anmrccnosf Canker SPod Starch Graias Fig. 285. — How a Parasitic Fungus works. Anthracnose on a bean pod entering the bean beneath. (Whetzel.) the rust. The ceJar apple is another rust, producing the curious swellings often found on the branches of red cedar trees. In the spring the teleutospores ooze out from the "apple" in brown- ish yellow masses. It has been found that these attack various fruit trees, producing aecidia on their leaves. Fig. 285 explains how a parasitic fungus works. Puffballs, mushrootns, toadstools, and shelf fungi. — These represent what are called the higher fungi, because of the size and complexity of the plant body as well as from the fact that they seem to stand at the end of one line of evolution. The mycelial threads grow together in extensive strands in rotten wood or in the soil, and send out large complex growths of mycelium in con- STUDIES IN CRYPTOGAMS 195 nection with which the spores are borne. These aerial parts are the only ones we ordinarily see, and which constitute the '' mush- room " part (Fig. 131). Only asexual spores {ba- sidiospores) are produced, and on short stalks {basidia) (Fig. 286). In the puff- balls the spores are inclosed and constitute a large part of the "smoke." In the mushrooms and toadstools they are borne on gills, and in the shelf fungi (Fig. 134) on the walls of minute pores of the underside. The my- celium of these shelf fungi frequently lives and grows for a long time concealed in the substratum before the visible fruit bodies are sent out. Practically all timber decay is caused by such growth, and the damage is largely done before the fruiting bodies appear counts of mushrooms, see Cliap. XIV. Fig. 286. — Part of Gill of the Cul- tivated Mushroom. tr, trama tissue; sh, hymenium; b, basidium; st, sterigma; sp, spore. (Atkinson.) For other ac- X Lichens Fig. 287. — Lichen on an Oak Trunk. (A species of Physcia.) Lichens are so common everywhere that the attention of the student is sure to be drawn to them. They grow on rocks, trunks of trees (Fig. 287), old fences, and on the earth. They are thin, usually gray ragged objects, ap- parently hfeless. Their study is too difficult for beginners, but a few words of explanation may be useful. Lichens were formerly supposed to be a distinct or separate division of plants. They are now known to be or- ganisms, each species of which is a con- stant association of a fungus and an alga. The thallus is ordinarily made up of fun- gous mycelium or tissue within which the imprisoned alga is definitely dis- tributed. The result is a growth unlike either component. This association of 196 PLANT BIOLOGY alj^a and fungus is usually spoken of as symbiosis, or mutually heli)ful growth, the alga furnishing some things, the fungus others, and both together being able to accomplish work that neither could do intlependently. By others this union is considered to be a mild form of parasitism, in which the fungus profits at the expense of the alga. As favorable to this view, the facts are cited that each component is able to grow independently, and that under such conditions the algal cells seem to thrive better than when imprisoned by the fungus. Lichens propagate by means of soredia, which are tiny parts separated from the body of the thallus, and consisting of one or more algal cells overgrown with fungus threads. These are readily observed in many lichens. They also produce spores, usually ascospores, which are always the product of the fungus element, and which reproduce the lichen by germinating in the presence of algal cells, to which the hyphae immediately cling. Lichens are found in the most inhospitable places, and, by means of acids which they secrete, they attack and slowly disin- tegrate even the hardest rocks. By making thin sections of the thalUis with a sharp razor and examining under the compound microscope, it is easy to distinguish the two components in many lichens. Liverworts The liverworts are peculiar flat green plants usually found on wet cliffs and in other moist, shady places. They frequendy occur in greenhouses where the soil is kept constantly wet. Fig. 288. Fig. 289. Plants of Marcha.ntia. One of the commonest liverworts is Marchantia polymorpha, two plants of which are shown in Figs. 288, 289. The plant consists of *a ribl)on-like thallus that creeps along the ground, becoming repeatedly forked as it grows. The end of each branch STUDIES IN CRYPTOGAMS 197 is always conspicuously notched. There is a prominent midrib extending along the center of each branch of the thallus. On the under side of the thallus, especially along the midrib, there are numerous rhizoids which serve the purpose of roots, absorbing nourishment from the earth and holding the plant in its place. The upper surface of the thallus is di- vided into minute rhombic areas that can be seen with the naked eye. Each of these areas is per- forated by a small breathing pore or stomate that leads into a cavity just beneath the epitlermis. This space is surrounded by chlorophyll- bearing cells, some of which stand in rows from the bottom of the cavity (Fig. 290). The delicate assimilating tissue is thus brought in close communication with the outer air through the pore in the thick, protecting epidermis. At various points on the midrib are little cups containing small green bodies. These bodies are buds or gemmcB which are outgrowths from the cells at the bottonioniie~cup^ They become loosened and are then dispersed by the rain to other places, where they take root and grow into new plants. The most striking organs on the thallus of marchantia are the pecuUar stalked bodies shown in Figs. 288, 289. These are termed archegoniophores and antheridiophores or i-ecepiacles. Their structure and function are very interesting, but their parts are so minute that they can be studied only with the aid of a microscope magnifying from 100 to 400 times. Enlarged drawings will guide the pupil. Fig. 290. — Section of Thallus OF Marchantia. Stomate at a. Fig. 291. — Section through Antheridiophore of Marchantia, showing antheridia. One antheridium more magnified. The antheridiophores are fleshy, lobed disks borne on short stalks (Fig. 291 ). The upper surface of the disk shows openings scarcely visible to the naked eye. However, a section of the disk, such as is drawn in Fig. 291, shows that the pores lead into oblong cavi- igS PI.AXT BIOLOGY Fig. 292.— Archego- N'lUM OK Marcha.ntia. ties in the receptacle. From tlie base of each cavity there arises a tliick, chib-sha])ed body, the antheridiiim. Within the anther- idium are formed many sperm -cells which are capa- ble of swimming about in water by means of long lashes or cilia attached to them. When the anther- idium is mature, it bursts and allows the ciliated sperm cells to escape. The anht'gouiophon's are also elevated on stalks (Fig. 289). Instead of a simple disk, the recepta- cle consists of nine or more finger-like rays. Along the under side of the rays, between delicately fringed curtains, peculiar flask-like bodies, or arche- gonia, are situated. The archegonia are not visible to the naked eye. They can be studied only with the microscope (x about 400). One of them much magnified is represented in Fig. 292. Its principal parts are the long neck, a, and the rounded venter, b, inclosing a large free cell — the egg-cell. We have seen that the antheridium at maturity discharges its sperm-cells. These swim about in the water provided by the dew and rain. Some of them finally find their way to the archegonia and egg-cells, the latter being fertilized, as pollen fertilizes the ovules of higher plants. After fertilization the egg-cell develops into the spore capsule or sporogoniion. The mature spore capsules may be seen in Fig. 293. They consist of an oval spore-case on a short stalk, the base of which is imbedded in the tissue of the receptacle, from which it derives the neces- sary nourishment for the development of the sporogonium. At maturity the sporogonium is ruptured at the apex, setting free the spheri- cal spores together with numerous filaments having spirally thickened walls (Fig. 294). These filaments are called elaters. When drying, they exhibit rapid movements by means of which the spores are scattered. The spores germinate and again produce the thallus of marchantia. I'k;, 293. — Arche- (joniophore, WITH SPORO- GONiA, OF Mar- chantia. Fig. 294. — Spores and Ei-atkrs ok Marchantia. i- STUDIES IN CRYPTOGAMS Mosses (Bryophyta) 199 If we have followed carefully the development of marchantia, the study of one of the mosses will be comparatively easy. The mosses are more familiar plants than the liver- worts. They grow on trees, stones, and on the soil both in wet and dry places. One of the common larger mosses, known as Polytrichum commune, may serve as an example, Fig. 295. This plant grows on rather dry knolls, mostly in the borders of open woods, where it forms large beds. In dry weather these beds have a reddish brown appearance, but when moist they form beautiful green cushions. This color is due, ■in the first instance, to the color of the old stems and leaves, and, in the second in- stance, to the peculiar action of the green living leaves under the influence of chang- ing moisture-conditions. The inner or upper surface of the leaf is covered with thin, lon- gitudinal ridges of delicate cells which contain chloro- phyll. These cells are shown in cross-section in Fig. 296, as dots or granules. All the other tissue of the leaf consists of thick-walled, corky cells which do Fig. 295. — Polytrichum commune. /,/, fertile plants, one on the left in fruit; tn, antheridial plant. Fig. 296. —Section of Leaf of Polytrichum commune. not allow moisture to penetrate. When the air is moist the green leaves spread out, exposing the chlorophyll cells to the air, but in 200 PLANT BIOLOGY dry weather the margins of the leaves roll inward, and the leaves fold closely against the stem, thus protecting the delicate assimi- lating tissue. The anthcridia and anhri^onia of i)olytrichum are borne in groups at the ends of the branches on different plants (many mosses bear both organs on the same branch). They are sur- rounded by involucres of characteristic leaves termed perichcetia ox perichtetal leaves. Multicellular hairs known as /anz/'/n'J^i' are scattered among the archegonia and antheridia. The involucres with the organs borne within them are called receptacles, or, less appropriately, " moss flowers." As in marchantia, the organs are very minute and must be highly magnified to be studied. The antheridia are borne in broad cujvlike receptacles on the antheridial plants (Fig. 297). They are much like the antheridia of marchantia, but they stand free among the paraphyscs and are not sunk in cavities. At maturity they burst and allow the sperm cells or spermatozoitls to escape. In poly- trichum, when the receptacles have fulfilled their function, the stem con- Fio. 297. -Section through a tinues to grow from the center of RECEPTACLE OF PoLYTRi- the cup (/;/, Fig. 205 ) . The archc- CHUM COMMUNE, showing 1 -u 4. 1 , . ,. ^ gonia are borne in other receptacles parapnyses and antheridia. " ,. ^r , , , m-i i-i on different plants. Ihey are like the archegonia of marchantia except tliat they stand erect on the end of the branch. The sporogoiiiiiin which develops from the fertilized egg is shown in a, l>, Fig. 295. It consists of a long, brown stalk bearing the spore-case at its summit. The base of the stalk is imbedded in the end of the moss stem by which it is nourished. The capsule is entirely inclosed by a hairy cap, the calyptra, b. The calyptra is really the remnant of the arcliegonium, which, for a time, increases in size to accommodate and protect the young growing capsule. It is finally torn loose and carried up on the spore-case. The mouth of the capsule is closed by a circular lid, the operculum, having a conical ])rojection at the center. The operculum soon drops, or it may be removed, displaying a fringe of sixty-four teeth guarding the mouth of the capsule. This ring of teeth is known as the peristome. In most mosses the teeth exhibit peculiar hygroscopic movements ; i.e. when moist they bend outwards, and upon drying curve in toward the mouth of the capsule. This motion, it will be seen, serves to disperse the spores gradually over a long period of time. Not the entire capsule is filled with spores. There are no elaters, but the center of the capsule is occupied by a columnar STUDIES IN CRYPTOGAMS 20I Strand of tissue, the columella, which expands at the mouth into a thin, membranous disk, closing the entire mouth of the capsule except the narrow annular chink guarded by the teeth. In this moss the points of the teeth are attached to the margin of the membrane, allow- ing the spores to sift out through the spaces be- tween them. When the spores germinate they form a green, branched thread, the protonema. This gives rise directly to moss plants, which appear as little buds on the thread. When the moss plants have sent their little rhizoids into the earth, the pro- tonema dies, for it is no longer necessary for the support of the little plants, and the moss plants grow independently. Funaria is a moss very common on damp, open soil. It forms green patches of small fine leaves from which arise long brown stalks termi- nated by curved capsules (Fig. 298). The struc- ture is similar to that of polytrichum, except the absence of plates on the under side of the leaves, the continuous growth of the stem, the curved capsule, double peristome, monoecious rather than dioecious re- ceptacles, and nearly glabrous unsymmetrical calyptra. Fig. 298. — Fu- naria HY- GROSCOPICA. K Equisetums, or Horsetails (Pteridophyta) There are about twenty-five species of equisetum, constituting the only genus of the unique family Equisetacece. Among these E. arz'ense (Fig. 299) is common nn rl^iyey and sandv soils;. In this species the_work of nutrition and_ that of spnre production are performed by separate shoots from an underground rhizome. The fertile hrnnrhes npppnr early in spring. The^m, which is % to 6 inches high, consists of a number of ryjindr'^-^', furrowed int_ernocles, each sheathed at the base by a circle of S£ale leaves. The shoots are of a pale yellow color. They containjio chtnniphyll, and are nonrish^fd by the food stored in the rhizome (Fig. 299). The spores are formed on specially developed fertile leaves or sporophylls which are" collected into a spike or cone at the end o f the_stalk {a. Fig. 299). A single sporophyll is shown at h. It consists of a short stalk expanded into a broad, mushroom-like head. Several large sporan^^ia are borne on its under side. The spores formed in the sporangia are very interesting and beautiful 202 PLANT BIOLOGY objects when examined under the microscope (X about 200). They are spherical, green bodies, each surrounded by two spiral bands attached to the spore at their intersection, s. These bands exhibit hygroscopic movements by means of which the spores be- come entangled, and are held together. This is of advantage to the plant, as we shall see. All the spores are alike, but some of the//v- thallia grow to a greater size than the others. The large prothallia produce only archegonia while the smaller ones produce anlhcridia. Both of these organs are much like those of the ferns, and fertili- Fin. 299. — Equisf.tum arvf:.\se. st, sterile shoot; _/, fertile shoot showing the spike at a ; b, sporophyll, with sporangia; J, spore. zation is accomplished in the same way. Since the prothallia are usually dioecious, the special advantage of the spiral bands, holding the spores together so that both kinds of prothallia may be in close proximity, will be easily understood. As in the fern, the fertilized egg-cell develops into an equisetum plant. The sterile shoots (^/, Fig. 299) appear much later in the season. They give rise to repeated whorls of angular or furrowed branches. The leaves are very much reduced scales, situated at the inter- nodes. The stems are provided with chlorophyll and act as assimilating tissue, nourishing the rhizome and the fertile shoots. Nutriment is also stored in special tubers developed on the rhi- zome. STUDIES IN CRYPTOGAMS 203 Mi Other species of equisetum have only one kind of shoot — a tall, hard, leafless, green shoot with the spike at its summit. Equise- tum stems are full of silex, and they are sometimes used for scour- ing floors and utensils ; hence the common name " scouring rush." IsoETES (Pteridophyta) Isoetes or quillwort is usually found in water or damp soil on the edges of ponds and lakes. The general habit of the plant is seen in Fig. 300, a. It consists of a short, perennial stem bear- ing numerous erect, quill-like leaves with broad sheathing bases. The plants are commonly mis- taken for young grasses. Isoetes bears two kinds of spores, large roughened ones, the niacrospores, and small ones or viicrospores. Both kinds are formed in sporangia borne in an excavation in the expanded base of the leaf. The niacrospores are formed on the outer and the microspores on the inner leaves. A sporangium in the base of a leaf is shown at /'. It is partially covered by a thin membrane, the velum. The minute triangu- lar appendage at the upper end of the sporangium is called the ligule. The spores are liberated by the decay of the sporangia. They form rudimentary prothaUia of two kinds. The microspores produce prothallia with antheridia, while the niacrospores produce pro- thallia with archegonia. Ferti- lization takes place as*vhn the mosses or liverworts, and the fertihzed egg-cell, by contini^^d'gfowth, gives rise again to the isoetes plant. a\ Fig. 300. — Isoetes, showing habit of plant at a ; b, base of leaf, show- ing sporangium, velum, and ligule. Club-Mosses (Pteridophyta) The clnb-mosses are low trailing plants of moss-like looks and habit, although more closely allied to ferns than to true mosses. Except one genus in Florida, all our club mosses belong to thq 204 PLANT BIOLOGY genus Lycopodiiim. They grow mostly in woods, having i -nerved evergreen leaves arranged in four or more ranks. Some of them make long strands, as the ground pine, and are much used for Christmas decorations. The spores are all of one kind or form, borne in i-celled sporangia that open on the margin into two valves. The sporangia are borne in some species (Fig. 301) Fig. 301. —A LvcopoDruM WITH Sporangia in THE AXII.S OF THE FO- LIAGE Leaves. {Lyco- podium lucidulutn.) Fig. 302. — A Club-moss {Lycopodium complanatum) . as small yellow bodies in the axils of the ordinary leaves near the tip of the shoot; in other species (Fig. 302) they are borne in the axils of small scales that form a catkin-like spike. The spores are very numerous, and they contain an oil that makes them inflammable. About 100 species of lycopodium are known. The plants grown by florists under the name of lycopodium are of the genus Selaginella, more closely allied to isoetes, bearing two kinds of spores (microspores and macrospores) . ANIMAL BIOLOGY CHAPTER I THE PRINCIPLES OF BIOLOGY Biology (Greek, bios, life; logos, discourse) means the science of life. It treats of animals and plants. That branch of biology which treats of animals is called zoology (Gr, zoon, animal ; logos, discourse). The biological science of botany (Gr. botajie, plant or herb) treats of plants. Living things are distinguished from the not living by a series of processes, or changes (feeding, growth, develop- ment, multiplication, etc.), which together constitute what is called life. These processes are called functions. Both plants and animals have certain parts called oigans which have each a definite work, or function; hence animals and plants are said to be organized. For example, men and most animals have a certain organ (the mouth) for taking in nourishment; another (the food tube), for its digestion. Because of its organization, each animal or plant is said to be an organism. Living things constitute the organic kingdom. Things without life and not formed by life constitute the inorganic, or viineral, kingdom,. Mark I for inorganic and O for organic after the proper words in this list: granite, sugar, lumber, gold, shellac, sand, coal, paper, glass, starch, copper, gelatine, cloth, air, potatoes, alcohol, oil, clay. Which of these things are used for food by animals .-* Conclusion.? ANIMAL BIOLOGY Energy in the Organic World. — We see animals exerting energy; that is, we see them moving about and doing work. Plants are never seen acting that way; yet they need energy in order to form their tissues, grow, and raise themselves in the air. Source of Plant Energy. — \Vc notice that green plants thrive only in the light, while animal growth is largely in- dependent of light. In fact, in the salt mines of Poland there are churches and villages below the ground, and children are born, become adults, and live all their lives below ground, without seeing the sun. (That these people are not very strong is doubtless due more to want of fresh air and other causes than want of sunlight.) The need of plants for Surfaces of a Leaf, magnified. siinlight shows that they VI list obtain something from the sun. This has been found to be energy. This enables them to lift their stems in growth, and form the various structures called tissues which make up their stems and leaves. (See Part I, Chap. XIII.) It is noticed that they take in food and water from the soil through their roots. Experiments also show that green plants take in through pores (Fig. I), on the surface of their leaves, a gas composed of carbon and oxygen, and called earlwn dioxid. The energy in the sunlight enables the plant to separate out the carbon of the earbon dioxid and build mineral and water and carbon rbonioAcid Gas m the Air going into the Leaf ■^ater Kk;. 2. — a Lf.af storing Energy in Sunlight. THE PRINCIPLES OF BIOLOGY into organic substances. The oxygen of the carbon dioxid is set free and returns to the air (Fig. 2). Starch, sugar, oil, and woody fiber are examples of substances thus formed. Can you think of any fuel not due to plants } How Animals obtain Energy. — You have noticed that starch, oil, etc., will burn, or oxidize, that is, iinite with the oxyge7i of tJie air ; thus the sun's energy, stored in these substances, is changed back to heat and motion. The oxidation of oil or sugar may occur in a furnace; it may also occur in the living substance of the active animal. .k^^>>- Fig. 3. — Colorless plants, as MusH- A green leaf, even after it is cut, gives ROOMS, give off no oxygen. off oxygen (O) if kept in the sun. Fortunately for the animals the plants oxidize very little of the substances built up by them, since they do not move about nor need to keep themselves warm. We notice that animals are constantly using plant substances for food, and constantly drawing the air into their bodies. If the sun- light had not enabled the green plant to store up these substances and set free the oxygen (Fig. 3), animals would have no food to eat nor air to breathe; hence we may say that the sunlight is indirectly the source of the life and energy of animals. Mushrooms and other plants without green matter cannot set oxygen free (Fig. 3). 4 ANIhfAI. BIOLOGY Experiment to show the Cause of Burning, or Oxidation. — Obtain a large glass bottle (a pickle jar), a short candle, and some matches. Light the candle and put it on a table near the edge, and cover it with the glass jar. The flame slowly smothers and goes oj.it. Why is this .'' Is the air now in the jar different from that which was in it before the candle was lighted .-' Some change must have taken place or the candle would continue to burn. To try whether the candle will burn again under the jar without changing the air, slide the jar to the edge of the table and let the candle drop out. Light the candle and slip it up into the jar again, the jar being held with its mouth a little over the edge of the table to receive the candle (Fig. 5). The flame goes out at once. Evidently the air in the jar is not the same as the air outside. Take up the jar and wave it to and fro a few times, so as to remove the old air and admit fresh air. The candle now burns in it with as bright a flame as at first. So we conclude that the candle will not continue to burn unless there is a constant supply of fresh air. The gas formed by the burning is carbon dioxid. It is the gas from which plants extract carbon. (See Plant Biology, Chap. V.) One test for the presence of this gas is that it forms a white, chalky cloud in lime water ; another is that it smothers a fire. Experiment to show that Animals give off Carbon Dioxid. — Place a cardboard over the mouth of a bottle containing pure air. Take a long straw, the hollow stem of a weed, a glass tube, or a sheet of stiff paper rolled into a tube, and pass the tube into the bottle through a hole in the cardboard. Without drawing in a deep breath, send one long breath into the bottle through the tube, emptying the lungs by the breath as nearly as possible (Fig. 4). Next invert the bottle on the table as in the former experiment. THE PRINCIPLES OF BIOLOGY afterward withdrawing the cardboard. Move the bottle to the edge of the table and pass the lighted candle up into it (Fig. 5). Does the flame go out as quickly as in the former experiment .'' If you breathe through a tube into clear lime water, the water turns milky. The effect of the breath on the candle and on the lime water shows that carbon dioxid is continually leaving our bodies in the breath. Fig. 4. — Breathing into a bottle. l FiG. 5. — Testing the air in the bottle.* Oxidation and Deoxidation. — The union of oxygen with carbon and other substances, which occurs in fires and in the bodies of animals, is called oxidation. The separa- tion of the oxygen from carbon such as occurs in the leaves of plants is called deoxidation. The first process sets energy free, the other process stores it up. Animals give off carbon dioxid from their lungs or gills, and plants give off oxygen from their leaves. But plants need some energy in growing, so oxidation also occurs in plants, but to a far less extent than in animals. At night, because of the absence of sunlight, no deoxidation is taking place * From Coleman's " Physiology for Beginners," Macmillan Co., N.Y. 6 ANIMAL BIOLOGY in the plant, but oxidation and growth continue ; so at night the plant actually breathes out some earhon dioxid. The deepest part of the lungs contains the most carbon dioxid. Why was it necessary to empty the lungs as nearly as possible in the experiment with the candle ? Why would first drawing a deep breath interfere with the experi- ment ? Why does closing the draught of a stove, thus shutting off part of the air, lessen the burning ? Why does a " firefiy " shine brighter at each breath ? Why is the pulse and breathing faster in a fever? Very slow in a trance ? The key for understanding any animal is to find how it gets food and oxygen, and how it uses the energy thus obtained to grow, move, avoid its enemies, and get more food. Because it moves, it needs senses to guide it. The key for understanding a plant is to find Jioiv it gets food and su)ilight for its growth. It makes little provision against enemies ; its food is in reach, so it needs no senses to guide it. The plant is built on the plan of having the nutritive activities near the surface (e.g. absorption by roots ; gas exchange in leaves). The animal is built on the plan of having its nutritive activities on the inside (^e.g. digestion; breathing). Cell and Protoplasm. — Both plants and animals are composed of small parts called eells. Cells are usually microscopic in size. They have various shapes, as spheri- cal, flat, cylindrical, fiber-like, star-shaped. The living substance of cells is called protoplasm. It is a stiff, gluey fluid, albuminous in its nature. Every cell has a denser spot or kernel called a nucleus, and in the nucleus is a still smaller speck called a nucleolus. Most cells are denser and tougher on the outside, and are said to have a cell zvall, but many cells are naked, or without a wall. Hence the indispensable part of a cell is not the wall but the nucleus, THE PRINCIPLES OF BIOLOGY and a cell may be defined as a bit of protoplasm containi7ig a nucleus. This definition includes naked cells as well as cells with walls. One-celled Animals. — There are countless millions of animals and plants the existence of which was not sus- pected until the invention of the micro- scope several centuries ago. They are one-celled, and hence microscopic in size. It is beUeved that the large animals and plants are descended from one-celled ani- mals and plants. In fact, each individual plant or animal begins life as a single cell, called an Q.gg cell, and forms its .organs by the subdivision of the egg cell into many cells. An egg cell is shown in Fig. 6, and the first stages in the development of an &^^ cell are shown in Fig. 7. The animals to be studied in the first chapter are one- celled animals. To understand them we must learn how Fig. 6. — Egg cell of mammal with yolk. Fig. 7. — Egg cill subdivides into many cells forming a sphere (morula) containing a liquid. A dimple forms and deepens to form the next stage (gastrula). they eat, breathe, feel, and move. They are called Pro- tozoans (Greek protos, first; zoon, life). All other animals are composed of many cells and are called Metazoans (Greek meta, beyond or after). The cells composing the mucous membrane in man are shown in Fig. 8. The cellu- lar structure of the leaf of a many-celled plant is illustrated in Fig. I. (See also Chap. I, Human Biology.) 8 AX IMA I. BIOLOGY Method of Classifying Animals. — The various animals display differences more or less marked. The question arises, are not some of them more closely related than others .-' We conclude that they are, since the differ- ence between some animals is very slight, while the difference between others is quite marked. To show the different steps in classi- fying an animal, we will take an ex- ample,— the cow. Even little children learn to recognize a cow, although indi- vidual cows differ somewhat in form, size, color, etc. The varieties of cows, such as short-horn, Jersey, etc., all form one species of animals, having the scientific name taurus. Let us include in a larger group the animals closest akin to a cow. We see a cat, a bison, and a dog ; rejecting the cat and the dog, we see that the bison has horns, hoofs, and other similarities. We in- FiG. 8. — Mucous Mem- clude it with the cow in a genus called BRANE formed of one Bos, Calling the COW Bos taurus, and layer of cells. A few r) u- -x^v, j cells secrete mucus. ^"^ blSOU, BoS blSOn, 1 he Sacred COW of India (Bos indicus) is so like the cow and buffalo as also to belong in the genus Bos. Why is not the camel, which, like Bos bison, has a hump, placed in the genus Bos .'' The Old World buffaloes, — most abundant in Africa and India, — the antelopes, sheep, goats, and several other genera are placed with the genus Bos in a family called the holloiv-liorneil animals. This family, because of its even number of toes and the habit of chewing the cud, resembles the camel family, THE PRINCIPLES OF BIOLOGY ' 9 the deer family, and several other families. These are all placed together in the next higher systematic unit called an order, in this case, the order of ruminants. The ruminants, because they are covered with hair and nourish the young with milk, are in every essential respect related to the one-toed horses, the beasts of prey, the apes, etc. Hence they are all placed in a more inclusive division of animals, the class called mammals. All mammals have the skeleton, or support of the body, on the inside, the axis of which is called the verte- bral column. This feature also belongs to the classes of reptiles, amphibians, and fishes. It is therefore consistent to unite these classes by a general idea or conception into a great branch of animals called the vertebrates. Returning from the general to the particular by succes- sive steps, state the branch, class, order, family, genus, and species to which the cow belongs. / The Eight Branches or Sub-kingdoms. — The simplest classification divides the whole animal kingdom into eight branches, named and characterized as follows, be- ginning with the lowest: I. Protozoans. One-celled. II. Sponges. Many openings. III. Polyps. Circular; cup-like ; having only one opening which is both mouth and vent. IV. EcHiNODERMS. Circular ; rough-skinned ; two openings. V. Mollusks. No skeleton ; usually with ex- ternal shell. VI. Vermes. Elongate body, no jointed legs. VII. Arthropods. External jointed skeleton; jointed legs. VIII. Vertebrates. Internal jointed skeleton with axis or backbone. CHAPTKR II PROTOZOA (One-celled Animals) The Ameba Suggestions. — Amebas live in the slime found on submergen stems and leaves in standing water, or in the ooze at the bottom. Water plants may be crowded into a glass dish and allowed to decay, and after about two weeks the anieba may be found in the brown slime scraped from the plants. An ameba culture sometimes lasts only three days. The most abundant supply ever used by the writer was from a bottle of water where some oats were germinating. Use i or ^ inch objective, and cover with a thin cover glass. Teachers who object to the use of the compound microscope in a first course should require a most careful study of the figures. Flu. 9. — AMKliA I'koTiX's, much enlarged. 10 PROTOZOA II Fig. 10, , contractile vacuole; ec, ectoplasm; en, endoplasm; «, nucleus; ps, pseudopod; /j', pseudopod forming; ectoplasm pro- trudes and endoplasm flows into it. Form and Structure. — The ameba (also spelled amoeba) looks so much like a clear drop of jelly that a beginner cannot be certain that he has found one until it moves. It is a speck of protoplasm (Fig. 9), with a clear outer layer, the ectoplasm ; and a granular, internal part, the endoplasm. Is there a dis- tinct line between them .'' (Fig. 10.) Note the central portion and the slender prolonga- tions or pseiidopods (Greek, false feet). Does the endoplasm extend into the pseudo- pods .'' (Fig. 10.) Are the pseudopods arranged with any regularity .'' Sometimes it is possible to see a denser appearing por- tion, called the nucleus ; also a clear space, the contractile vacuole (Fig. 10). Movements. — Sometimes while the pseudopods are be- ing extended and contracted, the central portion remains in the same place (this is mo- tion^. Usually only one pseudo- pod is extended, and the body flows into it ; this is locomotion (Fig. 11). There is a new foot made for each step. Feeding. — If the ameba crawls near a food particle, the pseudopod is pressed against it, or a depression occurs (Fig. 12), and the particle is soon embedded in the endoplasm. Often a clear space called 2l food vacuole is noticed around the food particle. This is the water that is taken in with Fig. II. — The same ameba seen at different times. 12 ANIMAL BIOLOGY the particle (Fig. 12). The water and the particle are soon absorbed and assimilated by the endoplasm. Excretion. — If a particle of sand or other indigestible matter is taken in, it is left bcJiind as the anieba moves on. There is a clear space called the contractile vacuole, which slowly contracts and disappears, then reap- pears and expands (Figs. 9 and 10). This possibly aids in excreting oxidized or useless material. Circulation in the ameba consists of the movement of its protoplasmic particles. It lacks special organs of circulation. Feeling. — Jarring the glass slide seems to be felt, for it causes the activity of the ameba to vary. It does not take in for food every particle that it touches. This may be the beginning of taste, based upon mere chemical affinity. The pseudopods aid in feeling. Reproduction. — Sometimes an ameba is seen dividing into two parts. A narrozving takes place in the middle ; the nucleus also divides, a. part going to each portion (Fig. 13). The mother ameba finally divides into two daughter amebas. Sex is wanting. Source of the Ameba's Energy. — We thus see that the ameba moves without feet, eats without a mouth, digests without a stomach, feels without nerves, and, it should also be stated, breathes without lungs, for oxjgen is absorbed from the water by its whole fig. 13. — ameba, dividing. Fig. 12. — Thk Ameba tak- ing food. I PROTOZOA 13 surface. Its moveniejits require energy ; this, as in all ani- mals, is furnished by the ujiiting of oxygen zvith the food. Carbon dioxid and other waste products are formed by the union ; these pass off at the surface of the ameba and taint the water with impurities. Questions. — Why will the ameba die in a very small quantity of water, even though the water contains enough food? Why will it die still quicker if air is excluded from contact with the drop of w^ater? The ameba never dies of old age. Can it be said to be immortal? According to the definition of a cell {Chapter /), is the ahieba a unicellular or multicellular animal? Cysts. — If the water inhabited by a protozoan dries up, it encysts, that is, it forms a tough skin called a cyst. Upon return of better conditions it breaks the cyst and comes out. Encysted protozoans may be blown through the air : this explains their appearance in vessels of water containing suitable food but previously free from proto- zoans. The Slipper Animalcule or Paramecium Suggestions. — Stagnant water often contains the Paramecium as well as the ameba ; or they may be found in a dish of water con- taining hay or finely cut clover, after the dish has been allowed to stand in the sun for several days. A white film forming on the surface is a sign of their presence. They may even be seen with the unaided eye as tiny white particles by looking through the side of the dish or jar. Use at first a i or 1 in. objective. Restrict their movements by placing cotton fibers beneath the cover glass ; then examine with \ or \ objective. Otherwise, study figures. Shape and Structure. — The Paramecium's whole body, like the ameba's, is only one cell. It resembles a slipper in shape, but the pointed end is the hind end, t\\Q front end being rounded (Fig. 14). The paramecium is propelled by the rapid-beating of numerous fine, threadlike append- 14 ANIMAL BIOLOGY ages on its surface, called cilia (Latin, eyelashes) (Figs.). The cilia, like the pseudopods of the ameba, are merely prolongations of the cell protoplasm, but they are permanent. The sepa- ration between the outer ectoplasm and the interior granular cndoplasm is more marked than in the ameba (Fig. 14). Nucleus and Vacuoles. — There is a large nucleus called the macro- nucleus, and beside it a smaller one called the micronucleus. They are hard to see. About one third of the way from each end is a clear, pul- sating space (bb. Fig. 15) called the pulsat- ing vacuole. These spaces contract until they disappear, and then reappear, gradually ex- panding. Tubes lead frolii the vacuoles which probably serve to keep the contents of the cell in circulation. Feeding. — A depression, or groove, is seen on one side, this serves as a mouth (Figs.). A tiibe which serves as a gullet leads from the mouth-groove to the in- terior of the cell. The mouth-groove is lined with cilia which sweep food particles inward. Fig. 16. — Two Paramkcia exchanging parts of their nuclei. The particlcs accumulate Fig. 14. — Paramecium, showing cilia, c. Two contractile vacuoles, cv\ the macronucleus, tng; two micronuclei, mi; the gullet {CE), a food ball forming and ten food balls in their course from gullet to vent, a. Fig. 15. PROTOZOA 15 iOOq in a mass at the inner end of the gullet, become separated from it as 2i food balli¥\g. 14), and sink into the soft pro- toplasm of the body. The food balls follow a circular course through the endoplasm, keeping near the ectoplasm. Reproduction. — This, as in the ameba, is by division, the constriction being in the middle, and part of the nucleus going to each half. Sometimes two individ- . uals come together with their mouth-grooves touching and exchange parts of their nuclei (Fig. 16). They then separate and each divides to form two new individuals. We thus see that the Para- mecium, though of only one cell, is a fntcch more complex and advanced animal than the ameba. The tiny paddles, or cilia, the mouth-groove, etc., have their special duties similar to the specialized organs of the many-celled animals to be studied later. If time and circumstances allow a prolonged study, sev- eral additional facts may be observed by the pupil, e.g. Does the paramecium swim with the same end always foremost, and same side uppermost .-' Can it move backwards } Avoid obsta- cles .'' Change shape in a narrow passage .'' Does refuse fig. 19.— shellofaRadiolarian Fig. 17. — VoRTi- CELLA (or bell animalcule), two extended, one withdrawn. Fig. 18.— Euglena. l6 ANIMAL BIOLOGY matter leave the body at any particular place ? Trace movement of the food particles. Draw the paramecium. Which has more permanent parts, the amcba or para- vtcciitvi ? Name two anatomical similarities and three dif- ferences ; four functional similarities and three differences. The ameba belongs in the class of protozoans called Rhizopoda "root footed." Other classes of Protozoans are the Infusorians (in the broad sense of the term), which have many waving cilia (Fig. 17) or one whip-like flagellum (Fig. 18), and the Foramiiiifcrs, which possess a calcareous shell pierced with holes (Fig. 19). Much chalky limestone has been formed of their shells. To which class does the paramecillm belong } Protozoans furnish a large amount of food to the higher animals. To the Teacher. If plant, animal, and human biology are to be given in one year as planned, and full time allowed for practical work, the portions of the text in small type, as Chapter III, may be omitted or merely read and discussed. Any two of the three parts forming the course may be used for a year's course by using all of the text and spending more time on practical and field work. CHAPTER III SPONGES Suggestions. — In many parts of the United States, fresh-watei sponges may, by careful searching, be found growing on rocks and logs in clear water. They are brown, creamy, or greenish in color, and re- semble more a cushion-like plant than an animal. They have a char- acteristic gritty feel. They soon die after removal to an aquarium. A number of common small bath sponges may be bought and kept for use in studying the skeleton of an ocean sponge. These sponges should not have large holes in the bottom ; if so, too much of the sponge has been cut away. A piece of marine sponge preserved in alco- hol or formalin may be used for showing the sponge with its flesh in place. Microscopic slides may be used for showing the spicules. The small fresh-water sponge (Fig. 2:) lacks the more or less vase- like form typical of sponges. It is a rounded mass growing upon a rock or log. As indicated by the arrows, where does wa/er e;ifer the sponge? This may be tested by putting color- ing matter in the water near the living sponge. Where does ^JI^"^^ '^ ^^^^-^^^3^^ ' \\\e wat€7' co7)ie out! {Y\%. 22.) _ "^ ' ' rr V, : Does it pass through ciliated Fig. 22. — Section of fresh-water sponge '^ ° (enlarged). chambers \w\\.s zonxse? Is the c 17 Fig. 21. Fresh-water Sponge. i8 AXIMAL BIOLOGY Fig. 23. — Eggs and spici'LES of fresh-water sponge (enlarged). surface of the sponge rough or smooth ? Do any of the skeletal spiitihs show on the surface? (Fig. 21.) Docs the sponge thin out near its edge? The <-c§' of this sponge is shown in Fig. 23. It escapes from the parent sponge through the osculiim, or large outlet. As in most sponges, the first stage after the egg is ciliated and free-swim- ming. Marine Sponges. — The grantia (Fig. 24) is one of the simplest of marine sj^onges. What is the shape of grantia? What is its length antl tliameter? How does the free end differ from the fixed end? Are the spicules projecting from its body few or many? Where is the osculum, or large outlet? With what is this surrounded? The osculum opens from a central cavity called the cloaca. The canals from the pores lead to the cloaca. Buds are sometimes seen growing out from the sponge near its base. These are young sponges formed asexually. Later they become detached from the parent sponge. Commercial " Sponge." — What part of the complete animal remains in the bath sponge? Sloiu growing sponges grow more at the top and form tall, simple, tubular or vase-like animals. Fast growing sponges grow on all sides at once and form a complicated system of canals, pores, and oscula. Which of these habits of growth do you think belonged to the bath sponge ? Is there a large hole in the base of your specimen? If so, this is because the cloaca was reached in trimming the lower part where it was attached to a rock. Test the elasticity of the sponge when dry and when wet by squeezing it. Is it softer when wet or dry? Is it more elastic when wet or dry? Fig. 25. — FL-in of How many oscula does your specimen have? a sponge. How many inhalent pores to a square inch? Fig. 24.— Grantia. SPONGES 19 Using a probe (a wire with knob at end, or small hat pin), try to trace the canals from the pores to the cavities inside. Do the fibers of the sponge appear to interlace, or join, according to any system? Do you see any fringe-like growths on the surface which show that new tubes are be- ginning to form? Was the sponge growing faster at the top, on the sides, or near the bottom ? Burn a bit of the sponge ; from the odor, what would you judge of its composition? Is the inner cavity more conspicuous in a simple sponge or in a compound sponge like the bath sponge? Is the bath sponge Fig. 26. — Bath Sponge. Fig. 27. — Bath Sponge. Fig. 28. — Bath Sponge. branched or lobed? Compare a number of specimens (Figs. 26, 27, 28) and decide whether the common sponge has a typical shape. What features do their forms possess in common? Sponges are divided into three classes, according as their skeletons are flinty (silicious), limy (calcareous), or horny. Some of the silicious sponges have skeletons that resemble spun glass in their delicacy. Flint is chemically nearly the same as glass. The skeleton shown in Fig. 29 is that of a glass sponge which lives near the Philippine Islands. The horny sponges do not have spi- cules in their skeletons, as the flinty and FlG.29.-Skeletonofa ^'^^^y ^P^"^^^ h^^^' ^"^ ^^^^ skeleton glass sponge. is Composed of interweaving fibers of 20 AXlAfAf. BIOLOGY Fig. 30. — A hornv sponge. spotii^n, a durable substance of the same chemical nature as silk (Figs. 30 and 31). The /itny sponges have skeletons made of numerous spicules of lime. The three-rayed spicule is the commonest form. The commercial sponge, seen as it grows in the ocean, appears as a roundish mass with a smooth, dark exterior, and having about the consistency of beef liver. Several large o])enings (oscula), from which the water flows, are visible on the upper surface. Smaller holes (inhalent pores — many of them so small as to be indistinguishable) are on the sides. If the sponge is disturbed, the smaller holes, and perhaps the larger ones, will close. The outer layer of cells serves as a sort of skin. Since so much of the sponge is in contact with water, most of the cells do their own breathing, or absorp- tion of oxygen and giving off of carbon dioxid. Nutriment is passed on from the surface cells to nourish the rest of the body. Reproduction. — Egg-cells and sperm-cells are produced by certain cells along the canals. The egg-cell, after it is fertilized by the sperm-cell, begins to divide and form new cells, some of which possess cilia. The embryo sponge passes out at an oscu- lum. By the vibration of the cilia, it swims about for a while. It afterwards settles down with the one end attached to the ocean floor and remains fixed for the rest of its life. The other end de- velops oscula. Some of the cilia continue to vibrate and create currents which bring food and oxygen. The cilia in many species are found only in cavities called ciliated chambers. (Figs. 22, 32.) There are no distinct organs in the sponge and there is very little specialization of cells. The ciliated cells and the reproductive cells are the only specialized cells. The sponges were for a long time considered as colonies of separate one-celled animals classed as protozoans. They are, Fig. 31. — Section of horny sponge. SPONGES 21 without doubt, many-celled animals. If a living sponge is cut into pieces, each piece will grow and form a complete sponge. That the sponge is not a colony of one-celled animals, each like an ameba, but is a many-celled animal, will be realized by exam- ining Fig. 32, which shows a bit of sponge highly magnified. A sponge may be conceived as having developed from a one-celled animal as follows : Sev- eral one-celled animals happened to live side by side ; each possessed a thread-like flagellum (E, Fig. 32) or whip-lash for striking the water. By lashing the water, they caused a stronger cur- rent (Fig. 25) than pro- tozoans living singly could cause. Thus they obtained more food and multipHed more rapidly than those living alone. The habit of working together left its impress on the cells and was trans- mitted by inheritance. Cell joined to cell formed a ring ; ring joined to ring formed a tube which was still more effective than a ring in lashing the water into a current and bringing fresh food (particles of dead plants and animals) and oxygen. Few animals eat sponges ; possibly because spicules, or fibers, are found throughout the flesh, or because the taste and odor are unpleasant enough to protect them. Small animals sometimes crawl into sponges to hide. One sponge grows upon shells in- habited by hermit crabs. Moving of the shell from place to place is an advantage to the sponge, while the sponge conceals and thus protects the crab. Special Report : Sponge " Fisheries." (Localities; how sponges are taken, cleaned, dried, shipped, and sold.) Fig. 32. — Microscopic plan of ciliated chamber. Each cell lining the chamber has a nucleus, a whip-lash, and a collar around base of whip-lash. Question : State two uses of whip-lash. CHAPTER IV POLYPS (CUPLIKE ANIMALS) A li... The Hydra, or Fresh Water Polyp Suggestions. — Except in the drier regions of the United States, the hydra can usually be found by careful search in fresh water ponds not too stagnant. It is found attached to stones, sticks, or leaves, and has a slender, cylindrical body from a quarter to half an inch long, varying in thickness from that of a fine needle to that of a common pin. The green hydra and the brown hydra, both very small, are common species, though hydras are often wiiite or colorless. •. They should be kept in a large glass dish filled with water. They may be distinguished by the naked eye but are not studied satisfactorily without a magnifying glass or microscope. Place a living specimen attached to a bit of wood in a watch crystal filled with water, or on a hol- lowed slip, or on a slip with a bit of weed to support the cover glass, and examine with hand lens or lowest power of microscope. Prepared microscopical sections, both transverse and longitudinal, may be bought ofdealers in mi- croscopic sup- plies. One is shown in Fig. 39. Is the hy- dra's body round or two- sided .'' (Fig. 35.) What is its general shape ? Does one individual keep the same shape.-' (Fig. 34.) How does the length of the thread- FlG. 34. — Forms assumed by Hydra. POLYPS (CUPLIKE ANIMALS) 23 like tentacles compare with the length of the hydra's body ? About how many tentacles are on a hydra's body ? Do all have the same number of tentacles ? Are the tentacles knotty or smooth ? (Fig. 35.) The hydra is usually ex- tended and slender ; sometimes it is contracted and rounded. In which of these conditions is the base (the foot) larger around than the rest of the body.'' (Fig. 34.) Smaller? How many openings into the body are visible .'' Is there a depression or an eminence at the base of the tentacles .-* For what is the openbig on top of the body probably used ? Why are the tentacles placed at the top of the hydra's body } Does the inoutJi have the most con- venient location possible .-* The conical projection bear- ing the mouth is called /lypo- stome (Fig. 34). The mouth opens into the digestive cavity. Is this the same as the general ■y body cavity, or does the stomach have a wall distinct from the body cavity ? How far down does the body cavity extend .'' Does it extend up into the tentacles .-' (Fig. 39.) If a tentacle is touched, what happens? Is the body ever bent? Which is more sensitive, the columnar body or the tentacles ? In searching for hydras would you be more likely to find the ten- tacles extended or drawn in? Is the hypostome ever extended or drawn in? (Fig. 34.) Locomotion. — The round surface, or disk, by which the hydra is attached, is called its foot. Can you move on one foot without hopping } The hydra moves by alter- FiG. 35. — Hydra (much enlarged) . 24 ANIMAL PIOLOGY Fig. 36. — Nettling Cell. II. discharged, and I. not discharged. nately elongating and rounding the foot. Can you dis- cover other ways by which it moves ? Does the hydra always stand upon its foot ? Lasso Cells. — Upon the tentacles (Fig. 35) are numer- ous cells provided each with a thread-like process (Fig. 36) which lies coiled within the cell, but which may be thrown out upon a water flea, or other minute animal that comes in reach. The touch of the lasso paralyzes the prey (Fig. 37). These cells are variously called lasso cells, nettling cells, or thread cells. The thread is hollow and is pushed out by the pressure of liquid within. When the pressure is withdrawn the thread goes back as the finger of a glove may be turned back into the glove by turning the finger outside in. When a minute animal, or other particle of food comes in contact with a tentacle, how does the tentacle get the food to the mouth .'* By bending and bringing the end to the mouth, or by shortening and changing its form, or in both ways .■* (Fig. 34, C.^ Do the neighboring tentacles seem to bend over to assist a tentacle in securing prey .? (Fig. 34, C.) Digestion. — The food parti- I'lG. 37. — HVDRA captunnga cles break up before remaining water flea. POLYPS {CUPLIKE ANLMALS) 25 long in the stomach, and the nutritive part is absorbed by the lining cells, or endoderm (Fig. 39). The indiges- tible remnants go out through the mouth. The hydra is not provided with a special vent. Why could the vent not be situated at the end opposite the mouth } Circulation and Respiration. — Does water have free access to the body cavity .'' Does the hydra have few or nearly all of its cells exposed to the water in which it lives ."* From its structure, decide whether it can breathe like a sponge or whether special respiratory cells are necessary to supply it with oxygen and give off carbon dioxid. Blood vessels are unnecessary for transfer- ring oxygen and food from cell to cell. Reproduction. — Do you see any swellings upon the ^'^- s^- - hydras on pondweed. side of the hydra .-' (Fig. 34, A.) If the swelling is near the tentacles, it is a spermary ; if near the base it is an ovary. A sperm coalesces with or fertilizes the ovum after the ovum is exposed by the breaking of the ovary wall. Sometimes the sperm from one hydra unites with the ovum of another hydra. This is called cross-fertilizatioii. The same term is applied to the process in plants when the male element, developed in the pollen of the flower, unites with the female element of the ovule of the flower on another plant. The hydra, like most plants and some other animals, is hermaphrodite, that is to say, both sperms and ova are produced by one individual. In the autumn, eggs are produced with hard shells to withstand the cold until spring. Sexual reproduction takes place when food is AXIMAL BIOLOGY scarce. Asexual (generation (by budding) is common with the hydra when food supply is abundant. After the bud grows to a cer- tain size, the outer layer of cells at the base of the bud con- stricts and the young hydra is detached. Compare the sponge and the hydra in the fol- lowing respects: — many celled, or one celled ; obtaining food ; breathing; tubes and cavities ; openings ; re- production ; loco- motion. Which ranks hisfher Fig. 39.- Longitudinal section of hydra (microscopic and diagrammatic). among the metazoa .-' The metazoa, or many celled ani- mals, include all animals except which branch .'* Figure 39 is a //ticroscopic view of a vertical section of a hydra to show the structure of the body wall. There is an outer layer called the ectoderm, and an inner layer called the endoderm. There is also a thin supporting layer (black in the figure) called the tnesoglea. The mesoglea is the thinnest layer. Are the cells larger in the endoderm or the ectoderm ? Do both layers of cells assist in forming the reproductive bud ? The ecto- derm cells end on the inside in contractile tails which form a thin line and have the effect of muscle fibers. They serve the hydra for its remarkable changes of shape. VVIien tlie hydra is cut in pieces, each piece makes a complete hydra, provided it contains both endoderm and ectoderm. POLYPS (^CUPLIKE ANIMALS) 2/ In what ways docs the h3-dra show " division of labor " ? Answer this by explaining the classes of cells specialized to serve a different purpose. Which cells of the hydra are least specialized? In what par- ticulars is the plan of the hydra different from that of a simple sponge? An ingenious naturalist living more than a century ago, asserted that it made no difference to the hydra whether the ectoderm or the endoderm layer were outside or inside, — that it could digest equally well with either layer. He allowed a hydra to swallow a worm attached to a thread, and then by gently pulling in the thread, turned the hydra inside out. More recently a Japanese naturalist showed that the hydra could easily be turned inside out, but he also found that when left to itself it soon reversed matters and returned to its natural condition, that the cells are really specialized and each layer can do its own work and no other. Habits. — The hydra's whole body is a hollow bag, the cavity extending even into the tentacles. The tentacles may increase in number as the hydra grows but seldom exceed eight. The hydra has more active motion than locomotion. It seldom moves from its place, but its ten- tacles are constantly bending, straightening, contracting, and expanding. The body is also usually in motion, bend- ing from one side to another. When the tentacles ap- proach the mouth with captured prey, the mouth (invisible without a hand lens) opens widely, showing five lobes or lips, and the booty is soon tucked within. A hydra can swallow an animal larger in diameter than itself. The endoderm cells have ameboid motion, that is, they extend pseudopods. They also resemble amebas in the power of intra-cellular digestion ; that is, they absorb the harder particles of food and digest them afterwards, re- jecting the indigestible portions. Some of these cells have flagella (see Fig. 39) which keep the fluid of the cavity in constant motion. Sometimes the hydra moves after the manner of a small caterpillar called a "measuring worm," that is, it takes hold first by the foot, then by the tentacles, looping its 28 ANIMAL BIOLOGY body at each step. Sometimes the body goes end over end in slow somersaults. The hugtJi of the extended hydra may reach one half inch. When touched, both tentacles and body contract until it looks to the unaided eye like a round speck of jell v. This shows sensibility. Fig. 40.— Hydroid Colony, with ' ■' nutritive (yo) reproductive p/) and and a fcw small star-shapcd defensive (5) hydranths. ^g|jg ^^^ believed to be tierve cells, but the hydra has not a nervous system. Hydras show their liking for light by moving to the side of the vessel or aquarium whence the light comes. The Branch Polyps (sometimes called Civlen- terata). — The hydra is the only fresh water rep- resentative of this great branch of the animal kingdom. This branch is characterized by its members having only one opening to the body. The polyps also include the salt water animals called hydroids, jelly- fishes, and coral polyps. Hydroids. — Figure 40 shows a hydroid, or group of hydra-like growths, one of which Fig. 41. — " Portuguese Man-o'-war" (compare with Fig. 40). A floating hydroid colony with long, stinging (and sensory) streamers. Troublesome to bathers in Gulf of Mexico. Notice balloon-like float. POLYPS {CUPLIJCE ANIMALS) 29 eats and digests for the group, another defends by nettling cells, another produces eggs. Each hydra-like part of a hydroid is called a Jiydranth. Sometimes the buds on the hydra remain attached so long that a bud forms upon the first bud. Thus three generations are represented in one organism. Such growths show us that it is not always easy to tell what consti- tutes an indi- vidual animal. Hydro ids may be con- ceived to have been developed by the failure of budding hy- dras to sepa- rate from the parent, and by the gradual formation of the habit of living together and assisting each other. When each hydranth of the hydroid devoted itself to a special function of digestion, defense, or reproduction, this group lived longer and prospered ; more eggs were formed, and the habits of the group were trans- mitted to a more numerous progeny than were the habits of a group where members worked more independently of each other. As the sponge is a simple example of the devotion of special cells to special purposes, the hydroid is a primitive and simple example of the occurrence of organs, that is of special parts of the body set aside for a special work. Fig. 42. — The formation of many free swimming jelly- fishes from one fixed hydra-like form. The saucer-like parts (h) turn over after they separate and become like Fig. 43 or 44. Letters show sequence of diagrams. 30 AA'IMAL BIOLOGY How nianv iiKiturc hydranths arc seen in the hydroid shown in Vv^. 40? Why arc the defensive hydranths on the outside of the colony ? Which hy- dranths have no tenta- cles ? Why not ? Jellyfish. — Alterna- tion of Generations. — Medusa. — With some species of hydroids, a very curious thing hap- pens. — The hydrantli that is to produce tJie eggs falls off and be- comes independent of the colony. More sur- prising still, its appear- ance changes entirely and instead of being hydra-like, it becomes the large and complex creature called jellyfish (Fig. 43). But the egg of the jellyfish pro- duces a small hydra -like ani- w^/ which gives rise by budding to a hydroid, and the cycle is complete. The bud for reproductive hydranth) of the hydroid Fig. 44. — a Jkllyfjsh rmedusa). Fig. 43. — A Jellyfish. POLYPS (^CUPLIKE ANIMALS) 3 1 does not produce a hydroid, but a jellyfish ; the egg of the jellyfish does not produce a jellyfish, but a hydroid. This is called by zoologists, alternation of generations. A complete individual is the life from the germination of one ^g'g to the production of another. So that an "individual" con- sists of a hydroid colony fixed in one place together with all the jellyfish produced from its buds, and which may now be floating miles away from it in the ocean. Bathers in the surf are sometimes touched and stung by the long, streamer-like tentacles of the jellyfish. These, like the tentacles of the hydra, have nettling cells (Fig. 41). The umbrella-shaped free swimming jellyfish is called a medusa (Fig. 44). Coral Polyps. — Some of the salt water relatives of the hydra produce buds which remain attached to the parent without, ^^^^ 45.^ coral polyps (tenta- however, becoming different cies, a multiple of six). Notice r ,1 , . hypostome. from the parent in any way. The coral polyps and corallines are examples of colonies of this kind, possessing a common stalk which is formed as the process of multiplication goes on. In the case of coral polyps, the separate animals and the flesh connecting them secrete within themselves a hard, limy, supporting structure knoivn as coral. In some species, the coral, or stony part, is so developed that the polyp seems to be inserted in the coral, into which it withdraws itself for partial protection (Fig. 45). The corallines secrete a smooth stalk which affords no protection, but they also secrete a coating or sheath which incloses both themselves and the stalk. The 32 AMMAL BIOLOGY coating has apertures through which the polyps pro- trude in order to feed when no danger is near (Fig. 46). Fig. 46. — Rku Coral- line with crust and polyps {eight tentacles) . Flc;. 47. — Sea I-'aN (a curaiiine). The red " corals " used for jewelry are bits of stalks of cor- allines. The corallines (Figs. 47, 48) are not so abundant 1 nor so important as the coral polyps (Figs. 45, 49). Colonies of coral polyps grow in countless numbers in the tropical seas. The coral formed by successive colo- nies of polyps accu- mulates and builds up many islands and important addi- tions to continents. The Florida " keys," or islands, and the southern part of the mainland of Florida were so formed. Fig. 48. — Organ Pitk " Coral " (a coralline). POLYPS {CUPLIKE ANIMALS) 33 The Sea Anemone, like the coral polyp, lives in the sea, but like the fresh water hydra, it deposits no limy support for its body. The anemone is much larger than the hydra and most coral polyps, many spe- c i e s at- taining a height of several inches. It does not form colo- nies. When its arms are drawn in, it looks like a large knob of shiny but opaque jelly. Polyps used to be called zoophytes {plant- animals), because of their flower-like appearance (Figs. 50, 51). Fig. 49. — Upright cut through coral polyp X 4. ms, mouth; mr, gullet; Is, /j, fleshy partitions (mesen- teries) extending from outer body wall to gullet (to in- crease absorbing surface) ; s, s, shorter partitions ; mi, fb, stony support (of lime, called coral) ; t, tentacles. Fig. 50. — Sea Anemone. Fig. 51. — Sea Anemones. niAPTKR V ECHINODERMS (SPINY ANIMALS) Fig. 52. — Starfish on a rocky shore. The Starfish Suggestions. Since the echinoderms are aberrant though inter- esting forms not in the regular line of development of animals, this chapter may be omitted if it is desired to shorten the course. — The common star- fish occurs along the At- lantic coast. It is captured by wading along the shore when the tide is out. It is killed by immersion in warm, fresh water. Specimens are usually preserved in 4 per cent formalin. Dried starfish and sea urchins are also useful. A living starfish kept in a pail of .salt water will be instructive. External Features. — Starfish are usually brown or yellow. Why ? (See Fig. 52.) Has it a head or tail? Right and left sides? What is the shape of the <^isk, or ])art which bears the five arms or rays? (Kig. 53.) Does the body as a whole have symmetry on two sides of a line (bilateral symmetry), or around a point (radial symmetry) ? Do the separate rays have 34 Fl(".. 53. — Pl.A.N of Starfish ; III, madrcporite. ECHINODERMS {SPINY ANIMALS) 35 Fig. 55. — Starfish (showing Madreporite). bilateral symmetry ? The skeleton consists of limy plates embedded in the tough skin (Fig. 54). Is the skin rough or smooth? Hard or soft? Are the projections (or spines) in the skin long or short? The skin is hardened by the limy plates, ex- cept around the mouth, which is at the center of Fig. 54. — LiMV Plates in portion of a ray. the lower side and surrounded by a mem- brane. Which is rougher, the mouth side, (<7ra/side) or the opposite (^aboral %\^€) ? Which side is more nearly flat ? The veiit is at or near the center of the disk on the aboral surface. It is usually very small and sometimes absent. Why a vent is not of much use will be understood after learning how the starfish takes food. An organ peculiar to animals of this branch, and called the madreporic plate, or madreporite, is found on the aboral surface between the bases of two rays (Fig. 55). It is wartlike, and usually white or red. This plate is a sieve ; the small openings keep out sand but allow water to filter through. Movements : the Water-tube System. — The water, which is filtered through ^ the perforated madreporite, is needed (^/j*— /'^^-n\2)jn to supply a system of canals (Fig. 56). ,^5^=7^1 /^v-nT^-^^ The madreporite opens into a canal called the stone canal, the wall of which is hardened by the same kind of mate- rial as that found in the skin. The stone canal leads to the ring canal which sur- rounds the mouth (Fig. 56). The ring canal sends radial canals into each ray to supply the double row of tube feet found in the groove at the lower side of each ray (Fig. 57). Because of their arrangement in rows, the feet are Fig. 56. — Water tube System of starfish. m, madreporite; stc, stone canal; a/, ampulla. 36 AMMAL BIOLOGY ^r^r.^ Av- also called amhuhxnal feet (Latin awhulacm, "forest walks"). There is a water holder {ampulla), or muscular water bulb at the base of each tube foot ( Fig. 58). These con- tract and force the water into the tube feet and extend them. The cuplike ends of the tubes cling to the ground by suction. The feet contain delicate muscles by which they contract and shorten. Thus the animal pulls itself slowly along, hundreds of feet acting together. The tube feet, for their own protection, may contract and retire into the groove, the water which extended them being sent back into the ampulla. This system of water vessels (or water- vascular system) of the echinodermata is characteristic of them ; i.e. is not found elsewhere in the animal kingdom. The grooves and the plates on each side of them occupy the ambulacral areas. The rows of spines on each side of the grooves are freely movable. (What advantage?) The spines on the aboral surface are not freely movable. Fig. 57. — Starfish, from below; tube feet extended. Fic. 58. — Section ui- one ka\' and central portion of staifisli. yi.yj. ./ji> '"''c feet more or less extended; au, eye spot: /•, gi'ls; e ring around the mouth, which sends off a branch along each ray. These branches may be seen by separating the rows of tube feet. They end in a pigmented cell at the end of each ray called the eye-spot. The food of starfish consists of such animals as crabs, snails, and oysters. When the prey is too large to be taken into the mouth, the starfish turns its stomach inside out over the prey (Fig. 59). After the shells separate, the stomach is applied to the soft digestible parts. After the animal is eaten, the stomach Fig. 59. — Starfish eat- , .1 rT-i • J J r i.- • ing a sea snail. is retracted. Ihis odd way of eatmg is very ^ . ,. . " i- , 3, stomach everted. economical to its digestive powers, tor only that part of the food which can be digested and absorbed is taken into the body. Only the lower part of the stomach is wide and extensible. The upper portion (next to the aboral surface) is not so wide. This portion receives the secretion from five pairs of digestive glands, a pair of which is situated in each ray. Jaws and teeth are absent. (Why?) The vent is sometimes wanting. Why? Reproduction. — There is a pair of ovaries at the base of each ray of the female starfish (Fig. 58). The spermaries of the male have the same position and form as the ovaries, but they are lighter colored, usually white.^ Regeneration after Mutilation. — If a starfish loses one or more rays, they are replaced by growth. Only a very ignorant oyster- man, angry at the depredations of starfish upon his oyster beds, ^The sperm cells and egg cells are poured out into the water by the adults, and the sperm cell, which, like nearly all sperm cells, has a vibratory, tail- like flagellum to propel it, reaches and fertilizes the egg cell. -»>'.i'"-.-. -'-c ™,. , /^ ' hiG. 65. — Sea Cucumbers. ^ ■ but their bodies are elon- ^._^ -^ - gated, and the'limy plates ^g are absent or very mi- nute. The mouth is sur- rounded by tentacles (Fig. 65). The brittle stars resem- ble the starfish in form, but their rays are very slender, more distinct from the disk, and the tube feet are on the edges of the rays, not under them (^Fig. 66j. Fig. 66. ■ A Brittle Star. ECHINODERMS {SPINY ANIMALS) 41 Fig. 67. — Ckinoid, arms closed. The crinoids are the most ancient of the echino- derms. (Figs. 67, 68.) Their fossils are very abundant in the rocks. They inhabited the geological seas, and it is believed that some of the other echinoderms de- scended from them. A few now inhabit the deep seas. Some species are fixed by stems when young, and later break away and become free- swimming, others remain fixed throughout life. The four classes of the branch echinoderms are Starfish {asteroids), Sea urchins (echinoids), Sea cucumbers (holothurians), and Sea lilies (crinoids). Comparative Review Make a table like this as large as the page of the notebook will allow, and fill in without guessing. Fig. 68. — Disk of Cri- NOID from above, show- ing mouth in center and vent near it, at right (arms removed). Ameba Sponge Hydra Coral Polyp Starfish Is body round, two- sided, or irregular What organs of sense Openings into body Hard or supporting parts of body How food is taken . How move How breathe CHAPTER VI WORMS Suggestions : — Earthworms may be found in the daytime after a heavy rain, or by digging or turning over planks, logs, etc., in damp places. They may be found on the surfoce at night by searching with a lantern. Live specimens may be kept in the laboratory in a box packed with damp (not wet) loam and dead leaves. They may be fed on bits of fat meat, cabbage, onion, etc., dropped on the surface. When studying live worms, they should be allowed to crawl on damp ])aper or wood. An earth- worm placed in a glass tube with ricli, damp soil, may be watched from day to day. External Features. — Is the body bilateral? Is there a dorsal and ventral surface t Can you show this by a test with live worm ? Do you know of an animal with dorsal and ventral surface, but not bilateral ? Can you make out a head .■' A head end ? A neck } Touch fk;.69.-am:m<.hw..km. ^^g ^^^^ ^^^^ jg^^ whether it can be made to craw4 backwards. Which end is more tapering ? Is the mouth at the tip of the head end or on the upper or lower surface .-^ How is the vent situated .'' Its shape .-* As the worm lies on a horizontal surface, is the body anywhere flattened .'' Are there any very distinct divisions in the body ? Do you see any eyesf Experiment to fmd whether the worm is sensitive (i) to touch, (2) to li^ht, (3) to strong odors, (4) to irritating liquids. Does it show a sense of taste ? The experiments should show whether 42 WORMS 43 Fig. 70. — Mouth and Set.^. it avoids or seeks a bright light, as a window ; also whether any parts of the body are especially sensitive to touch, or all equally sensitive. What effect when a bright light is brought suddenly near it at night ? Is red blood visible through the skin ? Can you notice 2LXiy pulsations in a vessel along the back? Do all earth- worms have the same number of divisions or rings ? Com- pare the size of the rings or segments. Can it crawl faster on glass or on paper "i A magnifying glass will show on most species tiny bristle- like projections called setcB. How are the setae arranged .'' (^, Fig. 70.) How many on one ring of the worm .-' How do they point } Does the worm feel smoother when it is pulled forward or backward between the fingers } Why } Are setae on the lower sur- face } Upper surface .-• The sides ? What is the use of the setae .-' Are they useful below ground } Does the worm move at a uniform rate } What change in form occurs as the front part of the body is pushed forward .'' As the hinder part is pulled onward .-* How far does it go at each movement .-' At certain seasons a broad band, or ring, appears, covering several segments and making them seem enlarged (Fig. 71). This is ^ _ the clitcllum, or reproductive girdle. Is this girdle Earth- nearer the mouth or the tail } WORM, -rv , • r 1 mouth end Draw the exterior of an earthworm. above. Dorsal and Ventral Surfaces. — The earthworm always crawls with the same surface to the ground ; this is called the ventral surface, the opposite surface is the dorsal surface. This is the first animal studied to which ANIMAL BIOLOGY these terms are applicable. What are the ventral and dorsal surfaces of a fish, a frog, a bird, a horse, a man ? The name " worm " is often carelessly applied to various crawling things in general. It is prop- erly applied, however, only to segmented atiimals 7inthout jointed appendages. Although a caterpillar crawls, it is not a worm for several reasons. It has six jointed legs, and it is not a developed animal, but only an early stage in the life of a moth or but- terfly. A " grubworm " also has jointed legs (Fig. 167). It does not remain a grub, but in the adult stage is a beetle. A worm never develops into nv- another animal in the latter part of its life ; its setae are not jointed. The Food Tube. — The earthworm has no teeth, and the food tube, as might be inferred from the form of the body is simple and straight. Its parts, recognizable because of slight differences in size and structure, are named the pharynx (muscular), gullet, crop, gizzard (muscular), and stomach-intestine. The last ex- tends through three fourths of the length of the body (Fig. 72). The functions of the parts of the food tube are indicated by their names. Circulation. — There is a large dorsal blood vessel above the food tube (Fig. 73). From the Fig. 72. — Food Tube of earth- worm. (Top view.) Fig. 73. — Food Tube ' and Blood Vfj>- SELS of earth- worm showing the ring-like hearts. (Side view.) WORMS 45 front portion of this tube arise several large tubular rings or "hearts" which are contractile and serve to keep the blood circulating. They lead to a ventral vessel below the food tube (Fig. 74). The blood is red, but the coloring matter is in the liquid, not in the blood cells. Nervous System. — Between the ventral blood vessels is a nerve cord composed of two strands (see Fig. 75). There is a slight swelling, or ganglion, on each strand, in each segment (Fig. 75). The strands sepa- rate near the front end of the worm, and a branch goes up each side of the gullet and enters the two pear-shaped cerebral ganglia, or "brain" (Fig. 75). Food. — The earthworm eats earth contain- ing organic matter, the inorganic part passing through the vent in the form of circular casts; these are found in the morning at the top of the earthworm's burrow. The earthworm has no teeth. It excretes through the mouth an alkaline flnid which softens and partly digests the food before it is eaten. When this fluid is poured out upon a green leaf, the leaf at once turns brown. The starch in the leaf is also acted upon. The snout aids in pushing the food into the mouth. Kidneys. — Since oxidation is occurring in its tissues, and impurities are forming, there must be some way of removing impurities from the tissues. The earthworm does not possess one-pair organs like the kidneys of higher animals to serve this purpose, but it has numerous pairs of small tubular organs called nepJiridia which serve the purpose. Each one is simply a tube with several coils. There is a pair on the floor of each segment. Each neph- FlG. 75.— Ganglia NEAR Mouth and part ot nerve chain of earthworm. 46 AXIMAI. BIOLOGY Fig. 76. — Two pairs OF Nei'IIRIDIA in a worm (diagram). ridium has an inner oj)cn end within the body cavity, and it.s Dutcr end oj^ens by a pore on the surface between the scta\ The ncphridia absorb waste lri)ni the liquid in the cclovi, or body cavity surrounding the food tube, and convey it to the outside. Respiration. — The skin of the earthworm is moist, and the blood capillaries approach so near to the surface of the body that the oxygen is constantly passing in from the air, and carbon dioxid passing out ; hence it is constantly breathing through all parts of its skin. // needs no lungs nor special respiratory organs of any kind. Reproduction. — When one individual animal produces both sperm cells and egg cells, it is said to be hermaphrodite. This is true of the earthworm. The egg cell is always fertilized, however, not by the sperm cells of the same worm, but by sperm cells formed by another worm. The openings of these ovaries consist of two pairs of small pores found on the ventral surface of the fourteenth segment in most species (see Fig. 77). There are also two pairs of small receptacles for temporarily holding \.\\q foreign sperm cells. One pair of the openings from these receptacles is found (with diffi- culty) in the wrinkle behind the ninth segment (Fig. 77), and the other pair behind the tenth segment. The sperm- aries are in front of the ovaries (Fig. 77), but the sperm ducts are longer than the oviducts, and open behind them on the fifteenth segment (Figs. 77, 78). The worms exchange sperm cells, but not Flc. 77. — Sperm (f/) and egg glands («) of worm. WORMS A7 egg cells. The reproductive girdle, or clitellum, already spoken of, forms the case which is to hold the eggs (see Fig. 71). When the sperm cells have been exchanged, and the ova are ready for fertili- zation, the worm draws itself backward from the collar-like case or clitellum so that this slips over the head. As it passes the four- teenth segment, it collects the ova, and as it passes the ninth and tenth segments, it collects the sperm cells previously received from another worm. The elastic, collar-like clitellum closes at the ends after it has slipped over the worm's head, forming a capsule. The ova zx^ fertilized in this capsule, and some of them hatch into worms in a few days. These devour the eggs which do not hatch. The eggs develop into complete but very small worms before escaping from the capsule. Habits. — The earthworm is omnhwrojis. It will eat bits of meat as well as leaves and other vegetation. It has also the advantage, when digging its hole, of eating the earth which must be excavated. Every one has noticed the fresh " casts " piled up at the holes in the morn- ing. As the holes are partly filled by rains, the fig. 78.— 11 r • <-i^i • r Side view, casts are most abundant after rams. The chief showing sette enemies of the earthworm are moles and birds, nephridia The worms work at night and retire so early in reproductive the morning that the very early bird has the openings, advantage in catching worms. Perhaps the nearest to an intelligent act the earthworm accomplishes is to con- ceal the moutJi of its hole by plugging it with a pebble or bit of leaf. Worms hibernate, going below danger of frost in winter. In dry weather they burrow several feet deep. The muscular coat of the body wall is much thicker than the skin. It consists of two layers : an outer layer of fibers which 7-nn around the body just beneath the skin, and an 48 AN J MA L BIOLOGY inner, thicker layer of fibers %vhic/i run hngthwise. The worm crawls by shortening the longitudinal muscles. As the bristles {sctic) point backward, they prevent the front part of the body from slipping back, so the hinder part is drawn forward. Next, the circular muscles contract, and the bristles preventing the hind part from slipping back, the fore portion is pushed forward. Is the worm thicker when the hinder part is being pulled up or when the fore part is being thrust forward } Docs the earthworm pull or push itself along, or does it do both } Occasionally it trav- els backward, e.g. it sometimes goes backward into its hole. Then the bristles are directed forward. The right and left halves of the body are counterparts of each other, hence the earthworm is bilaterally syinvictrical. The lungs and gills of animals must always be kept moist. The worm cannot live long in dry air, for respiration in the skin ceases when it cannot be kept moist, and the worm smothers. Long immersion in water is injurious to it, perhaps because there is far less oxygen in water than in the air. Darwin wrote a book called "Vegetable Mold and Earth- worms." He estimated that there were fifty thousand earth- worms to the acre on farm land in England, and that they bring up eighteen tons of soil in an acre each year. As the acids of the food tube act upon the mineral grains that pass through it, the earthworm renders ^Tr^'^ aid in form- ing soil. By burrowing it makes the soil movQ porons and brings up the subsoil. Although without eyes, the worm is sensitive to light falling upon its anterior segments. When the light of a lantern suddenly strikes it at night, it crawls quickly to its burrow. Its sense of touch is so keen that it can detect a light puff of breath. Which of the foods kept in a box of WORMS 49 damp earth disappeared first? What is indicated as to a sense of taste ? Why is the bilateral type of structure better adapted for development and higher organization than the radiate type of the starfish ? The earthworm's body is a double tube ; the hydra's body is a single tube ; which plan is more advantageous, and why ? Would any other color do just as well for an earthworm ? Why, or why not ? The sandworm (Nereis) lives in the sand of the seashore, and swims in the sea at night (Fig. 79). It is more advanced in structure than the earth- worm, as it has a distinct head (Fig. 80), eyes, two teeth, two lips, and several pairs of antennae, and two rows of muscular projections which serve as feet. It is much used by fishermen for bait. If more easily obtained, it may be studied instead of the earthworm. There are four classes in the branch Vermes : i) the worms, including sandworms and leeches; 2) the roHudwonns, including trichina, hairworms, and vinegar eels ; 3) flatzvorms, including tapeworm and liver fluke ; 4) rotifers, which are microscopic aquatic forms. The tapeworm is a flatworm which has lost most of its organs on account of its parasitic life. Its egg is picked up by an herbivorous animal when grazing. The embryo under- goes only partial development in the body of. the herbivorous animal, e.g. an ox. The next stage will not develop until the beef is eaten by a carnivorous animal, to whose food canal it attaches itself and soon develops a long chain of segments called a "tape." Each segment absorbs fluid food through its Fig. 79. — Sand Worm x § (Nereis). Fig. 80. — Head OK Sandworm (enlarged). 50 AM MAI. BIOLOGY body wall. As the sej^ments at the older end mature, each becomes full of eggs, and the segments become detached and pass out of the canal, to be dropped and perhaps picked up by an herbivorous animal and repeat the life cycle. The trichina is more dangerous to human life than the tapeworm. It gets into the food canal in uncooked pork (bologna sausage, for example), multiplies there, migrates into the muscles, causing great pain, and encysts there, remaining until the death of the host. It is believed to get into the bodies of hogs again when they eat rats, which in turn have obtained the cysts from carcasses. Summary of the Biological Process. — An earthworm is a living machine zi'hic/i docs zuork (digging and crawling; seizing, swallowing, and digesting food; pumping blood; growing and reproducing). To do the work it must have ^ cov\\\x\\\:\\ siipp/y of energy. The energy for its work is set free by the protoplasm (in its microscopic cells) under- going a destructive chemical change {oxidation). The waste products from the breaking down of the protoplasm must be continually removed {excretion). The broken- down protoplasm must be continually replaced if life is to continue (the income must exceed the outgo if the animal is still growing). The microscopic cells construct more protoplasm out of food and oxygen {assimilation) supplied them by the processes of nutrition (eating, digesting, breathing, circulating). This protoplasm in turn oxidizes and releases rnore energy to do work, and thus the cycle of life proceeds. CHAPTER VII CRUSTACEANS Crawfish Suggestions. — In regions where crawfish are not found, a live crab may be used. Locomotion and behavior may be studied by providing a tub of water, or better, a large glass jar such as a broad candy jar. For suggestions on study of internal structure, see p. 58. Habitat. — Do you often see crawfish, or crayfish, mov- ing about, even in water where they are known to be abun- dant? What does your answer suggest as to the time when they are probably most active ? Why do you never see one building its chimney, even where crawfish holes are abundant ? Is the chimney always of the same color as the surface soil ? Are the crawfish holes only of use for protection .-' In what kind of spots are crawfish holes always dug .'' Why ? What becomes of crawfish when the pond or creek dries up .-' How deep are the holes? How large are the lumps of mud of which the chimney is built ? How does it get them out of the hole ? Why is the mud built into a chim- ney instead of thrown away ? (What would happen to a well with its mouth no higher than the ground ?) Why are crawfish scarce in rocky regions, as New England ? How does the color of the crawfish compare with its surroundings ? Is its color suited to life in clear or muddy water ? Define protective coloration. 5' 52 AMMAL BIOLOGY Habits. — Does the crawfish walk better in water or out of it ? Why ? Does it use the legs with the large claws to assist in walking? Do the swimmercts (under the ab- domen) move fast or slow? (Observe it from below in a large jar of clear water.) What propels it backward? Forward ? Does the crawfish move at a more uniform rate when swimming backward or forward ? Why ? In which way can it swim more rapidly ? Do the big legs with claws offer more resistance to the water while it is swimming backward or forward? How does it hold the tail after the stroke, while it is darting backward through the water ? Hold a crawfish with its tail submerged and its head up. Can the tail strike the water with much force ? Allow it to grasp a pencil : can it sustain its own weight by its grip ? Feeding. — Offer several kinds of food to a crawfish that has not been alarmed or teased. Does it prefer bread, meat, or vegetables ? How does it get the food to its mouth? Does it eat rapidly or slowly ? Does it tear the food with the big pincers ? Can it gnaw with the small appendages near the mouth ? Breathing. — Does the crawfish breathe with gills or lungs ? Place a few drops of ink near the base of the hind legs of a crawfish resting quietly in shallow water. Where is the ink drawn in ? Where does it come out ? To ex- plain the cause and purpose of this motion, place a craw- fish in a large glass jar containing water, and see the vibratory motion of the ])arts under the front portion of the body. There is a gill paddle, or gill bailer, under the shell on each side of the body that moves at the same rate. Senses. — Crawfish are best caught with a piece of meat or beef's liver tied to a string. Do they always lose hold as soon as they are lifted above the water ? What do you CRUSTACEANS 53 conclude as to the alertness of their senses ? Does the cov- ering of its body suggest the possession of a delicate or dull sense of touch ? Of what motions are the eyes capable? Touch one of the eyes. The result ? Can a crawfish see in all direc- tions ? To test this, place a crawfish on a table and try whether you can move to a place where you can see the '^--•••V^. Fig. 8i. — Crawfish (dorsal surface). Fig. 82. 1 crawfish without seeing its eyes. What are the advantages and disadvantages of having the eyes on stalks } Touch the body and the several appendages of the crawfish. Where does it seem most sensitive to tonch ? Which can reach farther, the antennae or the big claws .-^ Why are short feelers needed as well as long ones .-' Make a loud and sudden noise without jarring the craw- fish. Is it affected by sound? External Anatomy (Figs. 81, 82, 83, 84). — Is the body of the crawfish rounded out (convex) everywhere, or is any part of its surface either flat or rounded in (concave) } 54 AXIMAL BIOLOGY What color lias the crawfish ? Is this color of any use to the crawfish ? Make out the two distinct regions or divisions of the body (Fit;. 81). The anterior (front) region is called the head- chest or cephalothorax, and the posterior (rear) region is called the tail. y Which region is larger ? Why ? Which is flex- ible? Why? Is the covering of the body hard Fic. 83. —Lateral VIEW OK Crawfish. ^ - -tin ^ or soft ? What is the advantage of such a covering ? What are its dis- advantages ? How is the covering modified at the joints to permit motion ? Tail. — How many joints, or segments, of the tail ? ( Figs. 81, 83.) Does the hard covering of each segment slip under or over the segment behind it when the tail is straight ? Does this lessen friction while swimming forward ? Is there a pair of sivimnicrcts to each segment of the tail? (Figs. 82, 86.) Notice that each swimmeret has a main stalk (protopod), an outer branch (exopod), and an inner branch (endopod) (Fig. 84). Are the stalk and the branches each in one piece or jointed ? The middle part of the tail fin is called the telson. By finding the position of the vent, decide whether the food tube goes into the telson (Fig. 82). Should it be called an abdominal segment. Are the side pieces of the tail fin attached to the telson or to the sixth segment ? Do these side pieces correspond Fig. 84.— Fourth Anuo- MiNAi, Segment OK Crawkish with swimmeret. CHUSTACEAXS 55 to swimmerets ? Do they* likewise have the Y-shaped structure? (Fig. 86.) If the swimmerets on the first abdominal segment are large, the specimen is a male. If they are small, it is a female. Which sex is shown in Fig. 82 .'' Fig. 86 } Carapace. — The covering of the head chest (cephalothorax) is called the cara- pace. Has it free edges .' The gills are on the sides of the body and are covered by the carapace (Fig. S7). The projection in front is called the rostrum, meaning beak. Does the rostrum project beyond the eyes } There is a transverse groove across the cara- pace which may be said to divide the head from the abdomen. Where does this groove end at the sides .' Legs. — How many legs has the crawfish } How many are provided with large claws } Small claws .'' Is the outer claw hinged in each of the large grasping pincers .' The inner claw 1 Appendages for Taking Food. — If possible to watch a lixdng craw- fish eating, notice whether it places the food directly into the mouth with the large claws. Bend the large claws under and see if they will reach the mouth. Attached just in front of the legs the crawfish has three pairs of finger-like appendages, called foot jaws(maxilli- peds), with which it passes the food from the large pincers Fig. 85. — I, mandi- ble ; 2,3,maxillas; 4, 5, 6, maxillipeds. Fig. S6. — Crawfish (ventral surface). 56 A.XIMAL BIOLOGY to its mouth (Figs. 85, 86). They are in form and use more like fingers than feet. In front of the foot jaws are two pairs of thin jaws (maxilte) and in front of the thin jaws are a pair of stout jaws (mandi- bles) (Fig. 85). Do the jaws move sidewise or up and down } Which of the jaws has a jointed finger (palp) attached to it ? Do all of the appen- dages for taking food have both exopod and endopod branches on a basal stalk or protopod ? Which of the appendages have a scalloped edge? How would you know from looking at the crawfish that it is not merely a scavenger? Why are there no pincers on the hind feet ? Sense Organs. — Find the antcnnce, or long feelers (Figs. 82, 90). Are the antennae attached above or below the eyes? (Fig. 87.) Fig. 87. Gill cover removed and gills exposed. Mp, gill bailer. r r Fig. 88. — Lengthwise Section of M.\le Cr.vwfish. r, heart: w4f, artery to head; .^ a, artery to abdomen; A'»«, stomach; />, intestine; Z., liver; 7", spermary; <7<7, opening of sperm duct; £7, brain; iV, nerve chain. Find the pair of anteunulcs, or small feelers. Are their divisions like or unlike each other? Compare the length of the antennules and the antennae. Compare the flex- ibility of the antennae with that of the other appendages. CR US TA CEANS 5 J Observe the position of the eyes (Figs. 8i, ^^\ How long are the eyestalks ? Is the stalk flexible or stiff ? Touch the eye. Where is the joint which enables the stalk to move .'' Is the outer covering of the eye hard or soft .-' A mounted preparation of the transparent covering (cornea) of the eye, seen with lower power of microscope, reveals that the cornea is made up of many divisions, called facets. Each facet is the front of a very small eye, hundreds of which make up the whole eye, which is therefore called a com- pound eye. The elongated openings to the ear sacs are located each on the upper side of the base of a small feeler just below the eye. Respiratory System. — The respiratory organs are gills located on each side of the thorax in a space between the carapace and body (Fig. ^J^ The gills are white, curved, and feathery. Is the front gill the largest or the smallest i"' The gills overlap each other; which is the outermost gill i*' On the second maxilla is a thin, doubly curved plate called a gill bailer (Fig. 85). The second maxilla is so placed that the gill bailer comes at the front end of the gill chamber. The bailer paddles continually, bringing the water forward out of the gill. The gills are attached below at the base of the legs. Are the gills thick or thin .'' How far upward do they go .'' Does the backward motion in swimming aid or hinder the passage of the water through the gills .'' Does a crawfish, when at rest on the bottom of a stream, have its head up or down stream } Why .'' Openings. — The slitlike vent is on the under side of the telson (Figs. 82, 88). The mouth is on the under side of the thorax behind the mandibles. At the base of the long antennae are the openings from the green glands^ two glands in the head which serve as kidneys (Fig. 89). The openings of the reproductive organs are on the third 5S AX/MAI. mo LOGY Fio. 89. — Level length wise section showing h, heart. d, green gland. le, liver. kit, gills. kh, gill cavity, ma, stomach. (.\fter Huxley.) to the vent. or small? Straight or curved? The powerful fle.xor muscles of the tail lie in the abdomen below the intestines. Compare the size of these muscles with the extensor muscle above the intestine (Fig. 90). Why this difference? Does the food tube ex- tend into the telson? Lo- cate the vent (Fig. 90). jjair of logs in the female, and the fifth jiair of legs in the male (Fig. 88). The eggs are carried on the swimmerets. Internal Structure. — Si'ot ihstions. If stutlied by dissection, it will be necessary to have several crawfish for each pupil, one for gaining general knowledge, and others for studying the systems in detail. Specimens should have lain in alcohol for several days. The Food Tube. — Is the stomach in the head portion of the cephalothorax or in the thoracic portion? ( F"igs. 88, 89). Is the stomach large or small? What is its general shape? I)oes the gullet lead upward or backward? Is it long or short? (Fig. 88.) The mid tube, which is the next portion of the food tube, is smaller than the stomach. On each side of it are openings from the bile ducts which bring the secretion from the digestive gland, sometimes called the liver. Does this gland extend the whole length of the thorax? Is it near the floor or the top of the cavity? The third and last portion of the food tube is the intestine. It extends from the thorax Is it large Fig. 90. — Sfxtion of Crawfish showing stomach .;, liver //', and vent a. CRUSTACEANS 59 The Circulation. — The blood is a liquid containing white cor- puscles. It lacks red corpuscles and is colorless. The heart is in the upper part of the thorax. It is sur- rounded by a large, thin bag, and thus it is in a chamber (called the pericardial sinus). The blood from the pulmonary veins enters this sinus before it enters the heart. The origin of this pericardial sinus by the fusing of veins is shown in Fig. 1 30. Does one artery, or do several arteries, leave the heart ? There is a larger dorsal artery lying on the intestine and passing back to the telson ; there are three arteries passing forward close to the dorsal surface (Figs. 89, 91). One large artery (the sternal) passes directly downward (Figs. 88, 91), and sends a branch forward and another backward near the ventral surface. The openings into the heart from the sinus have valvular lips which prevent a backward flow of blood into the sinus. Hence, when the heart contracts, the blood is sent out into the sev- ^ eral arteries. The arteries take a supply of fresh blood H \ to the eyes, stomach, muscles, liver, and the various organs. After it has given oxygen to the several organs and taken up carbon dioxid, it returns by veins to pass through the gills on each side, where it gives out the use- less gas and takes up oxygen from the water. It is then led upward by veins into the pericardial sinus again. The central nervous system consists of a double chain of ganglia (Fig. 92). This main nerve chain lies along the ventral surface below the food tube (Fig. 90), except one pair of ganglia which he above the esophagus or gullet (Fig. 88), and are called the supra-esophageal ganglia, or brain. Fig. 91. — Showing heart and main blood vessels. I Crustacea. — The crawfish and its kindred are placed in the class called Crustacea. 6o ANIMAL BIOLOGY Fig. 93. — Crab from UELOW. Fig. 94. — Hkrmit Crab, using shell of sea snail for a house. Decapods. — All crustacca which have ton feet i)elong in the oriler called decaji'oda (ten-footed). This order includes the crabs, lobsters, shrimp, I. i ' etc. The crabs and lobsters are of ^>^ . . r' , X considerable importance because of use as food. Small boys sometimes catch crawfish, and in some instances are known to cook and cat them for amusement, the only part cooked being the muscular tail. The crab's tail is small and flat and held under the body (Fig. 93). Since the limy covering to serve the purpose of protection is not soft enough to be alive and growing, it is evident that the Crustacea are hampered in their growth by their crusty covering. Dur- ^r;-^ ^S^^ ing the first year the craw- fish sheds its covering, or molts three times, and once each year thereafter. It grows very fast for a few days just after molt- ing, while the Fig. 95. — Devei.oi'ment of a Crar. covering is soft a, naupliusjustafter hatching; i,c,'»^ calculates that the farmers of the FIG. 120. -Front yy^^^. ^^^^ $200,000,000 because of grass- Leg of Mole ° Cricket, x 3, hopper ravages in 1874-5. INSECTS 71 The cockroaches (Fig. 116), kindred of the grasshoppers, are household pests that have migrated almost everywhere that ships go. The praying mantis (Fig. 117), or devil's horse, also belongs to this order. It is beneficial, since it destroys noxious insects. Which of its legs are specialized .-' The ivalking stick (Fig. 121) and cricket (Fig. 118), like most members of the order, are vegetarian. Are grasshoppers more common in fields and meadows, or in wooded places .-* How many different colors have you seen on grasshoppers .■' Which colors are most common } Grasshoppers are very scarce in Europe as they love dry, warm countries. Why do lo- custs migrate .'' Give an in- stance in ancient times. How long do most grass- hoppers live .'' Does a grass- hopper spread its wings before it flies .'' Does it jump and fly together .'' Can it select the place for ahghting } Note to Teacher. — Field work in Zoology should be systematic. Every trip Fig. 121. - Four Walking Stick has a definite region and definite hne of study in view, but every animal seen should be noted. The habitat, adapta- tion by structure and habits to the environment, relations to other animals, classification of animals seen, should be some of the ideas guiding the study. The excursions may be divided somewhat as follows, according as opportunities offer : Upland woods, lowland woods, upland pastures, fields, swamps, a fresh- water lake, a pond, lower sea beach, higher sea beach, sand hills along shore, roadside, garden, haunts of birds, insect visits to flowers, ground insects, insects in logs. An alphabetical letter file may be used for filing individual field observations. These should be placed before the class orally or in writing. If accepted as reliable (repeated and revised if necessary), the observations should be filed 72 ANIMAL BIOLOGY away and credit given the student on a regular scale. Thus will grading and marks he placed to encourage intelligent study of nature rather than book or laboratory cram. One percent to be added to the final grade may be cred- ited for every species of pupa, every rare insect (with an observeil fact as to its habits) brought in, every biril migration observed, every instance of protective coloration, mimicry (p. 146), outwitting of enemy, instance of injurious insects, and how to combat them, etc. Sharp eyes and clear reasoning will then count as much on school grailes as a memory for words or mechanical following of laboratory directions. On scale of too, class work = 50, examination = 25, field work = 25. Collecting Insects. — In cities and towns insects, varying with the season, are attracted by electric lights. Beetles and bugs will be found under the lights, moths on posts near the hghts, grass- hoppers and crickets and other insects in the grass near by. A lamp placed by a window brings many specimens. In the woods and in rocky places insects are found under logs and stones, and under the bark of dead trees. In open places, prairies, meadows, and old fields with grass and flowers, it will be easy to find grass- hoppers, butterflies, and some beetles. Ponds and streams are usually rich in animal forms, such as bugs and beetles, which swim on or under the surface, and larvre of dragon flies crawling on the bottom. Dragon flies and other insects that lay eggs on the water are found flying in the air above. (In the spring, newly hatched crawfish, tadpoles, and the eggs of frogs and toads should also be collected, if found.) Moths may be caught at night by daubing molasses or sirup made from brown sugar upon the trunks of several trees, and visiting the trees at intervals with a lantern. An insect net for catching butterflies and for dredging ponds may be made by bending a stout wire into a circle one foot in diameter, leaving enough straight wire to fasten with staples on an old broomstick. To the frame is fastened a flour sack, or cone made of a piece of mosquito netting. Butterflies and moths should be promptly killed, or they will beat their wings to pieces. The quickest method is by dropping several drops of gasoline upon the ventral (under) side of the thorax and abdomen. (Caution : Gasoline should never be used near an open fire, or lamp, as explosions and deaths result from INSECTS 73 the flame being led through the gasoline-saturated air to the vessel containing it.) A cigar box and a bottle with a notched cork may be used for holding specimens. Cigar boxes may be used for holding collec- tions of dried insects. Cork or ribbed packing paper may be fixed in the bottom for supporting the insect pins. Moth balls or tobacco may be placed in each box to keep out the insect pests which infest collections. It is pleasant and profitable to take to the fields a small book like this one, or even Comstock's " Manual of Insects," or Kel- logg's "American Insects," and study the insects and their habits where they are found. Captured insects which, in either the larval or perfect stage, are injurious to vegetation, should always be killed after studying their actions and external features, even if the internal structure is not to be studied. Beneficial insects, such as ladybugs, ichneumon flies, bees, mantis (devil's horse), dragon flies, etc., should be set free uninjured. x^NATOMY AND GENERAL CHARACTERISTICS OF THE ClASS Insecta The body of an insect is divided by means of two marked narrowings into three parts : the head, chest, and ab- domen. The head is a freely movable cap- sule bearing four pairs of append- ages. Hence it is regarded as having been formed by the union of four rings, since the ancestor of the insects is believed to have con- sisted of similar rings, each ring bearing a pair of unspecialized legs. fig. 122.— yellow fever The typical mouth parts of an Mosquito showing head. ■^ ^ ^ thorax, abdoiiien. insect (Fig. 123) named in order fromx above, are (i) an upper hp (labrum, ol), (2) a pair 74 A.XIMAL BlOl.OCy Fig. 123. — Moi'TH Parts ok Bkkti.k. ^Xf»^ of biting jaws (mandibles, ok'\ (3) a pair of graspincr jaws (niaxilhc, A, />), and (4) a lower lip (labium, w/, a, b). /. The grasping jaws bear two pairs of ' Nv jointed jaw fingers (maxillary palpi, n, C\ and the lower lip bears a pair of similar lip fingers (labial palpi, d). The biting jaws move sideways ; they usually have several pointed notches which serve as teeth. Why should the grasping jaws be beneath the chewing jaws .'' Why is it better for the lower lip to have fingers than the upper lip .'' Why are the fingers (or palpi) jointed .-' (Watch a grasshopper or beetle eating.) Why does an insect need grasping jaws .'' The chest, or thorax, consists of three rings (Fig. 124) called the front thorax (prothorax), middle thorax (mesothorax) and hind thorax (metathorax), or first, second, and third rings. The first ring bears the first pair of legs, the second ring bears the second pair of legs and the upper or front wings, and the third ring bears the third pair of legs and the under or hind wings. The six feet of insects are characteristic of them, since no other adult animals have that number, the spider having eight, the craw- fish and crabs having ten, the centipedes still more, while the birds and beasts have less than six. Hence the insects Fk; 124. — ExTKKNAL Parts OF A Beetle. i Fig. 125. — Leg OF Insect. INSECTS 75 are sometimes called the Six-Footed class {Hexapoda). The insects are the only animals that have the body in three divisions. Man, beasts, and birds have only two divisions (head and trunk) ; worms are not divided. Define the class insccta by the two facts characteristic of them {i.e. possessed by them alone), viz. : Insects are ani- mals with and . Why would it be ambig- uous to include " hard outer skeleton " in this definition } To include "bilateral symmetry ".'' "Segmented body ".'' The definition of a class must include all the individuals of the class, and exclude all the animals that do not belong to the class. The leg of an insect (Fig. 125) has five joints (two short joints, two long, and the foot). Named in order from above, they are (i) the hip (coxa), (2) thigh ring (trochanter), (3) thigh (femur), (4) the shin (tibia), (5) the foot, which has five parts. Which of the five joints of a wasp's leg (Fig. 122) is thickest? Slenderest? Shortest? One joint (which?) of the foot (Fig. 122) is about as long as the other four p^^ i26.-FooT1)f joints of the foot combined. Is the relative fly, with climbing length of the joints of the leg the same in P^^s. grasshoppers, beetles, etc., as in the wasp (Figs.)? Figure 125 is a diagram of an insect's leg cut lengthwise. The leg consists of thick-walled tubes {o, 11) with their ends held together by thin, easy-wrinkling membranes which serve as joints. Thus motion is provided for at the expense of strength. When handling live insects they should never be held by the legs, as the legs come off very easily. Does the joint motion of insects most resemble the motion of hinge joints or ball-and-socket joints? Answer by tests of living insects. There are no muscles in the foot of an insect. The claw is moved by a muscle (/«) in the thigh with which it is connected by the long tendon (3, s, /, ?'). In which part are the breathing muscles? As the wings are developed from folds of the dorsal skin, the wing has two layers, an upper and a lower layer. These inclose the so-called " nerves " or ribs of the wing, each of which consists of a blood tube inclosed in an air tube. 76 AXIMAI. BIOLOGY The abdomen in various sjiecics consists of from five to eleven ovcrlapj)ing rings with their foldlike joints be- tween them. Does each ring overlap the ring in front or the one behind it ? The food tube (Fig. 127) begins at the mouth, which usually bears salivary glands (4, Fig. 127, which repre- sents internal organs of the grasshopper). The food tube expands first into a croplikc enlargement ; next to this is an organ (6, Fig. 127), which resembles the gizzard \ Fig. 127. — Viscera of Grasshopper. Key in text. Compare with Fig. 114. Fig. 128. — Air Tubes of I.nsect. in birds, as its inner wall is furnished with chitinous teeth {b, Fig. 1 14). These reduce the food fragments that were imperfectly broken up by the biting jaws before swallow- ing. Glands comparable to the liver of higher animals open into the food tube where the stomach joins the small intestine. At the junction of the small and large intestine (9) are a number of fine tubes (8) which correspond to kidneys and empty their secretion into the large intestine. The breathing organs of the insects are peculiar to them (see Fig. 128). They consist of tubes which are INSECTS 77 I he Fig. 129. Insect's Heart (plan). kept open by having in their walls continuous spirals of horny material called cJiitiii. Most noticeable are the two large membranous tubes filled with air and ve situated on each side of the body. Do these tubes extend through the thorax? (Fig. 128.) The air reaches these two main tubes by a number of pairs of short windpipes, or trachcas, which begin at openings {^spiracles). In which division are the spiracles most numerous.'' (Fig. 128.) Which division is .vm>j1L_ ,/ik> yirx. "l^'IKc without spiracles .? ^Cy^K /^K^ P II C Could an insect PCT^K jl|^ '3 ll C be drowned, i.e. «wj.klw\./> J'Vf'C ""7 11 I smothered, by holding its body under water } Could it be drowned by immersing all of it but its head 1 The motion of the air through the breathing tubes is caused by a bellowsHke motion of the abdomen. This is readily observed in grasshoppers, beetles, and wasps. As each ring slips into the ring in front of it, the abdomen is shortened, and the impure air, laden with carbon dioxid, is forced out. As the rings slip out, the abdomen is extended and the fresh air comes in, bringing oxygen. The Circulation. — Near the dorsal surface of the abdomen (Fig. 131) extends the long, slender //mr/ (Fig. 129). The heart has divisions separated by valvelike partitions. The blood comes into each of the heart compartments through a pair of openings. The heart contracts from the rear toward Fig. 130. — Diagrams of Evolition OF Pericardial Sac around in- sect's heart from a number of veins (Lankester). Fig. 131. — Position of Insect's Heart, food tube, and nerve chain. 78 AXIM.il. lilOI.OGY the front, drivin<^ the blood forward. The blood contains bodies correspondinj^^ to the ichitc corf^iisclcs of human blood, but lacks the red corpuscles and the red color. The bl(n)d is sent evcn^ to the wings. The veins in the wings consist of horny tubes inclosing air tubes surrounded bv blood spaces, and the purification of the blood is taking place throughout the course of the circulation. Hence the im- perfect circulation is no disadvan- tage. The perfect provision for supplying oxygen explains the remarkable activity of which in- sects are capable and their great strength, which, considering their size, is unequaled by any other animals. The Nervous System. — The heart in backboned animals, e.g. man, is ventral and the chief nerve trunk is dorsal. As already stated, the heart of an insect is dorsal ; its chief nerve chain, consisting of a double row of ganglia, is near the ventral surface (Fig. 131). All the ganglia are below the food tube except the first pair in the head, which are above the gullet. This pair may be said to correspond somewhat to the brain of backboned animals ; the nerves from the eyes and feelers lead to it. With social insects, as bees and ants, it is large and complex (Fig. 132). In a typical insect they are the largest ganglia. The Senses. — The sense of svicll of most in- sects is believed to be located in the feelers. The organ of hearing is variously located in different in- sects. Where is it in the grasshopper "i The organs of FlC. 132. — N'F.RVOUS Sys- 1 EM OK Bee. Fio. 133.— Feei.er of a beetle. INSECTS 79 Flc. 134. — Diagram of simple eye of insect. L, lens; iV, optic nerve. sight are highly developed, and consist of two compound eyes on the side of the head and three simple eyes on the top or front of the head between the com- pound eyes. The simple eye has nerve cells, pigments, and a lens resembling the lens in the eyes of vertebrates (Fig. 134). The compound eye (Fig. 135) has thousands of facets, usually hexagonal, on its surface, the facets being the outer ends of cones which have their inner ends directed toward the center of the eye. It is probable that the large, or compound, eyes of insects only serve to distinguish bright objects from dark objects. The simple eyes afford dis- tinct images of objects within a few inches of the eye. In gen- eral, the sight of insects, contrary to what its complex sight organs would lead us to expect, is not at all keen. Yet an insect can fly through a forest without striking a twig or branch. Is it better for the eyes that are immovable in the head to be large or small } Which has comparatively larger eyes, an insect or a beast .'' Inherited Habit, or Instinct. — Insects and other ani- mals inherit from their parents their particular form of body and of organs which perform the different functions. For example, they inherit a nervous system with a struc- ture similar to that of their parents, and hence with a ten- dency to repeat similar impulses and acts. Repeated acts constitute a habit, and an inherited habit is called an in- Fig. 135. —Compound Eye OF Insect. I, hexagonal facets of crystalline cones. 6, blood vessel in optic nerve So ANIMAL BIOLOGY stinct. Moths, for example, are used to finding nectar in the night-blooming flowers, most of which arc white. The habit of going to white flowers is transmitted in the struc- ture of the nervous system ; so we say that moths have an instinct to go to white objects ; it is sometimes more obscurely expressed by saying they are attracted or drawn thereby. Instincts are not Infallible. — They are trustworthy in only one narrow set of conditions. Now that man makes many fires and lights at night, the instinct just mentioned often causes the death of the moth. The instinct to provide for offspring is necessary to the perpetuation of all but the simplest animals. The dirt dauber, or mud wasp, because of inherited habit, or instinct, makes the cell of the right size, lays the egg, and provides food for offspring that the mother will never see. It seals stung and semiparalyzed spiders in the cell with the ^2,%. If you try the experiment of removing the food before the cell is closed, the insect will bring more spiders ; if they are removed again, a third supply will be brought; but if taken out the third time, the mud wasp will usually close the cell without food, and when the egg hatches the grub will starve. The Development of Insects. — The growth and molting of the grasshopper from Q^^g to adult has been studied. All insects do not develop exactly by this plan. Some hatch from the ^gg in a condition markedly different from the adult. The butterfly's egg j^oduces a wormlike cater- pillar which has no resemblance to the butterfly. After it grows it forms an inclosing case in which it spends a quiet period of development and comes out a butterfly. This change from caterpillar to butterfly is called the metamorphosis. The life of an insect is divided into four 1 i INSECTS 8i Fig. 136. — Measuring worm, the larva of a moth. Stages : (i) egg, (2) larva, (3) pupa, and (4) imaga, or per- fect insect (Figs. 136, 137, 138). The Q.gg stage is one of development, no nourishment being absorbed. The larval stage is one of voracious feed- ing" and rapid growth. In the pupa stage no food is taken and there is no growth in size, but rapid devel- opment takes place. In the per- fect stage food is eaten, but no growth in size takes place. In this stage the eggs are produced. When there is very little resemblance between the larva and imago, and no pupal stage, the metamorphosis, or change, is said to be complete. When, as with the grasshopper, no very marked change takes place between the larva and imago, there being no pupal stage, the metamorphosis is said to be in- complete. By studying the illustrations .and specimens, and by thinking of your past observations of insects, determine which of the insects in the following list have a complete metamorphosis : beetle, house fly, grass- hopper, butterfly, cricket, wasp. Fig. 137. — Pupa of a mosquito. Fig. 138. — The Four Stages of a Botfly, all enlarged. a, egg on hair of horse (bitten off and swallowed) ; b, larva; c, larva with hooks for holding to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly. C 82 ANIMAL BIOLOGY RECOGNITION-CHARACTERS FOR THI-: PRINCIPAL ordi:rs of ADii/r winged insects (All are wingless when young, and wingless adult forms occur in all the orilers : order Afiera lacks wing-bearing thoracic structures.) A single pair of wings is characteristic of the order Dipteh4. A jointed beak, that is sheath-like, inclosing the other mouth parts, is characteristic of the order Hkmiimeka. A coiled sucking proboscis and a wing covering of dust-like microscopic scales are characteristic of the order Lkpidopiera. Horny sheath-like fore wings, covering the hind wings and meeting in a straight line down the middle of tlie back, will dis- tinguish the order Coleoitera. Hind wings folded like a fan beneath the thickened and over- lapping fore wings, will distinguish most members of the order Orthoptera. The possession of a sting (in females) and of two pairs of thin membranous wings — the small hind wing hooked to the rear mar- gin of the fore wjng — will distinguish the common Hvmenoptera. Besides these, there remain a number of groups most of which have in the past been included under the order Neurofiera, among which the Mayflies will be readily recognized by the lack of mouth parts and by the possession of two or three long tails ; the dragon flies by the two pairs of large wings, enormous eyes, and minute bristle-like antennae ; the scorpion flies, by the possession of a rigid beak, with the mouth parts at its tip ; the caddis flies, by their hairy wings and lack of jaws ; the lace wings, by the exquisite regularity of the series ^f cross veins about the margin of their wings, etc. INSECTS 83 Fig, 139. — May Fly. What order (see table)? Exercise in the Use of the Table or Key. — Write the name of the order after each of the fol- lowing names of insects : — Wasp (Fig. 122) Weevil (Fig. 163) Squash bug ( Fig. 184) Ant lion (Fig. 170) Dragon fly (Fig. 177) Ichneumon fly (Fig. 159) House fly (Fig. 172) Flea (Fig. 173) Silver scale or earwig (Fig. 140) Codling moth (Fig. 141 ) Botfly (Fig. 138) Fig. 140. — Silver Scale. (Order?) Moths and Butterflies. — Order -.? Why (p. 82).? The presence of scales on the wings is a never-faiHng test of a moth or butterfly. The wings do not fold at all. They are so large and the legs so weak and delicate that the butterfly keeps its balance with difficulty when walking in the wind. The maxillae are developed to form the long sucking proboscis. How do they fit together to form a tube } (See Fig. 147.) The proboscis varies from a fraction of an inch in the "miller" to five inches in some tropical moths, which use it to extract nectar from long tubular flowers. When not in use, it is held coiled like a watch spring under the head (Fig. 148). The upper lip (labrum), under lip (labium), and lip fingers (labial palpi) are very small, and the mandibles small or wanting (Fig. 146). The metamorphosis is complete, the contrast between the caterpillar or larva of the moth and butterfly and the adult form being very great. The caterpillar has the three pairs of jointed legs typical of insects ; these are 84 ANIMAL BIOLOGY found near the head (Fig. 141). It has also from three to five pairs of fleshy unjointcd proplcgs, one pair of which is always on the last segment. How many pairs of proplcgs has the silkworm caterpillar? (Fig. 143.) The measuring worm, or looper ? (Fig. 136.) The pupa has a thin shell. Can you see external signs of the antennae, wings, and legs in this stage .^ (Fig. 143.) The pupa is concealed by protective coloration, and is some- times inclosed in a silken cocoon which was spun by the caterpillar before the last molt. Hairy caterpillars arc uncomfortable for birds to cat. The naked and brightly marked ones (examples of warning coloration) often con- tain an acrid and distasteful fluid. The injuries from lepidoptcra are done in the caterpillar stage. The codling rnpth (Fig. 141) destroys apples to the estimated value of $6,000,000 annually. The clothes moth (Fig. 171) is a household pest. The tent caterpillar denudes trees of their leaves. The only useful caterpillar is the silkworm. i Fig. 143). In Italy and Japan many of the country dwellings have silk rooms where thousands of these caterpillars are fed and tended by women and children. Why is the cab- bage butterfly so called } Why can it not eat cabbage "*. Why does sealing clothes in a paper bag prevent the ravages of the clothes moth .'' Flight of Lepidoptera. — Wnich appears to use more ex- ertion to keep afloat, a bird or a butterfly .'* Explain why. Of all flying insects which would more probably be found highest up mountains .-• How does the butterfly suddenly change direction of flight .'* Does it usually fly in a straight or zigzag course ."^ Advantage of this.-* liright colors are protective, as lepidoptera are in greatest danger when at rest on flowers. Arc the brightest colors on upper or under side of wings of butterfly .-' Why .-' (Think of the i INSECTS 85 colors in a flower.) Why is it better for moths to hold their wings flat out when at rest ? Where are moths dur- ing the day? How can you test whether the color of the wings is given by the scales ? State how moths and butterflies differ in respect to : body, wings, feelers, habits. J_7^ Insects and Flowers. — Perhaps we are indebted to in- sects for the bright colors and sweet honey of flowers. Flowers need insects to carry their pollen to other flowers, • as cross-fertilization produces the best seeds. The insects need the nectar of the flowers for food, and the bright colors and sweet odors are the advertisements of the flowers to attract insects. Flowers of brightest hues are the ones that receive the visits of insects. Moths, butter- flies, and bees carry most pollen (see Plant Biology, Chap. VI). Comparative Study. — Make a table like this, occupying entire page of notebook, leaving no margins, and fill in accurately : — Grass- hopper Butter- fly Fly pp. 92, 93 Dragon Fly, p. 93 Beetle pp. 90, 91 Bee pp. 88, 89 Number and kind of wings Description of legs Antennae (length, shape, joints) Biting or sucking mouth parts Complete or incom- plete metamor- phosis S6 Illustrated Studies Fir.. 141. — Coni.iNG Moth, from egg to adult. (See Fanners' Bulletin, p. 95.) Fig. 142. — CAiiHA(;K bu 1 ii-.km.v, male and female, larva and pupa. ^ iij) i \i) li<;. 143. — Like Histurv of Silkworm. Fin. 144. — Scales from HunERFLIE.S' WlNCS, as seen under microscope. Illustrated Studies ^7 To THE Teacher : These illustrated studies require sloxver and more careful study than the text. One, or at 7nost tivo, studies will suffice for a lesson. The questions can be ans-ivered by studying the figures. Weak observers will often fail and they should not be told, but should try again until they succeed. Figs. 141-148. Illustrated Study of Lepidoptera. — Study the stages in the development of codling moth, silk- worm moth, and cabbage butterfly. Where does each lay its eggs ? What does the larva of each feed upon ? Describe the pupa of each. Describe the adult forms. Find the spiracles and prologs on the silkworm. Compare antenncs of moth and butterfly. Which has larger body compared to size of wings ? Describe the scales from a butterfly's wings as seen under microscope (144). How are the scales arranged on moth's wing (145) ? By what part is scale attached to wing ? Do the scales overlap ? Study butterfly's head and proboscis (Figs. 146-148). What shape is compound eye ? Are the antennae jointed ? Is the proboscis jointed ? Why not call it a tongue ? (See text.) Which mouth parts have almost disappeared ? What is the shape of cut ends of halves of proboscis ? How are the halves joined to form a tube ? If you saw a butterfly on a flower, for what purpose would you think it was there? What, if you saw it on a leaf? How many spots on fore wing of female cabbage butterfly? (Fig. 124, above.) Does the silkworm chrysalis fill its cocoon ? Eggs may be obtained from U. S. Dept. of Agriculture. Fig. 145. — Scales ON Moth's Wing. Fig. 146. — Head of Butterfly. Fig. 148. — Head of Butterfly (side view). Fig. 147. — Section OF Proboscis of butterfly showing lapping jo'int and dovetail joint. 88 Illustrated Studies ?%•• Fig. 155. Fig. 156. Fig. 157. Anatomv of bee. Figs. 149-161. Illustrated Study of Bees and their Kin- dred. — Head of worker (Fig. 149) : o, upper lip ; oi, chew- ing jaws; ui, grasping jaws; if, jaw finger : //, lip finger ; z, tongue. How do heads of drone (150) and queen (151) differ as to mouth, size of the two compound eyes, size and position of the three simple eyes ? Is the head of a worker more like head of drone or head of queen ? Judging by the head, which is the queen, drone, and worker in Figs. 154-156 ? Which of the three is largest ? Smallest ? Broadest ? Figure 152 shows hind leg of worker. What surrounds the hollow, us, which serves as pollen basket ? The point, /A, is a fool for removing wax which is secreted (c. Fig. 157) between rings on abdomen. In Fig. 158, find relative positions of heart, v, food tube, and nerve chain. Is crop, /, in thorax or abdo- men ? In this nectar is changed to honey, that it may not spoil. Compare jierve chain in Fig. 132. Illustrated Studies 89 Compare the cells of bumble bee (Fig. 153) with those of hive bee. They differ not only in shape but in material, being made of web instead of wax, and they usually contain larvae instead of honey. Only a few of the queens among bumble bees and wasps survive the winter. How do ants and honey bees provide for the workers also to survive the win- ter ? Name all the social insects that you can think of. Do they all belong to the same order ? The ichneumon fly shown enlarged in Fig. 159 lays its eggs under a caterpillar's skin. What becomes of the eggs ? The true size of the insect is shown by the cross lines at a. The eggs are almost microscopic in size. The pupae shown (true size) on caterpillar are sometimes mistaken for eggs. The same mistake is made about the pupa cases of ants. Ichneumon flies also use tree-borers as " hosts ■■ for their eggs and larva. Is this insect a friend of man ? The digging -wasp (Figs. 160 and i6i) supplies its larva with caterpillars and closes the hole, sometimes using a stone as pounding tool. Among the few other uses of tools among lower animals are the elephant's use of a branch for a fly brush, and the ape's use of a walking stick. This wasp digs with fore feet a dog and kicks the dirt of the wav with its hind like out feet. Are the wings of bees and wasps more closely or less closely veined than the wings of dragon flies? (Fig. 177.) For an interesting account of the order " Joined-wings " (bees and their kindred) see Comstock's " Ways of the Six- footed," Ginn & Co. Fig. 161. — Wasp using pebble. From Peckham's " Soliury Wasps," Houghton, Mifflin & Co. 90 Illustrated Studies Illustrated Study of Beetles. I Fig. it>2. — Diving beetle {Dysticus), with larva, a. FlG. 163. —Weevil. Fig. 169. — Colorado beetle (potato bug). Illustrated Studies 91 Illustrated Study of Beetles (Figs. 162-169). — Write the life history of the Colorado beetle, or potato bug (Fig. 169;, stating whero the eggs are laid and describ- ing the form and activities of each stage (the pupal stage, b, is passed in the ground). Do the same for the May beetle (Figs. 167-168). (It is a lar^'a — the white grub — for three years; hogs root them up.) Beetles, like moths, maybe trapped \vith a lantern set above a tub of water. Where does a Scarab (or sacred beetle of the Egyptians, also called tumble Lug (Fig. 164), lay its eggs (Fig. 165)? Why? How does the click beetle, ox jack snapper (Fig. 166), throw itself into the air? For what purpose ? The large proboscis of the weevil (Fig. 163) is used for piercing a hole in which an egg is laid in grain of corn, boll of cotton, acorn, chestnut, plum, etc. How are the legs and body of the diving beetle suited for swimming (Fig. 162) ? Describe its larva. What is the shape of the lady bug (Fig. 97) ? It feeds upon plant lice (Fig. 185) . Is any beetle of benefit to man ? Fig. 170. • Life hislorv of ant lion. niustrated Study of Ant Lion, or Doodle Bug (Fig. 170). — Find the pitfall (what shape?) ; the larva (describe it) ; the pupa case (ball covered with web and sand) ; the imago. Compare imago with dragon fly (Fig. 177). How does ant lion prevent ant from climbing out of pitfall (see Fig. 170) ? What is on edge of nearest pitfall ? E.xplain. Ant lions may be kept in a box half filled with sand and fed on ants. How is the pitfall dug ? What part of ant is eaten ? How is unused food removed ? How long is it in the larval state? Pupal state? Keep net over box to pre- vent adult from flying away when it emerges. Illustrated Studies lIG, 171. Fig. 173. — Metamorphosis of flea. Fig. 172. — Metamor- phosis of house fly (enlarged). Fig. 174. — Louse and its eggs attached to a hair. Natural size and magnified. Fig. 175. — Bed bug. x 5. Fig. 176. — Life history of mosquito. Illustrated Studies 93 Illustrated Study of Insect Pests (Figs. 171-176). — Why does the clothes moth {171) lay its eggs upon woolen clothing? How does the larva conceal itself? The larva can cut through paper and cotton, yet sealing clothes in bags of paper or cotton protects them. E.xplain. The house fly eats liquid sweets. It lays its eggs in horse dung. Describe its larval and pupal forms. Banishing horses from city would have what beneficial effect ? Describe the louse and its eggs, which are shown attached to a hair, natural size and enlarged. Describe the bed bug. Benzine poured in cracks kills bed bugs. Do bed bugs bite or suck ? Why are they wingless ? Describe the larva, f, pupa, g, and the adult flea, all shown enlarged. Its mandibles, b, b, are used for piercing. To kill fleas lather dog or cat completely and let lather remain on five minutes before washing. Eggs are laid and first stages passed in the ground. How does the mosquito lay its eggs in the water without drowning (176) ? Why are the eggs always laid in still water ? Which part of the larva (wiggletail) is held to the surface in breathing ? What part of the pupa (called tumbler, or bull head) is held to the surface in breathing ? Give differences in larva and pupa. Where does pupa change to perfect insect ? Describe mouth parts of male mosquito (at left) and female (at right). Only female mosquitoes suck blood. Males suck juice of plants. Malarial mosquito alights with hind end of body raised at an angle. For figure see Human Biology, Chap. X. Why does killing fish and frogs increase mosquitoes? i oz. of kerosene for 15 ft. of surface of water, renewed monthly, prevents mosquitoes. What is the use to the squash bug (Fig. 184) of having so bad an odor ? j^: Fig. 177. Illustrated Study of Dragon Fly. — 3 shows dragon fly laying its eggs in water while poised on wing. Describe the larval form (water tiger). The extensible tongs are the maxilte enlarged. The pupa (i) is active and lives in water. Where does transformation to adult take place (5) ? Why are eyes of adult large ? its legs small ? Compare front and hind wings. Do the eyes touch each other ? Why is a long abdomen useful in flight ? Why would long feelers be useless ? What is the time of greatest danger in the development of the dragon fly ? What other appropriate name has this insect ? Why should we never kill a dragon fly ? 94 Illustrated Studies Fu;. 179. — Trap-door spider. Fig. 178. — The tarantula. Fig. 182. — Laying egg. Fig. 183. — Foot of spider. Illustrated Study of Spiders (Figs. 178-183).— The tarantula, like most spi- ders, has eight simple eyes (none compound). Find them (Fig. 178). How do spiders and insects differ in body ? Number of legs ? Which have more joints to legs? Does trap-door spider hold the door closed (Fig. 179)? How many pairs of spinnerets for spinning web has a spider {Sfnu, i8o) ? Foot of spider has how many claws ? How many combs on claws for holding web ? Spiders spin a cocoon for holding eggs. From what part of abdomen are eggs laid {E, 182; 2,181)? Find spider's air sacs, /a, Fig. 181 ; spinning organs, J/ ; fang,/^; poison gland, ^; palpi, X-/; eyes, a« ; nerve ganglia, 0^, ?/^; sucking tube, jr; stomach, «/; intestine, ma; liver, le; heart, h, (black) ; vent, a. Give two reasons why a spider is not an insect. How does it place its feet at each step (Fig. no) ? (Does the size of its nerve ganglia indicate great or little intelligence? Why do you think first part of body corresponds to both head and thorax of insects ? INSECTS 95 Fig. 184. — Squash bug, or stink bug. The following Farmer's Bulletins are available for free distribution to those interested, by the U. S. Department of Agriculture, Washington, D.C. : — Farmer's Bulletin No. 47, Insects affecting the Cotton Plant; No. 59, Bee Keeping; No. 70, The Principal Insect Enemies of the Grape ; No. 80, The Peach Twig Borer ; No. 99, Three Insect Enemies of Shade Trees; No. 120, The Principal Insects affecting the Tobacco Plant ; No. 127, Important Insecticides; No. 132, The Principal Insect Enemies of Growing Wheat; No. 145, Carbon Bi- sulphid as an Insecticide ; No. 146, Insecticides and Fungicides; No. 152, revised, Mange in Cattle; No. 153, Orchard Enemies in the Pacific Northwest; No. 155, How Insects affect Health in Rural Districts; No. 159, Scab in Sheep; No. 165, Silkworm Culture; No. 171, The Control of the Codling Moth; No. 172, Scale In- sects and Mites on Citrus Trees; No. 196, Usefulness of the Toad ; No. 209, Controlling the Boll Weevil in Cotton Seed and at Ginneries ; No. 211, The Use of Paris Green in controlling the Cotton Boll Weevil ; No. 212, The Cotton Bollvvorm ; No. 216, The Control of the Boll Weevil; No, 223, Miscellane- ous Cotton Insects in Texas ; No. 247, The Control of the Codling Moth and Apple Scab. The following bulletins of the Bureau of Entomology may be obtained from the same source at the prices affixed : Bulletin No. 25 (old series), Destructive Locusts, 15c.; No. i (new series). The Honey Bee, 15c. ; No. 3, The San Jos6 Scale, loc. ; No. 4, The Principal Household Insects of the U. S., loc. ; No. 11, The Gypsy Moth in America, 5c. ; No. 14, The Periodical Cicada, 15c.; No. 15, The Chinch Bug, loc. ; No. 16, The Hessian Fly, loc. ; Nos. 19, 23, and 2,2,, Insects Injurious to Vegetables, loc. Fig. 185 Female plant louse, with and without wings (enlarged). 96 A.M.MAI. BIOLOGY each; No. 25, Notes on Mosquitoes of the U. S., loc. ; No. 42 Some Insects attacking the Stems of (".rowing Wheat, Rye, Barley, and Oats, 5c. ; No. 50, The Cotton Holhvorm, 25c. ; No. 51, The Mexican lioU Weevil, 25c. lUireau of Plant J.ndustry — Bulletin No. 88, Weevil-resisting Adaptations of the Cotton Plant, IOC This gives an instructive account of the struggle of a plant for existence against an insect enemy. FlC. 186. — Gall fly (enlarged) ami oak gall with larva, and one from which a developed insect has escaped. Fig. 187. — Weevil on a Corylus or filbert. CHAPTER IX MOLLUSKS The Fresh-water Mussel Suggestions. — The mussel is usually easy to procure from streams and lakes by raking or dredging. In cities the hard- shelled clam, or quahog, is for sale at the markets, and the follow- ing descriptions apply to the anodon, unio, or quahog, with slight changes in regard to the siphons. Mussels can be kept alive for a long time in a tub with sand in the bottom. Pairs of shells should be at hand for study. External Features. — The shell is an elongated oval, broader and blunter at one end (Fig. i88). Why does the animal close its shell .'' Does it open the shell .-' Why .'' Does it thAist the foot forward and pull up to it, or thrust the foot back and push ? (Mussels and clams have no bones.) Does it go with the blunt or the more tapering end of the shell forward .-* (Fig. i88.) Can a mussel swim ? Why, or why not ? H 97 98 AX/AfAI. BIOLOGY Lay the shells, fitted together, in your hand with t/ir /tinge sit/f ii'uuiY from yon and the bliitit lud to the Lft ( V\^. i88). Is the rii2;ht or the left shell uppermost ? Which is the top, or dorsal, side ? Which is the front, or anterior, end ? Is the straight edge at the top or the bottom ? Our word " valve " is derived from a word meaning shell, because the Romans used Is the mussel a univalve or a The snail ? Can you Fig. i88. ■ Anodon, or fresh-water mussel. shells for valves in pumps. bivalve ? Which kind is the oyster .'' Does the mussel have bilateral symvictry ? find a Jiorny coveiifig, or epidermis, over the limy shell of a fresh specimen .'' Why is it necessary .' Does water dissolve lime .'' Horn .'* Find a bare spot. Does any of the shell appear to be missing there .'* The bare projection on each shell is called the tunbo. Is the umbo near the ventral or the dorsal line .-• The posterior or anterior end } Is the surface of the umbones worn } Do the umbones rub against the sand as the mussel plows its way along .' How are the shells held together .'' Where is the ligament attached .'' (Fig. 189.) Is it opposite the um- bones or more to the front or Fig. 189. — Diagram of Shell open and closed, showing mus- cle, w, and ligament, b. rear.'' (Fig. 189.) Is the liga- ment of the same material as the shell.'' Is the ligament in a compressed condition when the shell is open or when it is closed .-* (Fig. 189.) When is the muscle relaxed t II MOLLUSKS 99 Fig. 190.— Mussel crawl- ing in sand. Notice the lines on the outside of the shell (Figs. 188 and 190). What point do they surround .-' They are li7i€s of growtJi. Was each Une once the margin of the shell.-' If the shell should increase in size, what would the present margin become .-' (Fig. 191.) Does growth take place on the margin only .-' Did the shell grow thicker as it grew larger .-" Where is it thinnest } Draw the outside of the shell from the side. Draw a dorsal view. By the drawings write the names of the margins of the shell (p. 98) and of other parts learned, using lines to indicate the location of the parts. Study the surface of the shell inside and out. The inside is called mother-of-pearl. Is it of lime .-• Is the deeper layer of the shell of lime .'' (When weak hydro- chloric acid or strong vinegar is dropped on limy substances, a gas, carbon dioxid, bubbles up.) Compare the thickness of the epidermal layer, the middle cJialky layer, and the viycvQX, pearly layer. Anatomy of the Mussel. — What parts protrude at any time beyond the edge of the shell .-* (Fig. 190.) The shell p..ar.i. 13. is secreted by two folds of the outer layer of the soft body of the mus- sel. These large, fiaplike folds hang down on each side, and are called the mantle. The two great flaps of the mantle hang down lower than the rest of the body and line the shell which it secretes (Fig. 192). The epidermis of the mantle secretes the shell just as the epidermis of the crawfish secretes its crust. Can you find Fig. 191. — Diagram. Change of points of attach- ment of muscles as mussel enlarges. (Morgan.) 100 ANIMAL BIOLOGY Fig. 192. — Cross Section OK Ml'SSEL. (Diagram, after Piirktr.) the pallial line, or the line to which the mantle extended on each shell when the animal was alive ? A free portion of the manllc extended like a fringe below the jiallial line. The shells were held together by two large adductor muscles. The anterior adductor (Fig. 193) is near the front end, above the foot. The posterior adductor is toward the rear end, but not so near the end as the anterior. Can you find both muscle scars in the shells ? Are they nearer the ventral or dorsal surface .-' The points of attachment traveled down- ward and farther apart as the ani- mal grew (see Fig. 191). Higher than the larger scars are small scars, or impressions, where the protractor and retractor muscles that extend and draw in the foot were attached. The muscular/(?(V extends downward in the middle, half- way between the shells (Fig. 193). On each side of the foot and behind it hang down the two pairs of gills, the outer pair and the in- ner pair (Fig. 192). They may be compared to four V-shaped troughs with their sides full of holes. The water enters the troughs through the holes and overflows above. Is there a marked difference in the size of the two pairs of gills .-' A kind of POSl* ADD«MU«.. Fic. 193. — Anatomy of Mussel. (Beddard.) MOLLUSKS lOI chamber for the gills is made by the joining of the mantle flaps below, along the ventral line. . The mantle edges are separated at two places, leaving openings called exJialent and inJialcnt sipJions. Fresh water with its oxygen, propelled by cilia at the opening and on the gills, enters through the lower or inhalent siphon, passes between the gills, and goes to an upper passage, leaving the gill chamber by a slit which separate*^ the gills from the foot. For this passage, see arrow (Fig. 194). The movement of the water is opposite to the way the arrow points. After going upward and backward, the water emerges by the exhalent siphon. The gills originally consisted of a great number of filaments. These are now united, but not completely so, and the gills still have a perforated or lattice structure. Thus they present a large surface for absorbing oxy- gen from the water. Fig. 194.- A, left shell and mantle flap removed. B, section through body. Question: Guided by other figures, identify the parts to which lines are drawn. The mouth is in front of the foot, between it and the anterior adductor muscle (Fig. 194). On each side of the mouth are the labial palps, which are lateral lips (Fig. 195). They have cilia which convey the food to the mouth after the inhalent siphon has sent food beyond the gill chamber and near to the mouth. Thus both food and oxygen enter at the inhalent siphon. The foot is in the position of a lower lip, and if regarded as a greatly extended lower lip, the animal may be said to have what is to us the absurd habit of using its lower lip as a foot. The foot is some- lo: A.MMAI. BIOLOGY times said to be hatchct-shapcd (I'ig. 195). Do you see aiiv resemblance ? Does the foot penetrate deep or shal- low into the sand ? (Fig. 190.) Why, or why not ? The food tube of the mussel is com- paratively sinii)lc. IJehind the mouth it enlarges into a swelling called the stom- ach (Fig. 193). The bile ducts of the neighboring liver empty into the stomach. The intestine makes several turns in the substance of the upper part of the foot, and then jiassing upward, it runs ap- ])r()ximately straiglit to the vent (or anus), which is in the wall of tlie exhalent si|)hon. The intestine not only runs through the pericaniial cavity (celome) surrounding the heart, but through the ventricle of the heart itself (Fig. 196). The kidneys consist of tubes which open into the pericardial chamber above and into the gill chamber below {Neph., Fig. 193). The tubes are surrounded by numerous blood vessels (Fig. 198) and carry off the waste matter from the blood. The nervous system consists of three pairs of ganglia and nerves (Fig. 197). The ganglia are distinguishable because of ^ their orange color. The pedal ganglia on the front of the foot are easily seen also ; the vis- ceral ganglia on the posterior adductor muscle may be seen without removing the mussel from the shell (Fig. 193). The reproductive organs {•10. 197. open into the rear portion of the gill cavity (Fig. 193). The sperms, having been set free in the water, are drawn into the ova by the same current that brings the food. The eggs A l"ii;. 195. — MlssKL. From below. Level cut across both shells. Sf, palp; P, foot; O, mouth; G, liver; Gg, I'g, Pg, gan- glia. Fig. 196. — Heart of Missel, with intestine passing through it. MOLL USKS 103 are hatched in the gills. After a while the young mussels go out through the siphon. Summary. — In the gills (Fig. 198) the blood gains what? Loses what? From the digestive tube the blood absorbs nourish- ment. In the kidneys the blood is partly purified by the loss of nitrogenous waste. The cilia of the fringes on the inhalent, or lower, siphon, vibrate continually and drive water and food particles into the mouth cavity. Food particles that are brought near the labial palps are conveyed by them to the mouth. As the water passes along the perforated gills, its oxygen is absorbed ; the mantle also absorbs oxygen from the water as it passes. The water, as stated before, goes next through a passage between the foot and palp into the cavity above the gills and on out through the ex- halent siphon. By stirring the water, or placing a drop of ink near the siphons of a mussel kept in a tub, fig. 198. the direction of its flow may be seen. The pulsations of the heart are plainly visible in a living mollusk. Habits of the Mussel. — Is it abundant in clear or muddy water ; swift, still, or slightly moving water t Describe its track or furrow. What is its rate of travel .'' Can you distinguish the spots where the foot was attached to the ground .'' How long is one " step " compared to the length of the shell .-' The animal usually has the valves opened that it may breathe and eat. The hinge ligament acts like the case spring of a watch, and holds the valves open un- less the adductor muscles draw them together (Fig. 189). / Diagram of cut across, showing mantle, ma ; gills, kie ; foot, f\ heart, h ; in- testine, ed. I04 AX/AfAL BIOLOGY Fig. 199. — Oyster. C, mouth ganglia gill. a, vent: gig", int, mantle; b. When the mussel first hatches from the egg, it has a tri- angular shell. It soon attaches itself to some fish and thus travels about ; after two months it drops to the bottom again. Other Mollusca. — The oyster s shells are not an exact pair, the shell which lies upon the bottom being hollowed out to contain the body, and the upper shell being fiat. Can you tell by ex- amining an oyster shell which was the lower valve .'' Does it show signs of having been attached to the bottom .'' The young oyster, like the young mus- sel, is free-swimming. Like the arthropoda, most niollusks undergo a metamorphosis to reach the adult stage (Fig. 199). Examine the shells of clams, snails, scallops, and cockles. Make drawings of their shells. The slug is very similar to the snail except that it has no shell. If the shell of the snail shown in Fig. 202 were removed, there would be left a very good representation of a slug. Economic Importance of Mollusca. — Several species of clams are eaten. One of them is the liard-shell clam (quahog) found on the At- lantic coast from Cape Cod to Texas. Its shell is white. It often burrows slightly beneath the surface. The soft-shell clam is better liked as food. It lives along the shores of all northern seas. It burrows a foot beneath the surface and extends its siphons Fig. 200. — TkocH us. FiG. 201. — Cypr.«;a. (Univalve, with a long opening to shell.) MOLLUSKS 105 through the burrow to the surface when the tide is in, and draws into its shell the water containing animalcules and oxygen. Oysters to the value of many millions of dollars are gath- ered and sold every year. The most valuable oyster fish- eries of the United States are in Chesapeake Bay. The young oysters, or "spat," after they attach themselves to the bottom in shallow water, are transplanted. New oyster beds are formed in this way. The beds are sometimes strewn with pieces of rock, broken pottery, etc., to encourage the oysters to attach themselves. The dark spot in the fleshy body of the oyster is the digestive gland, or liver. The cut ends of the tough adductor muscles are noticeable in raw oysters. The starfish is very destructive in oyster beds. Pearls are deposited by bivalves around some irritating particle that gets between the shell and the mantle. The pearl oyster furnishes most of the pearls ; sometimes pearls of great value are obtained from fresh-water mussels in the United States. Name articles that are made partly or wholly of mother- of-pearl. Study of a Live Snail or Slug. — Is 'U A A /, mouth; z/, /(/, feelers; ^, opening of egg duct; ^w, foot; Its DOCly dry or ,«a, mantle; /«, opening to lung; «, vent. moist ? Do land snails and slugs have lungs or gills? Why? How many pairs of tentacles has it? What is their relative length and position? The eyes are dark spots at bases of tentacles of snail and at the tips of the rear tentacles of slug. Touch the tentacles. What happens? Do the tentacles simply stretch, or do they turn inside Ju Fig. 202. — A Snail. io6 ANIMAL BIOLOGY out as they are extended ? Is the respiratory opening on the right or left side of the body ? On the mantle fold or on the body? (Figs. 202-3-4.) How ;'tf''a^^ >f often does the aperture open and close ? Place the snail in a Fio. 203. — .\ Sluj. moist tumbler. Does the whole under surface seem to be used in creeping? Does the creeping surface change shape as the snail creeps ? Do any folds or wrinkles seem to move either toward the front or rear of its body? Is enough mu- cus left to mark the path traveled? The fold moves to the front, adheres, and smooths out as the slug or snail is pulled forward. Cephalopods. — The highest and best de- veloped molhisks are the cephalopods, or " head-footed " mollusks. Surrounding the mouth are eight or ten appendages which serve both as feet and as arms. These appendages have two rows of sucking disks by which the animal attaches itself to the sea bottom, or seizes fish or other prey with a firm grip. The commonest examples are the squid, with a long body and ten arms, and the octopus, or devil- fish, with a short body and eight arms. Cephalopods have strong biting mouth parts and complex eyes somewhat resem- bling the eyes of backboned, or vertebrate, animals. The large and staring eyes add to the uncanny, terrifying appearance. The sepia or " ink " discharged through the siphon of the squid makes a dark cloud in the water and favors its escape from Fia 204. — Circulation and Rksim ration IN Snail. a, mouth; b, b, foot; c. vent; d, d, lung; h, heart. Blood vessels are black. (Pcrrier.) Fig. 205. — a Squid. MOLLUSKS 107 I enemies almost as much as its swiftness (Fig. 205). Tlie squid sometimes approaches a fish with motion so slow as to be imper- ceptible, and then sud- denly seizes it, and quickly kills it by bit- ing it on the back be- hind the head. The octopus is more sluggish than the squid. Large species called devilfish sometimes have a spread of arms of twenty-five feet. The pearly nautilus (Fig. 206) and the female of the paper argo- naut (Fig. 207) are examples of cephalopods that have shells. The cuttlefish is closely related to the squid. Fig. 206. — Pearly Nautilus. (Shell sawed through to show chambers used when it was smaller, and siphuncle, S, connecting them. Ten- tacles, T.) Fig. 207. — Paper Argonaut (female). X % (i.e. the animal is three times as long and broad as figure). Fig. 208. — Paper Argo- naut (male), x i/g. General Questions. — The living parts of the mussel are very soft, the name mollusca having been derived from the Latin word mollis, soft. Why is it that the softest animals, the mollusks, have the hardest coverings .■* To which class of mollusks is the name acephala (head- less) appropriate } Lamellibranchiata (platelike gills).'' io8 ANIMAL BIOLOGY Why is a smooth shell suited to a clam and a rough shell suited to an oyster ? Why are the turns of a snail's shell so small near the center? Why docs the mussel have no use for head, eyes, or pro- jecting feelers? In what position of the valves of a mussel is the hinge ligament in a stretched condition ? How does the shape of the mussel's gills insure that the water cur- rent and blood current are brought in close contact ? The three main classes of mollusks are : the pelecypoda (hatchet-footed); gastropoda (stomach-footed); and cepha- lopoda (head-footed). Give an example of each class. Comparison of Mollusks Mussel Snail Sqdid Shell Head Body foot Gills Eyes Comparative Review. — (To occupy an entire page in notebook.) Grass- hopper Spider Crayfish Centipede Mussel Bilateral or radiate Appendages for lo- comotion Names of divisions of body Organs and method of breathing Locomotion CHAPTER X FISHES Suggestions. — The behavior of a live fish in clear water, preferably in a glass vessel or an aquarium, should be A skeleton may be prepared by placing a fish in the reach of ants. Skeletons of animals placed on ant beds are cleaned very thoroughly. The study of the perch, that follows, will apply to almost any common fish. Movements and External Features. — What is the gen- eral shape of the body of a fish .'' How does the dorsal, or upper, region differ in form from the ventral .'' Is there a narrow part or neck where the head joins the trunk.'' Where is the body thickest ? What is the ratio between the length and height .? (Fig. 209.) Are the right and left sides alike .■' Is the symmetry of the fish bilateral or radial } The body of the fish may be divided into three regions, — the head, trunk, and tail. The trunk begins with the foremost scales ; the tail is said to begin at the vent, or anus. Which regions bear appendages } Is the head movable independently of the trunk, or do they move together ? State the advantage or disadvantage in this. Is the body depressed (flattened vertically) or compressed 109 no AXI.V.IL BIOLOGY (rtattcned laterally)? Do both forms occur among fishes? (Sec figures on pages 123, 124.) How is the shape of the body iidvaiitagcons for inove- viint ? Can a fish turn more readily from side to side, or up and down ? Why ? Is the head wedge-shaped or coni- cal ? Are the jaws fiattcncd laterally or vertically ? The fish swims in the water, the bird swims in the air. Account for the differences in the shape of their bodies. Is the covering of the body like the covering of any ani- mal yet studied ? The scales are attached in little pockets, 1 ''^' •','/■'■ I.' '.'.Vi'. < ' ' ' v^^^^^^'A^ Fig. 209. — White Perch {Morone Americana). or folds, in the skin. Observe the shape and size of scales on different parts of the body. What parts of the fish are without scales ? Examine a single scale ; what is its shape ? Do you see concentric lines of growth on a scale ? Sketch a few of the scales to show their arrangement. What is the use of scales ? Why are no scales needed on the head ? How much of each scale is hidden ? Is there a film over the scale ? Are the colors in the scale or on it ? The Fins. — Are the movements of the fish active or sluggish ? Can it remain stationary without using its fins? FISHES 1 1 1 Can it move backward ? How are the fins set in motion ? What is the color of the flesh, or muscles, of a fish ? Count the fins. How many are in pairs ? (Fig. 209.) How many are vertical } How many are on the side .-' How many are on the middle line .'' Are the paired or unpaired fins more effective in balancing the fish .-' In turning it from side to side } In raising and lowering the fish } In pro- pelling it forward.' How are some of the fins useful to the fish besides for balancing and swimming } The hard spines supporting the fins are called the fin rays. The fin on the dorsal line of the fish is called the dorsal fin. Are its rays larger or smaller than the rays of the other fins t The perch is sometimes said to have two dorsal fins, since it is divided into two parts. The fin forming the tail is called the tail fin, or caudal fin. Are its upper and lower corners alike in all fishes } (Fig. 228.) On the ventral side, just behind the vent, is the ventral fin, also called the anal fin. The three fins mentioned are unpaired fins. Of the four-paired fins, the pair higher on the sides (and usually nearer the front) are the pectoral fins. The pair nearer the ventral line are the pelvic fins. They are close together, and in many fish are joined across the ventral line. The ventral fins are compared to the legs, and the pectoral fins to the arms, of higher verte- brates. (Fig. 244.) Compare fins of fish, pages 123, 124, Make a drawing of the fish seen from the side, omit- ting the scales unless your drawing is very large. Are the eyes on the top or sides of the head, or both } Can a fish shut its eyes .'' Why, or why not .'' Is the eye- ball bare, or covered by a membrane .-• Is the covering of the eyeball continuous with the skin of the head .-' Is there a fold or wrinkle in this membrane or the surround- ing skin .-^ Has the eye a pupil } An iris .-* Is the eye of 112 ANIMAL BIOLOGY Fig. 2IO.— BL/\ckboard Outline of Fish. the fish immovable, sHghtly movable, or freely movable ? Can it look with both eyes at the same object.-' Is the range of vision more upward or downward .-* To the front or side ^ In what direction is vision impossible .-' Can a fish close its eyes in sleep .'' Does the eyeball appear spherical or flat- tened in front .'' The ball is really spherical, the lens is very convex, and fish are nearsighted. Far sight would be useless in a dense medium like water. In what direction are the nostrils from the eyes .-" (Fig. 211.) There are two pairs of nostrils, but only one pair of nasal cavities, with two nostrils opening into each. There are no nasal passages to the mouth, as the test with a probe shows that the cavities do not open into the mouth. What two functions has the nose in man } What func- tion has it in the fish .-' There are no external ears. The ear sacs are embedded in the bones of the skull. Is hearing acute or dull .'' When fish- ing, is it more necessary not to talk or to step lightly, so as not to jar the boat or bank } What is the use of the large openings found at the back of the head on each side .'' (Fig. 211.) Under the skin at the sides of the head are thin membrane bones formed from the skin ; they aid the skin in protection. Just under these membrane bones are the gill covers, of true bone. Which Fig. 211. — Head of Carp. FISHES 113 consists of more parts, the membranous layer, or the true bony layer in the gill cover? (Figs. 211 and 212.) Is the mouth large or small ? Are the teeth blunt or pointed ? Near the outer edge, or far in the mouth ? (Fig. 212.) Does the fish have lips .-' Are the teeth in one continuous row in either jaw.'' In the upper jaw there are also teeth on the premaxillary bones. These bones are in front of the maxillary bones, which are with- out teeth. Teeth are also found in the roof of the mouth, and the tongue bears horny appendages similar to teeth. Are the teeth of the fish better suited for chewing or for Fig. 212. — Skeleton of Perch. grasping.'' Why are teeth on the tongue useful.'' Watch a fish eating : does it chew its food .'' Can a fish taste .-* Test by placing bits of brown paper and food in a vessel or jar containing a live fish. Is the throat, or gullet, of the fish large or small .-' The skeleton of a fish is simpler than the skeleton of other backboned animals. Study Fig. 212 or a prepared skeleton. At first glance, the skeleton appears to have two vertebral columns. Why .'' What bones does the fish have that correspond to bones in the human skeleton .'' Are the projections (processes) from the vertebrae long or short .'' The ribs are attached to the vertebrae of the trunk, the last rib being above the vent. The tail begins at the 114 AXIMAL BIOLOGY vent. Are there more tail vertebnr or trunk vertebrae ? Are there any neck (cervical) vertebrae {i.e. in front of those that bear ribs)? The first few ribs (how many ?) are attached to the central body of the vertebrae. The re- Fi<;. 213. maining^ ribs are loosely attached to processes on the vertebrce. The ribs of bony fishes are not homologous with the ribs of the higher vertebrates. In most fishes there are bones called intermuscular bones attached to the first ribs (how many in the perch ?) which are possibly homol- ogous to true ribs ; that is, true ribs in the higher verte- brates may have been developed from such beginnings. Which, if any, of the fin skeletons (Fig. 214) are not attached to the general skeleton.-' Which fin is composed chiefly of tapering, pointed rays '^ Which fins consist of rays which sub- divide and widen toward the end } Which kind are stiff, and which are flexible.? Which of the fin rays are segmented, or in two portions .'' The outer segment is called the radial, the inner the basal segment. Which segments are longer } There is one basal segment that lacks a radial segment; find it (Fig. 212). Fig. 214. — Soit-rayed ant) Spiny-rayed Fins. FISHES 115 Fig. 215. — Carp, with right gill cover removed to show gills. What is the advantage of the backbone plan of struc- ture over the armor-plate plan .-* You have seen the spool- like body of the vertebra in canned salmon. Is it concave, flat, or convex at the ends .'' The gills are at the sides of the head (Fig. 215) under the opercula, or gill covers. What is the color of the gills .-* Do the blood vessels appear to be very near the surface of the gills, or away from the surface .'' What advan- tage in this } Are the gills smooth or wrinkled .^ (Fig. 215.) What ad- vantage } The bony supports of the gills, called the gill arches, are shown in Fig. 216 {k-^ to k^. How many arches on each side .-^ The gill arches have projections on their front sides, called gill rakers, to prevent food from being washed through the clefts between the arches. The fringes on the rear of the gill arches are called the gill filaments (rt'. Fig. 216). These filaments support the thin and much- wrinkled borders of the gills, for the gills are constructed on the plan of exposing the greatest possible surface to the water. Compare the plan of the gills and the human lungs. The gill opening on each side is guarded by seven rays {kh, Fig. 216) along the hinder border of the Fig. 216. — Skeleton around Throat of Fish. ii6 AX/MA L BIOLOGY gill cover. These rays grow from the tongue bone. {Zu, Fig. 216. This is a rear view.) W'atch a live fish and determine how the water is forced between the gills. Is the mouth ojicned and closed in the act of breathing .-' Are the openings behind the gill covers opened and closed .-* How Fig. 217.— Circulation l.N Gin^. Fig. 218. — Nostrum, Mouth, and Gill Openings of Sting- KAY. many times per minute does fresh water reach the gills .-• Do the mouth and gill covers open at the same time } Why must the water in contact with the gills be changed constantly .'' Why does a fish usually rest with its head up stream .? How may a fish be kept alive for a time after it is removed from the water .-• Why does drying of the gills prevent breathing .'' If the mouth of a fish were propped open, and the fish re- turned to the water, would it suffocate .' Wlty, or why not .^ Fig. 219. Gill Openings of Eel. Food Tube. — The gullet is short and wide. The stomach is elongated (Fig. 220). There is a slight constriction, or narrow- ing, where it joins the intestine. Is the intestine straight, or does it lie in few or in many loops? (Fig. 220.) The liver has a gall bladder and empties into the intestine through a bile duct. Is the FISHES 117 liver large or small? Simple or lobed? The spleen {mi, Fig. 220) lies in a loop of the intestine. The last part of the intestine is straight and is called the rectum. Is it of the same size as the other portions of the intestine? The fish does not possess a pan- creas, the most important digestive gland of higher vertebrates. Fig. 220. — Anatomy of Carp. (See also colored figure 4.) bf, barbels on head (for feeling) ; h, ventricle of heart; as, aortic bulb for regulating flow to gills; 7/^, venous sinus; «(?, dorsal aorta ; wjo, stomach; /, liver: ^i, gall cyst; w?", spleen; d, small intestine; md, large intestine; a, vent; j, j, swim bladder; ni,ni, kidney; hi, ureter; hb, bladder: ro, eggs (roeU Tnhe, opening of ducts from kidney and ovary. Questions : Are the kidneys dorsal or ventral ? The swim bladder ? Why ? Why is the swim bladder double ? Does blood enter gills above or below .' The oz'ary lies between the intestine and the air bladder. In Fig. 220 it is shown enlarged and filled with egg masses called roe. It opens by a pore behind the vent. The silver lining of the body cavity is called the peritoneum. (See Chap. VII, Human Biology.) Is \.h& air bladder simple or partly divided in the perch? In the carp? (Fig. 220.) Is it above or below the center of the body? Why? The air bladder makes the body of the fish about as light as water that it may rise and sink with little effort. When a fish dies, the gases of decomposition distend the bladder and the abdomen, and the fish turns over. Why? Where are the kidneys? (Fig. 220.) Their ends unite close under the spinal column. The ureters, or tubes, leading from them, unite. and after passing a small urinary bladder, lead to a tiny urinary pore just behind the opening from the ovary. (Colored figure 4.) The Circulation. — The fish, unlike other vertebrates, has its breathing organs and its heart in its head. The gills have already been described. The heart of an air-breathing vertebrate is near iiS AS'IMAI. BIOLOGY its lungs. Why? The heart oi a fish is near its gills for the same reason. The heart has one auricle and one ventricle. (Colored figure I.) Hlood returning to the heart comes through several veins into a sinus, or antechamber, whence it passes down through a valve Fii^. 221.— 1'i.AN OK Circulation. Ab, arteries to gills; Ba, aortic bulb; /', ventricle. into \k\t auricle ; from the auricle it goes forward into 'C^o. ventricle. The ventricle sends it into an artery, not directly, but through a bulb {as. Fig. 220), which serves to maintain a steady flow, without pulse beats, into the large artery {aorta) leading to the gills. The arteries leading from the gills join to form a dorsal aorta {Ao, Fig. 221), which passes backward, inclosed by the lower processes of the spinal column. After going through the capillaries of the various organs, the blood returns to the heart through veins. The color of the blood is given by red corpuscles. These are nucleated, oval, and larger than the blood corpuscles of other ver- tebrates. The blood of the fish is slightly above the temperature of the water it in- habits. Notice the general shape of the brain (Fig. 222). Are its subdivisions distinct or indistinct? Are the lobes in pairs? The middle portion of the brain is the widest, and consists of the two optic lobes. From these lobes the optic nerves pass beneath the brain to the eyes {Sn, Fig. 223). In Fig. 222. — Brain ok Perch, from above. «, end of nerve of smell; au, eye; v, z, »i, fore, mid, and hind brain; //, spinal bulb; r, spi- nal cord. FISHES 119 front of the optic lobes lie the two cerebral lobes, or the cerebrii7n. The small olfactory lobes are seen (Fig. 224) in front of the cere- brum. The olfactory nerves may be traced to the nostrils. Back of the optic lobes (mid brainj is the cerebellum (hind brain), and back of it is the medulla oblongata, or beginning of the spinal cord. r^- Fig. 224. — Brain ok Perch, from above. Fig. 223. — Brain of Perch, side view. Taking the eyeball for comparison, is the whole brain as large as one eyeball? (Fig. 222.) Judging from the size of the parts of the brain, which is more important with the fish, thinking or per- ception? Which is the most important sense? The scales along a certain hne on each side of the fish, called the lateral line, are perforated over a series of lateral line sense organs, supposed to be the chief organs oi touch (see Fig. 209). Questions. — Which of the fins of the fish have a use which corresponds to the keel of a boat .'' The rudder ? A ^-^' S?^^^M^~. ,^^^^;^«K'*-*-««iff-«#''v -551- FlG. 225.— The Stickleback. Instead of deposiring the eggs on the bottom, it makes a nest of water plants— the only fish that does so — and bravely defends it. • I20 AXIMAL BIOLOGY Fig. 226. — Artificial Fecundation. The egg-cells and sperm-cells are pressed out into a pan of water. paddle for sculling? Anoar.-* State several reasons why the head of the fish must be very large, although the brain is very small. Does all the blood go to the gills just after leaving the heart .'' Make a list of the different species of insh found in the waters of your neigh- borhood ; in the markets of your town. Reproduction. — The female fish deposits the unfertilized eggs, or ova, in a secluded spot on the bottom. Afterward the male fish deposits the sperms in the same place (see Fig. 225). The eggs, thus unprotected, and newly hatched fish as well, are used for food by fish of the same and other species. To compensate for this great destruction, most fish lay (spawn) many thousands of eggs, very few of which reach maturity. Higher vertebrates {e.g. birds) have, by their superior in- telligence, risen above this wasteful method of reproduction. Some kinds of marine fish, notably cod, herring, and salmon, go many miles up fresh rivers to spawn. It is possible that this is because they were originally fresh-water species ; yet they die if placed in fresh water except during the spawning season. They go Fig. 227. — Newly hatched Trout, with yolk-sac adhering, eyes large, and fins mere folds of the skin. (Enlarged.) FISHES 1 2 1 because of instinct, which is simply an inherited habit. Rivers may be safer than the ocean for their young. They are worn and exhausted by the journey, and never survive to lay eggs the second time. Fig. 228. — A Shark {Acanthlas vulgaris). The air bladder is developed from the food t2ibe in the embryo fish, and is homologous with lungs in the higher vertebrates. Are their functions the same ? Fish that feed on flesh have a short intestine. Those that eat plants have a long intestine. Which kind of food is more quickly digested ? There are miicons glands in the skin of a fish which supply a secretion to facilitate movement through the water ; hence a freshly caught fish, before the secretion has dried, feels very slippery. The air bladder, although homologous to lungs, is not a breathing organ in common fishes. It is filled by the formation of gases from the blood, and can be made smaller by the contraction of muscles along the sides of the body ; this causes the fish to sink. In the gar and other ganoids, the air bladder contains blood vessels, is con- nected with the gullet, and is used in breathing. Organs serving the same purf^ose in different animals are said to be analogous. To what in man are the gills of the fish analo- gous } Organs having a like position and origin are said to be homologous. The air bladders of a fish are homologous with the lungs of man ; but since they have not the same use they are not analogous. I 22 A.V/AfAL BIOLOGY How docs the tail of a shark or a gar differ from the tail of common fishes? (Fig. 228.) Do you know of fish destitute of scales ? Do you know of fish with whiplike feelers on the head ? (F"igs,) Why are most fishes white on the under side ? Comparative Review. — (Copy table on one page or two facing pages of notebook. ) Is THERE A Head? A Neck? 1 Method of Feeding DiGESTIX'E Organs and Digestion Reproduc- tion Senses Ameba Sponge Hydra Starfish Earthworm Wasp Mussel 1 Fish Fig. 229. — Drawing the Seine. Fig. 234. — TURBOT. Fig. 239. — Salmon. Seven Food Fish. Three Curious Fish. Special Reports. (Encyclopedia, texts, dictionary.) 123 Fi<;. 2^o. — Sea Huksk ( HtppOLampus) , with incubat- ing pouch, Br/. tic. 243. — Lantern Fish {lAncyphryne lucifer). (After CoUett.) Fig. 244. — Lung Fish of Australia {^Ceratodus miolepls). Fig. 242. — Torpedo. Elec- trical organs at right and left of brain. Fig. 246. — Seaweed Fish, x^ (Fhyllopteryx eques). Remarkable Fish. Special Reports. (Encyclopedia, texts, dictionary.) 124 GENERAL CLASSIFICATION 125 RECOGNITION GROUP CHARACTERS The commoner members of the several branches may be recog- nized by the following characters : — 1. The Protozoans are the only one-celled animals. 2. The Sponges are the only animals having pores all over the body for the inflow of water. 3. The Polyps are the only many-celled animals having a single opening into the body, serving for both mouth and vent. They are radiate in structure, and usually possess tentacles. 4. The Echinoderms are marine animals of more or less radiate appearance, having a food tube in the body separate from the body wall. The following groups are plainly bilateral : that is, dorsal and ventral surfaces, front and hind ends are different. 5. The Vermes have usually a segmented body but lack jointed legs. 6. The Arthropods have an external skeleton and jointed legs. 7. The Mollusks have soft bodies, no legs, no skeleton, but usually a limy shell. 8. The Vertebrates have an internal skeleton of bones, and usually two pairs of legs. ^ CHAPTER XI BATRACHIA The theory of evolution teaches that animal life began in a very simple form in the sea, and that afterward the higher sea animals lost their gills and developed lungs and legs and came out to live upon the land ; truly a marvelous procedure, and incredible to many, although the process is repeated every spring in count- less instances in pond and brook. In popular language, every cold-blooded vertebrate breathing with lungs is called a reptile. The name reptile is properly applied only to lizards, snakes, turtles, and alligators. The com- mon mistake of speaking of frogs and salamanders as reptiles arises from considering them only in their adult condition. Rep- tiles hatch from the egg as tiny reptiles resembling the adult forms ; frogs and salamanders, as every one knows, leave the egg in the form of tadpoles (Fig. 248). The fact that frogs and salamanders begin active life as fishes, breathing by gills, serves to distinguish them from other cold-blooded animals, and causes naturalists to place them in a separate class, called batrachia (twice breather) or amphibia (double life). Tadpoles Suggestions. — Tadpoles may be studied by placing a number of frog's eggs in a jar of water, care being taken not to place a large number of eggs in a small amount of water. When they hatch, water plants {e.o^. green algae) should be added for food. The behavior of frogs may be best studied in a tub of water. A toad in captivity should be given a cool, moist place, and fed well. A piece of meat placed near a toad may attract flies, and the toad may be observed while catching them, but the motion is so swift as to be almost imperceptible. Live flies nay be put into a glass jar with a toad. Toads do not move about until twilight^ except 126 BATRACHIA 127 in cloudy, wet weather. They return to ponds and brooks in spring at the time for laying eggs. This time for both frogs and toads is shown by trilling. All frogs, except tree frogs, remain in or near the water all the year. Fig. 248. — Metamorphoses of the Frog, numbered in order. Do eggs hatch and tadpoles grow more rapidly in a jar of water kept in a warm place or in a cold place .'' In pond water or drinking water .'' Can the tadpoles be seen to move in the eggs before hatching .'' When do the external gills show .'* (Fig. 248.) What parts may be described in a tadpole .-' What is the shape of the tail } Compare the tadpole with tJie fisJi as to (i) general shape, (2) cover- ing, (3) fins, (4) tail, (5) gills. Do the exter- nal gills disap- pear before or after any rudiments of limbs appear } (6, 7, Fig. 248.) Can you locate the gills after they be- come internal .'' (Fig. 249.) Fig. 249. — TAnpoLE, from below, showing intestine and internal gills. (Enlarged.) 128 ANIMAL BIOLOGY In what state of growth are the legs when the tadpole first goes to the surface to breathe ? Which legs appear first ? What advantage is this ? What becomes of the tail ? Is the tail entirely gone before the frog first leaves tlie water ? Are tadpoles habitually in motion or at rest ? Is the intestine visible through the skin ? (Fig. 249.) Is it straight or coiled ? Remembering why some fish have larger intestines than others, and that a cow has a long intestine and a cat a short one, state why a tad- pole has a relatively longer intestine than a frog. Compare the mouth, jaws, eyes, skin, body, and habits of tadpole and frog. Frogs Prove that frogs and toads are beneficial to man. Did you ever know of a frog or toad destroying anything useful, or harming any one, or causing warts .-' How many pupils in class ever had warts .■' Had they handled frogs before the warts came .-' Frogs are interesting, gentle, timid animals. Why are they repulsive to some people .-* Environment. — WJicre are frogs found in greatest numbers .-' What occurs when danger threatens them } What enemies do they have .-' What color, or tint, is most prominent on a frog } Does the color " mimic " or imi- tate its surroundings } What is the color of the under side of the body .'' (Fig. 250.) Why is there greater safety in that color .'' What enemies would see water frogs from below } Do tree frogs mimic the bark .-' The leaves } Can a frog stay under water for an indefinite time } Why, or why not .-* What part of a frog is above the BATRACHIA 129 surface when it floats or swims in a tub of water ? Why ? Do frogs croak in the water or on the bank ? Why do they croak after a rain ? Do toads croak ? Are the eggs laid in still or flowing water ? In a clear place or among sticks and stems ? Singly, or in strings or in masses? (Fig. 248.) Describe an Q.^g. Why do frogs dig into the mud in autumn in cold climates ? Why do they not dig in mud at the bottom of a pond ? Why is digging unnecessary in the Gulf states ? Fig. 250. — Painted Frog {Choropkilus otnatus),oi'^le-ii\co. Describe the position of the frog when still (Fig. 250). What advantage in this position .-' Does the frog use its fore legs in swimming or jumping .'' Its hind legs .'' How is the frog fitted for jumping .'' Compare it in this respect with a jumping insect; a jumping mammal. How is it fitted for swimming.'' Is the general build of its body better fitted for swimming or jumping.'' How far can a frog jump .■* External Features. — The frog may be said to have two regions in its body, the head and trunk. A neck hardly I30 ANIMAL BIOLOGY exists, as there is only one vertebra in front of the shoul- ders (Fii;. 252), while mammals have seven neck (cervical) vertebra?. There arc no tail (caudal) vertebrae, even in the tadpole state of frogs and toads. The head appears triangular in shape when viewed from what direction ? The head of a frog is more pointed than the head of a toad. Is the skull a closed case of broad bones or an open structure of narrow bones .-* (Fig. 252.) Describe the })ioutJi. Observe the extent of the mouth opening (Fig. 251). Avq tcct/i present in the upper jaw,? The lower jaw } Are the teeth sharp or dull } Does the frog chew its food .-" Is the tongue slender or thick.'* (Fig. 251.) Is it attached to the front or the back of the mouth .'' In what direction does the free end extend when the tongue lies fiat.-' Is the end pointed or lobed .-• How far out will the tongue stretch .-' For what is it used ? Why is it better for the teeth to be in the upper jaw rather than in the lower jaw .-* That the teeth are of little service is shown by the fact that the toad with simi- lar habits of eating has no teeth. Will a toad catch and swallow a bullet or pebble rolled before it } The toad is accustomed to living food, hence prefers a moving insect to a still one. The Senses. — Compare the eyes with the eyes of a fish in respect to position and parts. Are the eyes pro- truding or deep-set } Touch the eye of a live frog. Can it be retracted .-' What is the shape of the pupil } The color of the iris ? Is the eye bright or dull .'' What probably gave rise to the superstition that a toad had a jewel in its head .-* Is there a third eyelid .'' Are the Fig. 251. — Head of Frog. BATRACHIA 131 upper and lower eyelids of the same thickness ? With which lid does it wink ? Close its eye ? Observe the large oval car drum or tympanum. What is its direction from the eye? (Fig. 251.) The mouth.? Is there a projecting ear.? Does the frog hear well.? What reason for your answer .? As in the human ear, a tube (the Eustachian tube) leads from the mouth to the inner side of the tympanum. How many nostrils? (Fig. 251.) Are they near to- gether or separated .? Large or small .? A bristle passed into the nostril comes into the mouth not far back in the roof. Why must it differ from a fish in this .? How do \hQ.fore and Jiind legs dx'^ox} How many toes on the fore foot or hand .? On the hind foot .? On which foot is one of the toes rudimentary .? Why is the fore limb of no assistance in propelling the body in jumping .? Do the toes turn in or out.? (Fig. 250.) How does the frog give direction to the jump .? What would be the disadvantage of always jumping straight forward when fleeing.? Which legs are more useful in alighting ? Divisions of the Limbs. — Distinguish the upper arm, fore- arm, and hand in the fore limb (Figs. 252 and 253). Compare ivitJi skeleton of man (Fig. 399). Do the arms of a man and a frog both have one bone in the upper arm and two in the forearm ? Both have several closely joined bones in the wrist and Fig. 252. — Skeleton of Frog. V32 ANIMAL BIOLOGY five separate bones in the palm. Do any of the frog's fingers have three joints ? Compare also the leg of man and the hind leg of the frog (Figs. 253 and 399). Does the tJiin'Ji have one bone in each ? The shank of man has two bones, shin and splint bone. Do you see a groove near the end in the shauk bone of a frog (Fig. 252), in- dicating that it was formed by the union of a shin and FIG. .53. -SKELETON OK FROG. ^^^^^^ ^^^^ p ^^^ first two of the five bones of the ankle are elongated, giv- ing the hind leg the appearance of having an extra joint (Fig. 253). The foot consists of six digits, one of which, like the thumb on the fore limb, is rudimentary. The five developed toes give the five digits of the typical verte- brate foot. Besides the five bones cor- responding to the instep, the toes have two, three, or four bones each. How is the hind foot specialized for swim- ming.-' Which joint of the leg con- tains most muscle.' (Fig. 254.) Find other bones of the frog analogous in position and similar in form to bones in the human skeleton. Fig. 254. — Leg Mus- cles OF Frog, BATRACHIA 133 Is the skin of a frog tight or loose ? Does it have any appendages corresponding to scales, feathers, or hair of other vertebrates ? Is the skin rough or smooth ? The toad is furnished with glands in the skin which are some- times swollen ; they form a bitter secretion, and may be, to some extent, a protection. Yet birds and snakes do not hesitate to swallow toads whole. Show how both upper and under surfaces of frog illustrate protective coloration. All batrachians have large and ninneroiis blood vessels in the skin by which gases are exchanged with the air, the skin being almost equal to a third huig. That the skin may function in this way, it must not become dry. Using this fact, account for certain habits of toads as well as frogs. If a frog is kept in the dark or on a dark surface, its skiji will be- come darker than if kept in the light or on a white dish. Try this experi- ment, comparing two frogs. This power of changing color is believed to be due to the diminution in size of certain pigment cells by contrac- tion, and enlargement from relaxation. This power is possessed to a certain degree not only by batrachians but also by many fishes and reptiles. The chameleon, or green lizard of the Gulf states, surpasses all other animals in this respect (Fig. 280). What advantage from this power .'' Digestive System. — The large mouth cavity is connected by a short throat with the gullet, or esophagus (Fig. 255). Fig. 255. — Digestive Canal of Frog. Mh, mouth; Z, tongue pulled outward; 5", opening to larynx; Of, gullet; vT/, stom- ach; D, intestine; P, pan- creas; L, liver; G, gall bladder; R, rectum; Hb, bladder; CI, cloaca; A, vent. 134 ANIMAL BIOLOGY ceives ^c ductSj^M.f A slit called the glottis opens from the throat into the lungs (Kig. 255). Is the gullet long or short? Broad or narrow? Is the stomach short or elongated? Is the division distinct between the stomach and gullet, and stomach and intestine ? Is the liver large or small ? Is it simple or lobed ? The pancreas lies between the stomach and the first bend of the intestines (Fig. 255). What is its shape ? A bile duct connects the liver with the small intestine {Dc, Fig. 255). It passes through the pancreas, from which it re- several pancreatic ifter many turns, the lestine joins the large intestine. The last part of the large intestine is called the rectum (Latin, straight). The last part of the rectum is called the cloaca (Latin, a drain), and into it the ducts from the kidneys and repro- ductive glands also open. The kidneys are large, elongated, and flat. They lie under the dorsal wall. The urinary bladder is also large. Does the salamander have a similar digestive system ? (Fig. 256.) Why are the liver and lungs (Fig. 256) longer in a sala- mander than in a frog ? Respiration. — -How many lungs? Are they simple or lobed? (Fig. 256.) A lung cut open is seen to be baglike, with numerous ridges on its inner surface. This increases the surface with which the air may come in contact. In the walls of the lungs are numerous Fig. 256. — A.NATOMY of Sala- mander. /a, heart; 2, lungs: _y a, stomach; _ji, in- testine; J r, large intestine; 4, liver; S, egg masses; 10, bladder; //, vent. BATH A CHI A 1 35 capillaries. Does the frog breathe with month open or closed f Does the frog have any ribs for expanding the chest ? What part of the head expands and contracts ? Is this motion repeated at a slow or rapid rate ? Regu- larly or irregularly ? There are valves in the nostrils for opening and closing them. Is there any indication of opening and closing as the throat expands and contracts ? The mouth and throat (pharynx) are filled with air each time the throat swells, and the exchange of gases (which gases .'') takes place continually through their walls and the walls of the lungs. At intervals the air is forced through the glottis into the lungs. After a short time it is expelled from the lungs by the muscular abdominal walls, which press upon the abdominal organs, and so upon the lungs. Immediately the air is forced back into the lungs, so that they are kept filled. In some species the lungs regularly expand at every second con- traction of the throat. This is shown by a slight out- ward motion at the sides. Does the motion of the throat cease when the frog is under water .'' Why would the frog be unable to breathe (except through the skin) if its mouth were propped open ? Why does the fact that the breathing is so slow as to almost cease when hibernat- ing, aid the frog in going through the winter without starving .'' (Chap. I.) W^hy must frogs and toads keep their skins moist .'' Which looks more Uke a clod } Why .■' The Heart and Circulation. — What is the shape of the heart? (Fig. 257.) Observe the two auricles in front and the conical ventricle behind them. The great arterial trunk from the ventricle passes forward beyond the auricles ; it divides into two branches which turn to the right and left (Fig. 257). Each branch im- mediately subdivides into three arteries (Fig. 257), one going to the head, one to the lungs and skin, and a third, the largest, 136 ANIMAL BIOLOGY passes backward in the trunk, where it is united again to its fellow. (Colored Fig. 2.) Both of the pulmonary veins, returning to the heart with pure blood from the lungs, empty into the left auricle. Veins with the impure blood from the body empty into the right auricle. Both the auricles empty into the ventri- cles, but the pure and impure blood are prevented from thoroughly mix- ing by ridges on the inside of the ventricle. Only in an animal with a four-chambered heart does pure blood from the lungs pass unmixed and pure to all parts of the body, m*i •Pi Fig. 257. — Plan of Frog's Circulation. Venous system is black; the arterial, white. A U, auricles; K, ventricle; Z., lung; Z//', liver. Aorta has one FiG. 258. — Frog'S Blood (magnified 2500 branch to right, another to left, which areas). Red cells oval, nucleated, and reunite below. Right branch only j^rger than human blood cells. Nuclei of persists in birds, left branch in beasts j^.^ ^.,,i,g ^^,,3 ^j^jble near center, (Pea- and man. , , . body.) and only such animals are warm-blooded. The purer (i.^. the more oxygenated) the blood, the greater the oxidation and warmth. The red corpuscles in a frog's ^/ifis{i.>^. mud terrapin). They have three instead of two joints in the middle toe of each foot. The term tiirth- may be applied to species which are partly terrestrial aiiil partly aquatic {e.g. snapping turtle (Fig. 271)). Usage, however, is by no means uniform. Fig. 271. — SXArPlNC. Turtle {Chehdm serpentina). Most reptiles eat animal food ; green terrapins and some land tortoises eat vegetable food. Would you judge that carnivorous chelonians catch very active prey .-* The fierce snapping turtle, found in ponds and streams, sometimes has a body three feet long. Its head and tail are very large and cannot be withdrawn into the shell. It is carnivorous and has great strength of jaw. It has been known to snap a large stick in two. The box tortoise is yellowish brown with blotches of yellow, and like its close kinsman, the pond turtle of Europe (Fig. 266), with- draws itself and closes its shell completely. Both lids of the plastron are movable, a jieculiarity belonging to these two species. The giant tortoise of the Galapagos Islands, ac- REPII/JA 145 cording to Lyddckcr, can trot cheerfully along with three full-grown men o\\ its back. " Tortoise shell " used for combs and other articles is obtained from the overlapping scales of the haivkbill turtle, common in the West Indies. T\i^ diamond-back terrapin, found along the Atlantic Coast from Massachusetts to Texas, is prized for making soup. Fig. 272. — a Rattlesnake. Venomous snakes of United States named in order of virulence : I. Coral snakes, Elaps, about sev- enteen red bands bordered with yel- low and black (colored figure 6) (fatal). 2. Rattlesnakes (seldom fatal). 3. Copperhead (may kill a small animal size of dog). 4. Water moccasin (never fatal). 5. Ground rattler. —i^_^V.l') 'Y\}KX\J^{Platysternum 7negalocephaluin). x J. China, This and Fig. 282 suggest descent of turtles from a lizardlike form. Figure 282 shows earlier ancestors to have been gill breathers. CHAPTER XIII BIRDS Suggestions. — The domestic pigeon, th.'' fowl, and the English sparrow are most commonly within the rf dch of students. The last bird has become a pest and is alraoit the only bird whose destruction is desirable. The female is oC mewhat uniformly mot- tled with gray an 1 brown in fine markings. The male has a black throat with the other markings of black, brown, and white, in stronger contrast than the marking of the female. As the different species of birds are essentially alike in structural features, the direc- tions and questions may be used with any bird at hand. When studying feathers, one or more should be provided for each pupil in the class. The feet and bills of birds should be kept for study. \ Does the body of the bird, like the toad and turtle, have a head, trunk, tail, and two pairs of limbs ? Do the fore and hind limbs differ from each other more or less than the limbs of other backboned animals ? Does any other vertebrate use them for \sS purposes as widely different ? Eye. — *\ Does the eyeball have parts corresponding to the eyeball of a fish or frog; viz., cornea, iris, pupil? Which is more movable, the upper or lower eyelid? Are there any lashes.'' The bird (like what other animal.'') has a third eyelid, or nictitating membrane. Compare its thickness with that of the other lids. Is it drawn over the eyeball from the inner or outer comer of the eye } Can you see in the human eye any wrinkle or growth which might be regarded as remains, or vestige, of such a membrane .'' 150 BIRDS 151 How many nostrils? In which mandible are they located ? Are they nearer the tip or the base of the mandible ? (Fig. 284.) What is their shajDC ? Do the nasal passages go directly down through the mandible or do they go backward? Is the inner nasal opening into the mouth or into the throat ? The beak or bill consists of the upper and lower man- dibles. The outside of the beak seems to be of what kind of material ? Examine the decapitated head of a fowl or of a dissected bird, and find if there is a covering on the bill which can be cut or scraped off. Is the mass of the bill of bony or horny material ? With what part of the human head are the mandibles F'^- 284— Skull of Domestic fowl. , ^ •. , -r-^. o \ y, quadrate ("four-sided") bone by which lower homologous? (rig. 284.) jaw is attached to skull (wanting in beasts, pres- Ears.— Do birds have '"' '" '"?"'"= '" ^''^- '"^• external ears ? Is there an cxtcriial opening leading to the ear ? In searching for it, blow or push forward the feath- ers. If found, notice its location, size, shape, and what surrounds the opening. There is an owl spoken of as the long-eared owl. Are its ears long ? The leg has three divisions: the uppermost is the tJiigh (called the "second joint" in a fowl); the middle division is the s J tank {ox "drumstick"); and the lowest, which is the slender bone covered with scales, is formed by the union of the ankle and instep. (The bones of the three divisions are named the femur, tibiotarsus, and tarsometa- tarsus.) T\\Q, foot consists entirely of toes, the bones of which are called phalanges. Is there a bone in each claw ? (See Fig, 285.) Supply the numerals in this sentence : '5^ A. VIM. -if. BIOLOGY toes, the — joints ; The pi<^eon has - hind tt)C ha\in_<; of the three front toes, the inner has joints (count the chiw as one joint), the Fig. 286.- - Skeleton of Bird. Rk, vertebrae; CI, clavicle; Co, coracoid; Sc, scap- ula; St, sternum; //, humerus: R, radius; U, ulna; /", thumb; />, femur; 7", tibia. See Fig. 394. Questions : Which is the stiffest portion of the vertebral column ? How are the ribs braced against each other ? Which is longer, thigh bone or shin ? Compare shoulder blade with man's ( Fig. 399) . Which is the extra shoulder bone ? Compare tail verlebrx with those of extinct bird. Fig. 290, Fig. 285. — Leg Bones OF Bird. middle has joints, and the outer toe has joints (Fig. 285). Is the thigh of a bird bare or feathered.'' The shin.'' The ankle .-* Where is the ankle joint of a bird .-* Do ' you see the remains of another bone (the splint bone, or fibula) on the shin bone of the shank.? (Fig. 285 or 286.) Why would several joints in the ankle be a disadvan tage to a bird .'* BIRDS 153 The tJiigJi hardly projects beyond the skin of the trunk, as may be noticed in a plucked fowl. The thigh extends forward from the hip joint (Figs. 286, 299) in order to bring the point of support forward under the center of weight. Why are long front toes more necessary than long hind toes .'* As the bird must often bring its head to the ground, the hip joints are near the dorsal surface and the body swings between the two points of support somewhat like a silver ice pitcher on its two pivots. Hence stooping, which makes a man so unsteady, does not cause a bird to lose steadiness. The wing has three divisions which correspond to the upper arm, forearm, and hand of man (Fig. 286). When the wing is folded, the three divisions He close alongside each other. Fold your arm in the same manner. The similarity of the bones of the iirst and second divisions to the bones of our upper arm and forearm is very obvious (Fig. 286). Ex- plain. ^h.Q. Jiajid oi a bird is furnished with only three dig- its (Fig. 287). The three palm bones (metacarpals) are firmly united (Fig. 287). This-^^ives firmness to^. the stroke in flying. That the bird is descended from ani- mals which had the fingers and palm bones less firmly united is shown by comparing the hands of a eJiick and of an adult fowl (Figs. 287, 288). The wrist also solidifies with age, the. 0S.2 0S.3 Fig. 287. — Hand and Wrist of Fowl (after Parker). DG. 1-3, digits; MC. 1-3, metacarpals; CC. 3, wrist. isT.orGT Fig. 288. — Hand, Wrist (c). Forearm, and Elbow of Young Chick (after Parker). 154 AXIMAI. BIOLOGY Fic. 289. — Breast- IK)NE ANnSlIOl'I.- DER Bonks ok Cassowary. five car[ials of the chick bciiij::: reduced to two in the fowl (Figs. 287, 2S8). 'riie thumb or i'lrst dit;it has a separate covcrinj;- of skin from the other digits, as may be seen in a plucked bird. The de- generate hand of the fowl is of course useless as a hand (what serves in its place ?) but is well fitted for firm support of the feathers in flying. The two bones of the forearm are also iirmly joined. There are eighteen movable joints in our arm and hand; the bird has only the three joints which enable it to fold its wing. The wrist joint is the joint in the forward angle of the wing. Since the fore limbs are taken up with loco- motion, the grasping function has been as- sumed by the Jiiius. How does their shape adapt them to this use ? For the same reason the Jicck of a bird surpasses the necks of all other ani- mals in what respect.'' Is the trunk of a bird flexible or inflexible .-' There is thus 2LCor- rclation between struc- ture of neck and trunk. Explain. The same correlation is found in which of the reptiles? (Why does rigidity of trunk require flexibility Question: Find two resemblances to reptiles in 01 neck ."^^ Why docs thisextinct bird absent from skcletonsof extant birds. Y\c.. 290. — A Fossil, Bird {archceoptcryx) found in the rocks of a former geological epoch. BIRDS 155 the length of neck in birds correlate with the length of legs? Examples? (See Figs. 314, 315, 332.) Exceptions? (Fig. 324.) Why does a swan or a goose have a long neck, though its legs are short ? To make a firm support for the wings the vertebrae of the back are immovably joined, also there are three bones in each shoulder, the collar bone, the shoulder blade, and the coracoid bone (Fig. 286). The collar bones are united (why ?) and form the " wishbone " or " pulling bone." To furnish sur- face for the attachment of the large flying muscles there is a prominent ridge or keel on the breastbone (Fig. 286). It is lacking in most birds which do not fly (Fig. 289), The feathers are perhaps the most characteristic feature of birds. The large feathers of the wings and tail are called quill featJiers. A quill feather (Fig. 291) is seen to consist of two parts, the shaft, or supporting axis, and the broad vane or web. What part of the shaft is round ? Hollow ? SoHd ? Is the shaft straight ? Are the sides of the vane usually equal in width ? Can you tell by looking at a quill whether it belongs to the wing or tail, and which wing or which side of the tail it comes from ? Do the quills overlap with the wide side of the vane above or beneath the next feather ? Can you cause two parts of the vane to unite again Fig. 291. — Quill Feather. D, downy portion. 156 ANIMAL BIOLOGY by pressing together the two sides of a split in the vane ? Does the web separate at the same place when pulled until ^ it splits again ? The hollow part of the shaft of a quill feather is called the quill. The part of the shaft bearing the vane is called the rachis (rii-kis). The vane consists of slender barbs which are branches of the shaft (II, Fig. 292). As the name indicates (see dictionary), a barb resembles a hair. The barbs in turn bear second- ary branches called bar-, bides, and these again have shorter branches called bar- FiG. 292. — I, Contour Feather. II, III. Parts of Quill Feather, enlarged. bicels (III, Fig. 292). These are sometimes bent in the form of booklets (Fig. 292, III), and the booklets of neighboring barbules interlock, giv- ing firmness to the vane. When two barbules are split apart, and then re- united by stroking the vane between the thumb and finger, the union may be so strong that a pull upon the vane will cause it to split in a new place next time. There are four kinds of feathers, (i) the quill feathers, just studied; (2) the contour feathers (I, Fig. 292), which form the general surface of the body and give it its outlines; (3) the doimiy^iz2X\iQX's, (Fig. 293), abundant on Fig. 293. — a Down Feather, enlarged. BIRDS 157 nestlings and found among the contour feathers of the adult but not showing on the surface ; (4) the pin feathers, which are hair-like, and which are removed from a plucked bird by singeing. The contour feathers are similar in structure to the quill feathers. They protect the body from blows, overlap so as to shed the rain, and, with the aid of the downy feathers retain the heat, thus accounting for the high temperature of the bird. The downy feathers are soft and fluffy, as they possess few or no barbicels; sometimes they lack the rachis (Fig. 293). The pin feath- ers are delicate horny shafts, greatly resembling hairs, but they may have a tuft of barbs at the ends. A feather grows from a small projection (or papilla) found at the bottom of a depression of the skin. The quill is formed by being molded around the papilla. Do you see any opening at the tip of the quill for blood vessels to enter and nourish the feather .-' What is in the quill } (Fig. 291.) The rachis } A young con- tour or quill feather is in- closed in a delicate sheath which is cast off when the feather has been formed. Have you seen the sheath incasing a young feather in a 'molting bird .-' There are considerable areas or tracts on a bird's skin without contour feath- ers. Such bare tracts are found along the ridge of the breast and on the sides of the neck. However, the contour feathers lie so as to over- lap and cover the whole body perfectly (Fig. 294). The shedding of the feathers is called molting. Feathers, Fig. 294. — Dorsal and Ventral View of Plucked Bird, showing regions where feathers grow. 158 AX IMA I. BIOLOGY like the leaves of trees, are delicate structures and lose perfect condition with a-c. Hence the annual renewal of the feathers is an advantage. Most birds shed twice a year, and with many the summer plum- age is brighter col- ored than the winter plumage. When a feather is shed on one side, the corre- sponding feather on the other side is always shed with it. (What need for this .?) A large oil gland is easily found on the dorsal side of the tail. How does the bird apply the oil to the feathers .'' Fic. 295. — Wing of Bird. /, false quills (on thumb); 3, primaries; 3, secondaries; tcrtiaries 'dark) are one above another at right; a, b, coverts. A Fig. 296. A, point dividing primaries from second- aries; B, coverts. In describing and classifying birds, it is necessary to know the names of the various external regions of the body and plum- age. These may be learned by studying Figs. 295, 296, 297, 298 Fig. 297. — Cedar Waxwing, with regions of body marked. S, forehead; Sc, crown (with crest); Hh, nape; K, throat; Br, breast; Ba, lower parts; /?, back; .A"/, tail; B, tail coverts; P, shoulder feathers (scapulars) ; 7", wing coverts; HS, primaries; .,4 5', secondaries; Al, thumb feathers. The quills on the hand BIRDS 159 are called primaries, those on the forearm are the sec- ondaries, those on the upper arm are the tertiaries. Those on the tail are called the tail quills. The feathers at the base of the quills are called the coverts. The thumb bears one or more quills called the spurious quills. Is the wing concave on the lower or upper side ? What advantage is this when the bird is at rest ? When it is flying ? Control of Flight. — Did you ever see a bird sitting on a swinging limb .'' What was its chief means of balancing itself .-^ When flying, what does a bird do to direct its course upward t Downward .'' Is the body level when it turns to pj^_ 298. -Plan of bird. either side."" Birds with long, j, center of gravity. pointed wings excel in what respect .'' Examples } Birds with great wing surface excel in what kind of flight .-' Ex- amples. Name a common bird with short wings which has a labored, whirring flight. Is its tail large or small .'' Does it avoid obstacles and direct its flight well } Why or why not .-* When a boat is to be turned to the right, must the rudder be pulled to the right or the left .'' (The rudder drags in the water and thus pulls the boat around.) When the bird wishes to Fig. 299. — Position of go upward, must its tail be turned up Limbs of Pigeon. . .> tt 1 • • 1 or down t How when it wishes to go down ? When a buzzard soars for an hour without flapping its wings, does it move at a uniform rate } For what does it use the momentum gained when going with the wind t i6o AXIMAl. BiOLoay Flying. — When studying; the ciuill feathers of the wing, you saw that the wider side of the vane is beneath the feather next behind it. Diirincj the downward stroke of the wing tiiis side of the vane is pressed by the air against Fig. 300. a, clambering foot of chimney sweep; /', climbing foot of woodpecker; c, perching foot of thrush; d, seizing foot of hawk; f, scratching foot of pheasant; /, stalking foot of king- fisher; g, running foot of ostrich; //, wading foot of heron; /", paddling foot of gull; /t, swimming foot of duck ; /, steering foot of cormorant; >«, diving foot of grebe; n, skim- ming foot of coot. Question: Does any bird use its foot as a hand.' (.Fig. 320.) the feather above it and the air cannot pass through the wing. As the wing is raised the vanes separate and the air passes through. The convex upper surface of the wing also prevents the wing from catching air as it is raised. Spread a wing and blow strongly against BIRDS i6i its lower surface ; its upper surface. What effects are noticed ? Study the scales on the leg of a bird (Fig. 300). Why is the leg scaly rather than feathered from the ankle down- ward .-* Which scales are largest.-* (Fig. 300.) How do the scales on the front and back differ } What can you say of the scales at the bottom of the foot ; at the joints of the toes .'' Explain. How does, the covering of the nails and bill compare in color, texture, hardness and firm- ness of attachment with the scales of the leg .-' Draw an outline of the bird seen from the side. Make drawings of the head and feet more detailed and on a larger scale. Why does a goose have more feathers suitable for making pil- lows than a fowl } In what country did the domestic fowl originate.'' (Encyclopedia.) Why does a cock crow for day } (Consider animal life in jungle.) Activities of a Bird. — Observe a bird eating. Does it seem to chew or break its food before swallowing .'' Does it have to lift its head in order to swallow food ? To swallow drink .'' Why is there a difference .-' After feed- ing the bird, can you feel the food in the crop, or enlargement of the gullet at the base of the neck } (Fig. 304.) Feel and look for any move- M Fig. 301. — An Altrical Bird, i.e. poorly developed at hatch- ing. Young pigeon, naked, beak too weak for eating. Fig. 302. — A Precocial Bird (well developed at hatching). Feathered, able to run and to pick up food. Precocity is a sign of instinctive life and low intelligence. A baby is not pre- cocious. Question: Is pigeon or fowl ex- posed to more dangers in infancy ? l62 AXD/.IL BIOT.OGY merits in btratJting. Can you find how often it breathes per minute ? Place hand under the bird's wing. What do you think of its temperature ; or better, what tempera- ture is shown by a thermometer held under its wing ? Do you see any connection between the breathing rate and the temperature? Test (as with the crayfish) whether a bird can see behind its head ? Notice the movements of the nictitating membrane. Does it appear to be transparent.-' Watch a bird Jij' around a closed room and review the questions on Control of Flight. Be/i(/ a bird's leg and see if it has any effect upon its toes. Notice a bird (especially a large fowl) walk to see if it bends its toes as the foot is lifted. Pull the rear tendon in a foot cut from a fowl for the kitchen. Does the bird have to use muscular exertion to grasp a stick upon which it sits .^ Why, or why not .? When is this bending of the toes by bending the legs of special ad- vantage to a hawk 1 To a duck } A wading bird } Why is a fowl safe from a hawk if it stands close to a tree .'' Do you see any signs of teeth in the bird's jaws .-* Why are duck's " teeth " (so called by children) not teeth } .f Can the tongue of a bird be pulled forward } (Fig. 303.) What is its shape .-' If there is opportunity, dissect and study the slender, bony (hyoid) apparatus to which the base of the tongue is attached (Fig. 303), the open- ing of the windpipe, or trachea, the slit-like opening of windpipe which is so narrow as to prevent food falling into the windpipe. Fir.. 303. — Head of Woodpecker. c, tongue; a, b, d, hyoid bone; e, q. wind- pipe; f, salivary gland. BIRDS 163 The Internal Organs, or Viscera (Figs. 304 and 305), — The viscera (vis'se-ra), as in most vertebrates, include the food tube and its glands; the lungs, the heart, and larger blood vessels; the kidneys and bladder and the reproductive organs. The lower part, or gullet, is en- larged into a crop. It is largest in grain-eating birds. It Fig. 304. — Anatomy of Dove x%. hk, keel of breastbone; C, g, brain; Ir, windpipe; lu, lung; h, heart; sr, gul- let; k^ crop; dr, glandular stomach; mm, gizzard; d, intestine; n, kidney; hi, ureter; eil, openings of ureter and egg duct into cloaca, kl. Fig. 305. — Food Tube of Bird. P, pancreas; C, caeca. Question: Identify each part by means of Fig. 304. is found in the V-shaped depression at the angle of the wishbone, just before the food tube enters the thorax. The food is stored and softened in the crop. From the crop the food passes at intervals into the glandular stomach. Close to this is the muscular stomach, or gizzard. Are the places of entrance and exit on opposite sides of the gizzard, or near together .-' (Fig. 304.) Is the lining of the gizzard 164 ANIMAL BIOLOGY rougli or smooth ? Why? Is the gizzard tough or weak? Why are small stones in the gizzard ? Why do not hawks and other birds of prey need a muscular gizzard ? The liver and pancreas empty their secretions into the intestines by several ducts a little way beyond the gizzard. Beyond the mouths of two cceca (Fig. 305) the many-coiled intestine empties into the straight rectum, which terminates in a widened part called the cloaca. Not only the intestine, but the two ureters of the urinary system and the two genital ducts of the reproductive system all empty into the cloaca (Figs. 304, 305). The lungs have their rear sur- faces attached to the spinal column and ribs (///, Fig. 304). They are connected with thin- walled, transparent air sacs which aid in purifying the blood. When inflated with warm air, they prob- ably make the body of the bird more buoyant. For the names, location, and shape of several pairs of air sacs, see Fig. 306. The connection of the air sacs with hollows in the humerus bones is also shown in the figure. Many of the bo7ies are holloiv ; this adds to the buoyancy of the bird. The pulmonary artery, as in man, takes dark blood to the lungs to exchange its carbon dioxide for oxygen. Of two animals of the same weight, which ex- pends more energy, the one that flies, or the one that runs the same distance ? Does a bird require more oxygen Fig. 306. — Position of Lungs AND Air Sacs (Pigeon). Tr, windpipe; P, lungs; Lm, sac under clavicle with prolongation (Z.//) into humerus; La, sacs in abdomen. BIRDS 165 Fig. 307. — Position of Vocal Cords {str) of Mammal and Bird. Question : Does a fowl ever croak after its head and part of its neck are cut off? Explain. or less, in proportion to its weight, than an animal that lives on the ground ? Are the vocal cords of a bird higher or lower in the wind- pipe than those of a man? (Fig. 307.) The heart of a bird, Hke a man's heart, has four cham- bers ; hence it keeps the purified blood separate from the impure blood. Since pure blood reaches the or- gans of a bird, oxidation is more perfect than in the body of any animals yet studied. Birds have higher temperature than any other class of animals whatsoever. Tell how the jaws, tail, and wings of the fossil bird Archaeopteryx differed from living birds (Fig. 290). Suggestions. — In the field work, besides seeking the answers to definite questions, pupils may be required to hand in a record of the places and times of seeing a certain number of birds (20 to 40), with the actions and features which made each distinguishable. Also, and more important, each pupil should hand in a record of a careful and thorough outdoor study of one common species (see below) as regards habits, nesting, relation to environment, etc. Field Study of a Common Species. — {For written report.) Name of species. Haunts. Method of locomotion when not flying. Flying (rate, sailing, accompanying sound if any, soaring). What is the food? How obtained? Association with birds of its own species. Fetation to birds of other species. Where does it build its nest ? Why is such a situation selected? Of what is the nest built? How is the material carried, and how built into the nest? Does the bird's body fill the nest? Describe the eggs. Does the male bird ever sit or otherwise assist female before hatching? Does it assist after hatching? i66 ANIMAL BIOLOGY How long is taken to lay a sitting of eggs? How long before the birds are hatched? When hatched are they helpless ? Blind ? Feathered? (Figs. 301, 302.) Do the nest- lings require much food ? How many times is food brought in an hour? How distributed? Even if the old birds some- times eat fruit do they take fruit to the young? What do they feed to the young? How long be- &^li? Fir,. 308. — KuKoPKAN TDMnT-i Nisi What are the advantages of its shapt ' fore they leave the nest? Do the parents try to teach them to fly? Do the par- ents care for them after the nest is left? What songs or calls has the bird? General Field Study. — {For7oritte)i report.^ Name the best and poorest flyers you know ; birds that fly most of the time ; birds that seldom fly. Observe birds that pair; live in flocks. Does their sociability vary with the season? Do you ever see birds (juarreling? Fig. 309. — Tailor Bird's Nest (India). Instinct for nest building highly perfected. BIRDS 167 Fighting? What birds do you observe whipping or driving birds larger than themselves? Which parent do young birds most re- semble ? Name the purposes for which birds sing. Which senses are very acute? Why? Dull? Why? Can you test your state- ments by experiment? A partridge usually sits with 18 to 24 eggs in nest. About how long after laying first egg before sitting begins? Do several partridge hens lay in the same nest? Haiaits. — Name some birds that are found most often in the following localities : about our homes, in gardens and or- chards, fields and meadows, in bushes, in the woods, in secluded woods, around streams of water, in thick- ets, in pine woods. Size. — Name birds as large as a robin or larger, nearly as large, half as large, much smaller. Colors. — Which sex is more brilliant? What ad- vantage are bright colors to one sex? What advantage are dull colors to the other F'^- 310. -House Wren. sex? Which have yellow breasts, red patch on heads, red or chestnut breasts, blue backs, black all over? Habits. — Name the birds that walk, jump, swim, live in flocks, sing while flying, fly in undulations, in circles, have labored flight. Such books as Wright's "Birdcraft" (Macmillan, N. Y.), Clark's "Birds of Lakeside and Prairie " (Mumford, Chicago), and Pear- son's "Stories of Bird Life" (B. F. Johnson, Richmond), will be of great help. The last book is delightfully written, and is one of the few treating of bird life in the South, Economic Importance of Birds. — Farmers find their most valuable allies in the class aves, as birds are the dead- liest enemies of insects and gnawing animals. To the in- numerable robbers which devastate our fields and gardens, nature opposes the army of birds. They are less numerous 1 68 AMMAL BIOLOGY than insects and other robbers, it is true, but they are skillful and zealous in pursuit, keen of eye, quick, active, and remarkably vora- cious. The purely in- sectivorous birds are the most useful, but the omnivorous and grami- nivorous birds do not disdain insects. The perchers and the wood- Fig. 311. - Screech Owl {Megascops asio). peckers should be pro- QuestiOD : Compare posture of body, position of tCCtcd VtOSt Caveflllly. eyes, and size of eyes, with other birds. rr^, • 1 , 1 • i r The night birds of prey (and those of the day to a less degree) are very destructive to field mice, rabbits, and other gnawing animals. Some igno- rant farmers complain continu- ally about the harm done by birds. To destroy them is as unwise as it would be to destroy the skin which protects the hu- man body because it has a spot upon it ! It cannot be repeated too plainly that to hunt useful birds is a wrong and mischievous act, and it is stupid and barba- rous to destroy their nests. Injurious birds are few. Of course birds which are the ene- FiG. 312. — Goshawk, mies of other birds are enemies or chicken hawk. BIRDS 169 Fig. 313. —Road Runner, or chaparral bird (Tex. to Cal.). What order? (Key, p. 177.) of mankind, but examples are scarce (some owls and hawks). Many birds of prey are classed thus by mistake. Sparrow hawks, for instance, do not eat birds except in rare instances ; they feed chiefly upon insects. A sparrow hawk often keeps watch over a field where grasshoppers are plentiful and destroys great numbers of them. When a bird is killed because it is supposed to be injurious, the crop should always be examined, and its contents will often surprise those who are sure it is a harmful bird. The writer once found two frogs, three grasshoppers, and five beetles that had been swallowed by a " chicken hawk " killed by an irate farmer, but no sign of birds having been used for food. Fowls should not be raised in open places, but among trees and bushes, where hawks cannot swoop. Birds which live exclusively upon fish are, of course, opposed to human interests. Pigeons are destructive to grain ; eagles feed chiefly upon other birds. If the birds eat the grapes, do not kill the birds, but plant more grapes. People with two or three fruit trees or a small I70 AXIMAL BIOLOGY garden arc the only ones that lose a noticeable amount of food. We cut down the forests from which the birds ob- tain part of their food. We destroy insect pests at great cost of spraying, etc. The commission the birds charge for such work is very small indeed. (See pages 177-183.) Fig. 314. — Wood Duck, male [Aix sponsa). Nests in hollow trees throughout North America. Also called summer duck in South. Why ? The English sparrow is one bird of which no good word may be said. Among birds, it holds the place held by rats among beasts. It is crafty, quarrelsome, thieving, and a nuisance. It was imported in 1852 to eat moths. The results show how ignorant we are of animal life, and how slow we should be to tamper with the arrangements of nature. In Southern cities it produces five or six broods each year with four to six young in each brood. (Notice what it feeds its young.) It fights, competes with and drives away our native useful birds. It also eats grain and preys upon gardens. They have multiplied more in Aus- BIRDS 171 tralia and the United States than in Europe, because they left behind them their native enemies and their new ene- mies (crows, jays, shrikes, etc.) have not yet developed, to a sufficient extent, the habit of preying upon them. Nature will, perhaps, after a long time, restore the equilibrium destroyed by presumptuous man. Protection of Birds. — i. Leave as many trees and bushes standing as possible. Plant trees, encourage bushes. 2. Do not keep a cat. A mouse trap is more useful than a cat. A tax should be imposed upon owners of cats. 3. Make a bird house and place on a pole ; remove bark from pole that cats may not climb it, or put a broad band of tin around the pole. 4. Scatter food in winter. In dry regions and in hot weather keep a shallow tin vessel containing water on the roof of an outhouse, or out-of-the-way place for shy birds. 5. Do not wear feathers obtained by the killing of birds. What feathers are not so obtained } 6. Report all violators of laws for protection of birds. 7. Destroy English sparrows. Migration. — Many birds, in fact most birds, migrate to warmer climates to spend the winter. NaturaHsts were once content to speak of the migra- tion of birds as a wonderful instinct, and made no attempt to explain it. As lirds have the warmest covering of all animals, the winter mi- gration is not for the pur- FiG. 315. -Great Blue Heron, pose of escaping the cold ; it In flight, balancing with legs. jg probably to cscapc starva^ tion, because in cold countries food is largely hidden by snow in winter. On the other hand, if the birds remained 172 AXIAf.ll. BIOLOGY in the warm countries in .summer, the food found in north- ern countries in summer would be unused, while they would have to compete with the numerous tropical birds for food, and they and their eggs would be in danger from snakes, wild cats, and other beasts of prey so numerous in warm climates. These are the best reasons so far given for migration. The manner and methods of migration have been studied more carefully in Kuroj)e than in America. Migration is Fig. 316. — Europka:; Swallows (///>«»(/«^*^^^^^*^\ BIRDS 1 73 marsh bird would die of hunger on arriving in a very dry country. The landmarks of the route are mountains, rivers, valleys, and coast lines. This knowledge is handed down from one generation to another. It includes the location of certain places on the route where food is plentiful and the birds can rest in security. Siebohm and others have studied the routes of migration in the Old World. The route from ,^ the nesting places in Jiafl!^ ^ northern Eu- Africa fol- lows the Rhine, the Lake of Geneva, the Rhone, whence some spe- cies follow the Itahan and others the Span- ^ic, 317 —cranes ish coast line to Africa. Birds choose the Migrating, with lowest mountain passes. The Old World v^shaped HnT. martin travels every year from the North Cape to the Cape of Good Hope and back again ! An- other route has been traced from Egypt along the coast of Asia Minor, the Black Sea and Ural Mts. to Siberia. Field Study of Migration. — Three columns may be filled on the blackboard in an unused corner, taking several months in spring or fall for the work. First column, birds that stay all the year. Sccojid column, birds that come from the south and are seen in the summer only. Third column, birds that come from the north and are seen in winter only. Exact dates of arrival and departure and flight overhead should be recorded in notebooks. Many such records will enable American zoologists to trace the migration routes of our birds. Reports may be sent to the chief of the Biological Survey, Washington, D.C. 174 AX/M.il. filOIOGY Molting. Ili)\v do iiirds anani^c Ihcir feathers after they have been nittlcd ? Ho thcv e\er batlie in water? •■'>^.'^^--- FlG. 318. — Al'ihK\ X. of New Zealand. Size of a lun, wings ami tail rudimentary, feathers liair-like. In dust .-' Dust helps to remove old oil. At what season are birds brightest feathered } Why .-' Have you ever seen Fig. 319. — Golden, Silver, and Noble Pheasants, males. Order? (Key, p. 177.) Ornaments of males, brightest in season of courtship, are due to sexual selection (Figs. 321-7-9, 333). evidence of the molting of birds .-' Describe the molting process (page 120). BIRDS 175 1>:M.^^:^^^ Adaptations for Flying. — Flight is the most diffi- cult and energy- consuming meth- od of moving found among ani- mals, and care- ful adjustment is necessary. For balancing, the heaviest muscles are placed at the lower and central portion of the body. These are the flying muscles, and in some birds (humming birds) they make half of the entire weight. Teeth are the densest of ani- mal structures ; teeth and the strong chew- ing muscles required would make the head heavy and balancing difficult ; hence the chewing apparatus is transferred to the heavy gizzard near the center of gravity of the body. The bird's neck is long and excels all other necks in flexibility, but it is very slender (although apparently heavy), being inclosed in a loose, feathered skin. A cone is the best 1/6 AXIMAL BIOLOGY shajio to enable the body to penetrate the air, and a small neck would destroy the conical form. The internal organs are compactly arrani;ed and rest in the cavity of the breast bone. 'I'he bellows-like air sacs filled with warm air lighten the bird's weight. The bones are hollow and very thin. The large tail quills are used by the bird only in guiding its flight up and down, or balancing on a limb. The feet also aid a flying bird ni bal- ancing. The wing is so constructed as to present to the air a remarkably large surface com- pared with the small bony support in the wing skele- ton. Are tubes ever resorted to by human architects when lightness combined with strength is desired .-' Which quills in the wing serve to lengthen it? (Fig. 296.) To broaden it? Is flight more difficult for a bird or a butterfly ? Which of them do the flying machines more closely resemble? Can any bird fly for a long time without flapping its wings ? Fig. 322. — Herring Gull. (Order?) Exercise in the Use of the Key. — Copy this list and write the name of the order to wliicli each of the birds belongs. (Key, page 177.) Cockatoo (Fig. 320) Wren (Fig. 310) Pheasant (Fig. 319) Sacred Ibis (Fig. 328) Apteryx (Fig. 318) Wood Duck (Fig. 314) Screech Owl (Fig. 311) Lyre bird (Fig. 327) Jacana (Fig. 324) Nightingale (Fig. 325) Road Runner(Fig.3l3) Sea Gull (Fig. 322) Top-knot Quail (Fig. Ostrich (Fig. 332) Heron (Fig. 315) 329) Penguin (Fig. 330) iiawk (Fig. 312) BIRDS 177 KEY, OR TABLE, FOR CLASSIFYING. BIRDS {Class Aves) INTO ORDERS Orders Runners Divers Bill-strainers Sea-fliers GORGERS A J "Wings not suited for flight, 2 or 3 toes A2 Wings suited for flight (except the penguin) Bj Toes imitedby a web for swimming, legs short Cj Feet placed far back ; wings short, tip not reaching to base of tail (Fig. 300) Cg Bill flattened, horny plates under margin of upper bill (Fig. 323) C; Wings long and pointed, bill slender Q All four toes webbed, bare sac under throat B2 Toes not united by web for swimming Cj Three front toes, neck and legs long, tibia Waders (shin, or " drumstick ") partly bare C, Three front toes, neck and legs not long Dj Claws short and blunt {e. Fig. 300) Ej Feet and beak stout, young feathered, base of hind toe elevated Ej Feet and beak weak, young naked D2 Claws long, curved and sharp, bill hooked and sharp D3 Claws long, slightly curved, bill nearly straight Cg Two front and two hind toes (Fig. 300) D, Bill straight, feet used for climbing D^ Bill hooked, both bill and feet used for climbing Scratchers Messengers Robbers Perchers Foot-climbers Bill-climbers The Food of Birds. — Extracts from Bulletin No, 54 (United States Dept. of Agriculture), by F. E, L. Beal. The practical value of birds in controlling insect pests should be more generally recognized. It may be an easy matter to exterminate the birds in an orchard or grain field, but it is an extremely difficult one to control the insect pests. It is certain, too, that the value of our native sparrows as weed destroyers is not appreciated. Weed seed forms an important item of the winter food of many of these birds, and it is impossible to estimate the immense numbers of noxious weeds which are thus annually N 178 .i.y/.v.i/. /i JO/ 0(7}' destroyed. If < rows or blackbirds are seen in numbers about cornfields, or it woodpeckers are noticed at work in an orchard, it is perhaps not surprising that they are accused of doing harm. Careful in- vestigation, however, often shows that they are actually destroying noxious in- sects ; and also that even those which do harm at one season may compensate for it by eating insect pests at another. Insects are eaten at all times by the majority of land birds. During the breeding season most kinds subsist largely on this food, and rear their young exclusively upon it. Partridges. — Speaking of 13 birds which he shot, Dr. Judd says : These 13 had taken weed seed to the extent of 63 per cent of Fi<".. 323. — Heap of Divk. Fi'j. 324. — Jacana. (Mexico, Southwest Texas, and Florida.) Questions: What appears to be the use of such long toes? What peculiarity of wing? head? their food. Thirty-eight per cent was ragweed, 2 per cent tick trefoil, partridge pea, and locust seeds, and 23 per cent seeds of miscellaneous weeds. About 14 per cent of the quail's food for BIRDS 179 the year consists of animal matter (insects and their allies). Prominent among these are the Colorado potato beetle, the striped squash beetle, the cottonboU-weevil, grasshoppers. As a weed destroyer the quail has few, if any, superiors. Moreover, its habits are such that it is almost constantly on the ground, where it is brought in close contact with both weed seeds and ground-living insects. It is a good ranger, and, if undisturbed, will patrol every day all the fields in its vicinity as it searches for food. Fig. 325. — Nightingale, x I. Fig. 326. — Skylark, x j. Two celebrated European songsters. Doves, — The food of the dove consists of seeds of weeds, together with some grain. The examination of the contents of 237 stomachs shows that over 99 per cent of the food consists wholly of vegetable matter. Cuckoos. — An examination of the stomachs of 46 black-billed cuckoos, taken during the summer months, showed the remains of 906 caterpillars, 44 beetles, 96 grasshoppers, 100 sawflies, 30 stink bugs, and 15 spiders. Of the yellow-billed cuckoos, or "rain-crow," 109 stomachs collected from May to October, in- clusive, were examined. The contents consisted of 1,865 cater- pillars, 93 beetles, 242 grasshoppers, 37 sawflies, 69 bugs, 6 flies, and 86 spiders. i8o AXIMAL mOLOGY Woodpeckers. — Careful observers have noticed that, excepting a single species, these birds rarely leave any conspicuous mark on a healthy tree, except when it is affected by wood-borinc; larvne, wliich are accurately located, dis- lodged, and devoured by the wood- pecker. Of the flickers' or yellow- hammers' stomachs examined, three were completely filled with ants. Two of the birds each contained more 3,000 ants, ivliile Fig. 327. — Lyre Bird, male. than the third bird contained fully 5,000. These ants be- long to species which live in the ground. It is these insects for which the flicker is reaching when it runs about in the grass. The yellow-bellied woodpecker or sapsucker {Sphyrapicus variini) was shown to be guilty of pecking holes in the bark of various forest trees, and sometimes in that of apple trees, and of drinking the sap when the pits became filled. It has been proved, however, that besides tak- ing the sap the bird cap- tures large numbers of insects which are attracted by the sweet fluid, and that these form a very considerable portion of its diet. The woodpeck- ers seem the only agents FIG. s^s.^SACRKDiH.s. (Order?) ^^.j^j^,., ^an successfully cope with certain insect enemies of the forests, and, to some extent, with those of fruit trees also. For this reason, if for no other, they should be protected in every possible way. BIRDS I8I The night hawk, or " bull bat," may be seen most often soaring high in air in the afternoon or early evening. It nests upon rocks or bare knolls and flat city roofs. Its food consists of insects taken on the wing ; and so greedy is the bird that when food is plentiful, it fills its stomach almost to bursting. Ants (except workers) have wings and fly as they are preparing to propagate. In destroying ants night hawks rank next to, or even with, the woodpeckers, the acknowledged ant-eaters among birds. I-'l; 32^. — ToP-KiNOT Quail, or California Partridge. (West Texas to California.) The kingbird, or martin, is largely insectivorous. In an ex- amination of 62 stomachs of this bird, great care was taken to identify every insect or fragment that had any resemblance to a honeybee ; as a result, 30 honeybees were identified, of which 29 were males or drones and i was a worker. Blue Jay. — In an investigation of the food of the blue jay 300 stomachs were examined, which showed that animal matter com- prised 24 per cent and vegetable matter 76 per cent of the bird's diet. The jay's favorite food is mast {i.e. acorns, chestnuts, chinquapins, etc.), which was found in 200 of the 300 stomachs, and amounted to more than 42 per cent of the whole food. iSj AX/ MAI. BIOLOGY Fi'j. 330. — Pknouin of Pata- OONIA. Wings used ;is flip- pers for swimming. Crow. — That he docs pull up sprouting corn, destroy chickens, and rob the nests of small birds has been repeatedly proved. Nor are these all of his sins. He is known to eat frogs, toads, sala- manders, and some small snakes, all harmless creatures that do some good by eating insects. Kx])erience has shown that they may be prevented from pulling up young corn by tarring the seed, which not only saves the corn but forces them to turn their at- tention to insects. May beetles, " dor- bugs," or June bugs, and others of the same family. constitute the princi- pal food during spring and early sum- mer, and are fed to the young in immense quantities. Ricebird. — The annual loss to rice growers on account of bobolinks has been estimated at $2,000,000. Meadow Lark. — Next to grasshop- pers, beetles make up the most impor- tant item of the meadow lark's food, amounting to nearly 21 per cent. May is the month when the dreaded cut-worm begins its deadly career, and then the lark does some of its best work. Most of these caterpillars are ground feeders, and are overlooked by birds which habitually frequent trees, but the meadow lark finds and devours them by thousands. Sparrows. — Examination of many stomachs shows that in winter the tree sparrow feeds entirely u])on seeds of weeds. Probably each bird consumes about one fourth of an ounce a day. Farther south the tree s]>arrow is replaced in winter by the white-throated sparrow, the white-crowned sparrow, the fox spar- row, the song sparrow, the field sparrow, and several others ; so that all over the land a vast number of these seed eaters are at Flc. 331. — Umbrella holding the nests of social weaver bird of Africa; polygamous. BIRDS 183 work during the colder months reducing next year's crop of worse than useless plants. Robin. — An examination of 500 stomachs shows that over 42 per cent of its food is animal matter, principally insects, while the remainder is made up largely of small fruits or berries. Vegetable food forms nearly 58 per cent of the stom- ach contents, over 47 per cent being wild fruits, and only a little more than 4 per cent being possibly cultivated varieties. Cultivated fruit amounting to about 25 per cent was found in the stomachs in June and July, but only a trifle in August. Wild fruit, on the contrary, is eaten in every month, and constitutes during half the year a staple food. Questions. — Which of these birds are com- mon in your neighborhood? Which of them according to the foregoing report are plainly inju- rious? Clearly beneficial? Doubtful? Which are great destroyers of weed seeds? Wood-borers? Ants? Grain? Why is the destruction of an ant by a night hawk of greater benefit than the destruction of an ant by a woodpepker ? Name the only wood- pecker that injures trees. If a bird eats two ounces of grain and one ounce of in- sects, has it probably done more good or more evil? Fig. 332. — African Ostrich, x ,'5. (Order?) CHAPTER XIV MAMMALS (^BEASTS AND MAN) Suggestions. — A tame rabbit, a house cat, or a pet squirrel may be taken to the school and observed by the class. Domestic ani- mals may be observed at home and on the street. A study of the teeth will give a key to the life of the animal, and the teacher should collect a few mammalian skulls as opportunities offer. The pupils should be required to identify them by means of the chart of skulls (p. 194). If some enthusiastic students fond of anatomy should dissect small mammals, the specimens should be killed with chloroform, and the directions for dissection usual in laboratory works on this subject may be followed. There is a brief guide on page 223. The following outline for the study of a live mammal will apply almost as well to the rabbit or squirrel as to the cat. The Cat. — The house cat (Filis donustica) is probably descended from the Nubian c:i\.{Fc/ts vianicu/afa, Fig. 333) found in Africa. The wild species is about half again as large as the domestic cat, grayish brown with darker stripes ; the tail has dark rings. The lynx, or wild cat of America {Ljnx rufus), is quite different. Compare the figures (333, 335) and state three obvious differences. To which American species is the house cat closer akin, the lynx (Fig. 335) or the ocelot (Fig. 334).'' The domes- tic cat is found among all nations of the world. What is concluded, as to its nearest relatives, from the fact that the Indians had no cats when America was discovered .•* It was considered sacred by the ancient Egyptians, and after death its body was embalmed. The body of the cat is very flexible. It may be divided into five regions, the head, neck, trunk, tail, and limbs. Its 184 MAMMALS 185 ,^>^/''\ Fig. 333. — Wild Cat ok Aikila [/-f./s luaniculata), x %. eyes have the same parts as the eyes of other mammals. Which part of its eye is most peculiar? (Fig. 333.) What part is lacking that is present in birds ? How are the eyes especially adapted for seeing at night ? Does the pupil in the light extend up or down or across the iris ? Does it ever become round ? What is the shape and position of the cars ? Are they large or small compared with those of most mammals .-' They are fitted best for catching sound from what direc- tion } What is thus indicated in regard to the cat's habits .'' (Compare with ears of rabbit.) Touch the whiskers of the cat. What result .'' Was it voluntary or involuntary mo- tion .? Are the nostrils relatively large or small compared with those of a cow .'' Of man .'' Is the neck long or short ? Animals that have long fore legs usually have what kind of a neck .-* Those with short legs.-" Why? How many /(^r^- on a fore foot ? Hind foot? Why is this arrangement better than the reverse ? Some mammals are sole walkers {^plantigradc\ some are toe walkers {digiti grade'). To which kind does the cat 1 86 ANIMAL BIOLOGY ■■■■ i -f-' MteV l'«5l Kic. 334. — OCKI.cvr (/•'<•//> parJalis), of Texas and Mexico. X J. belong? Does it walk on the ends of the toes ? Does it walk with all the joints of the toes on the ground ? Where is the heel of the cat? (Fig. 334.) The wrist ^ To make sure of the location of the wrist, begin above : find the shoul- der blade, the ujiper arm (one or two bones ?), the lower arm (one or two bones?), the wrist, the palm, and the fingers (Fig. 337). Is the heel bone prominent or small ? In w^hat direction does the knee of the cat point ? The heel ? The elbow ? The wrist ? Compare the front and hind leg in length ; straightness ; heaviness ; number and position of toes ; sharpness of the claivs. What makes the dogs claws duller than a cat's ? What differences in habit go with this ? Judging from the toe that has become use- less on the fore foot of the cat, which toe is lacking in the hind foot ? Is it the cat's thumb or little finger that does not touch the ground? (Fig. 337.) Locate on your own hand the parts corresponding to the pads on the forefoot of a cat. Of what use are soft pads on a cat's foot? Some animals have short, soft fur and long, coarse over hair. Does the cat have both ? Is the cat's fur soft or coarse ? Does the fur have a color near the skin different MAMMALS 187 from that at the tip ? Why is hair better suited as a cover- ing for the cat than feathers would be? Scales? Where are long, stiff bristles found on the cat ? Their length suggests that they would be of what use to a cat in going through narrow places ? Why is it necessary for a cat to be noiseless in its movements ? Fig. 335. — Lynx {Lynx ru/us). The " Bob-tailed cat" (North America). Observe the movements of the cat. — W^hy cannot a cat come down a tall tree head foremost ? Did you ever see a cat catch a bird ? How does a cat approach its prey ? Name a jumping insect that has long hind legs; an am- phibian; several mammals (Figs. 362, 374). Does a cat ever trot ? Gallop ? Does a cat chase its prey ? When does the cat move with its heel on the ground ? The claws of a cat are withdrawn by means of a tendon (see Fig. 338). Does a cat seize its prey with its mouth or its feet ? How does a cat make the purring sound? (Do the lips move ? The sides ?) How does a cat drink ? Do a cat 1 88 ANIMAL BIOLOGY Fig. 336. Jaguar, of tropical America. and dog drink exactly the same way .-• Is the cat's tongue rough or smooth .-• How is the tongue used in getting the flesh off close to the bone .>' Can a cat clean a bone entirely of meat.'* In what state of development is a newly born kitten } With what docs the cat >iouris/i ils young? Name ten animals of various kinds whose young are simi- arly nourished. What is this class of ani- mals called .-* ^ Why does a cat bend its back when it is frightened or angry.'' Does a cat or a dog eat a greater variety of food .-' W^hich refuses to eat an animal found dead .-* Will either bury food for future use .'' Which is sometimes trouble- some by digging holes in the garden .-' Explain this in- stinct. Which lived a solitary life when wild .'' Which had a definite haunt, or home .'' Why are dogs more sociable than cats.'' A dog is more devoted to his master. Why.? A cat is more de- voted to its home, and will return if carried away. Why.'' Why does a dog turn around before lying down } (Con- sider its original environment. ) ^'""- 337-s*^i--le'on of cat. The Skeleton (Fig. 337). — Compare the spinal column of a cat in form and flexibility with the spinal column of a fish, a snake, and a bird. MAMMALS 189 The skull is joined to the spinal column by two knobs (or condyls), which fit into sockets in the first vertebra. Compare the jaws with those of a bird and a reptile. There is a prominent ridge in the temple to which the powerful chewing muscles are attached. There is also a ridge at the back of the head where the muscles which support the head are attached (Fig. 348). Count the ribs. Are there more or fewer than in man .-' The breastbone is in a number of parts, joined, like the vertebrae, by cartilages. Compare it with a bird's ster- num ; why the difference } The shoulder girdle, by which the front legs are attached to the trunk, is hardly to be called a gir- dle, as the collar bones (clavicles) are rudimentary. (They often es- cape notice during dissection, being hidden by muscles.) The shoulder blades, the other bones of this gir- dle, are large, but relatively not so ^'f; 33^-"^:!:^' '''" ^^l ' ° -' (i) retracted by ligament, and broad toward the dorsal edge as (2) drawn down by muscle 1 1 ij 1 1 1 T^i 1 attached to lower tendon. human shoulder blades. 1 he clav- icles are tiny because they are useless. Why does the cat not need as movable a shoulder as a man .'' The pelvic, or hip girdle, to which the hind legs are attached, is a rigid girdle, completed above by the spinal column, to which it is immovably joined. Thus the powerful hind legs are joined to the most rigid portion of the trunk. , Mammals. — The cat belongs to the class Mammalia or mammals. The characteristics of the class are that the young are not hatched from eggs, but are born alive, and nourished with milk (hence have lips), and the skin is covered with hair. The milk glands are situated ventrally. The position of the class in the animal kingdom was IQO ANIMAL BIOLOGY shown when the cow was classified (p. 9). Their care for the young, their intelligence, and their ability to surviv^e when in competition with other animals, causes the mam- mals to be considered the highest class in the animal kingdom. According to these tests, what class of vertebrates should rank nc.vf to uiavimalsf Compare the heart, lungs, blood, and parental devotion of these two highest classes of ani- mals. Fig. 339. — Skeleton of Lion (cat family). The first mammals, which were somewhat like small opossums, appeared millions of years ago, when the world was inhabited by giant reptiles. These reptiles occupied the water, the land, and the air, and their great strength and ferocity would have prevented the mammals from multiplying (for at first they were small and weak), but the mammals carried their young in a pouch until able to care for themselves, while the reptiles laid eggs and left them uncared for. The first mammals used reptilian eggs for food, though they could not contend with the great reptiles. Because birds and mammals are better parents than reptiles, they have conquered the earth, and the rep- MAMMALS 191 Fig. 340. — Walrus {Trichechus rosmarus). tiles have been forced into subordination, and have become smaller and timid. Classification of Mammals. — Which two have the closest resemblances in the following lists : Horse, cow, deer. Why } Cat, cow, bear. Why ? Monkey, man, sheep. Why } Rat, monkey, squirrel. Why.-' Giraffe, leopard, camel. Why? Walrus, cat, cow. Why } Check the five mammals in the following lists that form a group resembling each other most closely : Lion, bear, pig, dog, squir- rel, cat, camel, tiger, man. State your reasons. Gi- raffe, leopard, deer, cow, rat, camel, hyena, horse, monkey. State reasons. Teeth and toes are the basis for subdividing the class mammalia into orders. Although the breathing, circulation, and internal organs and pro- cesses are similar in all mammals, the external organs vary greatly be- cause of the varying en- vironments of different species. The internal structure enables us to place animals together which are essentially alike ; e.g. the whale and man are both mammals, since they resemble in breathing, circulation, and multiplication of young. The external organs guide us in separating the class into orders. The teeth vary according to the food Fig. 341. — Weasel, in summer; in Canada in winter it is all while but tip of tail. 192 AXJMAI. BIOLOGY Fig. 342. — Foot of Hkak (Pliintigrade). eaten. The feet vary according to use in obtaining food or cscajiinj; from enemies. This will explain the differ- ence in the length of legs of lion and horse, and of the forms of the teeth in cat and cow. Make a careful study of the teeth and limbs as shown in the figures and in all specimens accessible. Write out the deiital formulas as indi- cated at the top of page 194. The numerals above the line show the number of upper teeth ; those below the line show the number of lower teeth in one half of the jaw. They are designated as follows : /, incisors ; C, canine ; J/, molars. Multiplying by two gives the total number. Which skulls in the chart have the largest canines 1 Why } The smallest, or none at all .-' Why .-* Compare the molars of the cow, the hog, and the dog. Explain their differences. In which skulls are some of the molars lacking .-' Rudimentary .■* Why are the teeth that do not touch usually much smaller than those that do .-* Fig. 343. — Polar Bear {^Ursus mantimus). MAMMALS 193 KEY, OR TABLE, FOR CLASSIFYING MAMMALS {class Mammalia) INTO ORDERS Ai Imperfect Mammals, young hatched or pre- maturely born Bi Jaws a birdlike beak, egg-laying Be Jaws not beaklike, young carried in pouch A2 Perfect Mammals, young not hatched, nor prematurely born 'Cj Front part of both jaws lack teeth Co Teeth with sharp points for piercing shells of insects C3 Canines very long, molars suited for tearing C^ Canines lacking, incisors very large Bi Digits •with claws B2 Digits not distinct B3 Digits with nails or hoofs C^ Head large ; carnivorous Co Head small ; herbivorous C^ Five toes, nose prolonged into a snout C, Toes odd number, less than five C3 Toes even number, upper front teeth lacking, chew the cud C4 Toes even number, upper front teeth present, not cud-chewers C. All limbs having hands Ck Two limbs having: hands Orders Mon'otremes Marsu' pials Eden'tates Insect' Ivors Car'nivors Rodents Ceta'ceans Sire'neans Proboscid' eans E'quines Ru'jiilnants Swine Quad'rumans Bi'mans Exercise in Classification. — Copy the following list, and by refer- ence to figures write the name of its order after each mammal : — Ape (Figs. 405, 406) Cow (Figs. 344, 386) Antelope (Fig. 391) Walrus (Fig. 340) Monkey (Figs. 352, 401) Horse (Figs. 355, 395) Ant-eater (Figs. 354, 364) Rabbit (Fig. 345) Dog (Figs. 356, 408) Hog (Figs. 357, 393) Bat (Figs. 347, 370) Cat (Figs. 337, 348) Armadillo (Figs. 349, 365) Mole (Figs. 367, 368) Beaver (Figs. 372, 373) Duckbill (Fig. 359) Tapir (Fig. 384) Dolphin (379, 397) L^se chart of skulls and Figs. 381, 382, 395-400 in working out this exercise. o (194) Chart of Mammalian Skulls (Illustrated Study) Man's dental formula is (•" In like manner fill out formulas below Cow (M—C—/—)^=32 Rabbit (.1/— C— /-)2 = 28 Walrus (.1/— C — /— )- = 34 Bat (.1/— C- /— )2 = 34 Cat (.U— €—/—)-= 30 Armadillo (.1/— C—/—)^= 28 Horse (M— C— I—)- = 40 32. Whale (M—C—/—)^= o Am. Monkey. . . (.1/— C— /— )2 = 36 Sloth (.1/— C— /— )2 = 18 Ant-eaier (.'/— C — /— )2 = o Dog (.1/— C— /— )2 = 42 Hog (.l/-C-/-)2 = 44 Sheep (M— C-/— )2=32 Fig. 345. — Rabbit. A, B, incisors; C, molars. Fig. 348. — Cat. Chart of Mammalian Skulls (195) Fig. 349. — Armadillo. Fig. 354. — Ant-eater (Fig. 364). Fig. 353. — Sloth (Fig. 363) Fig. 358. — Sheep. 196 ANIMAL BIOLOGY The lowest order of mammals contains only two species, the duckbill anti the ]ioicui)ine ant-eater, both living in the Australian re- gion. Do you judge that the duckbill of Tasmania (Fig. 359) lives chiefly in water or on land } Fn.. 3sg. — DvCKKU.\. (Orni/AorAv»cAus/>aradoxus). ■^yj^y p j,, Jt prob- ably active or slow in movement? It dabbles in mud and slime for worms and mussels, etc. How is it fitted for doing this .'' Which feet are markedly webbed ? How far does the web extend ? The web can be folded back when not in use. It lays two eggs in a nest of grass at the end of a » burrow. Trace re- semblances and dif- ferences between this animal and birds. The porcupine ant- cater has numerous quill-like spines (Fig. 360) interspersed with its hairs. (Use?) De- scribe its claws. It has a long prehensile tongue. It rolls into a ball when attacked. Compare its jaws with a bird's bill. It lays one egg, which is carried Fir,. 360. — SriNY Ant-eater (Echidna acu- leata). View of under surface to show pouch. (After Haacke.) MAMMALS 197 in a fold of the skin until hatched. Since it is pouched it could be classed with the pouched mammals (next order), but it is • egg-laying. Suppose the two animals in this order did not nourish their young with milk after hatching, would they most resemble mammals, birds, or reptiles } Write the nanie of this order. (See Table, p. 193.) WJiy do you place them in this order ( ).'* See p. 193.) The name of the order comes from two Greek Fig. 361. — Opossum {Didelphys Virginianus). words meaning "one opening," because the ducts from the bladder and ^g^ glands unite with the large intestine and form a cloaca. What other classes of vertebrates are similar in this .'' Pouched Mammals. — These animals, like the last, are numerous in the AustraHan region, but are also found in South America, thus indicating that a bridge of land once connected the two regions. The opossinn is the only species which has penetrated to North America (Fig. 361). Are its jaws slender or short .'* What kinship is thus sug- gested } As shown by its grinning, its lips are not well de- 198 ANIMAL BIOLOGY veloped. Docs this mean a low or a well-developed mam- mal ? Where does it have a thumb? (Fig. 361.) Does the thumb have a nail ? Is the tail hairy or bare ? Why ? Do you think it prefers the ground or the trees ? State two reasons for your answer. It hides in a cave or bank or hollow tree all day, and seeks food at night. Can it run fast on the ground .-' It feigns death when captured, . . ■ , . , .. and watches for a chance for stealthy escape. The kangaroo (Fig. 362), like the opossum, gives birth to imperfectly developed young. ( Kinship with what classes is thus in- dicated .?) After birth, the young ( about three fourths of an inch long) are carried in a ventral pouch and suckled for seven or eight months. They begin to reach down and nibble grass before leaving the pouch. Compare fore legs with hind legs, front half of body with last half. Describe tail. What is it used for when kangaroo is at rest } In jump- ing, would it be useful for propelling and also for balanc- ing the body .'' Describe hind and fore feet. Order Why? See key, page 193. Imperfectly Toothed Mammals. — These animals live chiefiy in South America (sloth, armadillo, giant ant-eater) and Africa (pangolin). The sloth (Fig. 363) eats leaves. Its movements are remarkably slow, and a vegetable growth ' ^ &>l/V>Mi;^»r;>''*^— ■ Fig. 362. — Giant Kangaroo. MAMMALS 199 Fig. 363. — Sloth of South Amtrrica. resembling moss often gives its hair a green color. (What advantage ?) How many toes has it ? How are its nails suited to its man- ner of living ? Does it save exertion by hanging from the branches of trees instead of walking upon them ? Judging from the figures (363, 364, 365), are the mem- bers of this order better suited for at- tack, active resistance, passive resistance, or concealment when contend- ing with other animals ? The ant-eater's claws (Fig. 364) on the fore feet seem to be a hin- drance in walk- ing ; for what are they useful ? Why are its jaws so slender? What is prob- ably the use of the enormous bushy tail ? The nine-banded armadillo (Fig. 365) lives in Mexico and Texas. It is omnivorous. To escape its enemies, it burrows into Fig. 364. — Giant Ant-eater of South America. (See Fig. 354.) Find evidences that the edentates are a degenerate order. Describe another ant-eater (Fig. 360). 2CX5 AXIMAL BIOLOGY the ground with surprising; rajiidity. If unable to escape when pursued, its hard, stout tail and head arc turned under to protect ^'"^"""^^(^^X^ -.^ the lower side of the body where there are no scales. • ,. The three-banded species (Fig. 366) lives in Argentina. Compare the ears and tail of the two species ; give rea- sons for differences. Why are the eyes so small? The claws so large .'* Order Why? .:^,„^i^^^dSiSl^^^- ■^s^ Fio. 365. — NiNE-K.\NnEn Armadillo of Texas and .Mexico. (Dasypus noz'cmcinctus.) It is increas- ing in numbers; it is very useful, as it digs up and destroys insects. (See Fig. 347.) Fig. 366. — THREE-RANnF.n Armadillo (Tolypeutcs trUinctus). Insect Eaters. — The soft interior and crusty covering of insects makes it unnecessary for animals that prey upon them to have flat-topped teeth for grinding them to MAMMALS 20 1 powder, or long cusps for tearing them to pieces. The teeth of insect eaters, even the molars (Fig. 368), have many sharp tubercles, or points, for holding insects and piercing the crusty outer skeleton and reducing it to bits. As most insects dig in the ground or fly in the air, we are not surprised to learn that some insect-eating mam- FiG. 367. — The Mole. mals (the bats) fly and others (the moles) burrow. Are the members of this order friends or competitors of man .'' Fig. 368. — Skeleton of Mole. (Shoulder blade is turned upward.) Why does t/ic mole have very small eyes .'* Small ears .-• Compare the shape of the body of a mole and a rat. What difference .'' Why .-' Compare the front and the hind legs of a mole. Why are the hind legs so small and weak .■* Bearing in mind that the body must be arranged for digging and using narrow tunnels, study the skeleton 202 AXIMAL BIOLOGY (Fig. 368) in respect to the following: Bones of arm (length and shape), fingers, claws, shoulder bones, breast- bone (why with ridge like a bird ?), vertebra" (why are the first two so large?), skull (shape). There are no eye sockets, but there is a snout gristle ; for the long, sensitive snout must serve in place of the small and almost useless eves hidden deep in the fur. Is the fur sleek or rough ? \\ hy ? Close or thin ? It serves to keej) the mole clean. The muscles of neck, breast, and shoulders are very strong. Why .-' The mole eats earthworms as well as insects. It injures plants by breaking and drying out their roots. Ex])crinicnts show that the Western mole will eat moist grain, though it prefers insects. If a mole is caught, repeat the experiment, making a careful record of the food placed within its reach. d. c u r '1' d Fig. 369. — Skeleton of Bat. As with the mole, the skeletal adaptations of tlie bat are most remarkable in the hand. How many fingers .-' (Fig, 369.) How many nails on the hand.'* Use of nail when at rest .^ When creeping.-' (Fig. 369.) In- stead of feathers, the flying organs are made of a pair of extended folds of the skin supported by elongated bones, which form a framework like the ribs of an um- brella or a fan. How many digits are prolonged } Does MAMMALS 203 Fig. 370. — X'amI'IRE (P/!y//ostoiiia spectrum) ot South America. X \. the fold of the skin extend to the hind legs ? The tail ? Are the finger bones or the palm bones more prolonged to form the wing skeleton ? The skin of the wing is rich in blood vessels and nerves, and serves, by its sensitiveness to the slightest current of air, to guide the bat in the thickest darkness. Would you judge that the bat has sharp sight ? Acute hearing? The moles do not Jiibcrnate ; the bats do. Give the reason for the difference. If bats are aroused out of a trance-like condition in winter, they may die of starvation. Why .? The mother bat carries the young about with her, since, unlike birds, she has no nest. How are the young nourished } Order Why ? (Key, p. 193.) The Gnawing Mammals. — These animals form the most numerous order of mammals. They lack canine teeth. In- ference } The incisors are four in number in all species 204 AMMAL BIOLOGY except the rabbits, which h:ive six (see Fig. 345). They are readily recognized by their large incisors. These teeth grow throughout Hfe, cwid if they are not constantly worn Fig. 371. — PorCHED (iorHER {deomys bursarius) X {, a large, burrowing field lat, with cheek pouches for carrying grain. away by gnawing upon hard food, they become incon- veniently long, and may prevent closing of the mouth and cause starvation. The hard enamel is all on the front sur- face, the dentine in the rear being softer ; hence the in- cisors sharpen themselves by use to a chisel-like edge. .^t«?:'-^?5^^??^'" Fig. 372. — Hind toot a, lore looi b, tail c, of Beaver. Fig. 373. — Beaver. The molars are set close together and have their upper surfaces level with each other. The ridges on them run crosswise so as to form a continuous filelike surface for MAMMALS 205 reducing the food still finer after it has been gnawed off (Fig. 345). The lower jaw fits into grooves in place of sockets. This allows the jaw to work back and forth in- stead of sidewise. The rabbits and some squirrels have a hare lip ; i.e. the upper lip is split. What advantage is this in eating .? In England the species that burrow are called rabbits ; those that do not are called hares. Name six enemies of rabbits. Why does a rabbit usually sit motionless unless approached very close .-* Do you usually see one before it dashes off.-* A rabbit has from three to five litters of from three to six young each year. Squirrels have fewer and smaller litters. Why must the rabbit multiply more rapidly than the squirrel in order to survive .'' English rabbits have increased in Australia until they are a plague. Sheep raising is inter- fered with by the loss of grass. The Austrahans now ship them to England in cold storage for food. Rabbits and most rodents lead a watchful, timid, and alert life. An exception is the porcupine, which, because of the defense of its barbed quills, is dull and sluggish. The common rodents are : — Fig. 374. - Position of Limbs IN Rabbit. pouched gopher prairie dog prairie squirrel chipmunk ground hog field mouse squirrels beavers rabbits muskrats rats porcupines mice guinea pig Which of the above rodents are commercially important } Which are injurious to an important degree ? Which have long tails.? Why .'^ Short tails.' Why.' Long ears .' Why.' 206 ANIMAL BIOLOGY Short oars ? Whv ? Which are aquatic ? Which dig or bur- row ? Which arc largely nocturnal in habits? Which are arboreal ? Which are protected by coloration ? Which escape by running ? By seeking holes ? Economic Importance. — Rabbits and squirrels destroy the eggs and young of birds. Are rabbits useful } Do they destroy useful food .-* The use of beaver and muskrat skins as furs will probably soon lead to their extinction. Millions of rabbits' skins are used annually, the hair being made into Fi*"'- 375- — Flying Sqimrrei. {I'u-romys volucella). felt hats. There are also millions of squirrel skins used in the fur trade. The hairs of the tail are made into fine paint brushes. The skins of common rats are used for the thumbs of kid gloves. Order .. Why? Elephants. — Elephants, strange to say, have several noteworthy resemblances to rodents. Like them, elephants have no canine teeth ; their molar teeth are few, and marked by transverse ridges and the incisors present are promi- nently developed (Figs. 376, 377). Instead of four inci.sors, however, they have only two, the enormous tusks, for there are no incisors in the lower jaw. Elephants and rodents MAMMALS 207 Fig. 376. — Head of African Elephant. both subsist upon plant food. Both have peaceful disposi- tions, but one order has found safety and ability to survive by attaining enormous size and strength ; the other {e.g. rats, squirrels) has found safety in small size. Explain. Suppose you were to observe an elephant for the first time, with- out knowing any of its habits. How would you know that it does not eat meat .-' That it does eat plant food .■' That it can defend it- self .'* Why would you make the mistake of thinking that it is very clumsy and stupid '^ Why is its skin naked .-* Thick .? Why must its legs be so straight .-* Why must it have either a very long neck or a substitute for one .-' (Fig. 376.) Are the eyes large or small .-^ The ears.-* The brain cavity .'' What anatomical feature correlates with the long proboscis.'' Is the proboscis a new organ not found in other animals, or is it a specialization of one or more old ones } Reasons .-' What senses are especially active in the proboscis } How is it used in drinking .'' In grasping .■' What evidence that it is a development of the nose .'' The upper lip .-' The tusks are of use in up- rooting trees for their foliage and in digging soft roots for food. Can the elephant graze .'' Why, or why not .'' There is a iinger-like projection on the end of the snout which is useful in delicate manipulations. The feet have pads to prevent jarring ; the nails are short and hardly touch the ground. Order Why? Key, page 193. Fig. 377. — Molar Tooth of African Elephant. 208 AX IMA I. BIOLOGY Whales, Porpoises, Dolphins. — As the absurd mistake is sometimes maile of contusini;- loJiales with fish, the pupil may compare them in the following respects : eggs, nour- ishment of young, fins, skin, eyes, size, breathing, tem- perature, skeleton (Figs. 209, 379, and 397). hit.. 37a. — H.\Kl'(j(j.M.N<; (iKKENLANU W'HAl.t; (see Fig. 351). Porpoises and dolphins, which are smaller species of whales, live near the shore and eat fish. Explain the ex- pression " blow like a porpoise." They do not exceed five or eight feet in length, while the deep-sea whales are from thirty to seventy-five feet in length, being by far the largest animals in the world. The size of the elephant is limited by the weight that the bones and muscles support and move. The whale's size is not so limited. The whale bears one young (rarely twins) at a time. The mother carefully attends the young for a long time. The blubber, or thick layer of fat beneath the skin, serves to retain heat and keep the body up to the usual tempera- ture of mammals in spite of the cold water. It also serves, along with the ivivicnse hings, to give lightness to the body. MAMMALS 209 Why does a whale need large lungs ' The tail of a whale is horizontal instead of vertical, that it may- steer upward rapidly from the depths when needing to breathe. ~ The teeth of some FIG. 379. -DOLPHIN. whales do not cut the gum, but are reabsorbed and are replaced by horny plates of "whalebone," which act as strainers. Give evidence, from the flippers, lungs, and other organs, that the whale is descended from a land mammal (Fig. 397). Compare the whale with a typical land mammal, as the dog, and enumerate the specializations of the whale for living in water. What change took place in the general form of the body .'' It is believed that on account of scarcity of food the land ancestors of the whale, hundreds of thousands of years ago, took to living upon fish, etc., and, gradually be- coming swimmers and divers, lost the power of locomotion on land. Order Why ? Elephants are rapidly becoming extinct because of the value of their ivory tusks. Whales also furnish valua- ble products, but they will probably exist much longer. Why.? The manatees and dugongs (sea cows) are a closely re- lated order living upon water plants, and hence living close to shore and in the mouths of rivers. Order Why ? Fig. 380. — Manatee, or sea cow ; it lives near the shore and eats seaweed. (Florida to Brazil.) 2IO ANIMAL BIOLOGY Hoofed Mammals. — All the animals in this order walk on the tips of their toes, which have been adapted to this use by the claws having developed into hoofs. The order is subdivided into the odd-toed (such as the horse with one toe and the rhinoceros with three) and the cvcn-tocd (as the ox with two toes and the pig with four). All the even- toed forms except the pig and hippopotamus chew the cud and are given the name of ruminants. Horse and Man Compared (Figs. 381, 399). — To which finger and toe on man's hand and foot does the toe of a horse's foot correspond ? Has the horse kneecaps .-' Is its heel bone large or small .' Is the fetlock on toe, instep, or ankle ? Does the part of a horse's hind leg that is most elon- gated correspond to the thigh, calf, or foot in man } On the fore leg, is the elongated part the upper arm, forearm, or hand } Does the most elongated part of the fore foot correspond to the finger, palm, or wrist '^. On the hind foot is it toe, instep, or ankle } Is the fetlock at the toe, instep, or heel .-• (Fig. 385.) Is the hock at the toe, in- step, heel, or knee t Order Why ? Specializations of the Mammals. — The early mammals, of which the present marsupials are believed to be typical, had five toes provided with claws. They were not very rapid in motion nor dangerous in fight, and probably ate both animal and vegetable food. '^M^ FlC 381. — Left leg of man, left hind leg of dog and horse ; homologous parts lettered alike. MAMMALS 211 Fig. 382. — Skeletons of Feet of Mammals. /", horse; 77, dolphin: £■, elephant; ^.monkey; T, tiger; (?, aurochs; iliohippus F, sloth ; M, mole. Question: Explain how each is adapted to its specialized function. According to the usual rule, they tended to increase faster than the food supply, and there were continual contests for food. Those whose claws and teeth were sharper drove the others from the food, or preyed upon them. Thus the specialization into the bold flesh eating beasts of prey and the timid vegetable feeders began. Which of the flesh eaters has already been stud- ied at length .' The insectivora escaped their enemies and found food by learning to burrow or fly. The rodents accomplished the same result either by acquiring great agility in climbing, or by living in holes, or by running. The proboscidians acquired enormous size and strength. The hoofed animals found safety in flight. Orohppus. Fig. 383.— Feet of Ihe ancestors of the horse. 212 ANIMAL BIOLOGY ($'cW'^'^^'^ Fig. 384. — Tapir ok south America ( Tapirm; americanui). x ^. Questions: How does it resemble an elephant? (Fig. 376.) A horse ? (p. 210.) Ungulates, as the horse, need no other protection than their great speed, which is due to lengthening the bones of the legs and rising upon the very tip of the largest toe, which, to support the weight, developed an enor- mous toe-nail called a hoof. The cattle, not having developed such speed as the horse, usually have horns for defense. If a calf or cow bellows with distress, all the cattle in the neigh- borhood rush to the rescue. This unselfish instinct to help others was an aid to the survival of wild cattle living in regions infested with beasts of prey. Which of ^sop's fables is based upon this instinct .'' The habit of rapid grazing and the correlated habit of chewing the cud were also of great value, as it enabled cattle to obtain grass hur- FlG. 385. — Horse, descended from a small wild species still found in Western Asia. MAMMALS 213 Fig. 386. — Skeleton of Cow. Compare with horse (Fig. 395) as to legs, toes, tail, mane, dewlap, ears, body. riedly and retire to a safe place to chew it. Rudiments of the upper incisors are present in the jaw of the calf, show- ing the descent from animals which had a complete set of teeth. The rudiments are absorbed and the upper jaw of the cow lacks incisors entirely, as they would be useless because of the cow's habit of seizing the grass with her rough tongue and cutting it with the lower incisors as the head is jerked forward. This is a more rapid way of eating than by biting. Which leaves the grass shorter after grazing, a cow or a horse .'' Why } Grass is very .slow of digestion, and the ungulates have an alimentary canal twenty to thirty times the length of the body. Thorough chewing is necessary for such coarse food, and the ungulates which chew the cud (ruminants) are able, by leisurely and thorough chewing, to make the best use of the woody fiber (cellulose) which is the chief substance in their food. Ruminants have four divisions to the stomach. Their food is first swallowed into the roomy paunch in which, as in the crop of a bird, the bulky food is temporarily stored. It is not digested at all in the paunch, but after being moistened, portions of it pass successively into the honeycomb, which forms it into balls to be belched up and ground by the large molars as the animal lies with eyes half closed under the shade of a tree. It is then swal- 214 AXIMAI. BIOLOGY lowed a second time and is acted upon in the third divi- sion (or miDiypliis) and the fourth division (or ;vv,/ ). Next Fig. 387. — Food tiaced through stomachs of cow. (Follow arrows.) Fig. 3S8. — Section of cow's stomachs. Identify each. (See text.) it passes into the intestine. Why is the paunch the largest compartment.-' In the figure do you recognize the paunch by its size .'* The honeycomb by its lining } Why is it round .-' The last two of the four divisions may be known by their direct connection with the intestine. The true gastric juice ... _ is secreted only in the \ ' *^ ' fourth stomach. Since * -i. {. % the cud or unchewed food is belched up in balls from the round " honeycomb," and since a ball of hair is some- times found in the stom- ach of ruminants, some ignorant people make the absurd mistake of calling the ball of hair the cud. This ball accumulates in the paunch F;g. 389. — Ok API. This will probably prove to be the last large mammal to be discovered by civilized man. It was found in the for- ests of the Kongo in 1900. Questions: It shows affinities (find them) with girafle, deer, and zebra. It is a ruminant ungulate (explain meaning — see text). MAMMALS 215 because of the friendly custom cows have of combing each other's hair with their rough tongues, the hair sometimes Fig. 390. — Africa'N CAUEh (Camehes dromedarius). being swallowed. Explain the saying that if a cow stops chewing the cud she will die. Does a cow's lower jaw move sidewise or back and forth ? Do the ridges on the molars run sidewise or lengthwise? Is a cow's horn hollow .-" Does it have a bony core .-* (Fig. 344.) The permanent hol- low horns of the cow and the solid decidu- ous horns of the deer are typical of the two kinds of horns pos- sessed by ruminants. The prong-horned an- FiG. 391. — Prong-horned Antelope telope (Fig. 390 ^^ {Antelocarpa Atnericana) . Western States. 2l6 AMMAL BIOLOGY the United States, however, is an intermediate form, as its horns are hollow, but are shed each year. The hollow horns are a modification of hair. Do solid or hollow bones branch ? Which arc possessed by both sexes } Which are pointed } Which are better suited for fight- ing .'' Why would the deer have less need to fight than the cattle .'' Deer are polygamous, and the males use their Fig. 392. — Rocky Mountain ^wv.y.v {O-ois montana) . x^. horns mostly for fighting each other. The sharp hoofs of deer are also dangerous weapons. The white-tail deer (probably the same species as the Virginian red deer) is the most widely distributed of the American deer. It keeps to the lowlands, while the black-tailed deer prefers a hilly country. The moose, like the deer, browses on twigs and leaves. The elk, like cattle, eats grass. The native sheep of America is the big horn, or Rocky Mountain sheep (Fig. 392). The belief is false that they MAMMALS 217 alight upon their horns when jumping down precipices. They post sentinels and are very wary. There is also a native goat, a white species, living high on the Rocky Mountains near the snow. They are rather stupid ani- mals. The bison once roamed in herds of countless thou- sands, but, with the exception of a few protected in parks, it is now extinct. Its shaggy hide was useful to man in winter, so it has been well-nigh destroyed. For gain man is led to exterminate elephants, seals, rodents, armadillos, whales, birds, deer, mussels, lobsters, forests, etc. 'J^/y^/^y/ Fig. 393. — Peccary {Dkotyles torquatus) of Texas and Mexico. X jV Our only native hog is the peccary, found in Texas (Fig. 393). In contrast with the heavy domestic hog, it is slender and active. It is fearless, and its great tusks are dangerous weapons. The swine are the only ungulates that are not strictly vegetable feeders. The habit of fat- tening in summer was useful to wild hogs, since snow hid most of their food in winter. The habit has been pre- served under domestication. Are the small toes of the hog useless.'' Are the "dew claws" of cattle useless.'' Will they probably become larger or smaller .'' Order f 2l8 Illustrated Study Illustrated Study 219 Fig. 400. — Chimpanzee. (See Fig. 406.) Illustrated Study of Vertebrate Skeletons : Taking man's skeleton as complete, which of these seven skeletons is most incomplete ? Regarding the fish skeleton as the original verte- brate skeleton, how has it been modified for (r) walking, (2) walking on two legs, (3) flying? Which skeleton is probably a degenerate reversion to original type ? (p. 209.) How is the horse specialized for speed ? Do all have tail vertebras, or vertebrae beyond ► the hip bones ? Does each have shoulder blades ? Compare (i) fore limbs, (2) hind limbs, (3) jaws of the seven skeletons. Which has relatively the Fig. 3QQ. M.-xN. shortest jaws? Why? What seems to be the typical number of ribs ? limbs ? digits ? Does flipper of a dolphin have same bones as arm of a man ? How many thumbs has chimpanzee ? Which is more specialized, the foot of a man or a chimpanzee ? Is the foot of a man or a chiinpanzee better suited for supporting weight ? How does its construction fit it for this ? Which has a better hand, a man or a chimpanzee ? What is the difference in their arms ? Does difference in structure correspond to difference in use ? Which of the seven skeletons bears the most complex breastbone ? Which skeleton bears no neck (or cervical) vertebras ? Which bears only one 7 Are all the classes of vertebrates represented in this chart ? (p. 125.) 220 ANIMAL BIOLOGY Fig. 401. — Sacred Mo.nkkv ok India i^Semnopuhecus entellui). x ,^. Monkeys, Apes, and Man. — Study the figures (399, 400); compare apes and man and ex- plain each of the differences in the following list : ( i ) feet, three differences; (2) arms; (3) brain case; (4) jaws; (5) canine teeth; (6) backbone; (7) dis- tance between the eyes. A hand, unUke a foot, has one of the digits, called a thumb, placed opposite the other four digits that it may be used in grasping. Two-handed man and four-handed apes and 'c;^^'' monkeys are usually placed in fig. 402.-LEMrR (/,.^«r^c,«- ■' ^ ' goz) . X I's- Which digit bears a one order, the Priviatcs, or claw? MAMMALS 221 in two orders (see table, page 193). The lowest members of this order are the lemurs of the old world. Because of V, I / /;/;';!• Fig. 403. — Broad-nosed Monkey, x A- America. Fig. 404. — Narrow-nosed Monkey, x 12. Old World. their hands and feet being true grasping organs, they are placed among the primates, notwithstanding the long muzzle and expres- sionless, foxlike face. (Fig. 402.) Next in order are the tailed monkeys, while the tailless apes are the highest next to man. The primates of the New World are all monkeys with long tails and broad noses. They are found from Paraguay to Mexico. The monkeys and apes of the Old World hsive a t/iin partition be- tween the nostrils, and are thus distin- guished from the Fig. 405. — gorilla ANIMAL BIOLOGY monkeys of the New World, which have a tJiickcr par- tition and have a broader nose. (Figs. 403, 404.) The monkeys of America all have six molar teeth in each half jaw (Fig. 352); the monkeys and apes of the Old World have thirty-two teeth which agree both in number and arrangement with those of man. Which of the primates figured in this book appear to have the arm longer than the leg .'* Which have the eyes directed forward instead of sideways, as with cats or dogs .-* Nearly all the primates are fo)'est diuellers,2ind inhabit warm countries, where the boughs of trees are never covered with ice or snow. Their ability in climb- ing serves greatly to protect them from beasts of prey. Many apes and monkeys are able to assume the upright posi- FiG. 406. -CHIMPANZEE. ^^0^ ^^ Walking, but thcy touch the ground with their knuckles every few steps to aid in preserving the balance. The Simians are the highest family of primates below man, and include the gorilla, chimpanzee, orang, and gib- bon. Some of the simians weave together branches in the treetops to form a rude nest, and all are very affectionate and devoted to their young. How are apes most readily distinguished from monkeys? (Figs. 401, 406.) The study of man as related to his environment will be taken up in detail in the part called Human Biology. We will there examine the effect upon man's body of the rapid changes since emerging from savagery that he has made in food eaten, air breathed, clothing, and habits of life. MAMMALS 223 Fig. 407. — Anatomy OF Rabbit. fl, incisor teeth; rudimentary b, b' , 3", salivary vermiform ap- glands: pendix in man); k, larynx; m, carotid arte- i, windpipe; ries: c, gullet; «. heart; d, diaphragm «), aorta ; (possessed only /, lungs; by mammals) ; g, end of sternum ; r, spleen; i, kidney; t, ureters (from kidney to blad- der v) . 2 brain of rabbit: a, olfactory nerves; e, stomach; g, small intestine; h, h' , large intes- tine; /, junction of small and large intes- tine; g, g' , caecum, or blind sac fromy b, cerebrum: (corresponds to c, midbrain; the shrunken d, cerebellum Table for Review Fish Frog Turtle Bird Cat Horse Man Names of limbs Acutest sense Digits on fore and hind limb Locomotion Kind of food Care of young St. Bernard Eskimo Poodle Dachshund German mastiff English bloodhound Pointer Newfoundland BuHdog Shepherd Greyhound Spitz Fig. 408. — Artificial Selection. Its effects in causing varieties in one species. Which of the dogs is specialized for speed ? Driving cattle ? Stopping cattle ? Trailing by scent ? Finding game ? Drawing vehicles ? Going into holes ? House pet ? Cold weather ? In Mexico there is a hairless dog specialized for hot climates. The widely differing environments under various forms of domestica- tion cause " sports " which breeders are quick to take advantage of when wishing to develop new varieties. Professor De Vries by cultivating American evening primroses in Europe has shown that a sudden change of environment may cause not only varieties but new species to arise. 224 HUMAN BIOLOGY CHAPTER I -^s_2 INTRODUCTION To which branch of animals does man belong ? To which class and order in that branch ? (Animal Biology, pages 125, 193.) There is no other animal species in the same genus or oj'der with man. This shows a wide physi- cal difference be- tween man and V^-'-' ^ ^ l^ other animals, but man's mind iso- lates him among the other animals still more. The human species is divided into five varieties or races: i. Cau- casian ( Fig. I ). Skin fair, hair wavy, eyes oval. (Europe except Finns and Lapps, Western Asia, America.) 2. Mongolian. Skin yellow, hair straight and black, face flat, nose blunt, almond eyes. (Central Asia, China, Japan, Lapps and Finns of Europe, Eskimos of North America.) 3. Americatis. Skin copper red, hair straight, nose straight or arched. (North and South America.) 4. Malay. Skin brown, face flat, hair black. (Australia and Islands of Pacific.) 5. Ethi- B I Fig. I.— Facial Angles of Caucasian (nearly 90°) and Ethiopian (about 70°). The angle between lines crossing at front of upper jaw near base of nose, one line drawn from most prominent part of forehead, the other through hole of ear. 2 HUMAN BIOLOGY opian (Fig. i ). Skin dark, hair woolly, nose broad, lips thick, jaws and teeth prominent, forehead retreating, great toe shorter than next toe and separate. (Africa, America.) There is a strugi:;lc between the races for the possession of different lands. The Caucasian is gaining in Australia. Africa, and America. With difficulty the Mongolians are kept from the western shores of America. The Ethiopian in America shows a lessened rate of increase every decade ; this may be due to the tendency of the race to crowd into cities and the strain of suddenly changing from jungle life in less than two centuries. Cn'tlization is a strain upon any race. It is destroying the American Indian. The Mongolian and Caucasian survive civiliza- tion best, but insanity is increasing rapidly among the latter. Fk;. 2. — Indian Weapons: Lance and Arrow Heads. From a bank of mussel shells (remains of savage feast) at Keyport, N.J. Man's Original Environment. — Primitive man lived without the use of (ire or weapons other tlian sticks or stones. His first home was in the tropics, where his needs were readily supplied, and probably in Asia. Many nations have a tradition of a home in a garden (Greek, paradises). His food was chiefly tree frjtits and nuts. When because of crowding he left nature's garden, he acquired skill in hunting and fishing and the use of fire that flesh might sup- plement the meager fruits of colder climates. His weapons were of rough (chipped) stone at first — /;/ the old stone age. In this age the mammoth lived. He learned to polish implements in the new stone age. The Indians were in that stage when Columbus came to America (Figs. 2. 3). The cultivation of grain and the domestication of animals probably began in this age. The bronze and iron ages followed the stone age. Fig. 3. Indian Idmahawk. Stone. Keyport, N.J. Polished INTRODUCTION The Reaction between Man and his Environment. — The estimates by various geologists of the time man has existed as a species vary from 20,000 to 200,000 years. The active life out of doors whjch man led for ages (Fig. 4) has thoroughly adapted his body only for such a life. Now steam and other forces work for him, and his muscles dwindle ; his lungs are seldom fully expanded, and the unused portions become unsound ; he lives in tight houses, and the impure air makes his blood impure and his skin delicate ; he eats soft concentrated food, and his teeth decay and his too roomy food tube becomes sluggish. His nerves and brain are fully active and they become unsound from overwork and impure blood. ^ Fig. 4. — Primitive Man, showing clothing and weapons of chase and war. Degeneration of Unused Parts. — Several facts just stated illustrate the biological law that disuse causes degeneration. Man's Modification of his Environment. — The energy of the world, whether of coal, waterfall, oil, forest, or rich soil, has the sun as its source. All of these are being destroyed by man, often with recklessness and wantonness. The promised land which " flowed with milk and honey "is now almost a desert. Other examples are Italy, Carthage, Spain. The destruction of forests causes floods which wash away the soil. // is estimated that there are only one fourth as many song birds in the United States as there were fifteen years ago. Insects and weeds or deserts replace rich soil, noble quadrupeds, singing birds, and stately trees. Many farmers, however, preserve the fertility of the soil. To the erect posture is due man's free use of his hands and the cooperation of hands and senses. This has given man his intellectual 1 It has been prophesied that the future man will be a brownie-like crea- ture with near-sighted eyes, shrunken body, slim little legs and arms, large hairless head, toothless gums, a stomach using only predigested food, muscles suited only to push an electric button or pull a lever, and mind very active. But this disregards the indispensable need of a sound mind for a sound body. There cannot even be a play of emotion without a change in the circulation. 4 HCAfAN BIOLOGY development. The erect position has given greater freedom to the chest. Matt uses feuier origans of locomotion than any other animal. The opossum has two hands, but they are on the hind limbs. The ape has four hands, but must use them all in locomotion. (What is a hand ?) The erect ijosilion, however, makes spinal deformity easier to acquire, and the whole weight being upon one hip at each step man is liable to hip-joint diseases. In the horizontal trunk the organs lie one behind another; in man they lie one upon another., and are more liable to cro7Li(iing and displacement. The prone position in sickness heljjs to restore them. Large blood vessels at neck, armpits, and groins, which occupy protected positions in quadrupeds, are held to the front and exposed to danger. The open end of the vermiform appendix and of the windpipe are upward in the erect trunk of man. Valves are lacking in some vertical veins and present where little needed in hori- zontal veins. But iht freedom of the hands more than makes up for ail the disadvantages of erectness. The Survival of the Fittest. — Those who do not work degenerate. Those who overwork, or work with only a few organs, as the brain and nerves, degenerate. The workers survive and increase in numbers, the idle perish and lea^'e few descendants. What rate of adjustment to new environment is possi- ble for man.'' This has not been ascertained; it is prob- ably iniic/i slower than has been generally intagitted. The natives of Tasmania, New Zealand, and many of the Pacific Islands became extinct in less than a century after adopting clothing and copying other habits from Euro- peans. Life in the country in civilized lands differs less from the environment of primitive man than does life in cities. Cities have been likened to the lion's cave in the fable, to which many tracks led, but from which none led. The care of health in cities is now making rapid strides along the biological basis of purer air, more open space, less noise, simple food, and pure water. Biology, by supplying as a standard the conditions which molded man's body for ages, furnishes a simple and sure basis for hygiene. To mention one instance among many, man blundered for centuries in attempting the cure of consumption, and well- INTRODUCTION nigh gave up in despair. Yet it has recently been shown that if the sufferer returns only in a measure to the open- air habits of his remote ancestors, tuberculosis is one of the most preventable of diseases. The biological guide to health is surer and simpler than tinkering with drugs, fuss- ing with dietetics, and avoiding exposure. Man is of all animals least thoroughly adjusted to his environment, be- cause of his continual and rapid progress. Disease may be defined as the process by which the body adapts, or at- tempts to adapt, itself to so sudden a change of environ- ment that some organ has failed to work in harmony with the others. By disease the body comes into adjustment with the new condition, or attempts to do so. Protoplasm. — The life and growth of man's body, as the life and growth of all animals and plants, depend upon the activity of the living substance called proto- plasm, as manifested in "minute bodies called cells. In fact, protoplasm can- not exist outside of cells. The cells of the human body and their relation to the body as a whole will next be considered. Fig. 5. — An Ameba, highly magnified. nu, nucleus; psd, false foot. The Ameba. — Of all the animal kingdom, the minute creatures that can be seen only with a microscope are most different from man. One of the most interesting of these is the a-me'ba (Fig. 5 ; spelled also amceba, see Animal Biology, Chap. II). A thousand of them placed in a row would hardly reach an inch. Some may doubt whether the ameba is a complete animal. Study the figures of it, and no head, or arms, or legs, or mouth can be found. It appears, when, still, to be merely a lump of jelly. But the ameba can piish out any part of its body as a foot, and move slowly by rolling its body into the HUMAN BIOLOGY Fig. 6. -A White Blood Cell, magnified; forms noticed at intervals of one minute. foot. // can put out any part of its body as an arm, and take rn a speck of food ; or. if the food happens to be near, the ameba can make a mouth in any part of its body, and swallow the food l)y closing around it (Animal Hioloj^y, Fig. 12). The aineba lias no lungs, but brcallws ivitli all the surface of its body. Any ])art of its body can do anything that another part can do. When the ameba grows to a certain size, Lt multiplies by squeezing together near the middle (Animal Biology, Fig. 13) and dividing into two parts. Amebas have not been observed to die of old ai^t- ; starvation and accident aside, they are immortal. The Ameba and Man Compared. — The microscope shows us that the skin, the muscles, the blood, — in fact, all parts of the body, — contain numberless small parts called cells. These cells are continually chang- ing with the activi- ties of the body. One of the most interesting kinds of cells we shall find to be the 7uhite blood cells, or corpuscles. One is shown in Fig. 6, with the changes that it had undergone at intervals of one minute. The thought readily occurs that these cells, although part of man's body, resemble the ameba that lives an independent life. A man or a horse or a fish — in fact any animal not a protozoan — has something of the nature of a colony, or collection, of one-celled ani- mals. We are now prepared to understand a little as to how the body grows, and how a cut in the skin is re- paired. The cells take the nourishment brought by the blood, 7ise it, and grow and multiply like the atneba. Thus new tissue is formed. All animals and vege- tables — that is to say, all living things — are made of cells. A living cell always contains a still smaller body called a nucleus I'iG. 7. — Dia(;kam ok a (Fig. 7). There is sometimes a cell. small dot in the nucleus, called /, protoplasm: «, nucleus: «', nu- the nucleolus. The main body of the cell consists of the living substance called protoplasm, con- taining nitrogen. Usually, but not always, there is a wall INTR OD UCTION 7 surrounding the cell, called the cell wall. Workers with the microscope found long ago that animals and plants are constructed of little chambers which they called cells. It was found later that the soft contents in the little chambers is of more importance than the walls which the protoplasm builds around itself. A living cell is not like a cell in a honeycomb or a prison. In biology we define a cell as a bit of protoplasm containing a nucleus. No smaller part of living matter can live alone. The protoplasm of the nu- cleus is called nucleoplasm ; the rest of the protoplasm is called cytoplasm. \ fiber is threadlike, and is either a slender cell (Fig. 8), a slender row of cells (Fig. lo), or a branch of a cell. A Fig. 8. — A Cell (from involuntary muscle), so slender that it is c'aXl&As. fiber, tissue is defined as a netivork of fibers or a mass of similar cells serving the same purpose, or doing the same work, A membrane is a thin sheetlike tissue. The Nature of the Human Body. — The human body is a community of cells, and may be compared to a community of people. It is a crowded community, for all the citizens live side by side as they work. They are so small that it takes several hundred of them to make a line an inch long. We should never have suspected the existence of cells had it not been for the microscope ; but now we know that they eat and breathe and work and divide into young cells which take the place of the old ones. A child that is born in a community of people may become a railroad m.an and carry food and other freight from place to place ; so, in the great community of cells (see Fig. 9) making up the human body, the red blood cells, like the railroad man, are employed in carrying material from place to place. But the community is old-fashioned, for the 8 HUMAN BIOLOGY mecef/s^ cells from Uien^oiith - f Ce//sfro/7iifjetyj/?dpipe Musc/e cells citizens build canals instead of railroads for their commerce (see Fig. 84). Just as a child may grow up to be a fanner and aid in the con- version of crude soil into things suitalile for the use of man, so the digestive cells take the food we eat and change it into material with which the cells can build tissue. Some of the citizens of a community must, at times, take the part of soldiers and policemen, and protect the community against the attacks of ene- mies. The white blood cells, already referred to, may be called the soldiers ; for they go to any part attacked by injurious germs, a particle of poison, or other enemy, and try to destroy the ene- mies by devouring or digesting them. At other times they help to repair a break in the skin. If a splin- ter gets into the skin, the white blood cells form a white pus around the splinter and remove it. In fact, the white blood cell has been re- ferred to as a kind of Jack-at-all-trades. In the human community there are certain persons who reach the positions of teachers, law- makers, and s^overnors ; they instruct and direct the other members of the community. Just so, in the community of cells, there are certain cells called fierve cells (see Fig. 11) that have the duty of governing and directing the other cells. The nerve cells are most abundant in the brain. Large cities must have scavengers. Likewise in the human body, a community composed of millions of cells, there are certain celb in the skin and the kidneys which have this duty. They are continually removing impurities from the body.' Division of Labor. — There is a great advantage in each cell of the human body having its special work, instead of having to do everything for itself, as each ameba cell must do. Under this system each cell can do its own work better than a cell of any other kind can do it. Among wild tribes ' From Coleman's " Hygienic Physiology," The Macmillan Co., N.Y. Fig. 9. — Various Cki.i-s iif the body. (Jegi.) Tiny citizens of the bodily community. INTRODUCTION 9 there is very little division of labor. Each man makes his own weapons, each knows how to weave coarse cloth, how to cook, how to farm, etc. Savages do not have as good weapons as do people who leave the making of weapons to certain men whose special business it is. What kind of pocketknives or pencils do you think the boys of this country would have if each boy had to make his own pocketknife or pencil } What kind of scissors and thread would the girls have if each girl had to make them her- self .'' Our muscle cells can contract better than the ameba ; the cells in the lungs can absorb oxygen better than the ameba. We have just as great an advantage in digestion, feeling, and other processes ; for the ameba eats without a mouth, digests without a stomach, feels without nerves, breathes without lungs, and moves without muscles. Division of labor between the sexes also occurs among the higher animals. Those who desire that man and woman should have the same education and work would -violate the biological law of "progress by specialization," which could only cause race degeneration. A part of the body which is somewhat distinct from surrounding parts, and has special work to do, is called an organ ; the special work which the organ does is called its function. The eye is the organ of sight. The skin is an organ ; its function is to protect the body. This book will treat of (i) the structure, appearance, and position of each organ, or anatomy; (2) the function of each organ, or physiology; (3) the conditions of health for each organ, or hygiene ; (4) the conditions under which each organ worked in the primitive life of the race ; (5) the effects of change of environment ; (6) the anatomy of man compared with the lower animals. (5) belongs to the science of Ecology. These sciences are parts of the science of Biology. lO HUMAN BIOLOGY -'-n Fig. io. — Iiirki. Muscle Fibers frorfi the heart (showing the nu- clei of six cells). The Tissues. — As the on^ajis Jiavc dif- fiiriit finiitious, tlicy Diiist have different slntct lives that they may be adapted to their work. Jii.st as a house must have brick lor the chimney, shingles for the roof, and nails to hold the timbers and other parts together, so the body has various tissues to serve different purposes. The bones must not be constructed like the muscles, and the muscles cannot be like the skin. The chief work of the cells is to construct the tissues and repair them. During life changes are constantly going on. Careful little workmen are keeping watch over every part of the body; thrifty little builders are busy in repairing and restor- ing. No sooner is one particle removed than another takes its place. In one di- rection the cells, acting as undertakers, are hurrying away matter which is dead ; in the other direction the unseen builders are filling the vacant places with matter that is living. The Seven Tissues. — There are seven kinds of tissues. Two of them, the mu.s- cular and nervous tissues, are called the master tissues, since they control and ex- pend the energies of the body. The other five tissues are called the supporting tis- sues, since they supply the energy to the master tissues, support them in place, nourish and protect them. Fig. II. — Nerve Cells, showing their branches interlacing. w INTRODUCTION II Fig. 12.— Connective Tissue Cells, removed from among the fibers of fig- 13- «, c, nucleus; /, branches. The Master Tissues. — The muscular tissue consists chiefly of rows of cells placed end to end (Fig. lo). These cells have the remarkable property of becoming broader and shorter when stimulated by impulses from nerve cells The nerve tissue consists of cells with long, spiderlike branches (Fig. ii). Some nerve cells have branches several feet long, so long that they go from the backbone to the foot. The branches are called nerve fibers (Fig. 142). Nerve fibers which carry impulses to the nerve cells are called sensory fibers. The nerve fibers which carry impulses />v;;/ the nerve cells are called motor fibers. The organs are set to work by impulses through the motor fibers. Besides these two master tissues there are five supporting tissues. Connective tissue, like all other tissues, contains cells (see Fig. 12), but it consists chiefly of fine fibers. These fibers are of two kinds, — very fine zvhite fibers which are inelastic, and larger yellozv fibers which are very elastic (see Fig. 13). Connective tissue is found in every organ, binding together the other tissues and cells. It is inter- woven among the muscle cells, and the tendons at the '^^\^\ Fig. 13. — Connective Tissue Fibers. a, b, bundles of white fibers; c, a yellow fiber. 12 NUM. IX BIOLOGY ends of the muscles arc composed almost wholly of it. If every other tissue wore removed, the connective tissue would still give a perfect model of all the organs. How abundant this tissue is in the skin may be known from the fact that leather consists entirely of it. Fatty (Adipose) Tissue. — Fatty tissue is formed by the deposit of oil III coinicctivf tissue eells (see Fig. 14). Fat is held in meshes of connective tissue fibers. That fatty tissue consists not alone of fat, but of fibers also, is shown when hog fat is rendered into lard, certain tough parts called "crack- lings" being left. What is the differ- ence between beef fat and tallow .■' Epithelial tissue consists of one or more layers of dis- tinct cells packed close together (see Fig. 15). It con- tains no connective tissue or other fibers, and is the simplest of the tissues. Epithelial tissue forms the outer layer of the skin, called the epidermis, and the mucous membrane lining the interior of the body. It contains no blood ves- sels, the epithelial cells obtaining their nourishment from the watery portion of the blood which soaks through the Fig. 14. — Faitv Tissue. Five fat cells, held in bundles of connective tissue fibers. a is a large oil drop; >«, cell wall; nucleus («) and proto- plasm (/) have been pushed aside by oil drop (a). INTRODUCTION 13 underlying tissues. Epithelial cells are usually transparent ; for instance," the blood is visible beneath the mucous membrane of the lips. The finger nails are made of epithelial cells, and they are nearly transparent. There are tivo classes of epithelial cells ; one class forms protective cover- ings {¥\g. 15) ; the other class forms the lining of glands (Fig. 16). Glands are cavities whose lining of epithelial cells (Fig. 17) form either useful fluids called secretio7is to aid the body in its work, or harmful fluids called excretions to be cast out, or excreted. Most glands empty their fluids through tubes called ducts. Cartilag'inous tissue is tough, yet elastic. Cartilage or gristle may be readily felt in the ears, the windpipe, and the lower half of the nose. This tissue consists of cartilage cells embedded in an inteirelliclar substance through which run comiective tissue fiber's (see Fig. 18). If yellow fibers predominate, the cartilage is yellow and very elastic, as in the ear ; if white fibers predomi- nate, it is white and less elastic, as in the pads of gristle between the bones of the spinal column. Cartilage is to prevent jars, and, in movable joints, to lessen friction. Bony (Osseous) Tissue. — SoHd bone is seen under the microscope to contain Fig. 15. — Epithelial Tissue (epidermis ol skin, magnified). Fig. 16. — Epithelial Tissue; cells form- ing two glands in wall of stomach. Fig. 17. — Six Gland Cells : at left, shrunken after activ- ity ; at right, rested, full of granules. 14 HUM AX BIOLOGY ^^ :*>% many minute cavities (Fig. 19). In tlusc cavities the bone cells lie self-imprisoned in walls of stone ; for these cells have formed the bone by deposit- ing limestone and phosphate of lime around themselves. There are viiniite canals (3, Fig. 19), however, through which nourish- ment comes to the cells. The watery portion of the blood passes through these small canals from the blood vessels that flow through t/ie larger canals (i, Fig. 19). Bone cells may live for years, al- though some of the other cells of the body live only a few hours. New cells to repair the tissues are formed by subdivision of the cells, as with the ameba. Unlike protozoans, many-celled animals are mortal because the outer cells prevent the deeper cells from purifying themselves perfectly and ol)taining pure food and oxygen. 1 ISSUE. A thin slice highly magnified. a, b, c, groups of cells; m, inter- cellular substance. '-,4. , "t-^?' -^ J^ Fig. 19. — Bony Tissue. Thin slice across bone, a^ viewed through microscope. Larger blood tubes pass through the large holes (i); the cavities containing bone cells lie in cir- cles, and are connected by fine tubes (3) with the larger tubes. work without oxygen. Even the arteries of an old man become hard- ened by the deposit of mineral matter which the body has been unable to ex- crete. The body is kept alive and warm by burning, or oxidation. One fifth of the air is o.xygen gas. We breathe it during every min- ute of our existence. It is car- ried by the blood to all the tis- sues. Not one of the cells could Without it the body would soon be cold and dead, for oxygen keeps the body alive and warm INTRODUCTION 1 5 by uniting in the cells with sugar, fat, and all other sub- stances in the body except water and salt. Oxygen burns or consumes the substances with which it unites, and the process is called oxidation. Hence the cells have to be continually growing and multiplying to repair the tissue and replace the material used up by oxidation. Sugar and flour and fat oxidize, or burn, outside of the body, as well as in it, as can be proved by throwing them into a fire. Water and salt are two foods that do not burn. Hence they can furnish no heat or energy to the body. Water puts out a fire instead of helping it, and so does salt. Throw salt into a fire or on a stove ; it will pop like sand, but will not burn. The cells need the oxygen of fresh air ; they need food for the oxygen to unite with, but they are injured by many substances called poisons. Arsenic destroys the red blood cells. Strychnine attacks the nerve cells in the spinal cord. Alcohol attacks the epithelial cells lining the stomach and, when it is absorbed, attacks the nerve cells and other cells. Morphine attacks the nerve cells. Written Exercises. — Draw a series of seven pictures to show the seven tissues (Figs. 10, 14, 15, 18, 19). Write the ''Autobiography" of a White Blood Cell (see also pages 59 and 68). The Rewards of Caring for the Health. Health and the Disposition. Which is more important, a Thorough Knowledge of Geography or of Physiology? Five Things which people Value above Health (and lose health to ob- tain). The Blessings that follow Good Health. The Tissues Com- pared (function, proportion of cells, intercellular material and fibers, activity, rate of change). See also pages 50, 116. Pupils should choose their own subjects. chai'ti:r II THE SKIN Note to Teacher. — Tlie experiments should be assigned in turn to the pupils as each chapter is reached : e.g. this set of 13 will leave 3 pupils in a class of 39 to stand responsible for each experiment. Each pupil should do the work separately and credit may be given for the best results. Encourage (or require) each pupil to try every experi- ment and record them in a note book. Experiincnt i. (At home or in cla.ss.) Albinism. — Study a white rabbit as an example of albinism. Does albinism affect only the skin? What evidence that its blood is of normal color? Experiment 2. Use of Hairs on the Skin. — Let one pupil rest his hand upon the desk behind him while another touches a hair on his hand with a pencil. He should speak at the moment, if it is felt. Do the hairs increase the sensitiveness of the skin? What was their use with primitive man? Are the hands of all your acquaintances equally hairy? Are the hairs to be classed as rudimentary? Will they disap- pear? Will the race become baldheaded? Experiment 3. (Home or school.) Invisible Perspiration. — Hold a piece of cold glass near the hand or place the cheek near a cold win- dow pane and notice for evidence of moisture. Its source? Experiment 4. — Effect of Evaporation on Temperature. — Read a thermometer and cover its bulb with a moist cloth. Read again after twenty minutes. Repeat experiment in breeze. Experiment 5. Moisten one hand and allow^ it to dry. Touch the other hand with it. Explain result. Experiment 6. Absorbing Power of Fabrics. — Wet the hands and dry them upon a piece of cotton cloth. Repeat with woolen, linen, and sflk. Arrange in list according to readiness in absorbing water. Experiment 7. Rates of Drying. — Immerse the cloths in water and hang them up to dry. Test their rates of drying with dry powder or by touch. Experiment 8. Test Looseness of Weave of above cloths by measur- ing the distance pieces of equal lengtli will stretch. Experifnent 9. Does Cotton or Wool protect better from Radiant Heat? — Lay a thermometer in the sun for ten minutes, first covering 16 Coi.oKKD I-uJiRK I. — Section of Skin (dinsjram, enlarged 25 times). On the left the connective tissue fibers of tiic true skin are shown. In cutis (c), or dermis, find capillaries, nerve fibers, fat cells, two sweat glands and AwcX^, four oil glands (two in section), two hairs, three nerve papilla;, _/f-'^ papillae containing capillaries, two muscles for erecting hairs. In epidermis find flat cells, round cells, and pigment cells. Fig. 2. — Where THE Food is AUSORBED (villus of intestine). Fii;. 3. — Where THE Food is ISED (cells with lymph spaces). /^U3c/e ce//s 1^1^ Lymph B/ood capi7/ory KiG. 3. Fig. 2. i, J, jaws : ni, nerve of smell op, nerve of sight brain: /, tongue glottis: oe, gullet ///, thymus gland; ig, lung; //, heart. /, liver; g, stom- ach; s. splct /, pancreas k, kidney: <;. diaphragm; ni, muscle; », bladder; eh, spinal cord; f , ver tcbra;. TION OK Mammal. ompare with organs of man (colored Fig. 6). THE SKIN 17 it with a woolen cloth. Note change in reading. After it regains first reading, repeat, covering it with a cotton cloth of same weight and tex- ture ? Conclusion ? Expose wrists or arms to sun for five minutes, one protected by the cotton, the other by the wool. Result ? Conclusion? Experiment 10. Rates of Heat Absorption and Radiation by Different Colors. — Expose thermometer to sunlight, covered successively by pieces of cloth of same thickness, material, and texture. Use black, blue, red, yellow, and white cloth. Note rise of temperature for equal times in each case ; also the fall of temperature for equal times after removal to shade. Experiment 11. Effects of Dry Powders. — Prepare two squares from the same piece of leather {e.g. an old shoe). Moisten them both, and apply face powder to one. Which dries more quickly? Repeat after oiling them. Powder a portion of the face or arm daily for a week and compare with the clean portion. Experiment 12. Dissect the kidney of an ox or sheep, making out the parts mentioned in the text, p. 26. Experiment 13. (In class.) Emergency Drill. — Have one pupil wet an imaginary burn on the arm of another, treat it with flour or soda, and bandage. (See text.) The Skin has Two Layers. — The outer layer is called the epidermis ; it is thinner, more transparent, and less elastic than the inner layer, or dermis. The epidermis is com- posed of epithelial cells packed close together (see colored Fig. I). The dermis, or inner layer, is a closely woven sheet of connective tissue (colored Fig. i) containing a great num- ber of siveat and oil glands, roots of hairs, blood vessels, absorbent vessels (lymphatics), and nerves (colored Fig. i ). The dermis is sometimes called the true skin because it is of greater importance than the epidermis. It is united loosely to the underlying organs by a layer of connective tissue. It is in this layer that fat is stored. The upper surface of the dermis rises into a multitude of projections (see colored Fig. i) called papiV Ice (singular, papilla). The epidermis fits closely over them and completely levels up the spaces between them except on the palms and the soles. Here the papillae are in rows, and there is a fine I8 HlWfAX BIOLOGY ridge in the skin above each row of papillae (Fig. 24). In the jKipilla* are small loops of blood vessels and sometimes a nerve fiber (colored Fig. i ). The epidermis is composed of a tnass of cells held to- gether by a cement resembling the white of an egg. The cells near the surface are hard and flattened ; those deeper down near the dermis are round and soft (see Fig. 21). These cells are liv- ing cells. They are kept alive by the nourishment in the watery portion of the blood which soaks through from the blood tubes in the neighboring pa- pillct. Hence these cells are growing cells; they subdivide when they reach a certain size, and re- place those wearing away at the surface, thus constantly repairing the epider- mis. The dry outer cells wear away rapidly. They have no nuclei and are dead cells. The new cells forming be- neath push them so far away from the dermis that nour- ishment no longer reaches them, and they die. Pigment. — The cells in the lower layers of the epidermis contain grains of coloring matter, or pigment. All other cells of the epidermis are transparent ; the pigment has the function of absorbing and arresting light. Albinos or animals entirely without pigment have pallid skins and pink eyes (Exp. i). Ho. 20. — El'IDliKMlS OF Ethiopian. Fig. 21. — Epidkrmls OF Caucasi.an. THE SKIN 19 Immigrants from a Cloudy to a Sunny Climate. Adaptation. — The cells of the deeper tissues can readily be exhausted by the stimulation of too much light. The sunnier the climate, the greater the need of pigment ; hence the dark skin of the negro and the blonde skin and hair of the Norwegian. European immigrants to sunny America will grow darker. The Indian's skin is better suited to our climate than is a fair skin. Brunettes have a better chance for adaptation than blondes. The American type when developed will doubtless be brunette. The hair grows from a pit or follicle (Fig. 22). Blood vessels and a nerve fiber go to the root or bulb from which a hair grows. The hair will grow un- til this papilla, or bulb, is destroyed (Exp. 2). Adaptation of the scalp to a tight warm cov- ering is accomplished through the shedding of the hair rendered useless by the covering. It is impossible to stop the growth of superfluous hair unless the hair papillae are destroyed with an electric needle, such is the vitality of hair ; yet many men, by overheating the head and cutting off the circulation with tight hats, destrov much ^'^- ^^- ~ Develop- r ii 1 • u f 1 • -AW ' Ti MENT OF A Hair of the hair betore reaching middle age. The „ ^ * » . AND Two Oil health of the hair can be restored and its loss glaxds be stopped by going bareheaded except in the hot sun or in extremely cold weather. This frees the circulation : cold air and light stimulate the cells of the scalp. Some men wear hats, even at night in summer. The brain needs the protection of the hair. Beard protects the larynx or voice box, which is large and exposed in man. It was also a protection in hunting wild beasts and in war. Compare mane of lion, not possessed by lioness. " Goose-flesh " after a cold bath is caused by the contraction of small muscles (colored Fig. i), raising the now tiny hairs in an absurdly useless effort to keep the body warm. The nails are dense, thick plates of epidermis growing from a number of papillae situated in a groove, or fold, of the skin ; there are many fine papillae along the bed from which the nail grows. Since it grows from its under side as well as from the little fold of skin at its rcot, the nail is thicker at the end than near the root. 20 HUMAX BIOLOGY Fig. 23.— .-/, Development of Sweat Gland; B, Sweat TiHE Developed. The oil glands empty into the hair follicles (colored Fig. i ). They lurin \x\\ oil irom the blood that keeps the hair glossy and the surface of the skin soft and flexible l)y preventing e.\- cessivc drying. Ilair oil should never be used upon the hair, as the oil soon becomes rancid, and besides causes dust and dirt to stick to the hair. The sweat glands (Fig. 23), like the hair bulbs, are deep in the lowest part of the dermis. A S7veat gland lias the form of a tube coiled into a ^^//(colored Fig. i). This tube continues as a duct through the two layers of skin, and its opening at the surface is called -^ pore (Fig. 24). The perspiration evaporates as fast as it flows out through the pores, if the secretion is slow; but if poured out rapidly, it gathers into drops (Exp. 3). The perspiration is chiefly water, contain- ing in solution several salts, including common salt and a trace of a white, crystalline substance called nj-ea. The material for the perspiration is fur- nished by the blood flowing around the gland in a network of fine tubes. The amount of the perspiration is con- trolled in two ways : by nerves that regulate the activity of the epithelial cells lining the gland, and by nerves that regulate the sice of the blood ves- sels supplying the gland (Fig. 25). Fjg. 24. — Pores on ridges in palm of hand. Thought Questions. — Freckles, Warts, Moles, Scars. Proud Flesh, Pimples, Blackheads. Use these names in the proper places below: — THE SKIN 21 A rough prominence formed by several papillae growing through the epidermis at a weak spot and enlarging is called a . Small patches of pigment developing on the hands and face from much exposure to the sun are called . The growth of exposed dermis sprouting through an opening in the epidermis due to accident is called . (This should be scraped off and cauterized to aid the epidermis to grow over it again.) Sometimes a cut heals in such a way that no epidermis and therefore no pigment cells cover the place of injury, which is occu- pied only by white fibrous tissue (cicatricial tissue) of the true skin. In this case the mark left is called a cicatrice or . If pores or the openings of oil glands become clogged, but not enlarged, little swell- ings called may result. An enlarged pore filled with oil and dirt is called a . A spot present since birth, dark with pigment, and often containing hairs and blood vessels, is called a . Regulation of Temperature. — As is well known, rapid running or violent exercise of any kind causes profuse per- spiration. The sweat glands are connected with the brain by means of nerves, and when the body has too much heat, a nerve impulse from the lowest part of the brain causes the sweat glands to form sweat more rapidly. Heat and exer- cise may cause the activity of the sweat glands to increase to- forty times the usual rate. The evaporation of the sweat cools the body, for a large amount of heat is required to evaporate a small amount of water (Exp. 4 and 5). This is shown by the cooling effect of sprinkling water on the floor on a warm day. By fanning we hasten the cooling of the body (Exp. 4). Exercise tends to heat the body, but it also causes ns to breathe faster and causes much blood to flow througJi the skin. Both of these effects aid in cooling the body, for the cool air is drawn into the lungs, becomes warm, and takes away heat when it leaves ; and the warm blood flow- ing in the skin loses some of its heat to the cool air in con- tact with the skin. Effects of Alcohol upon the Skin. — The more blood goes to the skin, the more blood is cooled. The body 22 HUM AX BIOLOGY as a whole m;n' be cooler, but ive fctl icanmr w/ien there is more blood in the skin because of the effect of the ivarm blood upon the nenus of temperature. There are no nerves for perceiving temj^erature except in the skin and mucous membrane, and the body has jiractically no sensation of heat or cold except from the skin or mucous membrane. That alcoholic drinks make the skin red is commonly noticed. Often the skin is flushed by one drink ; the bloodshot eyes and purple nose of the toper are the results of habitual use. Can you explain why alcohol brings a deceptive feeling of warmth .'' Why does alcohol increase the danger of freezing during ex- posure in very cold weather.'' During the chill which pre- cedes a fever, the body (except the skin) is really warmer than usual. Exercise will relieve internal congestion and send the blood to the skin better than alcohol. This is the effect sought by sedentary people who use it to replace exercise. The long and sad experience of the race with alcohol proves that the attempt to adapt the body to its use should be given up. Thought Questions. The Functions of the Skin. — 1. State a fact which shows that the skin is a protection ; gives off offensive sub- stances; regulates the temperature. 2. What is lacking in the skin when it cracks or chaps? Why does this occur more often in cold weather? When the hands are bathed with great frequency? Effects of Indoor and Outdoor Life. — Those who live much out of doors, exposed to sunlight and pure, cold air, are robust and hardy ; while those whose occupations keep them constantly indoors, especially if no physical labor is necessary, show by their pale skins, their fat and flabbv. or their thin and emaciated bodies, the weakening effect of such a life. We are descended from ancestors who lived in the open air. and it is impossible for a human being to live much indoors without de- generation of the body and shortening of life. A Well-trained Skin. — We hear a great deal about training the muscles, the brain, the eye, the hand ; yet we may fail to realize that THE SKIN 23 the skin also can be trained and its powers developed, or it can be allowed to become weak and powerless. Soundness of the skin is as es- sential to health as soundness of any other organ. A rosy color indicates good health because of a well-balanced circulation. Paleness often means internal congestion and great liability to indigestion, colds, etc. Hence we think a rosy skin beautiful and a pale skin ugly. With the skin in a healthy condition, the danger of taking most diseases is removed. Characteristics of a Vigorous Skin. — A person who readily takes cold, who is fearful of drafts of air at all times, has a weak skin. To one who has a healthy skin drafts are dangerous only when the skin is moist with perspira- tion, and the body is *f inactive ; cold drafts may then do harm. Cold air and cold water are the best means of toughening a tender skin. A bath is to the skin what gyvinastic exercises are to the muscles. The muscle fibers in the walls of ■the blood vessels and the nerves controlling them need exercise as well as the rest of the body (Fig. 25). Importance of Bathing. — If zve followed the ont- door life and wore the scanty clothing of savage races, the rains, the cool air, and the sunlight would keep our skins vigorous and sound. But want of exercise to induce perspiration allows the sweat glands to become stopped up. The wearing of clothes is a very uncleanly custom. Clothes make the skin inactive, yet confine the impurities which the weakened skin may still be able to excrete. Thick and Fig. 25. — Blood Vessels, with the Vaso-motor Nerves which accompany and control them. 24 HUAfAN BIOLOGY heavy clothing and overheated rooms prevent the nerves from being stimulated by cold air and sunlight. The best way to counteract t/icse wcakotinq' conditions is by frequent cool or cold baths. An air bath, which consists of exposing the bare skin to the air for half an hour or more before dressing in the morning, may take the place of a cold bath. Even the lower animals bathe : birds, dogs, and many lower animals bathe in the rivers. An elephant sometimes takes a bath by showering water over his back with his trunk. Treatment of Burns. — Wet the burn with a little water and si)rinkle common baking soda or flour thickly on it. Bind with a narrow bajidage. For deeper burns soak a small square of cloth in a strong solution of baking soda, bandage it on wound, and keep it wet with the solution. Olive, cotton seed, and linseed oils are excellent for burns (Exp. 13). Hygiene of Bathing. — A bath should not be taken within an hour after a meal. Cold baths (i) should never be taken in a cold room nor when the skin is cold; (2) are more beneficial in summer and in warm cli- mates, but are necessary in winter for those who live in overheated houses or dress very warmly; (3) should be followed in winter by vigorous rubbing and a glowing re- action ; (4) should usually not last longer than one minute in winter. Warm baths (i) are more cleansing than cold baths; (2) should not be used alone but should always be followed by a dash of cold water ; (3) are better than cold baths if the body is greatly fatigued ; (4) are more benefi- cial when going to bed than upon rising. Cold baths and very hot baths are both stimulants to the nervous system and cause an expenditure of nervous energy. For one whose nervous energy is at a very low THE SKIN 25 ebb cold baths may be weakening if prolonged beyond a few seconds. For one with skin relaxed and body sluggish from indoor life, cool baths arouse activity, tone up the body, and may be as beneficial as outdoor exercise in restor- ing vigorous health. As with every hygienic measure, each person must find out by experience what suits him best. Clothing was first employed for ornament. In cold climates it aids in maintaining the uniform temperature of the body ; to it man owes his distinction of being the most widely distributed of animal species. Clothing prevents rapid escape of bodily heat by confining air, a non- conductor of heat, in its meshes. Hence, the effect of clothing varies with the weave; likewise with the tendency of its fibers to keep dry, for if water replaces air in the meshes, the body loses heat rapidly. For cool clothing the weave should be hard and tight, for warm clothing it should be soft and loose. The warmth of clothing is affected more by its weave than by its weight. The weave may be tested by stretching ; the fabric with softest weave will stretch the most (Exp. 8). Linen makes the coolest of all clothing because it weaves hard with small meshes ; silk ranks next in coolness. When warmth is desired, linen or cotton garments should be made of fabrics woven like stockings. "Linen and cotton both absorb water rapidly and dry rapidly (Exp. 6) ; if woo/en did also, it would make the warmest of all clothing, but it dries so slowly (Exp. 7) that it cools the body after the activity is over instead of drying rapidly and, as with linen and cotton, keeping the body cool during the exertion (Exp. o). Woolen weaves with the largest air meshes of all materials ; hence its warmth increases perspi- ration, but woolen removes perspiration most slowly and tends to relax the skin if the wearer has an active skin or makes active exertion. Woolen is best for underclothing during extreme cold only or for per- sons who never make such vigorous muscular exertion as to perspire. In general, cotton or linen is best for underwear. They possess the added advantages of less cost and of not shrinking out of size and shape when washed. A mixture of cotton and silk or of cotton and wool is more durable than either alone. Cotton and linen, unlike woolen, are not attacked by insect pests. It is better to depend more upon outer clothing than underclothing for warmth. In the Gulf states the wearing of woolen outer clothing indoors during warm weather (which lasts eight months) is unhealth- ful and uncleanly because of the perspiration absorbed ; this is as 26 J/L'MAX BIOLOGY absurd as to wear cotton outer clotliing in Nortliern states during the eight cold niuntlis. IMack clothing absorbs twice, blue almost twice, red and yellow almost one and a half times, as much heat as white clothing (Exp. lo). Which material protects best from radiant heat .' (Exp. 9.) Because large blood vessels are near the surface at the neck, wrists, and ankles very thin or no covering at those points aids greatly in keeping tlie body cool. High coll.ars. long sleeves, and higli shoes are unhealth- ful in warm climates and in summer. What objection to black shoes in summer .' Patent leather .'' Show how women dress more sensibly in hot weather than men. The kidneys are located on each side of the spinal col- umn in the " small of the back " and extend slightly above the level of the waist. They are bcan-sliaped or- gans about four inches long (Fig. 26). The kidneys of a sheep or ox closely re- semble those of man. They are outside of the perito- neum (Fig. 99) and at- tached to the rear wall of the abdomen. A large artery (12, colored Fig. 5) goes to each kidney and divides into many capilla- ries which surround tubules in the kidneys (Fig. 27). The secretion, containing nitrogenous impurities of the blood, is continually being deposited in the tubules, which take it to 2. fu7mel-s/iapcd cavity at the inner edge of the kidney (Fig. 26). From this cavity a white tube called the ureter leads down to a storage organ in the pelvis called the bladder. KA Fig. 26. — SEcrioN of Kidney. RA, renal arterj-; Py, pyramids surrounding hollow space from which the ureter {U) leads the secretion to the bladder. THE SKIN 27 1 iG. 27. — Plan of a Urinary Tubule, Tb, with artery A, and V in / V. Changes in Blood in the Kidneys. — The water holding the nitrogenous waste varies in amount with the amount of water drunk and with the activity of the skin, being less in sum- mer when the perspiration is great. The lungs aid the skin and kidneys in disposing of superfluous moisture. The kidneys have almost the entire responsibility of relieving the body of certain Diincral salts and a white crys- talline solid called iirca. This is very injurious if retained, causing headaches, rheumatism, and other troubles. Thought Questions. Hygiene of the Skin. — 1. What kind of a scar is not affected by freckles or tan? 2. Can a scar on a negro be white? 3. Does a scar on a child grow in size? 4. Why is heat most oppressive in moist weather? 5. How do you account for the shape and location of the usual bald spot? 6. How does the wearing away of the outer cells of the epidermis contribute to the cleanliness of the body? 7. Why does the palm of the hand absorb water more rapidly than the back of the hand? 8. Is it more necessary for mental workers to bathe often or change their clothes often? For physical workers? 9. Is cotton csr woolen clothing more liable to stretch or shrink out of shape or size ■' T' Experiment i. (At ! :; t Is :i:e .A^ch of the F::: Elisti:? — Wet the foot in a basin oi water ancL h r - :~:ng, piace " : ~ " upon a piece of paper. Draw the ou. r .he track, stand with your whole weight upon elusion? (Take sketches to schooL - r " r-: foot?) Devise a method for measur , , .e foot with and without the weight of the body up:„ ...._. _.-c.ciice? Con- dusion? ExperinuHt z. Composition of Bone. — Place a bone in a hot fire and let it remain for three or four hours. It wfll keep its shape however l/;;/ /j/' support arc thick and so/id ; those designed to aid in motion arc long and straight. I ncluding six small bones in the ear, there are two hundred and six bones ^ in the adult skeleton. Gross Structure of Bones. — The structure of a long bone is shown in Fig. 29. It has a long, hollow shaft of hard, compact bone, and enlarged ends composed The — O Marrow. \ % ... c , Compael . , -A 01- dense of spongy bonc. tissue hollow in the shaft is filled ivith yclloxv mar- roiv, which is conijjosed of blood vessels and fat, and aids in nourishing thebone. Thelongbones V are found in the limbs (Fig. 28). The ribs and other flat bones and the Fig. 29. -Femur, sawed irregular bones contain lengthwise. The red j^o ycllow marrow ; they blood cells are formed • • 1 in the red marrow of are spongy mside, and the spongy part. ^^rd and Compact near pj^ _ the surface. There is a red marroiv in the Front view of . . . , ,, /T-,. . Right Femur. cavities in the spongy parts of bones (h ig. 29). New red blood cells are formed in this marrow. The bones have a close-clinging, fibrous covering composed of con- nective tissue and blood vessels. It is QzWcd periostenm. THE SKELETON 31 Chemical Composition of Bone. — Experiments (2 and 3) show that the bones contain a mineral or eartJiy siibsta7ice, which makes them hard and stiff, and p_ ^^^^ _ a certain amount of animal matter, called gelatine, which binds the min- eral matter together and makes the bones tough and somewhat elastic. The fire burned out the animal matter of the first bone, and the acid dissolved out the mineral matter of the second bone. The mineral matter is cJiieJly lime, and makes up about two thirds of the weight of the bone. (Why is more mineral than animal matter needed }^ The animal gelatine is a gristly sub- stance. As the body grows old, the animal matter of the bones decreases, and they become lighter. They are more easily broken and do not heal so readily as the bones of young persons. The skeleton is subdivided into the bones of the head, trunk, and limbs. The bones of the trunk are those of the spine, the chest, the shoulder blades, collar bone, and hip bones. The spinal or vertebral column is made up of twenty-six bones (Fig. 31). It is the axis of the human skeleton, to which all other bones are directly or indirectly attached. Animals with inside skeletons have this column, and are called vertebrates. Fish, reptiles, birds, beasts, apes, and man are vertebrates. The spine, as this column is some- FiG. 31. — Vertebral Column. Side view. 3-' HUMAN BIOLOGY times called, is not only the main connecting structure and support of the body, but it forms a channel throus^h which passes the spinal cord. Fig. 32 shows a vertebra, or one of the bones that compose the column. The three projecting points or processes are for the attachment of ligaments and muscles. The main body of each vertebra is for supporting tlie weight transmitted by tiie column above. Just beliind this thick body is a )talf ring (Fig. 32), which with the half rings on the other vertebra; form the channel for the spinal cord. Between the vertebrae are thick pads of gristle, or cartilage, which act as cushions to prevent jars, and ijy compression allow bending of the spinal column in all directions. The Chest (see Fig. 75). — The twelve pairs of ribs are attached Fig. 32. — Side and Under to the spinal column behind, and View of a Verteuka. , , , 1 1 r r extend around toward the iront or the body, somewhat like hoops. The first seven pairs, called true ribs, are attached directly to the flat breastbone, or stcrtuiiu. Each of the next three pairs, zzW&di false ribs, is attached to the pair above it. The last two pairs, called floatiug ribs, are free in front. The Shoulder Girdle. — The collar bodies (Fig. 28) can be traced from the shoulders until they nearly meet on the breastbone at the top of the chest. The collar bone is shaped like the italic letter/; it helps to form the shoulder joint and holds the shoulder blade out from the chest that the motions of the arm may be free. The flat, triangular slioulder blade (Fig. 75) can be felt by reaching with the right hand over the left shoulder. It spreads over the ribs like a fan. Its edges can be made out, especially if the shoulder is moved while it is being THE SKELETON 33 Parietal Occipital MaxiU. Fig. 33. — Human Skull, disjointed. felt. The high ridge which runs across the bone can be felt extending to the top of the shoulder. The Pelvic Girdle. — The edges of the hip bones can be felt at the sides of the hips (Fig. 28). The hip bones, with the base of the spine, form a kind of basin called the pelvis. The skull (Fig. 33) rocks, or nods, on the top vertebra. It consists of the cranium, or brain case, and the bones of the face. The shapes and names of the bones of the skull are shown in Fig. 33. Adaptations of the Skull for Protection. — Its arched form is best for resisting pressure and turning aside blows. Like all flat bones, the skull has a spongy layer of bone between the layers of compact bone forming the outer and inner surfaces ; hence it is elastic and not easily cracked. The nose, brow, and cheek bones project around the eye for its protection. The delicate portions of the ear are embedded in the strongest portion of the skull. The branches of the nerves of smell end in the lining of the bony nasal chambers. The spinal cord rests securely in the spinal canal. The arms and legs have bones that closely correspond to each other. The Latin names of these bones, as well as of all the other bones, are given in Fig. 28. There are 30 bones in each arm and 30 in each leg (Fig. 34). Here is a Hst of the bones of the arm, followed by the names in brackets of the corresponding leg bones : upper arm bone [thigh bone], 2 forearm bones [shin bone and D 34 HUMAN BIOLOGY splint bone], 8 wrist hones [7 ankle bones], 5 palm bones [5 bones of instep], 14 finger bones [14 toe bones]. The shin bone is the larger bone between knee and ankle. The long, slender splint bone and the shin bone are bound side by side. Differences between Arm and Leg. — There is a saucer-like bone, called the knciCiip, embedded in the large liga- ment which passes over each knee. There is no such bone in the elbow. Tliere is one less bone in the ankle than in the wrist, hence there are the same number of bones in the arm and leg. The shoulder joint is more freely movable than the hip joint. The fin- gers are longer and more movable than the toes: the thumb moves far more freely than the big toe. The instep is much stronger than the palm ; for each instep must support, unaided, the weight of the whole body at each step, with any other weight that the person may be carrying. The palm is nearly flat, but the instep is arched to prevent jars. When the weight of the body is thrown on the foot at each step, the top of the arch is pressed downward, making the foot longer than before. The arch springs up when the weight is removed (Exp. i). Illustrated Study. The Shapes of Bones. -Write L, F, or / after these names (see Fig. 28. etc.), according as the bones are long, flat, or irregular : face, cranium, vertebra, hip, rib, breast- bone, collar bone, shoulder blade, upper arm bone, lower arm bones, wrist, palm, fingers, thighbone, shin bone, splint bone, ankle, instep, toes, kneecap. Fig. 34. — Bones of Arm a.\d Leg. THE SKELETON 35 Structure of Joints. — The meeting of two bones forms a joint (Exp. 4). Some of the joints are immovable. The skull bones join in zigzag lines called sutures, formed by the interlocking of sawUke projections (Fig. 35). These immovable joints are necessary for the protection of the brain, which is the most delicate of the organs. The brain attains almost its full size by the seventh year of life ; its bony case needs to grow very little after that. The joints of the pelvis are also immovable. All movable joints have two cartilages, and as the bones turn, one cartilage slips over the other. There is an intermediate class of joints found between the vertebrae and where the ribs join the breastbone. These joints de- fig. 35. — sutures pend for their motion upon the flexibility ^^ skull. and compressibility of their cartilages. They are called mixed, or elastic, joints, and allow slight motion. Such a joint has only one cartilage. Kinds of Movable Joints. — The movable joints are found chiefly in the limbs. When one end of the bone is rounded and fits into a cuplike hollow, the joint allows motion in all directions, and is known as a ball-and-socket joint. The hip joints and shoulder joints are examples. A Jiinge joint allows motion in only two (opposite) directions ; for exam- ple, the to-and-fro motion of the elbow. A pivot joint allows a rotary motion ; examples, the first vertebra on the second, one bone of forearm upon the other. A glid- ing joint consists of several bones that slide upon one another, as at the wrists and ankles. The Four Features presented by a Movable Joint (Fig. 36). — If not held in place, the bones would slip out of their sockets, hence there are ligaments, or tough bands, 36 HLWfAX BIOLOGY to oind the bones together. Sudden jolts would jar the bones and injure them ; shocks are prevented by a layer of elastic cartilage over the end of each bone. The mov- ing of one bone over another in bending a joint would wear the bone with friction un- less the cartilages were very smooth and lubricated with a fluid called the synovial fltiid. The synovial fluid would be constantly escaping into the surrounding tissues except for the collarlike ligament called Fir.. 36. — Diagram of a Joint. the capsule, which surrounds the joint and is attached to each bone entirely around the joint (Fig. 36). Thought Questions. The Kinds of Joints. — Write B,H, G, E, P, or /after these names according to the kind of joint (ball-and-socket, hinge, gliding, elastic, pivot, immovable) : between bones of skull, head nodding, head turning. vertebrae, lower jaw, ribs to breastbone (Fig. 75), shoulder, elbow, wrist, fingers, hip, knee, ankle, toes. Growth of Bones. — The blood vessels pass into the bones from the periosteum. If the periosteum is retnoved, the larger blood vessels are taken away and the bone beneath it perishes. If the underlying bone is removed and the periosteum left, the bone will be replaced. A curious proof of the active circulation in the bone is furnished when madder is mixed with the food of pigs. In a few hours the bones become a darker pink than usual : and if the madder is fed to the pigs for a few days, their bones become red. A child grows in height chiefly during three or four months in spring and summer ; but its body broadens and becomes heavier during autumn. Health of the Bones. — It is plain that a strong and free circulation of pure blood contributes to the health and strength of the bones ; good food and pure air make pure blood. Cases of '• delayed union," or slow mending of broken bones, occur more often with intemperate than with sober people. This is because the vitality of the bone cells has THE SKELETON 17 l.^« l.J/^ A been weakened by the use of alcohol. Many surgeons dislike to operate on an old drunkard. Posterior Curvature of the Spine. — The spine (see Figs. 28, 31) has two backward curves (opposite chest and hips) and two forward curves (at loins and neck). The deformity called posterior curvature is chiefly an exaggeration of the upper posterior curve. Round shoulders is the slightest, and hunchback the most marked, degree of this deformity. Causes : i, bending over the -work while either standing or sitting ; 2. slipping down in the seat, as in Fig- ure 51 ; 3, working habitually with the work low iti front, as reading and writing at too low a desk (Fig. 49), or bend- ing over while hoeing, sitting on the floor (Japanese and Chinese) ; 4, weak muscles in the back ; 5, wearing shoes with high heels ; 6, binding the ribs down with tight cloth- ing; 7, walking with the head drooped forward or the chest flat ; 8, wearing suspenders without a pulley, or lever, at the back ; 9, carrying the hands in the pockets. (Swing the arms to keep the hands out of the pockets and break the habit) ; 10, wearing a coat or vest that is tight at the back of the neck. This deformity is brought about by stretching the ligaments at the back side of the spine, and by compressing the cartilages until they become wedge-, shaped, with the thin part of the wedge in front. The flexibility of the spine is a great advantage, but it in- creases the risk of deformity. One of the most serious evils of posterior curvature is a flat chest and restricted breathing. Lateral Curvature of the Spine. — A perfect spine curves to neither side (Fig. 47), but is perfectly erect. The least habitual lateral curvature is deformity. Causes: i, writing at a desk that is too high ; 2, habitually carrying a book, satchel, or other weight in the same hand; 3, carrying the head on one side (Fig. 46) ; 4, habitually standing with the weight on the same foot ; 5, a certain defect of vision (astigmatism. Chap. IX). To overcome Spinal Deformities. — The work, or the manner of doing the work, should be so changed as to give extra labor to the tieglected tnuscles. Avoid the habits mentioned above as causing deformity. Sit and stand in the manner described in the next paragraph. Sleeping on the back upon a hard mattress without a pillow tends to cure posterior curvature and flat chest. Fig. 37. -- Incorrect POSTURE. '\^ M\ Fig. 38. — Correct POSTURE, but Strained and stiff. 38 HUMAN BIOLOGY The correct position in staiidinj; is : chest forward, chin in. hips back (Figs. 38, 39). To sit correctly, sit far tnuk in the chair (Kigs. 60, 61, 62) with the body erect and balanced. In youth the bones are soft and growing; they will readily grow into perfect shape, and will almost as readily grow deformed. Sprains. — Immerse the part in hot water for half an hour, then bandage to keep the part at rest. (Jse the limb as little as possible. It may be necessary for a physician to apply a plaster dressing to a very bad sprain where the ligament is torn from the bone. Broken Bones. — To prevent bone from cutting flesh and skin, do not move the person until a temporary splint has been provided by tying sticks or umbrellas around the limb with handkerchiefs. Practical Questions. The Skeleton. — 1. What kind of a chair back causes one to slide fonvard in the seat? 2. What fault in sitting is made necessary by using a chair with so large a seat that the front edge strikes the occupant behind the knee? 3. Why is the shoulder more often dislocated than the hip? 4. High pil- ows may cause what deformity? 5. Find three bones in the body not attached to other bones. Find twenty-five bones at- tached to other bones by one end only (Figs. 28 and 39). 6. What deformities may result from urging a young child to stand or walk? 7. Which bone is most often broken by falling upon the shoul- der? 8. Where in bones is fat stored for Tig. 39. — The Human Skeleton inaction. future use? 9. Lio^a- ments grow very slowly. Why is recovery from a sprain often tedious? CHAPTER IV THE MUSCLES It has already been stated that there are at least two muscles attached to a bone to move it in opposite direc- tions. Since there are two hundred and six bones, you are not surprised to learn that to move the bones and accomplish the various purposes just stated, there are five hundred and twenty-six (526) skeletal muscles. Two Kinds of Muscles. — All muscles are controlled by means of the nervous system. Some of them are directed by parts of the brain that work consciously ; others are controlled by the spinal cord and the parts of the brain that work unconsciously. Those of the first kind are usually controlled by the will, but they sometimes act invol- untarily. They are called voluntary muscles. They move the bones and are located in the limbs and near the surface of the trunk (Fig. 44). The other kind of muscles are never controlled by the will, and are called involuntary muscles. We cannot cause them to act, nor can we prevent them from acting. They contract more slowly than the voluntary muscles. Most of them are tubular and found in the cavity of the trunk. The involuntary muscles belong to the internal organs, and relieve the will of the responsi- bility and trouble of the activity of these organs ; other- wise, the mind would have no time for voluntary actions. Gross Structure of Voluntary Muscles. — A beefsteak is seen to be chiefly red, although parts of it are white or yellowish. The white or yellowish flesh is fat ; the red, 39 40 HUM AX BIOLOGY Fig. 40. — MrscLE Bundles bound to gether by connective tissue sheaths. lean flesh is voluntary muscle. If a piece of beef is thoroufjhly boiled, it may be easily separated into I'll )i dies the size of large cords. These bun- dles may, by the use of needles, be picked apart and separated into tlircad- like fibers (Fig. 40). Microscopic Structure of Muscles. — These threadlike fibers may, under a magnifying glass, be separated into fine strands called fibrils. These last are the true muscle cells ; they are shown by the micro- scope to be crossed by many dark lines (Fig. 48). Hence voluntary muscles are called striated or striped muscles. Pro- longed boiling and patient picking with a needle are needed to dissect muscle, because the bundles are held together by thin, glistening sheets of connective tissue by which they are surrounded. This connective tissue surrounds and holds in place the separate fibers of each bundle (Fig. 40). The fibrils of invol- untary muscles are sP indie - shaped (see Fig. 42 ). There are no cross lines on the fibrils ; hence involuntary mus- „ ^ cles are called smooth Fig, 42. — Invoi.u.ntary Muscle Cells (or fibers). or unstripcd muscles. Fig. 41. — Two Mus- cle Fibers of Heart. THE MUSCLES 41 The heart fibers are exceptional ; they are the only invol- untary muscle fibers that are striped (Fig. 41). Thought Questions. Classification of Some of the Muscles. — Copy the following list and mark / for involuntary and V for voluntary after the appropriate muscles. Muscles for chewing. Muscles of gullet. Muscles of the heart. Muscles that move arms. Muscles for breathing. Muscles in the skin that cause the hair to stand on end. Muscles that move eyelids. Muscles that contract pupil of eye. Muscles for talking. Muscles that contract and expand the arteries (in blushing and turning pale). Muscles that move eyeball. Muscles that give expression to the face. Tendons. — The connective tissue zvJiich binds the fibers of muscles into bundles, and forms sheaths for the bundles, extends beyond the ends of the muscles atid unites to form tough, inelastic zvhite cords called tendons. Some muscles are without tendons, and are attached directly to bones. Study the figures and find examples of this (see Figs. 44, 75). To realize the toughness of tendons, feel the tendons under the bent knee or elbow, where they feel almost as hard as wires. The tendons save space in places where there is not room enough for the muscles, and permit the bulky muscles to be located where they are out of the way. Wher- ever the tendons would rise out of position when a joint is bent, as at the wrist and ankle, they are bound down by a ligament. Arrangement of Voluntary Mus- cles. — Circular muscles, called sphincter muscles, are found around the mouth and eyes. Muscles that extend straight along the limb either bend it and are called flexors, or straighten 'it and are called extensors. Most of Fig. 43. — (For blackboard.) Biceps relaxed and contracted. 42 HUMAN BIOLOGY the voluntary muscles are arranged in pairs and cause motion in opi)osite directions ; they are said to be autago- uists. The bicejxs ( Fig. 43) bends the arm. Its antagonist is the triceps on the back ot the arm. By feeling them swell and harden as they shorten, locate on your own body the muscles mentioned in Fig. 44. How a Muscle grows Stronger ; its Blood Supply. — Nature has provided that any part of the body shall receive more blood when it is working than when it is resting. When it ivorks tJic hardest, the blood tubes expand the most and its blood supply is greatest. So whenever a muscle is used a great deal, an unusual amount of material is carried to it by the blood, the cells enlarge and multiply, and the muscle grows. The walls of the capillaries are so thin that the food which is in the blood readily passes from them to the muscle. Because of the oxidation taking pkice, a work- ing muscle is warmer than one at rest. By use a muscle grozvs large, firm, and of a darker red ; by disuse, it be- comes small, flabby, and pale. But if muscles are worked too constantly, especially in youth, their cells do not have time to assimilate food and oxygen, and their growth is stunted. Unless the meal has been a very light one, vigorous exercise should not be taken after eating, as the blood will be drawn from the food tube to the muscles and the secre- tion of the digestive fluids will be hindered. Persons whose entire circulation is weak may find that light exercise after a meal, such as walking slowly, may help circulation and digestion. Why the Muscles work in Harmony. — Wheti a boy throws a stone, almost every part of the body is e07icerned in the action. His arms, his legs, his eyes, the breathing, the beating of the heart, are all modined to assist in the effort. Illustrated Study of Muscular Function Draw a dotted line from each function mentioned on margin to the muscle or muscles having that function. Bows the head ? Draws shoulder back? Lifts the whole arm outward and upward? Draws whole arm downward and forward? Bends the elbow? Straightens toes Bends the fingers? Raises the body on the toes? Raises toes? Fig. 44. — Superficial Muscles after the Statue of "The Digger' (Lami). 43 44 inW/.-iX lilOI.OGY As the boy wills to tiirow the stone, nerve impulses are sent to all the organs that can assist, and they are excited to just the amount of action needed. The Nerve Impulse and the Contraction. — Each nerve that goes to a muscle is composed of many fibers; the fibers soon separate and go to all parts of the muscle, and each viusclc fiber receives its nerve fiber (see Fig. 45). In the brain each fiber is stimulated at once, and all the fibers shorten and thicken together. This change is spoken of as contraction ; but since the muscle does not be- come smaller, the word may be misleading. When the muscle shortens, it thickens in proportion and occupies as much space as it did when relaxed. Where does Muscular En- ergy come from? — The 7terve does not furnish the energy zvhich the muscle uses when contmctittg. The muscle cells have already stored up energy from the food and oxyge?i brought to them by the blood, and the process called oxida- tion sets free the energy. Activity of muscle may increase the carbon dioxid output fivefold. Mental work has prac- tically no effect upon it. How a Muscle stays Contracted. — The muscle relaxes at once after contraction ; and in order to keep it contracted, nerve impulses must be sent in quick succession, causing in fact many contractions ; the effect of this is sometimes Fig. 45— Motor Nerve Fibers, ending among fibrils of voluntary muscle. Compare with Fig. 48. THE MUSCLES 45 visible, as the trembling of the muscle. Figure 47 shows an easy standing posture. What causes Fatigue. — Fatigue or exhaustion is due to the using up of the living material in the nerve cells and muscle cells by oxidation. Rest is necessary to give cells opportunity to repair themselves. Why is it less fatiguing to walk for an hour than to stand perfectly still for ten minutes .-' Fig. 46. — Improper Position; causes spine to curve to side; raises one hip and shoulder above the other. Fig. 47. — Best Position; chest is free to expand, and weight is easily shifted from one foot to other. Degeneration of Muscles begins with habitual disuse. We dare not furnish a substitute for the work of a muscle, if we wish the muscle to remain sound. A belt or a stay at the waist will cause the muscles of the trunk to become flabby and the abdomen to relax and protrude. How Muscular Activity helps the Health. — Life is change, stagnation is death. Muscular activity uses up the 46 nr.UAX BIOI.OGY food, gives a good apf'cdtc, and sr/s the di<^csti7'c organs to work ; it uses up the oxygen and sets the /inigs to 7vork ; but most of all, evety contraction of a niuscle helps the blood to flow. As a muscle contracts, it presses upon the veins and lymphatics, and, by this i)rcssure, forces the blood and lymph along (Fig. 48). In any ordinary activity, dozens of mus- cles are being used. That the effect upon the circulation is very povv- erlul, is shown by the rosy skin, deep breath- ing, and rapid heart beat. The many benefits of an active circulation of the blood and lymph will be discussed in the next chapter. See page (yj. A grave danger from athletics is that of developing the muscles, including the heart, to an enormous extent by training ; then zuhen training ceases the muscles undergo fatty degeneration from disuse. Heart disease and other diseases may follow. Many athletes die young, killed by trying to turn their bodies into mere machines for run- ning, boxing, or rowing, instead of living complete lives. The athletic ideal is not the highest ideal of health ; gen- eral activity, resembling the occupations of hunting and farming by which the early race supported itself, is best for health. Many kinds of factory work use only one set of muscles. The savage did not lead a monoto- nous life, and monotony is bad for both muscles and nerves. Fig. 48. — C.'\PII.I.arif.S among fibers of voluntary (cross striped) muscle. (Peabody.) THE MUSCLES 47 Advantages of Work and Play over Gymnastic Exer- cises. — The interest that comes from doing something useful, makes muscular exer- tion doubly beneficial to the health. The lifting of dumb- bells, Indian clubs, and pulley weights, and letting them down again, tends to become very irksome, even though done with the knowledge that the exercise will benefit the health. Useful labor and games place definite objects in view and do not require so great an effort of the will nor exhaust the nerves so much as mere exercise. The interest in the work or the game serves to arouse all the nerves and muscles to work in harmony. An Advantage of Gymnas- tics over Work and Play. — Gymnastics can furnish any required variety of exercises and can develop exactly the muscles that need develop- ment and leaiie those idle that have become overdei>elopedhy doing constantly one kind of work or playing continually the same game. The deform- ity of a flat chest (and round shoulders which always ac- company it) does not so often indicate a weak chest or small lungs as it indicates weak or relaxed muscles of the back and the habit of sitting in a relaxed position at work (Figs. 49, 50, 51). Gymnas- FiG. 49. —Desk too Low. (Jegi.) Fig. 50. — Correct Position. Fig. 51. — SLiri'iNG down in Seat. 48 J/r.U.LV BIOI.OGY tic twrrcisf is not wholly an ortijicial ciistovi. Cats stretch themselves, stretching each leg in succession ; many animals gambol and play. A gymnastic drill, taken to music and with large numbers of pupils in the drill, is interesting as work or play, and should not be neglected for any study, however important. Environment of Early Man and Modern Man. — ^A well-developed man ot one luiiulred and fitty ])()unds wciglit siiould have sixty pounds of muscles. The proportion is often different in the puny bodies of the average civilized men, such as clerks, merchants, lawyers, and other men with sedentary occupations; tiieir bodies are as likely to be lean and scrawny or fat and flabby as to be correctly proportioned. Why does a normal man have sixty pounds of muscles instead of twenty pounds of puny strings such as would have sufficed for a clerk, student, or a writer? This is because, in his native condition, he had to seek his food by roaming through the forest, contending with wild beasts or with other savage men, often traveling many miles a day, climbing trees, etc. Too Rapid Change of Environment ; Destructive Tendencies of Civil- ization. — // is impossible for tlie liitvuDt body to ihange greatly in a few hundred years. The body of man served him for many ages for the manner of life outlined above. It was suited for these conditions, and the muscles and the organs that support them cannot accommodate themselves to changed conditions in a few generations. It has only been a few hundred years since the ancestors of the Britons and Ger- mans, for instance, were running wild in the German forests, clad in the skins of wild beasts. Yet civilized man lets his muscles fall into disuse, he takes a trolley car or horse vehicle to go half a mile, an elevator to climb to the height of thirty feet. He neglects all his muscles except those that move the tongue and the fingers of the right hand. He never makes enough exertion to cause him to draw a deep breath, and his lungs contract and shrivel. He seldom, looks at anything farther than a few inches from his nose, and his eyes become weak. At the same time that he neglects his muscles and his lungs, he overworks his brain and his stomach ; yet he expects his body to undergo the rapid changes to suit the demands of his life. Such rapid changes in the human race are impossible. A man that does not see that sound health is the most valuable tiling in the world, except a clear conscience, is in danger both of wrecking his own happiness and of failing in his duty to others. Thought Questions. Shoes. — 1. What the faults of shoes may be in size ; shape; sole; heel; toe: instep. 2. Name deformities re- sulting to skin of foot ; nails ; joints ; arch ; ankle ; spine. 3. State effects THE MUSCLES 49 of uncomfortable shoes on muscular activity ; mind and disposition. 4. State effect of aversion to walking on muscles ; circulation. 5. If a shoe is too loose, it slips up and down at the heel and chafes the skin there ; if too tight, there is pres- sure on the toes, which causes a corn or ingrowing nail. Have your shoes been correct, or have they been too loose or too tight ? According to this test, what pro- ^ , ^ , , *= ^ Fig. 52. — Arch of Foot. It forms an portion of people wear shoes that ^l^^ti^ ^p^i„g_ are too tight? 6. How many sprained ankles have you known among boys; girls? 7. Why is it that people who grow up in warm climates have high, arclied insteps, and short, broad, elastic feet, but people of the same race who pass their childhood in cold climates often have long narrow feet with low arches and sometimes have the deformity called " flat foot " ? Instinct as a Guide for using the Muscles. — The instinctive feeling called fatigKc tells us when to rest. Tliere is also a restless, uneasy feeling that comes over a normal human being when confinement and restraint of the tnuscles have reached an iinhealthy limit. This feeling should not be repressed for long at a time. Many, ruled by avarice, ambition, interest in sedentary work, a silly notion of respectability, or a false conception of duty, have repressed this feeling and have lost it. There is then a feeling of languor, and a disinclination to the very activity which health demands. An unheeded instinct is as useless as an alarm clock that has been habitually disregarded. Exercise and Climate. — In our warmest states and in the tropics, one hour's vigorous physical labor a day, combined with the ordinary activities of life, will keep a person in good condition. In the colder states, muscular exertion for several hours is needed daily. Complete Living. — Numberless people have devoted themselves to an intellectual occupation, and planned to keep their bodies sound by gymnastics and special exercises. Because of the monotony of exer- cises, they are soon given up in nearly every instance. The safest way is never to allow all the energies to be devoted to a one-sided occupation, but so to plan one'^s life and ivork that a part of the time is devoted to some physical work, whether it be in a garden, workshop, or orchard ; in walking a long distance to the office; at bookbinding, cooking, wood carving, or any one of various other useful occupations. The result of manual training shows that not only strength of body, but strength of mind, is promoted by physical labor. Problems of war and of the chase kept active both the body and mind of the savage. Hence he led E 50 HUMAN BIOLOGY a more nearly complete life than liis civilized descendants, and his body was strong accordingly. We should admit the hopelessness ot having permanent good health without muscular activity and should determine that muscular exertion shall be as much a habit and pleasure as eating and sleeping. Alcohol and Muscular Strength. — Henjamin Franklin, one of the wisest and greatest of Americans, was a printer when he was a young man. In his autobiography he gives an account of his experience as a printer in London. He says: "I drank only water; the otlier work- men, fifteen in number, were great drinkers of beer. On occasion I carried up and down stairs a large form of types in each hand, when others carried but one in both hands. They wondered to see, from this and several instances, that the Water-American, as they called me, was stronger than themselves, who drank strong beer. My companion at the press drank every day a pint before breakfast, a pint at breakfast with his bread and cheese, a pint between breakfast and dinner, a pint at dinner, a pint in the afternoon about 6 o'clock, and another when he had done his day's work. I thought it a detestable custom, but it was neces- sary, he supposed, to drink strong beer that he might be strong to labor." Exercises in Writing. — The Right and the Wrong Way to ride a Bicycle. Pay Day at a Factory. A Graceful Form : how Acquired ; how Lost. A Drinking Engineer and a Railway Wreck. Practical Questions. — 1. Can we always control the voluntary muscles? Do we shiver with the voluntary or involuntary muscles? 2. If a man had absolute control over his muscles of respiration, what might he do that he cannot now do? 3. Why is one who uses alcoholic drinks not likely to be a good marksman? 4. Why should a youth who wishes to excel in athletic contests abstain from the use of tobacco? 5. Is there any relation between the amount of bodily exertion necessary for a person's health and the amount of wealth or the amount of intelligence he possesses? 6. Can you relax the chewing muscles so that the lower jaw will swing loosely when the head is shaken ? Can you relax your arm so that it falls like a rope if another person raises it and lets it fall? 7. The average man has sixty pounds of muscle and two pounds of brain ; one half of the blood goes through the muscles and less than one fifth goes through the brain. What inference may you draw as to the kind of life we should lead? 8. Why is a slow walk of little value as exercise? 9. How can we best prove that we have admiration and respect for our wonderful bodies? 10. Why is the ability to relax the muscles thoroughly of great benefit to the health? How is this ability tested ? (Question 6.) 11. Why is it as correct to say that the muscles support the skeleton as the reverse? 1. Head arteries I carotid). 3 Nameless arteries (innominate). 3. Collar bone (sub- clavian) artery. 4. Great bend of the aorta. 18. Ascending vena cava. 19. Vein from liver (hepatic), ao. Vein from stom- ach (gastric), from cen. Pulmonary arteries. Thoracic aorta. 10. Abdominal aorta. Artery to liver (hepatic). Artery to spleen (splenic). Arterj' to in- testine (mesenteric). / Artery to • kidney (renal). Descending vena cava. \ Nameless vei:i ! , (innominate, Vx 15 and 16 b-;- fore branching), Collar bone vein (subclavian) Jugular vein, , Pulmonary vein. Vein from intestine. \'ein to liver I portal 1. Vein from kidney. Right auricle. ft auricle. 27. Kigh' ven- tricle. Left ventri- cle. . Thoracic duct. { 30. .stomach. 31. Spleen. 32. Liver. 33. Kidneys. 34. I^uodenum. 35. Ascending colon. 36. Descending colon. 37. Lymphatic glands of mesentery. Coi.oKiiu Fii;uRK 5. Diagram of Circulation. CHAPTER V THE CIRCULATION Experiment i . Anatomy of Mammalian Heart. — Get a sheep's or beef's heart from the butcher. Get the whole heart, not simply the ventricles (as usually sold). Note the blood vessels, four chambers, thickness of different walls, valves, cords, openings. Experiment 2. Does Gravity affect the Blood Flow? — Hold the right hand above the head for a few minutes. At the same time let the left hand hang straight down. Then bring the hands together and see which is of a darker red because of containing more blood. Now re- verse the position of the hands for a few minutes, and find whether the effect is reversed. (Entire class.) Experime)it 3. Study of Human Blood. — Examine a drop of blood under the microscope, first diluting it with a little saliva. See Fig. 60. Experi)nent 4. The Circulation in a Frog. — Wrap a small frog in a moist cloth, lay on a slip of glass, place under the microscope, and study the circulation in the web of its foot. Experiment 5. (Entire class.) Effect of Exercise upon the Pulse. — Tap a bell as the second hand of a watch begins a minute and let the pupils count the pulse at the radial artery on the wrist above base of thumb. Repeat standing, or after gymnastics or recess. Result? Experiment 6. The Action of the Valves in the Veins. — Place the tip of the middle finger on one of the large veins of the wrist ; 'with the forefinger then stroke the vein toward the elbow so as to push the blood from a portion of it, keeping both fingers in place. The vein remains empty between the fingers. Lift the finger nearer the heart and no blood enters the vein ; there is a valve above which holds it back. Lift the other finger and the vein fills instantly. Stroke a vein toward the hand, and notice that the the veins swell up into little knots where the valves are. Stroke in the reverse direction. Result? Experiment 7. Finding the Capillary Pressure. This is found by- pressing a glass plate or tumbler upon a red part of the skin. When the skin becomes pale the capillary pressure is counterbalanced. Experiment 8. Emergency Drill. — Let one pupil come forward, mark with blue chalk or pencil the position on his arm of a supposedly cut vein. Let another pupil use means to stop the imagined blood flow. 51 52 HUMAN BIOLOGY Experimfttt c). Let another pupil stop the flow from an imajrinary cut artery marked red. See text. Expct iiiwnt lo. In a case of nose bleed do not let pupil lean over a bowl. (Why?) Cause him to stand rather than lie. (Why? See Exp. 2.) Apply cold water to contract arteries to nose, also have pupil hold a small roll of paper or a coin under upper lip (to make muscular pressure on arteries to nose). Experiment 11. Let one pupil treat another for a bruise (see p. 62). Experiment 12. Emergency drill, restoration from faintinj; (see p. 57). The Cells have a Liquid Home. — The cells in the body of man, like the ameba. live in a watery liquid. This liquid is called lymph. The cells cannot move about as the ameba does to obtain food, so the blood brings the food near them and it soaks through the blood tubes into the lymph spaces next to the cells (see colored Fig. 3). The ameba gives off waste material into the water; the cells of the body give it off into the lymph to be carried off by the circulation. The blood, then, has two functions : (i) to take nourishment to the tissues; (2) to take awnv waste material from them. The Organs of Circulation. — These are the heart, which propels the blood ; the arteries, which take blood away from the heart ; the veins, which take the blood back to the heart ; and the capillaries (Fig. 53), which take the blood from the arteries to the veins. The heart is a cone-shaped organ about the size of its owner's fist. It lies in a diagonal position behind the breastbone, with the small end of the cone extending toward the left. The smaller end (Exp. i) taps or beats against the chest wall at a point be- tween the fifth and sixth ribs on the left side. The breastbone and ribs protect it from blows. An inclosing membrane called the pericardiuni secretes a serous fluid and lessens the friction from its beating. Why the Heart is Double. — There viiist be a pump to move the impure blood fro»i the body to the lungs to get oxygen Fig. 53. — Capillaries, connecting artery {b) with vein (a). THE CIRCULATION 53 from the air, and there must be another pump to send the pure blood from the lungs back to the body. Hence there are two pumps bound together into one heart, beating at the same time Uke two men keeping step, or Hke two car- penters keeping time with their hammers. There are valves in the heart, as in other pumps. These valves are so arranged that when any part of the heart contracts and forces the blood onward, the blood cannot return after that part of the heart relaxes. Are the pumps placed one behind the other .^ Or is one above the other .'^ Neither; they are side by side, with a fleshy partition between them (Fig. 54). The pump on the ^ right moves the impure blood <; from the body to the , , • , puTmonary lungs, and the one on the veins left moves the pure blood from the lungs to the body. There is no direct connection between the right and left sides of the heart. To trace one complete circuit of the blood (Fig. 54), let us begin with the blood in the capillaries of the outer tissues, such as the skin or muscles. The blood goes through small veins which unite into tivo large veins, through which it enters the receiving chamber, or rigJit auricle, goes through the tricuspid valve into the expelling chamber, or right ventricle, then through a semilunar valve into the pulmo- nary artery leading to the lungs. Becoming purified while Fig. 54. — Diagram of Heart. Notice the two dark spots in the right auricle, and four dark spots in left auricle, where the veins enter. Does the aorta pass in front of, or behind, the pulmonary artery.' 54 HUM AX BIOLOGY passing through the capillaries of the linijrs, the blood goes through the puhnouary veins to the left aiiriele (Fig. 54), then through the bicuspid or mitral valve, to the left ventri- cle, whence it is forced through a semilunar valve into the largest artery of the body, called \\\c great aorta {VV^. 54). Thence it goes to the smaller arteries, and then to the capil- lanes of the tissues in general, thus comi)lcting the circuit Fig. 55. — The Lkft Side of Heart (plan), showing the left ventricle at the mo- ment when relaxing and receiving the blood from the auricle; and the same at the beginning of contraction to send blood into aorta. Notice action of the valve. Structure of Veins and Arteries. — Seen under the micro- scope the arteries and veins show that they are made of three kinds of tissues arranged in three coats (¥\g. 56): a tissue resembling epithelial tissue (Chap. I), as a lining to lessen friction; an outer connective tissue (Chap. I), to give elasticity ; and a middle coat of muscular tissue to enable the vessels to change in size. Let us see why blood vessels must have these three properties .-* Why the Blood Vessels must be Elastic. — The aorta and its branches are always full of blood. When the left ventricle with its strong, mus- cular walls contracts, the blood in the aorta and small blood tubes can- 7iot mcroe forward fast enough to make room for the new supply so suddenly sent out of the ventricle. Where can this blood go ? If a THE CIRCULATION 55 In men cup is full, it cannot become more full; not so with an artery. The elastic connective tissue allows it to expand as a rubber hose does under pressure. The first part of the aorta having expanded to receive the incoming blood, the stretched walls contract because of the elas- ticity of the outer connective tissue coat and force blood into the por- tion of t lie aorta jnst ahead, forcing it to expand in turn. Thus a wave of expansion travels along the arteries. This wave is called the pulse. The Pulse may be most easily felt in the wrists and neck. As the artery stretches and springs back, one beat of the pulse is felt there are about se^'cnty heart beats or pulse beats a minute. In women the rate is about eighty a minute. It is slowest when one is lying down, faster while sitting, still faster when stand- ing, and fastest of all during running or violent exercise. (Exp. 5.) It should not be thought that the muscular or middle layer of the artery actively con- tracts and helps to send along the pulse wave ; for this wave is simply the pas- sive stretching and contracting of the outer connective coat, and travels like a wave crossing a pond when a stone is dropped into the water. The force of the pulse is furnished, not by the muscle fibers in the artery, but by the beat of the heart ; the outer, or con- nective tissue, coat enables the pulse to travel. Why must there be a mid- dle, or muscular^ coat for variation in size? Use of the Middle Coat ; Quantity of Blood and its Distribution. — The bodv of an adult contains about five quarts of blood. The blood furnishes the nourishment needed for the activity of each organ. The more vigorous the work of any organ, the greater is the amount of blood needed. The whole atnount of blood in the body catinot be suddenly increased, but the muscular coat of the arteries going to the workittg organ relaxes, and allows the arteries to become enlarged by the pressure from the heart. Consequently, more blood goes to the active organ, and the other organs get along with less blood for the time. When we are studying, our brains get more blood ; when running, the Fig. 56. — Section of Artery, A, AND Vein, V, showing inner coat, e (endothelial) ; middle coat, m (muscular) ; and third coat, a (connective tissue). 56 HUMAN BIOLOGY Fig. 57. — Capillaries Magni- FiEO, SHOWING CELLS forming their walls. Notice that each cell has a nucleus and three branches. If" muscles get more ; after a hearty dinner, the stomach and intestines got more than any other part of the body. Why is it difficult to do the J. best studying and digest a meal at the 7 f(/ii same time? We see that the muscu- ^^..-^(l lar coat of the arteries is a very useful coat, for // enables the supply of blood to be increased in any origan which is in temporary need of it. Why the Blood Vessels must be Smooth. — The inner coat of the heart and other blood vessels is made of tissue like the epithelial tissue which forms the epidermis and the smooth lining of the mouth and other organs. The purpose of this lining is to lessen friction, and thus save the work of the heart. The friction is greatest in the capillaries because of their small size. The inner coat of smooth cells is the only coat that is prolonged to form the capillaries (see Fig. 57). The capillaries are small, thin, short, and very numerous. They arc rcry small so that they may go in between the cells of the tissues. TJic capillaries are very thin so that the nourishment from the blood may pass readily into the tissues, and the waste material pass readily into the blood. They are very short so that the friction may be less ; and they are very numerous so that all parts of the tissues may be supplied with blood, and that the blood may flow very slowly through them. Because of the number of the cap- illaries, their total volume is several hundred times larger than the volume of the arteries that empty into them, or of the veins that flow from them. Hence the blood flows slowly through the capillaries, as water flows slowly through a lake along the course of a river. All the changes between the blood and the lungs, and between the blood and the tissues, take place in the capillaries, and THE CIRCULATION 57 the object of the other parts of the circulation is merely to move the blood continually through the capillaries. The effect of gravity is to retard the flow in certain parts of the body and aid the flow in other parts, according to the position of the body (Exp. 2). Fainting is usually due to lack of blood in the brain, which in turn results from a weakening of the heart beat. Since the brain cannot work with- out fresh blood, fainting is accompanied by unconsciousness. Recov- ery from fainting is aided by loosening the clothing at the neck and by placing the head of the patient a little lower than the body so that the weight of the blood may aid the flow to the brain. Dashing a little cold water in the face shocks the nerves and arouses the heart to stronger beats. The veins have valves placed frequently along their course (Fig. 58). These valves are pockets made by a fold in the inner coat of the wall of the vein. When a boy places his hand in his pocket, the pocket swells out ; but if he rubs his hand on the outside of the pocket from the bottom toward the top, it flat- tens down. So with the action of the blood upon the valves in the veins. (Repeat Exp. 6 in class.) I I I Fig. 58. — Valves in Veins. (jegi.) How Muscular Exercise aids the Heart. — When a inuscle contracts, it hardens and presses upon a vein which goes through the muscle, and the blood is pressed out of the vein (see Fig. 58). The blood cannot go toward the capillaries, for the valves fill and close when it starts that way ; so it must all go out toward the heart. When the tnuscle relaxes, the blood that has been pressed forward cannot go back because of the valves, but the valves nearer the capillaries open, and the veins are filed from the capillaries (Fig. 53). When the muscle con- tracts again, the same effect on the blood movement is repeated. We see, therefore, that every contracting muscle converts into a pump the vein running through it, and when a person works or exercises, many little pumps are working all over the body, aiding the heart in its function. 58 J/C.V.-i.V BIOLOGY This aid makes the blood flow faster and relieves the heart of part of its work, so that it beats faster, just as a horse nii«;ht trot faster if another horse helped to draw the load (Exp. 3). Tlic [iressure of a contracting muscle upon an artery does not aid the blood tiow in the arterv because tiie latter is destitute of valves. How Breathing aids the Heart. — Breathing is a blood-pumpinj;; pro- cess as well as an au-renewing process. When the chest e.xpands, blood is drawn into it. When the chest con- tracts, the flow of blood away from it is aided. As the ciiest expands, the downward pressure of a great, broad muscle, the diaphragm (Fig. 74; compresses the liver, stomach, and other ab- dominal organs, and forces the venous biood up- ward into the expanding chest, thus helping it on its way to the heart. But if the abdominal wall is weakened by tight lacing or by the pres- sure of belts and bands which support the cloth- ing, the weak abdominal wall yields to the downward pressure of the diaphragm, and no compression of the liver or aid to the circulation will result. How the Blood Vessels are Controlled. — Evi- dently the biood vessels are not regulated by the will. We cannot voluntarily increase the beat- ing of the heart, or cause it to slacken its action. Even an actor cannot cause his face to turn pale or to blush at will. This is because the tiny muscles in the walls of the blood vessels are involuntary muscles. They are controlled by nerves of the sympathetic system called vaso- motors. They are not subject to the wil' (see Fig. 25). The nerve cen- ter which controls the blood vessels is located in the top of the spinal cord at the base of the brain. When cold air strikes the skin the nerves near the arteries are stimulated, the arteries in the skin contract, and the skin turns white. When the heat from a hot fire strikes the skin, the nerves are soothed, the arteries relax, and the face becomes red. When the stomach is filled with food, the heart beats faster and sends more biood to aid in digestion. When we run fast, the heart beats fast to supply more blood to the muscles, but it slows down as sleep comes on. that the body and brain may rest. Parts of the Blood. — The blood which flows from a cut finger seems to be a bright red throughout. When a drop of it is looked at through a microscope, however, the Fic. 59. — The Ven- tricles OF A Dog's Heart relaxed (above), and contracted (be- low). THE CIRCULATION 59 liquid itself is seen to be almost as clear as water. This liquid is called the plasma. Floating in it are millions of biconcave disks contain- ing a pigment (hemo- globin) which gives the red color to the blood. The disks are called red corpuscles (Fig. 6o). A few irregularly shaped bodies, nucleated and almost transparent, and called wJiite corpuscles, are also found in the blood. The red corpus- cles go only where the plasma carries them (Exps. 3, 4). The white corpuscles sometimes leave the blood vessels entirely. At times one may be seen shaped like a dumb-bell, half of it through the wall of the blood vessel and half still in the blood vessel. After the corpuscle is out, no hole can be found to account for its mysterious passage. TJie zvliite corpuscles consist of protoplasm. The red corpuscles contain no protoplasm. Hence the latter are not really alive. The Use of Each Part of the Blood.— The plasma keeps the blood in a liquid state, so that it may flow readily ; the plasma also transports the food that has been eaten and digested, and carries carbon dioxid to the lungs and other waste material to the kidneys. The red Fig. 6o. — Human Blood Cells (magni- fied 40,000 areas), showing many red cells and a single white blood cell on left, larger than red cells. (Peabody.) Fig. 61. — Side and Front Views of Frog's AND Man's Red Corpuscles, drawn to same scale. Compare outline, concavity, diameters. 6o J/i'M.LV BIOLOGY cotfiisclis transport the oxygen from the lunf^s to the tis- sues. The w/iiti- C(>r/>//.u/is devour ivud destroy irritating particles, such as drugs, poisons, and germs. They are of great importance in purifying the blood and as a protec- tion against disease. One is shown in Fig. 60. The sounds of the heart beat may be heard by applying the ear to the chest. They are two, a A'w^, the bleeding-. The washing in cold water may do this. Elevating an injured arm or leg will aid the blood greatly in forming a clot at the opening. 3. Bandage firmly with a strip of cloth and sew the end. Keep wet the part of the bandage where the cut is ; this lowers the temperature of the wound. It may be necessary to hold a gaping wound closed with strips of surgeon's plaster placed across the cut. A handkerchief folded first into a triangle and then into a narrow bandage is often useful. A cut artery may be known from a cut vein by the brighter color of the blood, and by the flow being stronger at each heart beat, while the flow from a vein is uniform. Pressure to stop the' flow of blood from an artery should be applied between the cut and the heart ; but when the blood comes from a vein, the pressure should be applied to the side of the cut farthest frojn the heart. Apply hot water immediately for several minutes to a bruise. Either a bruise or a cut may be washed with a weak solution of some antiseptic such as carbolic acid. After washing a bruise it may be bound with a cloth soaked in witch hazel or arnica. The Lymphatic System This system contains and conveys a liquid called the lymph. It consists of lymph spaces, lymph tubes, THE CIRCULATION 63 (lymphatics), and lymphatic glands. Lymph corresponds nearly to the blood witJioiit the red corpuscles. It is the familiar liquid seen in a blister, or oozing out where the skin has been grazed without breaking a blood vessel. Necessity for Lymph and Lymph Spaces. — The body cannot be nourished with the albumin, sugar, oxygen, and other digested food in the blood, until this food passes out of the blood vessels. The food leaves the blood through the thin walls of the capillaries. Many of the cells do not touch the capillaries, and the lymph penetrates the spaces between the cells to reach them (see colored Fig. 3). If there were no lymph spaces, these cells could not get any food. The lymph bathes the cells, and the cells absorb what they want from the nourishing fluid. The red corpus- cles bearing the oxygen cannot pass through the capillary walls. Oxygen, being, a gas, readily passes through the walls and reaches the cells through the lymph in the lymph spaces. The waste materials must go back into the blood; carbon dioxid passes back through the capillary walls and is taken to the lungs ; how the other waste materials formed in the cells pass back will soon be explained. Need of Lymphatics. — The plasma continually passes into the tissues, but it cannot retjirn directly into the blood. The lymph contains waste material which must be removed, and also much unused food which nature, like an economical housekeeper, will offer to the tissues again. The7'e are vessels called lymphatics that take the lymph back ijito the blood (see Fig. 64). The Lymphatic Circulation (Fig. 64). — Ihe blood flow does not begin nor end. but makes a never ending circle. The countless lymphatics begin, with open ends, in the lymph spaces between the cells (colored Fig. 3). The smaller lymphatics unite into larger ones until finally they all unite into two large ones that empty into the large veins 64 HUMAN BIOLOGY under tlie collar hones, near the neck. The one that empties under the left collar bone (3, Kig. T/)) is called the thoraiic dint because it goes Fit;. 64. — Surface Lymphatics of Hand. up through the thorax just in front of the spinal column (i. Fig. 66). The other at the right side of the neck is called the 7-ight lymphatic duct (see Figs. 64. 65). In persons with the drofisy, the lymph accumulates in the lymph spaces and is not drained away by the lymph flow. Dropsy usually shows itself first by swcllinj^ of the feet and the leg below the knee. (Wiiy ? See Exp. 2.) There is a set of lymphatics called lacteals, situated in the abdomen, which have the func- tion of absorbing digested fats from the intes- tine (Fi.'" An inflamed part is red, swollen, hot, and painful. Prevention and Care of Colds. — A cold is an inflammatio7t of a mucous membrane. Colds are prevented by so living as to encourage 3. free, vigorous circulation, and especially by not coddling the body so tenderly that the circulation becomes deranged by the least exposure. The circulation may be deranged by overheating as well as by chilling the body ; usually it would be more appropriate to say that the person caught "a hot '" than -'a cold."' At the frst sign of a cold vigorous exercise, a cold bath, or going outdoors into cold air may aid in sending fresh blood to remove the stagnation and stop the inflammation. A warm foot bath and hot drinks may relieve by drawing blood from the congested mucous membrane. After the cold has become fixed such measures will not help, but the cure is aided by helping the skin to keep its full share of blood. The cold must run its course. The cells will be given every chance to repair the injury and destroy the germs (if any) by avoiding hard work, eating moderately of digestible food, avoiding drugs, especially infallible drugs advertised in newspapers, even if recommended by otherwise intelligent people. Repeated colds tend to become a disgusting disease called chronic catarrh. Con- stricting the blood vessels of the skin causes congestion of the (internal) mucous membranes. A skin tenderly protected constricts more readily than one accustomed to cold. Cold is the best prevetitive of cold. Cold baths, pure air, light clothing, free breathing, moderate eating, ward oiT colds. Fussing with sprays, gargles, and drugs will not ; for the main factor in bringing on a cold is not germs, nor temperature, but the state of the syste?n itself. Persons who have suffered much with colds have found that after substituting cotton underwear for woolen, colds became very rare. Linen will have a similar effect, but it is not as dur- able, soft, or heat-retaining as cotton (see p. 16). Practical Questions. — 1. Through what kind of skin do the blue veins in the wrist show most plainly? 2. Which is more com- pressible, a vein or an artery? 3. Why are those who take little exer- cise likely to have cold feet? (p. 57.) 4. Where does the so-called venous blood flow through an artery? 5. What vein begins and ends in capillaries? (The portal vein, colored Fig. 5.) 6. To what purifying organ, after leaving the lungs, does the heart send part of the blood for further purification. (Colored Fig. 5.) 7. What keeps the blood moving between the beats of the heart? CHAPTER VI THE RESPIRATION Experivietit i. (Home.) Study of the Throat. — Sit with the back to the light. Study tlie open nioutli and tliroat with a mirror and make out the uvula, tonsils, and other parts shown in Fig. 68. Experivietit 2. Anatomy of Lungs. — Study fresh lungs of sheep, hog. fowl, or frog. Will they float? Will they contract when expanded by air blown in through a quill or other tube? What is the structure of the windpipe? Can you distinguish the arteries from the veins by the stiffness of their walls? Which contain pure blood? Study branching of air tubes. Make a skctcii. Experiment 3. Tests of Expired Air. — Breathe upon a mirror, bright knife blade, or cold window pane. Result? State your conclusion? Experitncnt 4 Carbon dioxid added to limewater will cause a white cloud consisting of particles of limestone. Breathe through a tube or straw or the hollow stem of a reed into clear limewater. Result? Con- clusion? (Limewater may be had at druggist's or made by pouring water upon a lump of unslackened lime and draining it off when lime has settled.) Experiment 5. Breathe for several minutes upon the bulb of a thermometer. Result? Conclusion? Experiment d. Breathe a few times into a large, carefully cleaned pickle jar, or a bottle. Cork it tightly, and set it in a warm place for several days. Then uncork and smell the air in it. Result? Conclusion? Experiment']. Pierce a small hole in a card, place card over a wide-mouthed bottle, and breathe into bottle through a tube, lemonade straw, or hollow reed. Pull out straw. Place bottle, mouth downward, on table, and slip out card. Slide bottle to edge of table and lift lighted candle into bottle. Result? Experiment 8. Place bottle of fresh air over lighted candle. Result? Conclusion? (See Animal Biology, p. 14.) Experiment 9. (School.) Testing the Air of a Room. — Fill a fruit jar or large bottle with water, and take it into a room containing many people. Pour out the water. (This insures that all the air now in the jar is air obtained in the room to be tested.) Seal the jar if test is not to be made at once. Test by pouring in two tablespoonfuls of clear lime- water and shake. If the limewater turns milky, the ventilation is bad. Experiment \o. (Home and school.) Homemade Current Detector. — Dangle a bit of paper by means of a spider web or thread from the ' 70 THE RESPIRA TION 7 1 end of a walking stick or ruler. (Or test with the flame of a candle.) Hold it near cracks of window, above and below doors, and especially before openings intended for entry and exit of air, and test if air moves as desired. Experiment ii. Ventilation of the Schoolroom. — Let the whole class rise, and with the fingers test cracks around doors and windows. Wherever the air feels cold to the hand the air is entering. Experiment 12. Dust. — With a mirror cause a sunbeam to play like a search light into a closed room several hours after it has been swept. Result? Do the same in a room where every window and door were 0{>en during sweeping and left open afterwards. Result? Conclusion? Note also the amount of dust on the furniture of each room. Experiment 13. Study of Habitual Quiet Breathing. — Without any more disturbance of the breathing than can be helped, direct your atten- tion to your breathing while sitting quietly. Record motions of any parts of chest and abdominal walls that may be noticeable. If neces- sary, lay the hands successively against different parts of the wall to test for motion. Think of another subject, and later repeat observations. Experiment 14. Study of Deep Breathing. — Place your hands suc- cessively upon the front and sides of your chest, waist, and abdomen, while drawing in and sending out deep breaths. What motions of the several parts are observed at each stage ? Experiment 15. Study of Elasticity as a Factor in Breathing. — (i) Notice whether in quiet breathing there is an elastic rebound as the breath goes either in or out. If so, it is due to the elasticity of the cartilages or air cells of lungs, or both. (2) Breathe by inflating the lungs strongly at each breath. Is the air then forced out without effort? (3) Breathe by flattening the chest and abdomen as much as possible at each breath. Does the air then rush in without effort? Experitnent 16. Chest Breathing. — Try to breathe wholly by deep expansions and contractions of chest wall. What motions, if any, are noticed in abdominal wall as breath goes in? As it goes out? (Test motions with hand.) Experiment 17. Abdominal Breathing. — Try to hold the chest walls still and breathe by strong contraction and expansion of abdomen. Do the chest walls move at all ? Neither " chest breathing " nor " abdominal breathing " is the normal way. See text. Experiment 18. Full Breathing. — Try breathing by outward and inward movement of walls of chest, waist, and abdomen. Do you suc- ceed? This is normal breathing. Is the motion greater at the front or the sides of the waist? Put a belt around the waist tight enough to stay in place and repeat. Is the waist motion interfered with? 72 HUMA>7 BIO 1.0 GY Expfritnent 19. How the Ribs are Lifted. — Make a model like sketch to represent backbone, breastbone, and two ribs, usinj; pins to make joints loose at corners. Use cords for diagonals. What happens when cord ac is pullrd? When cord /^>i^i. \ Pi.o,...w other is the i'j'f/'//- agus or gullet. At the top of the trachea is the cartilaginous lar- ynx, or voice box. If the finger is placed upon the larynx or Adam's apple, it is plainly felt to move up and down when swallowing. The opening into the larynx is provided with a lid of cartilage, the epiglottis. Inside the larynx, the vocal cords are stretched from front to back. Just below the larynx comes the trachea proper, which is a tube about three fourths of an inch in diameter and about four inches long (Fig. 69). It consists of hoops of cartilage (Fig. 69) which are not complete circles, but are shaped somewhat like the letter C, being completed at FiG^69. - LUNGS p- with trachea. ^j^^ ^^^^ . involuntary mus- TA ; thyroid gland, th ; larynx, Z, ; ■' -' and hyoid bone, H. cular tissue, whose function P-— THE RESPIRATION 75 Fig. 70. — Lobule OF Lung. is to draw the ends together at times (for instance, during coughing) and reduce the size of the tube. The function of the hoops of cartilage is to keep the windpipe open at all times. If it should be closed by pressure, life might be lost. These rings of cartilage may be felt in the neck. The lower end of the trachea is just behind the upper end of the breastbone; there it divides into two large tubes. These subdivide into a great number of smaller branches called bron- cJiial tubes. Cartilage is found in the walls of all but the smallest of the tubes. The subdivision continues, somewhat like the branching of a tree, until the whole lung is penetrated by bronchial tubes. Each tiny tube finally ends in a wider funnel-shaped chamber called a lobule (Fig. 70), into which so many dilated sacs, called air cells, open, that the walls of the terminal chamber or lobule may be said to consist of tiny cups, or air cells, placed side by side. The lobules, or clusters of air cells, are chiefly near the surface of the lung. (The word " cell " is here used in its original sense to de- note a cavity or cham- ber, and not in the sense of a protoplasmic cell.) The air cells arc elastic Fig. 71. — Capillar] i;s AROUND Air Sacs and enlarge by stretch- OF Lungs (enlarged 30 diameters). Air j^^ ^^ ^j^^ ^j^^^j. ^^_ sacs in white spaces. Dark lines are capil- " laries. (Peabody.) pands ; hencc, the cells 76 HUM AX BIOLOGY must have many of the j<-/A'xc; elastic fibers of connective tissue in their walls. They are lined with an exceedingly thin membrane of epithelial cells through which oxygen and C(vlh>n dio.xid arc exchanged. In the walls of the air cells there is a nctzcork of capillaries (Fig. 71). The dark red blood comes into these capillaries from the i)ulmonary arteries, and is changed to a bright red by the time it leaves them to enter the pulmonary veins. The air leaves the lungs warmer, moister, and containing more carbon dioxid than when it entered. Most of the mucous membrane lining the air passages has a surface layer of ciliated cells. Cilia arc tiny thread- like projections (Fig. 72) which con- tinually wave to and fro, the quicker stroke always being outward ; for their function is to remove particles of dust and germs that may find entrance to the air passages. When the mucus containing the dust is raised nearly to the larynx, it may be thrown out by coughing. Near the opening of the nos- trils are placed many hairs, hundreds of times larger than cilia, through which the air is strained as it enters the nose. Hairs are multicellular; cilia are parts of cells. See Animal Biology, Fig. 14. The Lungs. — The entire chest cavity is occupied by the lungs except the space occupied by the heart, the larger blood vessels, and the gullet. The right lung has three lobes, or divisions, and the left lung has two lobes. The lungs are light pink in early life, but become grayish and darker as age advances. This change is more marked in those who dwell in cities, or wherever, the atmosphere is smoky and dusty. The lungs are covered and inclosed by Fl(-,. 72. — CiLIATKI) Cells, lining the air passages. THE RESPIRATION 77 a smooth membrane called the plctira. This membrane turns back and lines the chest wall, so that when the chest expands, the two sleek membranes glide over each other with far less friction than would be the case if the lungs and chest wall were touching (Exp. 2). The Respiratory Muscles. —(Repeat Exps. 13, 14, 15.) The chief breathing muscles are the diapliragm (see Figs. 73 and 74), the x^\\^z\q.s forming the abdominal walls (see Fig. 44), and tivo sets of short mus- cles (an internal and an external set), bctiveoi the ribs. They are called intercostals. (They are the flesh eaten when eating pork ribs.) The diaphragm, which is shaped like a bowl turned upside down, rounds up under the base of the lungs somewhat like a dome and sepa- rates the chest from the ab- domen. Its hollow side is toward the abdomen and its edges are attached to the lovvest ribs and the vertebra of the loins. Inspiration is brought about by the rising of the ribs and the descent of the dia- phragm. Expiration takes place when the ribs descend, the abdominal walls draw in, and the transmitted pressure lifts the relaxed diaphragm. Inspiration. — To cause inspiration the diaphragm con- tracts, it flattens and descends, since its edges are attached Fig. 73. — Vertical Section ov Trunk, showing dia- phragm, cavities of thorax and abdomen. 78 I/rM.iX BIOLOGY lower than its middle (Fis;- 71)'^ the lungs descend with it, thus lenj^thening the chest from top to bottom ; at the If ! ■ ifJB .>■ I h\V\\\ I V \^ •. Fig. 74. — Diaphragm (or midriff), seen from below. (Cunningham.) The central portion (light) is tendinous. As the diaphragm descends, it acts like the piston of a great pump and the blood is forced up through the vena cava, and the lymph through the thoracic duct (Fig. 66). same time the ribs are raised upward and outward (Fig. 76) by the contraction of the outer set of muscles between the ribs. Thus the c/icst is made longer, broader, and deeper from front to back. The lungs expand when the chest expands, and the air rushes in. Why is this? The lungs contain no muscles and cannot expand themselves; the air cannot be pulled in, for its parts do not stick to- gether. The true reason is that the air has weight. The THE RESPIRATION 79 atmosphere has a height of many miles, and the air above is pressing on that be- low. When the chest walls are raised there would be an empty space or vacuum be- tween these walls and the lungs, did not the pressure of t/ie outside air push air through the wifidpipe iuto the III ugs a n d cxp aud than (Exp. 19). Expiration. — - In very Fig. 76. — Blackboard Sketch, to show how the chest is expanded when the ribs move upward and outward. Fig. 75. — Framework of Chest. active breathing the abdominal walls actively contract so that they press strongly upon the digestive organs, which in turn press the diapltragui up. The ribs are also draivn dotvn and in. Thus the chest be- comes smaller and forces the air to flow out through the windpipe (Exps. 20 and 21). Thought Questions. — V\"hy brcatJiing with the waist is easier than breatJiing with tJie upper chest. Ep'ects of confining the uuu'st. I . There are two pairs of ribs below, while there are none 8o II I'M AN BIOLOGY above. 2. There are three pairs of ribs below, wliile there are none above, but all ribs of the upper chest are ribs. 3. The lower of the joints between the seven pairs of true ribs and the sternum are more flexible than the upper joints because . (Observe the joints in Fig. 75.) 4. The walls of the waist swing and , while the walls of the upper chest must move and . 5. The bones of the rest upon the upper chest. In upper chest breathing their weight, and the weight of both of the must, therefore, be lifted. (Fig. 28.) Test by trying it. Hygienic Habits of Breathing. — Chest breathing uses chest chiefly, abdominal breathing uses abdomen chiefly, Fig. 77. Fig. 78. Fig. 79. Fig. 77. — Female Figure encased in Cokset. Expansion at the w.iist is here impossi- ble and the breathing is called " collar-bone breathing." Fig. 78. — Male Figure. Here, owing to pressure of clothing and faulty position, expan- sion of chest is hindered and breath is taken by the "' abdominal method." Fig. 79. — Figure Properly Poised AND Free. Here the entire thorax can move freely, and natural breathing is the result. (For blackboard.) From Latson. full breathing uses both. These three forms depend upon whether the breathing is carried on by using the muscles of (i) the chest, (2) the abdomen, or (3) both (see Figs. TJ, 78, 79). There has been much debate among physicians, surgeons, and singers as to which of these methods is best. Probably this question would not have been raised but for the confining and deforming effect of clothing upon the waist. Full hrcathijig is used THE RESPIRATION 8 I by children of all races, by both men and ivomen of wild tribes, and by men of civilized countries. It is undoubtedly the natural way, as well as the easiest and most effective way (Exps. i6, 17, 18). Breathing with the upper chest is exhausting because of the stiffness of the upper part of the bony cage (see Fig. 75) ; for it is inclosed by true ribs fixed to the breastbone by short cartilages. The ribs in the waist (Fig. 75) are either floating in front or fixed by long cartilages to the ribs above. In pure abdominal breathing the diaphragm must con- tract more than in full breathing in order to descend, because its edges have been drawn together and fixed by binding the ribs at the waist. In full breathing the floating and false ribs at the waist (five pairs in all) float in and out as nature provided. As they move out, this broadens and deepens the chest, and aids the flattening of the dia- phragm by moving its edges farther apart. Those persons, perhaps one in a thousand, who voluntarily deform the body with tight clothing are beneath contempt. But so uniform is the pressure of tight clothes and shoes that the wearer soon becomes unconscious of them, and so powerful are the effects that not one person in a thousand escapes deformity and injury. Children's clothing should be supported by the shoulders, and adults' clothing by both shoulders and hips, but by the waist, never. Cellular Respiration. — The chemical activities within the cells and their need of oxygen, not the amount of oxygen in the lungs or blood, determine how much oxygen the cells absorb from the blood. Oxygen cannot be forced even into the blood beyond the required amount. Deep breathing movements, however, help the flow of the blood and lymph. Carried to excess, they tire the will and exhaust the nerves. • Changes in Blood while in the Lungs. — The coloring matter (or hemoglobin) of the corpuscles absorbs oxygen (and becomes oxy-hemoglobin). Carbon dioxid is given off from the plasma. The blood becomes a brighter red. Changes in Air in the Lungs. — The air entering the lungs consists of about one fifth oxygen and four fifths nitrogen. This nitrogen is of no use to the body, and is exhaled unchanged. A part of the oxygen inspired is taken up by the blood, atul carbon dioxid is sent out in its place. 82 HUMAN BIOLOGY About half a pint of water is «;ivcn off through the lungs in a day. Minute (|uantities of injurious animal matter are also given off in the breath from even the soundest person. The air leaves the lungs warmer, damper, and with more carbon dioxid than when it entered (Exps. 3 to 9). Persons witli decayed teetli, catarrh, indigestion, diseased lungs, or other unsoundness give off still more of this material. When many people are .issembled in a badly ventilated room, the amount of injurious animal matter in the air is much increa.sed, and is called '*■ crowd poison.'''' Its odor is strong and repulsive to one who just enters the room, but the sense of smell becomes dull to it in a few minutes. It would seem that nature gives a fliir warning against harm ; hut if we disregard the warning it soon ceases. People who are really Unclean. — Nature's plan seems to be for us to live out of doors. Air once breathed is impure. It is just as unfit to enter our bodies as muddy water or decayed food. Yet many who call themselves cleanly and refined, and "ivill not allow a speck of dirt to ret/niin on their clothes, nor use a spoon just used by another, do not object to breathing into their lungs, over and over again, the cast-off air from the lungs of others. If a window is opened for ventilation, they are horror-stricken for fear of drafts. Drafts are injurious only to persons perspiring, or to those who have coddled the skin by continu- ally overheating it. There are thousands of schools, churches, and theaters all over the land which reek daily with the malodorous particles from the lungs of their occupants. Although the air in them is odorless to those who occupy them, it is disgusting to any one who enters from the fresh air. Figure 80 shows the correct ventilation of a stove-heated schoolroom. 1 .»_- 1 ~ ■ '5 ^ a t / 1 \ flpff'ffffff Fig. 80. — Ventilation of Stove-heated Room.' How are the inlet and outlet situated with reference to the stove ? Dust causes catarrh of the bronchial tubes and chronic ^ From Coleman's Elements of Physiology (400 pp.). The Macmillan Co., N.Y. THE RESPIRATION 83 inflammation of the lungs ; it prepares for consumption, by gradually weakening the lungs of those who breathe it. Intelligence and common sense are necessary to pre- vent it from accumulating in the house. The chief pur- pose of the house cleaning should be not only to remove bits of paper from the floor, which do no harm even to the shoes, but to remove iinpitrities fi'om the air. It does no good to stir up the dust and a/low it to settle doivn again (Exp. 12). In many houses dust is thus allowed to accumulate for months. E.xperiments show that dust and germs floating in the air are not diminished to a great extent by a gentle draft through the room. The windows must be open and sweeping done in the direction of the air currents ; the windows should be left open for a long zvhile after the szveeping. A windy day is best for sweeping. The habit some housekeepers have of buying furnishings and bric- a-brac for the home until it looks like a retail store or junk shop, makes it almost impossible to clean their houses. A few articles, carefully selected, adorn a home more than many bought at random, and they do not litter the house and serve as traps for dust. With all precautions some dust may settle down. This should not simply be stirred up again with a feather duster, but the dusting should be done with a damp cloth. Ashes should be sprinkled before they are moved. Carpet sweepers, but never brooms, should be used upon carpets. Carpets and lace cur- tains are ti"uly dust traps, in which dust will accumulate without limit. Those who value the health will not use such uncleanly abominations, at least in bedrooms. Though linoleum, bare floors with movable rugs, oiled and painted floors, may not look so comfortable as a fixed carpet, they bring far more comfort in the end. The weakening effect of ordi- ftary dust is one of the chief causes of lung diseases, and prepares a fertile soil for the consumptive germ. The sputum coughed up by consump- tives falls upon the floor or street, soon dries, and the germs are driven about by the wind. In many cities there is a law against spitting in public places, and the streets are flushed with water before they are swept. Ventilation presents no difficulties in the summer time or in warm climates. The reason that it is a difficult 84 HUMAN BIOLOGY question in cold weather is because the air furnished must be not only pure, but warm. To keep cold air out often means to keep foul air in. Ucatiiii^ with hot air, by which system pure air is passed over a furnace, and fresh air con- stantly admitted, may be a good method (Figs. 80, 81), but is often a dismal failure because it dries out the air, which in turn dries out the skin. To prevent this, wide vessels of water should be set at the in- lets. Dry air is cooling. Why .•* Dr. Barnes proved that moist air at 65° is as comfortable as dry air at 71°. Air saturated with vapor at 60° will only be 50 f>cr cent sa titrated at 80°. Such air dries out the mucous membrane of eyes, nose, and throat. Heating by hot ivatcr circulating in pipes, or by steam, gives no means of introducing fresh air, and is likely to cause worse ventilation than any other method. The radiators should stand close to win- dows or other fresh-air. inlet, that the air may be heated as it enters, and the outlet for air should be farthest from the radiators. The same rules apply to heating by stoves. An oil stove for heating is an inconceivable KiG. 81. — The air enters through a special inlet and is warmed as it passes through hood sur- rounding the stove. Fio. 82. — Chimney with a passage be- hind fireplace, or grate, in which the air is warmed as it enters. THE RESPIRATION 85 iniquity to any but a person densely ignorant of hygiene. Heating by fireplaces (Fig. 82) is the most healthful of all methods, for there is a constant removal of air through the chimney, and this air will be replaced ; even if all doors and windows are closed, it will come in through tiny cracks. Radiaiit heat travels in straight lines from a fireplace and zvarms solid objects, but not the air passed through. Hence an open fire will keep the body warm with the room at a low temperature. Fireplaces, however, do not afford sufficient heat in severe cHmates. Stoves are not as healthful as fireplaces, for there is not so much air removed through the pipe as through the chimney. Carbon monoxid, unlike carbon dioxid, is an ac- tive poison causing the blood corpuscles to shrivel. It passes through red-hot iron or a cracked stove or furnace. Fig. 83. — Blackboard Sketch. Reasons for Breathing through the Nose (Fig. 83). — (i) The many blood vessels in the mucuous mem- brane lining the nasal passages so /leat the air that it does not irritate the bronchial tubes. (2) The hairs in the nostrits strain the air and catch dust ; the cilia of the nasal passages also do this. (3) A mouth-breather often swattows food before cJiewing it sufficiently, because he cannot hold his breath longer. (4) The nasal mucous membrane of an habitual mouth- breather dries and shrintcs and ob- structs the circulation, bringing on catarrh of the 7iose. (5) Mouth breath- ing causes an unpleasant expression of countenance (see Fig. 84). (6) The Fig. 84. — Facial expression in mouth breathing, and breath- ing through the nose. 86 //r.v.t.v Bioi.ocA breath does not come throuiili the nose as quickly as tlirough the mouth ; the luniks ate kept more expanded, and one does not ^et ** out of breath " so cjuickly. (7) The voice of the mouth breather has a hard twam^, not a full, resonant tone as when the nostrils are open. (8) Flavors and odors are better appreciated. Sometimes the sense of smell is almost lost by mouth breathers. If one cannot breathe through the nose, even for a short time, there is probably an adenoid, or tonsil-like, growth in nose or pharynx, and a physician should be consulted. ** .Ack'iioids" are glandular or grapelike in form. Diseases of the Respiratory Organs. — . / cold or catarrh is an injlam- ination of a mucous membrane. If the inflammation is in the nasal pas- sages, it is called a cold in the head ; if it is in the pharynx, it is called Si sore throat ; if it is in the larynx or voice box. there is hoarseness ; if it is in the bronchial tubes, it is bronchitis ; finally, if it is in the air cells, it is pneumonia. If the air is cut otV from access to the air cells, there is an attack of the painful disease called asthma, which is accom- panied by a feeling of suffocation. Some believe that asthma is caused by the mucous membrane lining the finest bronchial tubes becoming inflamed and swollen, and closing the tubes : others think that the muscles in the large bronchial tubes contract and close the tubes. Pleurisy is inflammation of the pleura and makes breathing painful. If much fluid forms between the pleuras, the inner pleura may pre.ss upon the lungs and interfere with breathing. Alcohol not only weakens the blood vessels near the sur- face, but the blood vessels in general. Weakened and congested blood vessels in the lungs make them more liable to pneumonia and other congestive diseases. Con- tinual congestion causes an abnormal growth of connec- tive tissue fiber in the walls of the cells. This diminishes the capacity of the lungs and interferes with the exchange of carbon dioxid and oxygen. Tobacco. — It is often asked why cigarettes are so much more injurious to the health than pipes and cigars. The nature of the paper of cigarettes and various other absurd reasons have been assigned. The true reason is that the cigarette smoker usually inJialcs the tobacco smoke. Cigar smoke, if drawn into the lungs, would usually be coughed up at once. Cigarette smoke is weaker — it is so weak THE RESPIRATION 87 that the smoker is not content simply to absorb the nicotine through the mucous membrane of the mouth ; he draws jt into the lungs. The very mildness of the smoke leads to injialation. Hence, as the surface of the lungs is a hundred times greater than the surface of the mouth, and its litmtg much tJiinner, cigarette smoking is far more injurious than cigar smokins:. The poison accumulates in the bowl of a pipe ; hence an old pipe is very injurious. The irritation of tobacco smoke often sets up a chronic dry catarrh of the air passages ; rarely it causes cancer of lips or tongue. Sir Henry Thompson says : " The only per- sons who enjoy smok- ing and find it tran- quillizing at times are those who smoke in great moderation. Men who are rarely seen without a cigar between the lips, have long ceased to enjoy smoking. They are confirmed in a habit, and are merely miser- able when the cigar is absent."" They do not smoke for pleasure, but to escape misery which wiser men escape by avoiding tobacco altogether. Fig. 86. Fig. 85. Fig. 85. — Flattened Chest and waist organs sunken from wearing tight clothing since the age of fourteen. Such women often walk with bodies bent forward to hide the prominent abdomen. Practical Qles- y\g. 86.— a Natural Woman. TiONS. — 1. State how in the case of a person with round shoulders a gradual remolding of cartilages (which ones ?), the strengthening of the muscles (which ones ?), and the practice of deep breathing may each contribute toward 88 nVMAN BIOLOGY acquiring an erect and perfect figure. 2. Should a hat be well venti- lated? (A punch for making the holes costs a dime.) Should a hat he stiff or soft ? 3. Name habits that im- l)air the power of the lungs. 4. How could you convince a person that a Ijedroom should be open while and after it is swept ? That it should be ventilated at night ? 5. Which is the more injurious to others, t<)l)acco chewin"; which causes the ground to be unclean, or smoking which renders the air impure ? 6. Why do those who stand straight up to hoe not get tired half so quickly as those who bend or " hump "^ over? (Chap. VI.) 7. Why do students who sit in rocking chairs, or from other causes lean the head forward when they study, often find that they recover from drowsiness if they sit erect, or sit in a straight chair? 8. How are high collars a fruitful source of bad colds ? 9. If the draft up the chimney of the fireplace, when the fire is burning, takes up a volume of air sufficient for many people, why is it unnecessary to open a window? 10. Why does cold impure air make a person colder than cold pure air ? (p. 14.) 11. Do the modem customs of uniformity in dress for all classes and climates, shipping foods from great distances, one section or nation imitating the wavs of another section or nation, lead toward health or disease? Do such customs violate or conform to the great biological law that life is a process of adaptation to environment? Fig. 87. — Suspenders should have a pulley or lever at the back, that the strap on one side may loosen when one shoulder is raised. COLOKKD FlCURE G. AA.-. ui iin: Trunk. cb, collar bone; r, ribs; z, tongue bone (hyoid) ; k, k, cartilages of larynx; /, windpipe; J, thyroid gland; rr', right ventricle; /z', left ventricle; r;/, right auricle; /«, left auricle; a, aorta; ka, artery to head (carotid); sa, subclavian artery; la, pulmonary artery; oh, superior vena cava; hi', jugular vein; /«, lungs; _/, diaphragm; Ih, liver; g^, gall bladder; s, stomach; x, spleen; «, mesentery with vessels; li, small intestine; gd, large intestine; b, cxcum; w, vermiform appendix; h, bladder. CHAPTER VII FOOD AND DIGESTION Experiment i . Tests for Acid. Alkaline, and Neutral Substances. . - Repeat tests described in General Introduction.^ Experiment 2. Test for Starch. — See General Introduction. Experiment 3. Test for Grape Sugar. — See General Introduction. Experiment 4. Test for Proteid. — See General Introduction. Experiment 5. Test for Fats. — See General Introduction. Experiment 6. Human Teeth. — Study the form of teeth from every part of th^ mouth. Get a handful from a dentist. Break some of the teeth to make out their structure. Classify them. Draw section, enlarged. Experiment 7. Study of the Teeth. (At home.) — Sit with the back to the light and look into a mirror, with the mouth wide open. Do you see the four kinds of teeth named in text ? Whicli are fitted for cut- ting ? Which for grinding? Are any suited for tearing? Are any of the teeth pointed? What is the ditference in the bicuspids and molars? Are there any decayed places? Are the teeth clean? Are the so-called canine teeth so long that they project beyond the line of the other teeth, as they do in a dog? Do the edges of the upper and lower incisors meet when the mouth is closed, or do they mi.ss each other like the blades of scissors? How many roots has each lower tooth? (See Fig. 92.) Which tooth has the longest root? Experiment 8. Structure of Mammalian Stomach. — Get a piece of tripe from the market. Study its several coats. The velvety inner coat is covered with mucous membrane. (Photomicrograph, Fig. 95.) Experiment 9. Model of Human Food Tube. — Make a model of the food tube out of yellow cambric, giving to each organ its correct size. Follow the dimensions given in text. Necessity for Foods. — Growing plants and growing ani- mals need new material to enable them to increase in size or grow. Plants never cease to grow while they live; most mammals attain their full size in one fifth of the time ^ See also Peabody's " Laboratory Exercises in Physiology," Holt, N.Y. 89 c)0 HUMAN BIOLOGY occupied by their whole lives. (Hy this rule how long ought man to live?) Animals, moreover, move from place to place, and xi'ork with their muscles. The energy for this comes from the food they eat. Plants do not use food for this purpose. Another need for food comes from the necessity for heat in all living things. The activities of animals cause the tissues to wear out, or break down, and food furnishes material with which new living matter is built up by the cells and the tissues repaired. We have already stated the role of o.xygen in setting free energy in the living substance of the cell by oxidizing it. There is no furnace in the body as in an engine, but the oxidation occurs in the cells themselves and the fuel is built up into living matter by the cells before it is oxidized. Plants must lift mineral from the inorganic to the organic world before it can be food for animals. Plants can assimilate minerals ; animals cannot. The body cannot make bone out of limewater. The iron in iron tonics cannot be used. Iron makes the grain brown, and the peach red. There is ten times as much iron in our food as the body needs. State four reasons why animals need food. Which of these reasons is very powerful with plants } Least powerful .-^ Absent altogether } Why is constant breathing necessary for life } When is breathing more rapid .'' Why .-• People who lead what kind of lives usually have poor appetites ."* Good appetites .-' Why .'' What was the first distinct or- gan evolved by animals ? (Animal Biology, Chap. IV.) The Body is a Machine for transferring Energy. — Energy cannot be destroyed, but it can be transferred and changed in form. When a coin is rubbed on the table, muscular energy, supplied by oxidation in the muscle, produces the motion. Friction may change motion into heat, and the coin will become very hot. The uniting of food and FOOD AND DIGESTION 9I oxygen in the cells of the body gives the heat and motion (energy) of the body. Only substances which will oxidize, or burn, are true foods. Water, salt, and carbon dioxid will not burn; hence, they cannot give rise to energy in the body. But the sun energy, acting in the green leaf, tears apart the carbon from the oxygen (Plant Biology, Chap. XIII), sets free the oxygen, and the carbon is stored in starch for future burning. Sunshine is energy (light and heat). The sun sustains the life of plants and through them the Ufe of animals. The oxidation in the body is so slow that it can hardly be called a burning, but it is faster than the oxidation of iron in rusting or of wood in rotting, and is about equal to the continual burning of two candles. The Four Kinds of Nutrients, or Food Stuffs. — The kinds of food ivJiicJi ive eat scan to be nnniberlcss, but tJicy con- tain only four kinds of food stuffs, — starches, fats, proteids, and minerals. Many foods contain all four classes of food stuffs. Milk contains sugar (a changed form of starch), cream (a fat), curd (a proteid), and water (a min- eral). Oatmeal contains starch, oil, gluten, and water. Uses of the Nutrients, or Food Stuffs 1. Proteids. The tissue-building foods (also of value as fuel). 2. Starches (and sugars) 1 Energy and heat (fuel) and 3. Fats (and oils) J fat producing foods. 4. Minerals (water, salt). Important aids in using other foods. Relative Fuel Value. — A pound of fat produces as much heat in the body as 2.3 lb. of proteid or 2.3 lb. of starch, the last two having equal fuel value in the body. Starch and the sugars are closely related; starch readily changes into sugar. They contain much carbon and are called carbohydrates. Starch is especially abundant in grains, seeds, and fleshy roots (Fig. 88). The sugar in ripe fruit and in honey is called //v/zV sugar. Milk siigat 92 h'LW/AX BIOLOGY %. ) 1 / is found in sweet milk. Grape sugar is found in grapes and honev ; the small i::rains seen in raisins consist of iirape suirar; it can also ■^^WJ^,'^ be prepared artificially from starch. Cane sugar is found in cane, in sap of the maple, and in the sugar beet (Exps. 2, 3). Fats include the fats and oils found in milk, flesh, and plants. A fat, such as tallow, is solid at the ordinary temperature ; while an oil, such as olive oil, is liquid at the same tem- perature. Tallow was oil while it was in the warm body of the ox. Sugar is transformed into fatty tissue as readily as is fatty food itself. Proteids are the only foods that contain the tissue- building nitrogen. Protoplasm cannot be formed without nitrogen. We do not often see a pure proteid food, for this food stuff is not so readily separated from foods containing it as are starch, sugar, and fat. Albu;«r;/, or white-of-egg, is proteid united with four times its weight of water. Pure proteid is also called albuw///. Coagulation by heat is one test for proteid (Exp. 4). These are the names of proteids, or albumins, found in several common foods : casciu, the curd or cheesy part of milk ; myosin of lean meat ; fibrin in blood ; Icgnniin in beans and peas ; gluten, or the sticky part of wet flour; gelatin in bones. Proteid is valuable to the body as fuel Fig. 88. — A Tiny Bit of Potato, highly magnified, showing cells filled with grains of starch. Cooking bursts these cells. FOOD AND DIGESTION 93 as well as a tissue builder. We could burn beans and peas as well as the strictly fuel foods, starch and fat, in an engine, and get heat to move the engine. If one takes up athletics or hard physical labor, he should increase the amount of fats and carbohydrates eaten, but not of proteid. Muscular activity increases the carbon waste but not the nitrogen waste of the body. Minerals. — The iron of the blood and the mineral salts in bone (carbonate and phosphate of lime) must enter the body in organic form in order to be used. Water and salt are mineral foods. The body is about two thirds water. The cells must do their work under water. They cannot live when dried. Water enables the blood to flow; and the blood is not only the feeder, but also the washer and cleanser of the tissues. Some persons get out of the habit of drinking plenty of water, and their health suffers thereby. In such a case drinking plenty of water will be safer and more effective than taking poisonous drugs to restore health. Adulteration of Food. — Sometimes cJieapcr vtaterials, of little or no value as food but of no great injury to health, are added to foods. Examples : water added to milk, sawdust to ground spices, chicory to coffee, glucose to maple syrup. Other forms of adulteration not only cheat the purse but tend to destroy JiealtJi, or actually do so. Examples : Boracic acid or formalin added to milk to prevent souring, copper to canned peas, etc., to give a bright green color ; salicylic acid or borax used in minute quantities as a preservative with canned corn, tomatoes, etc.; acids added to "apple" vinegar; dried fruit treated with sulphur to prevent a dull color. Pure food laws tend to repress these evils. It is best to buy foods in their original form. For instance, lemons are more reliable than vinegar. A bit of lemon at each plate, in house- 94 J/r.v.LV nioi.OGY liokls that can afford it, is far piL-fcrablo to vinegar. We should alwaws bii\' fix)iii neighbors when j)ossiblc. I'"urmcrs and gardeners should do their own drying and canning. For purity of water, see Chap. X. The Daily Ration. — A quarter of a f'outui (4 oz. ) of pro- tcid foods a fid oiii poiDid { 16 oz.) of fuel foods (total 20 oz. of water-free foods) are needed to replace the daily waste of the body. Hence a halaueed ration has proteid and fuel food in the ratio of 4 to 16, or i to 4. But recent experi- ments at Vale University indicate that 2 oz. of proteid daily are more strengthening than four. Appetite is a perfect guide for those lu/io lead an aetive life and eat slowly of simple food. Highly seasoned food and complex mixtures deprave the appetite ; it then leads astray, mstead of guiding safely. Of course the appetite cannot guide one to eat the right kind and quantity of food at a table where the food lacks any of the four neces- sary food stuffs, or where innutritions or indigestible food is provided. It is well to select one food for a meal be- cause it is rich in proteids, another because it is rich in fat, and the third because it is rich in starch or sugar. (See table, p. 95.) Intelligence in regard to diet enables a housekeeper to provide nourishing food for less money than an ignorant housekeeper often pays for food deficient in nourishing qualities. A Balanced Ration. — A deficiency of starch may be supplied by an excess of fat or sugar. It is most essential to provide proteid as it cannot be replaced by any other food stuff. An excess of proteid is most harmful. An ex- cess of starch or fat is oxidized into water and carbon dioxid, which are harmless waste products ; an excess of proteid is changed into urea which may become harmful by overworking the liver and kidneys which excrete it. FOOD AXD DIGESTION 95 Composition of One Ounce of Various Foods in Fractions of AN Ounce Daily Ration I. Nuts. II. III. Pecan . Walnut Almonds Cocoanut Chestnut Fruits. Peach . . Apple . . Blackberry Cherry . . Grape . Fig (dried) Banana Animal Food. Lean beef Fat pork . Smoked ham Whitefish Poultry Oysters Cow's milk Eggs . Cheese Butter . IV. Pods or Legumes. Beans .... Peas .... Peanuts V. Grains. \\Tieat flour (white) Wheat bread Oatmeal .... Maize (corn) Rice VI. Vegetables. Potatoes . Cabbage . Pro- TEIDS 4 oz. Fats .103 .158 •235 .056 •037 .007 .004 .005 .005 .125 .040 .050 .20 .098 .25 .181 .210 •175 •035 .125 •335 .003 .25 .217 .2947 .110 .080 .126 .100 .050 .012 .02 .708 •574 •53 ■51 .02 .014 •035 .489 •365 .029 .038 .005 .040 .120 •243 .910 .020 .019 .465 .020 .015 .056 .067 .008 .001 .030 Carbohv DRATES 14 OZ. •143 .16 .12 •38 Sugar •045 .072 .040 .10 •15 •50 .20 .009 .040 Starch •52 •577 .162 •703 .490 .630 .706 .832 .205 .058 Mineral Water Salts 2 qt. •03 .017 •03 .014 .078 •35 •54 .009 •85 .007 .84 .005 .86 .004 .84 .007 .70 .005 •75 •75 .016 •390 .023 .278 .101 .7S0 .010 .740 .012 .800 .015 .870 .007 •735 .010 .368 •054 .060 .021 .125 •035 .12 .028 .02 .028 .150 .017 .400 .012 .150 .030 •135 .014 .100 .005 .767 .009 .910 .007 .04 .02 .04 .05 .01 .02 .060 .032 •043 .003 .003 .016 .015 .040 .006 •015 96 //L.u.i.y HIOI.OCV studies based on Table. -What nuts arc ricli in protcids ? What fruits? Wlialauini.il foods? What lejjumcs? Wiiat ;;;rains? Wliatfoods are rich in fats? What are rich in carbohydrates? Which grains have much starch? Which nut? Which fruits have much sugar? A family was living chiefly on corn l)read. potatoes, syrup, cakes, and sweetmeats : what two of the four food stuffs were deficient in their diet? Another family lived cliiefly on fat pork, bread, rice, vegetaljjes. and fruit : wliicli food sturt" was deficient ? A dozen eggs weigh 1 \ II). Wliich give cheaper nourishment, eggs at 15 cents a dozen or beef at 15 cents a pound? Which is cheapest among the foods abounding in proteid? Fat? Carbohydrates? Which is cheaper food, a pound of beef at 20 cents or a pound of pecans at tlie same price? (Fig. loi.) Wiiat food contains most water? Least water? Which of the foods abounding in proteid is costliest? Clieapest? Notice that nearly all foods contain- ing much proteid are costly. Water and woody fiber are not counted as nutriment. What weight of nutriment in i oz. of cow's milk ? If a quart of whole milk costs 12 cts., what is a quart of .skimmed milk worth ? How the Right Proportions of Fuel Foods and Proteid are reached by Different Nations. — Milk has an e-xcess of nitrogen, and oatmeal an e.xce.ss of carbon ; oatmeal and milk form a popular food with the Scotch. Potatoes are mostly starch and water, and an Irishman who tried to live on potatoes alone would have to eat seven pounds a day to get enough proteid. The Irish peasant keeps a cow and chickens ; by eating milk and eggs he gets along on half the amount of potatoes named at)ove. The Mexicans eat bread made of corn meal, and supply the proteid by using beans as a constant article of diet. Hundreds of millions of people in Asia (the Hindus, Chinese, and others) subsist mainly on rice, which contains only five per cent of proteid and no fat; the chief addition they make is butter, or other fat, and beans, which contain vegetable proteid. Outline of Digestion. — The food is made soluble in the alimentary canal and is absorbed by the blood vessels and lymphatics in its walls. This canal is about thirty feet long (Figs. 89, 90) and consists of — (i) The mouth, where the food remains about a minute, while it is chewed and mixed with the saliva ; the saliva changes a portion of the starch to malt sugar. (2) The gullet, a tube nine inches long, running from FOOD AND DIGESTION 97 mouth to stomach and lying in front of the spinal column. Illustrated Study of Food Tract. Fig. 89. — Organs of Trunk from the side. Z, larynx; M, thyroid gland; 7", trachea; St, breastbone ; C, heart ; D, dia- phragm ; F, liver ; E, stomach ; /. intestine ; Co, colon ; R, rectum ; V, bladder. Question : Parts of which organs are far- ther back than spinal column? Com- pare this figure with colored Fig. 6. Fig. 90. — DiGESiivE Organs, from the front (liver turned up). I, gullet ; 2, stomach ; 3, spleen ; 4, pancreas ; 5, liver (turned upward) ; 6, gall bladder: 7, 8, 9, small intestine; 9', junction of small with large intestine ; 10, caecum (blind sac) ; II, vermiform appendix; 12, 12', 12", ascend- ing, transverse, and descending colon ; 13, rectum (straight) just below S-shaped flexure of colon. Question: Compare with Fig. 89, and colored Fig. 6. (3) The stomach, a large pouch where the food is stored, and from which it passes in the course of several hours. 98 HUMAN BIOLOGY liaving become semi-liquid, and the protcids having been partly digested by the gastric Juice, an acid secretion from the small glands in the stomach walls. (4) The small intestine, a narrow tube more than twenty feet long, where \.\\c fiifs are acted ujion for the first time, and where the starches and protcids are also acted upon, and where, after about ten hours, the digestion of the three classes of foods is comj^lctcd by pancreatic juice from the pancreas, and bile from tlie liver. (5) The large intestine, about five feet long, where the last remnant of nutriment is absorbed, and the indigestible materials in the food are gathered together (Exp. 9). The Teeth. — The main body of the tooth consists of bone- like dentine, or ivory. Hard, shining enamel protects the crown, or visible portion. The part of the tooth beneath the gum is called the neck, and the part in the bony socket is called the root. The enamel ends just beneath the gum, where it is overlapped by con cut of the root. There is a pulp cavity in every tooth (Fig. 91); it contains pulp made up of con- nective tissue, with nerves and blood vessels which enter at the tip of the root (Exp. 6). The temporary set of teeth is completed at about two years of age and consists of twenty teeth. The teeth cannot grow as the jaw grows, and soon a larger and permanent set starts to growing deeper in the Cement or cnista petrou AlTcoUr periott«uin or root- membrane Fig. 91. — Canine Tooth cut lengthwisk. FOOD AND DIGESTION 99 jaw. At the age of twelve or thirteen years all the permanent set have appeared except the four wisdom teeth, which appear between the ages of seventeen and 3rd molar 1st molar I 1st premolar y Lateral mcisor 2nd premolar Caiime Central incisor Slid molar Fig. 92. — The Permanent Teeth in right half of lower jaw. twenty-five. The second set not only replaces the twenty of the first set, but to fill the larger jaws twelve molars are added, three at the back in each half jaw, making thirty- two teeth in the second set (Exp. 7). The teeth in each quarter of the mouth, named in order from the front, are : two hicisors, one canine, two premolars, three molars. Care of the Teeth. — The best way to care for the teeth is to keep the digestion perfect. Perfect digestion tends to preserve the teeth, and sound teeth tend to keep the digestion perfect. The teeth should be ivasJied regularly. Prepared chalk is the best dentifrice. Do not rub across, but from gums to teeth, to prevent rubbing the gums loose from the teeth. An unclean brush may har- bor germs. Toothpicks and dental floss are useful. If one eats only soft food, in which the mill and the cooking stove have left no work for the teeth, the teeth will decay ; for it seems to be a law of nature that useless organs are removed. The pressure from cJicwing Fig. 93. Upper Jaw with Teeth. ICX) HUMAN BIOLOGY hard fihui is nu did to the teeth l)y helping the circulation anil nerves in the puli). ID take a very hoi or very cold drink into the mouth may cause the enamel to crack. If a tooth aches, or a small decayed place is found in it, a dentist should be consulted at once. A tooth is so valu- able to the health tliat no tooth should l)c extracted when it can be saved. The process of digestion consists in li({uefying the food that it may pass throu<;h the walls of the food tube into the blood, and through the walls of the blood vessels into the tissues. It is accomplished : ( i ) by uiechaiiical means, including the chewing muscles, the teeth, and three layers of muscles in the walls of the food tube; (2) by chemical means, or the action of alkalies and acids upon the food ; (3) by organic agency, or the action of ferments. A ferment (or enzyme) is a vegetable substance which has the power of producing a chemical change in large quanti- ties of substance brought in contact with it, without being itself changed. There is one ferment secreted in the mouth, two in the stomach, and three in the small intestine. Digestion in the Mouth. — Saliva is formed by six glands : one in the cheek in front of each ear, one at the angle of each lower jaw, and one pair is beneath the tongue. Each gland opens into the mouth by a duct. Saliva is ropy because it is mixed with mucus formed by the mucous membrane lining the mouth ; it usually contains air bub- bles. There is a ferment in the saliva called //j/^/z'//, which has the power of changing starch to malt sugar. If a bit of bread is chewed for a long time, it becomes sweet, because some of the starch is changed to sugar. The flow of saliva is caused by chewing, or by the sight, or even the thought, of agreeable food. Dryness of food is by far more powerful than anything else in causing the saliva to FOOD AND DIGESTION lOI flow. Saliva is secreted only one fourth as fast when eat- ing oatmeal and milk as when eating dry toast (Fig. 94). Fig. 94. — Cells of a Salivary Gland A, after rest, full of granules ; B, after short activity ; C, after prolonged activity, cells shriveled and granules lost. Starchy grains and fruits were eaten by early man without cooking, and required more chewing than sweet, ripe fruits or oils or proteids. Hence the saliva was given the power of acting upon the starch, for it must remain in the mouth longer. The saliva is alkaline ; and if the food is not thoroughly mixed with it, the stomach digestion will also be imperfect, for the alkaline saliva is necessaiy to excite an abutida)it flow of gastric juice in the stomach (Exp. i). Eating slowly is difficult because of the grinding and cooking of food ; hence the common practice of overeating. To eat slowly (i) do not take large mouthfuls ; (2) do not take a second morsel until the first has been swallowe-d ; (3) sit erect or lean back after putting food into the mouth ; (4) the hands should lie idle most of the time. To lean forward and keep food traveling to the mouth like coal into a chute means overeating with all its bad effects. Chewing gum is a coarse and impolite habit, and wastes the saliva, besides weakening the glands and irritating the stomach by the saliva that is continually swallowed. Chewing tobacco has several of these disadvantages, besides allowing the poison in the tobacco to be absorbed by the mucous lining of the mouth. The pharynx (far'inks), or throat, is a muscular bag sus- pended behind the nose and mouth. (See Fig. 89, also Fig. 83.) There are seven openings into the pharynx: two from the nostrils, two from the ears, one each from the mouth, larynx, and gullet. Which of these openings are downward .■' Forward .-' Lateral .-* The gullet (or esophagus) is a muscular tube about nine 102 HUMAN BIOLOGY inches long. (Sec Fig. 89.) Like the rest of the food tube, it is lined with mucous membrane. It has two layers of muscles in its walls, the fibers of one layer running length- wise, and the fibers of the other layer being circular. In sivalloii'iui^, the food does not fall down the gullet of its own weight, but the circular batnis of muscle in front of the food relax, and tliose be/iind it contract and push it ou into the stomitch. This wavelike motion is called peristalsis. The stomach, llie greatest enlargement of the food tube, is like a lar^e bag lying sideways. It lies to the left side of the abdomen. The walls of the stomach con- sist chiefly of muscular fibers zuhich run lengtJnvisc, crossivise, and slanttvisc, making three coats (Exp. 7, also Fig. 95). As soon as the food reaches the stomach, the layers of muscles begin to contract, changing the size of the stomach, first in length, J then in breadth, thus churning the food to and fro, and mixing it with the gastric juice, a fluid more active than the saliva. For as the food enters the stom- ach, the mucous membrane lining it turns a bright red, and many little gastric glands in the lining begin to secrete gastric juice. Digestion in the Stomach. — The stomach churns the food from two to four hours after the meal, according to Fi<;. 95. — Mrs( 11. AR and OTin;R Layers in Wall of Stomach. 1, mucous lining ; 2, layer of blood vessels and connective tissue ; 3, muscular layers (involuntary muscles) ; 4, con- nective-tissue fibers. (Peabody.) FOOD AND DIGESTION 103 the kind of food eaten, the way it has been cooked, and the thoroughness with which it has been chewed. The gastric juice is chiefly water, and contains two ferments called pepsin and roinin, and a small quantity of hydro- chloric acid. Rennin acts upon the curd of milk, and is abundant only during infancy. Hydrochloric acid kills germs that may enter the stomach, and changes the food which has been made alkaline by the saliva into an acid condition (Exp. i). This enables thQ pepsin to act upon the proteid part of the food, for pepsin will not act while the food is alkaline. Gastric juice digests lean meat, which is a proteid food, by first dissolving the connective tissue that holds the fibers in place, and they fall apart ; it then acts upon the fibers separately and makes them soluble. Like human fatty tissue (Fig. 14), fat meat consists of cells filled with fat and held together by threads of connective tissue. The cell walls and the threads, both being proteid, are soon dissolved by the gastric juice, and the free fat is melted into oil, but still undigested. The food is reduced in the stomach to a creamy, half-fluid mass called chyme. Where the stomach opens into the small intestine, there is a folding in or narrowing of the tube so as to form a kind of valve called XhQ pylorus. After the food has been changed to chyme, this fold relaxes every minute or two, and allows some of the chyme to escape into the intestine. The small intestine is about one inch in diameter and twenty feet long, with fig. 96. — a Portion many coils and turns in its course (Fig. °^ Small intes- ^ \ o TINE cut open to show 90). Its mucous lining is wrinkled into the folds m its lining. 104 II CM AN BIOLOGY nuniercnis folds in order to increase the secreting and absorbing surface (Fig. 96). On and lietween the folds are thousands of little threadlike ^!^JC ^^Ta^a^'g* jirojections called villi (Fig. 97), -•iX"^*i?>?'ix -i>?^ "^^v In each villus are found fine capil- T^'^*'— ■•'^yr^Yr^S^y. laries and a small lymphatic called a lacteal (colored Fig. 2). The villi yy.^-''''-^^?f-:^' are so thick that they make the lining of the intestine like velvet, Fig. 97. — Li.Ni.NG 01 , , . ^-u \^ -u smai l intestink ^"" enormously mcrease the absorb- magnified, showing villi Jiirr surfaCC. and mouths of intestinal _. . . , „ ,, - glands. Digestion in the Small Intestine. — This is by far the most active and important of the digestive organs. The mouth digests a small part of the starch, and the stomach digests a small part of the proteid ; tJic small intestine digests most of tJie starch, most of the proteid, and all of the fats. The food is in the mouth a few minutes, and in the stomach two or three hours ; it is in the small intestine ten or twelve hours. There are thousands of small glands called intestitial glands that open between the villi (Fig. 97) and secrete the intestinal juice, which digests cane sugar. Besides these, there are two very large and active glands, the pancreas and liver, which empty into the intestine by ducts. The Pancreas. — The small intestine is the most impor- tant of the digestive organs, chiefly because it receives the secretion from the pancreas, the most important of diges- tive glands. The pancreas is a long, flat, pinkish gland situated behind the stomach (see Fig. 90). The pancreatic juice contains three poweiful ferments, one of which (amy- lopsin) digests the starches, another (trypsin) digests pro- teids, and the third (steapsin), with the aid of the bile, FOOD AND DIGESTION 105 breaks up the fats into tiny globules. Fat in small glob- ules floating in a liquid is called an einn/sion; fresh milk is an emulsion of cream (Fig. 98). Fat is not changed to another substance by digestion, but it is emulsified, and in this condition it readily passes through the walls of the intestines and is absorbed by the lymphatics called lacteals (colored Fig. 5) found in the villi. It then ascends through the tJwracic duct to a large vein at the left side of the neck (Fig. 100). TJie digested proteid, starch, and stu^ar pass into the capillaries of the portal vein, and go to the liver on their way to the general circulation (Fig. 100). The portal circulation empties into the large ascending vein leading to the right auricle (Fig. 100), The Liver. — This large, chocolate-colored gland is located just beneath the diaphragm on the right side (Fig. 90, colored Fig. 6). It is on a level with the stomach, which it partly overlaps in front. The liver has three important functions: (i) // is a storeroom ; digested sugar and starch are stored in it as a substance called liver starch (or gly'cogen). (2) It is a guardian, and destroys poisonous substances which may be swallowed, and which would otherwise enter the blood. Twice as much morphine or other poison is necessary to kill a man when it is taken by the mouth and passes through the liver as when it is injected through the skin. Alcohol, morphine, coffee, and drugs are partly burned up in the liver. (3) // is a gland, and secretes bile. The bile is made chiefly from waste products and impurities in the Fig. 98. — Junction of Large and Small Intestine. io6 HUMAN BIOLOGY blood; it is an excretion. Although an excretion, it is of use on its way out of tlic body. It is alkalinu and helps to neutralize the acid in the chyme; it excites the peristalsis, or wavelike motion, of the intes- tines, and it aids the pancreatic juice to emulsify the fats. The large intestine, or colon, is about two and one half inches in tli;iniotcr and five feet long;. The sunxll intestine joins it in the lower right side of the abdomen (Fig. 90). There is a fold, or valve, at the juncture, and just below the juncture there is a tube attached to the large intestine, called the appendix, which sometimes be- comes inflamed, causing a disease called appendicitis (Figs. 90, 98). The appendix is a vestigial (^vesti- gium, trace) or rudimentary organ, long since useless. Absorption of the watery part of the food continues in the colon, but the colon secretes no digestive fluid. The undigested and innutritious parts of the food are regu- larly cast out of the colon. ^ The peri- tone' inn is a membrane with many folds that supports the food tube (Fig. 99). Absorption. — The way in which the various digested foods are absorbed has been stated in several preceding topics. What is the name of the organs of absorption in the small intestine } Which of the following pass into the lacteals, and wiiich into the capillaries of the portal vein : sugar, digested proteid, emulsified fats ? Water and salt need no digestion, and are absorbed all along the food ' No truly refined person will allow business, pleasure, haste, or neglect to interfere with regular attention to emptying the colon. This is more neces- sary for real cleanliness than regular baths. Fig. 99. — Diagram of Trunk to show the many folds of tlie pkki- TONEL'M supponins; the liver, stomach, and in- testines. FOOD AND DIGESTION 107 tube, the absorption beginning even in the mouth. What reasons can you give for the absorption of food being many times greater in the small intestine than in the stomach ? Through what large tube is the fat carried in passing from the lacteals to the veins ? Into what large vein do all the capillaries that take part in ab- sorption empty ? (Colored Fig. 5.) What is the provision for storing the sugar so that it will not pass suddenly into the blood after a meal, but may be given to the blood gradually .■* Food is assimilated, or changed into living matter (proto- plasm), in the cells. Blood and lymph (except the white corpuscles) are not living matter. (Fig. 100.) Fig. 100. — The Two Paths of Food Absorp- tion. Thoracic duct (for fats) ; through the portal vein and liver (for all other foods). Thought Questions. The Digestive Organs. — 1. In which of the digestive organs is only one kind of secretion fur- nished by glands? 2. In which organ are three kinds of secretions furnished by glands? 3. Which class of food goes through the lymphatics ? 4. Which classes of foods go through the liver ? 5. Which classes of foods are digested in only one organ ? 6. Which classes of foods are digested in two organs ? 7. Which division of the food tube is longest ? Broadest ? Least active ? Most active ? 8. Soup is absorbed quickly ; why does eating it at the beginning of a meal tend to prevent overeating? Hygienic Habits of Eating. — In hot weather much blood goes to the skin and little to the food tube, and di- gestion is less vigorous. Hearty eaters suffer from heat in summer because of much fuel, and because the blood is kept away from the skin where it would become cool and then cool the whole body. Some persons believe that the I08 HUM AX BIOLOGY Stomach should be humored and ^wcw nothing that it di- gests with difficulty ; others believe that it should be gradu- ally trained to dii^est any nutritious food. Some believe that no animal food should be eaten ; others believe that animal food is as valuable as any. Some believe that all food should be eaten raw, but this would irritate a delicate stomach. It is doubtless best to use no stimulant, either tea or coffee, pepper or alcohol. Some eat fast and drink freely at meals ; it is better to eat slowly and drink very little or none at all while eating, nor soon afterwards. Some eat five meals a day, and between meals if anything that tastes good is offered them ; others eat only two or three meals a day, and never between meals, thus allow- ing the digestive organs time to rest. Some omit break- fast and some omit supper. Some prepare most of the food with grease ; this is a tax upon digestion. Physical workers often believe in eating the peelings and seeds of fruits, and partaking freely of weedy vegetables, such as cabbage, turnip tops, string beans. Mental workers usually try to reject all woody fiber and indigestible pulp from the food before swallowing it. Some eat large quantities of food and digest a small portion ; others eat little but digest nearly all. The Power of Adaptation of the Digestive Organs. — Of course some habits of eatinu; arc Ixttcr for the heallli tlian others, yet the un- desirable ways often bring so little injurythat they are not discontinued. This shows that the food tube has great powers of adaptation to dif- ferent conditions. But there are limits to this adaptation ; there is an old saying that what is one man's meat is another man's poison. A brain worker cannot follow the same diet as a field hand without work- ing at a disadvantage. An irritable stomach may be injured by coarse food that would furnish only a healthful stimulus to a less sensitive one. A business man who has little leisure at noon should take the heavie.st meal after business hours. In general, it may be .said that it does not make so much difference what is eaten as how it is eaten, and how FOOD AND DIGESTION IO9 much is eaten. There is a common tendency to exaggerate tlie im- portance of dietetics. Thought Questions. Indigestion. — I. A Fetid Breath. 1. Name three causes of bad breath. 2. Let us investigate whether indigestion could cause a bad breath. In what kind (two qualities) of weather does meat spoil the quickest? 3. Suppose that meat or other food is put into a stomach with its gastric glands exhausted and its muscular walls tired out, what will be the rate of digestion, and what might hap- pen to the food ? 4. Odorous contents of the stomach i^e.g. onion) can be taken by the blood to the lungs where it will taint the breath. After answering the above questions, write in a few words how indi- gestion may cause a bad breath. II. A Coated or Foul Tongue. 1. When the doctor visits you, at what does he first look ? 2. What sometimes forms on old bread ? (p. 158.) 3. Do you think such a growth possible on undigested bread in the stomach ? 4. The microscope shows the coating on the bread to be a growth of mold. If it forms on the walls of the stomach, it may extend to what ? III. Stomach Ache. 1. How can you tell whether fruit preserved in a sealed glass jar is fermenting ? 2. What connection is there be- tween belching after eating "too freely of sweet or starchy food, and the observation above ? 3. A muscle gives pain when it is stretched. Why does belching sometimes give relief to an uneasy stomach ? 4. Can you, by using these facts, explain a cause of stomach ache ? For what Kind of Man were the Human Digestive Organs created ? — That food is best to which the food tube has been longest accustomed. It would be of the greatest value as a guide to diet if we knew the food eaten by early man during the many ages when he led a wild life in the open air. The organs of early man were doubtless perfectly adapted to the life he led. The food tube is adapted to the needs of those long ages, for a few centuries of civilization cannot change the nature of the digestive organs ; yet some people disregard natural appetites and try to force the digestive organs to undergo greater changes in a few months than centuries could bring about. To test whether an Article of Food belonged to Man's Original Diet. — Scientists agree that the human race began in a warm country ; that early man was without gristmills, stoves, or fire, and ate his food raw. If an article of food is pleasant to the taste in its raw, pure state, there is little doubt that it, or a similar food, was eaten by primitive man before he knew the use of fire in preparing his food. Apply this test to the following foods, underlining those foods that pass the test : apples, bananas, lettuce, turnip greens, turnips, fruits, nuts, beef, fowls. 1 10 II UMAX BIOLOGY Beef Bread Bananas Nuts Potatoes Lettuce eggs, oysters, green corn, cabbage, pork, watermelons, grains, crabs, fish, white or Irish potatoes, yams, tomatoes. The Order in which Man increased his Bill of Fare. — l-'icsli-e.itinL; animals iiave a short lood tube, as their food is digested quickly; they have long, pointed teeth lor tearing, sharp daws for holding, and a rougii tongue for rasp- ing meat from the bones. Man's even teeth, long food tube, soft and smooth tongue, and flattened nails, indicate that he is suited for a diet largely vegetable (see Table, p. III). The race at first probably ate tree fruits^ both nuts and fleshy fruits (Fig. loi). Because of famine, or after migration to colder climates, and after learning the use of fire, the race prob- ably began to use flesh for food. Afterw^ard the hunters became farmers and learned to cultivate grain, which formed a most important addition to the food supply, and made possible a dense population. Coarse, woody foods, like the leaves and stems of herbs, were probably added last of all. Woody fiber (cellulose) can be digested by cattle, but it cannot be digested by man. The Natural Guide in Eating is Taste. Man should preser\"e his taste uncorrupted as, next to his conscience, his wisest counselor and friend. It has been developed and trans- mitted through countless ages as a precious heritage. Simple food is more delicious to people with natural tastes than the most arti- ficial concoctions are to those with perverted taste. Animal Food. — 'Wkq. flesh of animals furnishes proteid and fat (Fig. 102). As cooking coagulates and hardens 1 .See Genesis i. 29. Some raw food should be eaten daily. Pecans are the most digestible of all nuts. .\ half dozen or more eaten regularly for breakfast will prevent constipation or cure it in ten days or le.ss. FOOD AND DIGESTION III albumin, raw or half-cooked meat is said to be more diges- tible than cooked meat ; but meat that is not thoroughly Fig. 102. — Diagram showing Cuts of Beef. cooked is dangerous because it may contain trichinae ("Animal Biology," p. 50) and other parasites. Lean meats contain much proteid. Some persons who cannot easily digest starch and sugar because of fermentation eat fat for a fuel food. Beef tea and beef extracts contain but a small part of the proteid in meat and all of the waste matter, including urea. Mammals compared Carnivora, or flesh-eaters Herbivora, or HERB-EATERS Omnivora, or all-eaters Frugivora, or fruit-eaters Examples, Cat, dog, lion. Cow, horse. Hog, peccary. Man, monkey. Length of food tube. 3 times length of body. 30 times length of body. 10 times length of body. 1 2 times length of head-trunk. Teeth. Pointed for tearing flesh. Canine teeth long. Layers of enamel and dentine form- ing ridges. Cutting teeth project. Ca- nines form tusks. Teeth even, close together. Canines not projecting. Digits. Sharp claws. Hoofs. Hoofs. Flattened nails. Colon. Smooth. Sacculated. Smooth. Sacculated. I \2 //{'.)/ I. V M/O/OCV Milk of cows is improperly called a perfect food l)y some writers. Altliough it contains the four classes of food stuffs, the proteid is in ex- cess, the fuel food bein<; deticient. Huttcrmilk is more dijjcstible than swet't milk. Huttcrmilk .iiul sugar form a valuable food for infants. Skimmed milk still contains the proteid, the most nutritious part of the milk. Sour milk, or "clabber," and curds pressed into "cottage cheese ■' are more digestible than sweet milk. Cream is more easily digested than butter, which is a solid fat. Cheese is a very concentrated proteid food, and should be eaten sparingly. /^XV-f ■'"'e a valuable food. Is there more proteid or fat in eggs? (See Tabli'.) Pork and veal are the most indigestible of meats. I'isli is nearly as nutritious as meat. There used to be a supposition th.it fish nourished the brain because it contains phosphates; but there are more phosphates in meat than in fish, and more in grains than in meat. Grains contain considerable piotcid (gluten), but tliry especiallv abound in starch. Wheat flour contains more gluten than corn meal, hence it is more sticky, and retains the bubbles of gas so that the dough rises well in bread making. Eggs are sometimes added to corn meal to make it sticky and cause it to rise well. Which grain has the largest percentage of oil? ' (See Table.) Of starch ? Of gluten? Which is poorest in gluten? Grains may be matte to resemble fruit by long cooking at a high temperature (300" Fahr. ), for their starch is tluis changed to dextrin, a substance resembling sugar. You learned tluit the starch of fruit is turned into sugar as the sun ripens it. Dex- trin is yellow and gives the dark color to toasted bread. It is changed to sugar almost instantly when brought in contact with saliva. It is used as a paste on postage stamps. I'effetables contain much water and woody Jibcr. White potatoes zxq underground stems and are one fifth starch. Yams, or sweet potatoes, resemble roots, and contain both starch and sugar. Beans and peas are very nutritious. They have been called " the lean meat of the vegetable kingdom."' They require boiling for several hours. If the skins are removed by pressing them through a colander, they are very easy of digestion. This puree of beans makes delicious soup. " Hull- less beans " and '* split peas '" are also sold by grocers. Practical Questions. — 1. Clothing and shelter for man or bea.st economize what kind of food? 2. Why should bread remain longer in the mouth than meat? 3. In snowl)alling. what is the ap- pearance of the hands when they itch frt)m cold? Extreme cold irri- tates and congests the stomach more quickly than it does the hands. Why is it that ice water does not satisfy the thirst, but often produces a craving to drink more water? 4. Should biscuits having a yellow FOOD AND DIGESTION 113 tint or dark spots due to soda be eaten or thrown awa}'? 5. Why, during an epidemic, are those who have used alcohol as a beverage usually the first to be attacked? 6. Do you buy more wood (cellulose) when you buy beans or when you buy nuts? (p-95.) 7. Do you buy more water when you buy bread or when you buy meat? 8. Why do people who live in overheated rooms often have poor appetites? (p. 90.) 9. Explain how the stomach may be weakened by the eating of predi- gested foods. 10. Whyare deep breathing and exercises that strengthen weak abdominal walls better for the liver than are drugs? (See p. 58.) 11. Sixty students at the University of Missouri found by doing with- out supper that their power to work was greater, their health better, and many of them gained in weight. So they ate only two meals thereafter. If sixty plowboys tried the experiment, would the result probably have been the same ? 12. If a person began to eat less at each meal, or only ate one meal a day. yet gained in weight, should he agree with a friend who told him he was starving himself ? Should he agree if, instead of gaining, he lost weight? 13. Why is half-raw or soggy bread harder to digest than the raw grain itself ? Which would be thoroughly chewed and cause a great flow of saliva ? 14. Ask a fat person whether he drinks much water. A lean person. 15. Why is one whose waist measures more than his chest a bad life insurance risk ? 16. What changes in habits tend to make a rheumatic middle-aged person more youthful? 17. How is the ingenious " fireless cooker " constructed? Atwater's Experiments with Alcohol. — A few years ago Professor Atwater proved that if alcohol is taken in small quantities, it is so completely burned in the body that not over two per cent is excreted. He inferred that it is a food, since it gives heat to the body and possibly gives energy also. His experiments did not show whether any organ was weakened or injured by its use. As alcohol is chiefly burned in the liver, it probably cannot supply energy as is the case with food burned in nerve cell and muscle cell. The heat supplied by its burning is largely lost by the rush of blood to the skin usually caused by drinking the alcohol. Dr. Beebe, unlike Professor Atwater, experimented upon persons who had never taken alcohol, and whose bodies had not had time to become trained to resist its evil effects. He found that it caused an increased I 14 //r.V.t.V RIOLOGY excretion of nitrogen. W'licu the body became used to it, this decreased, but the proteid excreted by the kidneys contained an abnornuil amount of a harmful material called uric acid. Uric acid, a substance which is present in rheumatism and other diseases, is usually destroyed by the liver. As the burden of destroying the alcohol falls chiefly ui)on the liver, it is not surprising to find that it is so weakened and injured by alcoholic drink that it cannot fully perform its important functions. Bright's disease and other diseases accompanied by uric acid are more frequent among persons who use alcoholic drinks. Definition of Food. — A food is anything which, after being absorbed by the body, nourishes the body without injuring it. Does alcohol or to! )acco conic within this definition? Advantages of Good Cooking. — Taste and flavor may be developed ; parasites are killed ; taste may be improved by combining foods ; starch grains are burst and the food softened. Thus digestion is aided. Disadvantages of Bad Cooking. — Proteid foods are hardened ; flavors may be driven off"; too many kinds of food may be mixed; cooked vegetables are more likely to ferment than raw vegetables ; palatable food may be made tasteless or soggy or greasy ; soda and other indiges- tible ingredients may be added ; food may be so highly seasoned as to cause catarrh of the stomach ; it may so stimulate the appetite that so much is eaten as to overload the stomach. Food may be made so soft that it cannot be chewed and is eaten too rapidly; for instance, bread shortened with much grease. The Five Modes of Cooking. — Food may be cooked (i) by heat radiating from glowing coals or a flame, as in broiling; (2) by hot air, as baking in a hot oven ; (3) by boiling in hot water or grease, as frying; (4) by hot water, not boiling, as in stewing; (5) by steaming. Radiant Heat. — Toasting bread and broiling meat are examples. The meat should be turned over every ten seconds to send its juices back and forth, thus preventing their escape, and broiling the meat in the heat of its own juices. /Coasting is an example of this method combined with the second method. The fire should be hot at first in order to sear the outside of the meat and prevent the escape of its juices. If the piece roasted is small, the hot fire may be kept up; but if it is large, a longer time is recjuired, and the fire should be decreased, otherwise the outside will be scorched before the central part FOOD AND DIGESTION II5 becomes heated. White, or Irish, potatoes roasted with their skins on best retain their flavor as well as valuable mineral salts (potash, etc.). Cooking by hot air can only be used with moist foods. Baking is an example. Foods only slightly moist are made hard, dry, and unpalatable if cooked by this method. Cooking by Boiling. — To boil potatoes so as to make them mealy instead of soggy, the water should be boiling when they are put in, and after they are cooked the water should be poured off and the pot set on the back of the stove for the potatoes to dry. Boiling onions drives off the acrid, irritating oil. Rapid boiling of vegetables gives less time for the water to dissolve out the nutrients. (See Steaming.) Raw cabbage is treated by the stomach as a foreign substance, and sent promptly to the intestine ; cabbage boiled with fat may remain in the stomach for five hours. Instead, it should be boiled in clear water for twenty minutes. Beans and peas require several hours' boiling. Cooking in hot liquid below the boiling point is better than boiling. \n frying meat, it should be put in hot grease that a cmst may be formed to prevent the grease from soaking in. Grease much above boiling point becomes decomposed into fatty acids and other indigestible products. Hence butter is more digestible than cooked fats. In whatever way meat is cooked, it should never be salted until the cooking is finished or the salt will draw out the juices which flavor it. Eggs may be .cooked by placing them in boiling water and setting the kettle off the stove at once to cool. A finely minced hard-boiled egg is as digestible as a soft-boiled egg. Since boiling for more than a very few minutes coagulates and hardens albumin, there is no such thing as boiling meat without making it tough and leathery throughout. It may be stewed, a process which belongs to the next method. In stewing meat, it may be plunged into boiling water for a few min- utes ; this coagulates the albumin on the surface. The fire should then be reduced, or the vessel set on the cooler part of the stove, or a metal plate should be placed beneath it, that the water may barely simmer. The water should show a temperature of 185° or 190^ if tested with a thermometer. A piece of meat cooked in this way is tender and juicy. Cooking by steam requires a double vessel or a vessel with a per- forated second bottom above the water, through which the steam may rise to the food that is to be steamed. Steamed vegetables have a better flavor and are more nutritious than those cooked in any other way. A steamer is different from a double boiler. Oatmeal should be cooked for at least forty minutes, and it is more digestible if steamed for several hours until it is a jelly. To do this, it may be cooked during the prepa- ration of two meals. Cooking that leaves it lumpy and sticky is a dis- advantage, and makes it more likely to ferment than if eaten raw. 1 1 6 HUMAN BIOLOGY Thought Questions. Cooking. — .lAv//. 1. In making soup, why should the meat be put in wliile the water is cold.'' 2. In roasting meat, why sliould the oven lie hot at first, and more moderate after- ward.' How should you regulate the temixrature in boiling or stewing meat? 3. What happens to .salt or anything salty on a cloudy, damp day? This is because the .salt attracts . This shows that meat should not be .salted until after it has been cooked, because if salted be- fore . 4. Very tough meat should be b — ed or st — ed, 5. Meat may be prevented from becoming grease-soaked when frying by having the grease very , use very . simply greasing the . 6. Bread. Bread crust causes the to be used more and cleans them. It will not together in the stomach like the crumb. It increases the quantity of the . and is more digestible than the cmmb. since the has been changed by slow heat to (p. 1 12). Therefore loaves or biscuit should be (large or small?) and they should (touch or be separated?) in a pan. 7. How can you tell whether the oven has been too hot while the bread was baking? 8. Why can you tell best about the digestibility of bread when you are slicing it? 9. Regulating the heat is the greatest art of the cook. How may the temperature of the oven be lowered by means of the datnper? The draft? The fuel? E.\ERCiSES IN Writing. — Story of a Savage who went to dwell in a City (his trouble with artificial ways). Is it easier to learn Phy.si- ology or to practice it? How 10 make Bread. Describe People seen in an Audience (tell what their appearance suggests). A Scene at a Dinner Table. Thoughts of a Physician on his Round of Visits. A Good Cook. \ Bad Cook. Is Cooking a Greater Accomplishment than Piano Playing? Common Causes of Illness. The Influence of Imperfect Digestion upon the Other Organs. Effect of Lack of Muscular Activity. The Way of the Transgressor is Hard. What Fools we Mortals be! Health Fads. Temperance in all Things. The Right Way the Easiest. Looking Back. Looking Forward. Hygiene of the Schoolroom. Patent Medicines. Microbes. Mind Cure. Nervous Women. Dissipated Men. How a Friend of mine lost his Health. Why a Friend of mine is Sound and Strong. Tobacco. It never pays to neglect the Health. Which does more Harm, an Ig- norant Cook or an Ignorant Janitor? A Visit to a Sick Room. Alco- hol and Crime. Natural Instincts and Appetites; how preserved, how lost. A Lesson about Alcohol based upon the Morning News. Effects of Alcohol upon the Greatness of our Country (workmen, voters, soldiers, children). Adam's Apothecary Shop. Adam's Ale (water). CHAPTER VIII THE NERVOUS SYSTEM Review Questions introducing this Subject. — What is a cell ? What are the five supporting tissues? What are the two master tissues? Why are they so called? What kind of cells have many branches? Does the food ever come in contact with the salivary glands? When you look at a basket of apples, the sight "makes your mouth water." Is there a connection between the eye and the mouth? What two tis- sues enable the skin to blanch and to blush? Do the different organs share the blood in the same proportions at all times? How can this proportion be changed? How is the brain protected from injury? Ho\v is the spinal cord protected? Is the hole for the spinal cord through the main body of the vertebra, or behind the main body? Harmonious Activity. — Strike suddenly at the eye of another, and the lids fall to protect it, and the hands rise to ward off the blow. If a grain of dust gets into the eye, the tear glands form tears to wash it out. If you touch the hand unexpectedly to a hot iron, the muscles of the arm jerk the hand away. If the foot of a sleeping person is tickled, the muscles of the leg pull it away. Many muscles cooperate in the act of running. If the human being were merely an assemblage of working organs, the organs might act independently, and there would be such confusion that the body would be powerless, and life could not be maintained. The nervous system enables the or- gans to work together for the common good. Why does an ameba not need a nervous system ? The Need of Nerve Centers as well as Nerves. — If there were no central office in a telephone system of one thou- sand subscribers, then every subscriber, in order to com- 117 ii8 Ili'MAX BIOLOGY -Me -Me AWe- Fig. 103. — Showing a NEU- RON, A, or nerve cell with all its parts — dendrites, cell body, and axon ; B, a portion of a white fiber highly magnified. (Jegi.) niunicatc with every other sub- scril)er, would need one thousand wires running into his house; all together, there would have to be several huiuired thousand (to be exact, 499,500) wires. With a cen- tral olTice only one thousand are needed. As a telephone system has central offices, so the nervous system has nerve centers. Nerve centers contain nerve cells. Al- though there are some subordinate nerve centers in the spinal cord, the greatest collection of nerve centers in our bodies is in the skull, and is called the brain. Fishes were the lowest animals studied in animal biology found to possess a true brain. The nervous system, unlike a telephone system, has other duties besides allowing covnnunication. It enables us to t/iink, and, after reflection, to will and to act by con- trolling the various organs. The Units of which the Nervous System is Constructed. — A nerve cell with all its branches, or fibers, is called a nrnroji (see Fig. 103); some neuron branches are several feet long. Neurons are the units that compose the nervous system. The living: substance in cells is THE NERVOUS SYSTEM 119 Fig. 104. — Large Nerve Trunk, such as supplies the muscles. Cross-section (magnified 6 diam- eters), showing bundles of nerve fibers. (Peabody.) zz}\t^ protoplasm. The protoplasm in nerve cells possesses the most marvelous and varied powers of any known sub- stance, for the nerve cells are the seat of the mind. Nerve Cells and Fibers. — The many branches of nerve cells make them the most remarkable of all cells for irregularity in shape. Since the protoplasm of the cell con- tinues into the Jibcrs, it is plainly wrong to consider the nerve cell as something apart from its fibers. It is not a complete cell without them. A cell usually has many short branches called dcndrons or dendrites {sQQ Fig, 103) for communicating with near-by cells, and one long branch called an axon (Fig. 103) for communicat- ing with distant parts. The axons form the fibers that go to the skin, muscles, and other organs. A Nerve. — These long branches, or axons, of nerve cells go all over the body and are often bound together into visible cords called ner'ves, or nerve trunks (Fig. 104). White and Gray Fibers (Fig. 105). — Some fibers have a fatty covering;- sur- FlG. 105. — f, a white _ j ^ £> fiber with its fatty rounding the thread of protoplasm ; they sheath (dark) ; d, ^^^ ^^j^-^^ ^^^ glistening, and are called two gray fibers '^ ^ (without sheath), wliite fibers . Others are without this fatty w I20 HUMAN BIOLOGY covorinf;, and arc called gray fibers, l^oth kinds of fibers have connective tissue on the outside to strengthen them. If we let a lead pencil represent a white fiber, the lead corresponds to the axis of protoplasm ; the wood corre- sponds to the white, shiny fat that surrounds it ; and the varnish corresponds to connective tissue on the surface of the fiber. A number of white fibers together makes a white mass that is called ivliite matter. The axis of a white fiber, of course, is not white. A mass of cells or of gray fibers is called gray matter. The oxidation of the gray matter, or protoplasm, in neurons gives rise to nerve energy. Feeling Cells and Working Cells. — Nerve cells are divided into two classes : sensory cei/s, which feel or receive impressions ; and motor cells, which send out impressions to the working organs. Those fibers which carry impres- sions to the receiving cells are called sensory fibers ; those which carry impulses from the cells to the working organs are called motor fibers. Ganglia and Nerve Centers. — Nerve cells are not scat- tered uniformly in nervous tissue, but are gathered into groups. A group of nerve cells is called a ganglion (Fig. io6). One or more ganglia having a single function, such as to control the muscles of breathing, form what is called a neri'c center. The brain consists of a number of nerve centers with their connect- ing fibers. Ganglion Gross Structure of the Spinal Cord. — The nerve fibers from nearly all over the body lead to cells situated in a large cord in the spinal column called the spinal cord. The spinal cord is separated by a deep fissure almost into halves (Fig. 107). The cells y THE NERVOUS SYSTEM 121 .?■■"" Fig. 107.— Cross-sfxtion of Spinal Cord, showing area of gray matter (dark). are situated in the central portion of each half, and the two masses of gray matter thus formed are connected by a narrow isthmus of gray matter. The outer part of the cord consists chiefly of white fibers. The zvJiite matter is thus on the outside of the cord (Fig. 107). The brain, unlike the cord, has the gray matter on the outside and the white matter on the in- side. For microscopic study of the spinal cord, see Fig. 108. The Work of the Spinal Cord. — There are two functions of the cord : reflex action and transmission of impulses from the body to the brain. Reflex action is action that takes place without the aid of the will. Reflex action never begins in the cord, but at the outer end of a sensory fiber, usu- ally located in the skin. The impression goes to the cord along a sensory fiber. It is received in a sensory cell and transferred by den- drons to a motor cell which sends back an impulse along a motor fiber to a muscle ; the muscle contracts and the action is complete. At least two nerve cells are necessary for reflex action. The actions of the lowest animals are almost entirely reflex. Fig. 108. — Section m Sri\\i, Cord, showing nerve cells (large black spots) with their branches (black dots and lines). Five bundles of nerve fibers are shown near upper margin. (Peabody.) 122 I/iWf.lX BIOLOGY Reflex Action, Consciousness, and Will. — Usually not all of the force of the impulse is transferred to the motor cell. The sensory cell bv means of another of its many branches mav transfif part of lite impulse to a cell tvliicli sends it to the brain. Hence a reflex act is not necessarily an uncon- scious one. If you unintentionally touch the hand to a hot stove pipe, you may be conscious of the pain and the involuntary jerking away of the hand at the same time. Reflex Action and the Will. — The will may inhibit, or prevent, an exi)ected reflex act. Yet many reflex acts occur in spite of the effort of the will to prevent them. One cannot always keep from closing the eyes before a threatened blow even if from the other side of a plate glass window, and it is known there is no danger. Sneezing is a reflex act and can- not always be prevented. The forming of saliva and other secretions are reflex acts. Reflex acts arc quicker tlian voluntary acts. An eighth of a second is about the time required for a person to press an electric button after seeing a signal ; a reflex act may occur in a shorter time. The Brain consists of Three Chief Parts. — (i) There is an enlargement at the top of the spinal cord called the medulla, or the medulla oblongata. It may be re- garded as the part of the spinal cord within the skull (see Figs. 109, no, 114). (2) Above the medulla is the cerebellum, or little brain. (3) The cerebrum, or large FIG. 109.- BRAIN ^^^^^ ^jjg ^jj ^j^g gj^^jj except the small AND Spinal ' ' Cord. part occupied by the medulla and cere- THE NERVOUS SYSTEM 123 Fig. 1 10. — The Brain (cerebrum, cerebellum, medulla). bellum. The cerebrum covers the cerebellum. (Fig. no.) Is this true of the monkey's brain.? (See Fig. The work of the medulla is chiefly to control the vital functions (see Figs, no, 114). Here are located the centers for regulating the breatJiing, the heart beat, the size of the blood vessels (thus regulating nutrition), and also the less important centers that control swallozving, secre- tion of saliva, and vomiting. The center for breathing is sometimes called the vital k?iot, because although the cerebrum and cerebellum may be removed from an animal without causing immediate death, the slightest injury to the vital knot kills the animal at once. In cases of hanging, death is caused by injury to this center. Automatic Action. — The center called the vital knot is said to regulate the breathing automatically, not reflexly. Reflex acts start in the skin ; automatic acts start in the interior of the body. The coftdition of the blood regulates the breathing automatically during sleep, and partly regulates it during waking. If too much carbon dioxid accumulates in the blood this excites the vital knot, which sends out stronger impulses to the respiratory muscles. Deeper breathing follows, which purifies the blood, and the breathing is then Fig. III. — Associ.\TioN Fibers, con- necting cells within the cerebrum. (Jegi.) 124 HUMAN BIOLOGY Fig. 112. — Sensory anu Muiok Fibers. (Jegi.) shallow or slow until carbon dioxid accumulates again. The Four Kinds of Nerve Action and the Centers that con- trol them. — The <('yv/ contii)ls chicHy njhx action; the medulla controls chiefly aiitovuitic action ; the cerebellum controls chiefly coordinate, or harmonizing;, action ; the cere- brum controls the purely vol- untary acts, for it is the seat of consciousness and thought. The medulla, like the cord, has the gray matter on the inside (Fig. 109). Structure of the Cere- bellum. — The cerebellum, like the cerebrum, has the gray matter or cells on the outside. The gray matter is folded into furrows that are not nearly so winding as the folds in the cerebrum (see Fig. 115). The fibers going to the surface cells have a branched arrange- ment called the arbor vita, or tree of life, which is shown where the cerebellum is cut. The cerebellum, like the cere- brum, is deeply cleft and thus divided into halves, called hemispheres, connected by a band of white matter. The work of the cerebellum is to aid the cerebrum in controlling the muscles. It coordinates the muscular move- FiG. 113. — Brain of a Monkey. Numerals show location of motor centers. (See Fig. 115.) THE NERVOUS SYSTEM 125 cerebrum ^^^^ Fig. 114. — The Lobes of the Right Side of Brain and their functions. (Jegi.) The speech center is true only for left-handed persons. Medulla is marked " Bulb." ments ; that is, it makes the muscles act at the right time and with due force in complex acts, such as stand- ing, walking, talking. A man could strike just as hard without the action of the cerebellum, but he would not be likely to hit what he aimed at. A drunken man staggers and fails to control the muscles in walk- ing because the alcohol has caused the blood to collect and congest around the cerebellum and press upon it. One whose cerebellum •has been injured by accident staggers like a drunken man. Coverings of the Brain. — Lin- ing the skull and covering the cere- brum are found two membranes which inclose a lymph-like fluid. Thus a kind of water bed \s made which surrounds the soft and deli- cate cerebrum Fig. 115. — Motor and Sensory Areas of Left Hemisphere. Speech center marked " Lips." ^T^O- protects It In what region are the motor centers? The sensory centers? irom jarS. J\ 126 HUMAN BIOLOGY membraneous net, or mcshwork, of blood vessels covers the cerebrum and plentifully supplies it with blood. Structure of the Cerebrum. — The gray matter, or cell mass ot the ccrcbruiii, ti)rnis a surface layer, called the rt>/-/^a- ("bark "), about one eighth of an inch thick. This gray layer is deeply folded^ the folds, or eonvolutions^ being separated by deep furrows, some of them an inch deep (see Fig. wo). Thus the area of the surface layer is increased to several times what it would be if smooth. Intelligence increases with increase in the number and depth of the convolutions. The greater part of the cere- brum is white matter. This consists largely of associa- tion alyf(5'r;'j" (Fig. Ill) zvhicli eoiDieet the eells in the gray matter with each other and with important interior ganglia at the base of the cerebrum (Fig. 112). These basal ganglia are the largest parts of the brains of the lower vertebrates (Animal Biology, Figs. 222, 259). Why do these animals not need large cerebrums .-* The human cerebrum comprises nearly seven eighths of the weight of the brain. A deep fissure divides it into the right and left cerebral hemispheres. A band of white matter con- nects the hemispheres. Functions of the Cerebrum. — The cerebrum is the seat of consciousness and thought, and of all activity controlled by the will. It also directs the ivork of tJie lower nerve centers in the spinal cord, medulla, and cerebellum. It receives sensory messages from all parts of the skin and through the special senses. It sends out motor mes- sages to all the voluntary muscles, and more indirectly to the involuntary muscles. The cerebral fibers are of three kinds : sensory, associational (connecting cells in cere- brum), and W(?/*^;- ( Figs. Ill, 112). It is estimated that the cerebrum alone contains 9,200,000,000 cells. THE NERVOUS SYSTEM 12/ Spinal and Cranial Nerves. — The nerves from the spinal cord go out through notches between the vertebrae. Since there are thirty-one pairs of spinal nerves (Fig. 109) and only twenty-four vertebras, some of the nerves go out through holes in the sacrum. The cranial nerves (to eyes, ears, tongue, nose, face, etc.) leave the brain through holes in the cranium, or skull. There are twelve pairs of them. Relation of the Cerebrum to the Lower Centers. — As already stated, nerve activities are of four kinds, — reflex, automatic, coordinate, and voluntary. A manufactory has more complex work than a shop. A man with a shop may enlarge it into a factory and leave trained assist- ants in charge of the different shops, keeping only the general man- agement for himself. If he should cease to control his assistants entirely, the work of the factory would soon be in disorder. If the manager should try to direct everything, he would become exhausted. So the cerebrum, the seat of the will and the reason, leaves the reflex centers in the spinal cord, medulla, and cerebellum to do most of the work. If the mind wishes the hand to move and grasp the hand of a friend, the motor center in the cerebrum sends a message to the cerebellum; and if the cerebellum has been well trained, the act is accurately performed. A less imperfect wisdom than that of the mind is in the lower nerve centers. The reason and will control the lower centers through the cerebrum, but the control is very limited. It is well that this is so, not only for the relief of the cerebrum, but for the safety of the body. Can you change the rate of the heart beat by the exercise of the will? Can you blush at will, or prevent the flushing of the capil- laries when you are embarrassed, or when you go close to a hot fire.'' It is impossible for a person to commit suicide by holding the breath. What change in the blood would soon force a breath to be taken? Repeat the two examples of reflex action triumphing over the will which have already been given. We shall next take up a system of nerves almost independent of the will. The ganglionic or sympathetic portion of the nervous system controls the viscera {z'is'se-ra), or internal organs, e.g. peristalsis of food tube, tone of arteries. The nerves that go to the viscera branch off from the spinal nerves not far from the spinal column, and enter a row of ganglia on each side of the spine (see Fig. 115). Each ganglion is connected by nerves with the one above and below it, so that they appear like two knotted cords suspended one 128 HUMAN BIOLOGY on each side of the spinal column and tied together below ; for both chains of ganglia end in the same ganglion in the pelvis. Some of the fibers from the spinal cord pass through these ganglia on their way to the viscera, losing their white sheaths in the ganglia and emerging as gray fibers. The spinal cord and brain with the fibers which do not pass through the double chain of ganglia are called the ccrcbro - spinal systan. The double chain of ganglia and the fibers which go through them are called the ganglionic or sympathetic system. Why these Nerves are called the Sympathetic System. — These nerves, after leaving the double chain of ganglia, form many intricate networks of ganglia and fibers. Each network is called a plexus (Fig. 1 16). The largest of the plexuses is just back of the stomach, and is called the solar plexus. A blow upon the stomach may paralyze this plexus The plexuses and fibers con- nect the viscera so perfectly that one organ cannot suffer without the others changing their activity, or sympathizing with it. An overloaded stomach causes the heart to beat faster and send it more blood ; a loss of appetite usually accompanies illness and allows the stomach to rest. This sympathy is necessary, for if one organ is Fig. ii6. — Diagram ok Sympa- thetic System showing double chain of ganglia ; also plexus at heart and solar plexus. and cause sudden death. THE NERVOUS SYSTEM 129 diseased, the others do not continue to work and tax the strength of the aihng organ. How the Sympathetic and Cerebro-spinal Nerves Differ. — The ganglionic nerves (i) contain mostly gray fibers ; (2) pass through ganglia after leaving the spinal cord ; (3) control the iinconscious activities of the body ; (4) pass to organs which contain slow-acting involuntary muscles, not to sense organs and quick-acting voluntary muscles ; (5) transm.it impulses sloivly (about 20 ft. instead of 100 ft. per second). Crawfish and insects have hardly more than the ganglionic system of nerves (Animal Biology, Figs. 92, 132, 197). Examples of the Supervisory Functions of the Sympa- thetic System. — Regulation of the heart beat and of the size of the blood vessels ; secretion of sweat glands ; con- traction of pupils of eyes in a bright light; peristalsis. Examples of Sympathetic Nerve Impulses reaching Con- sciousness.— Pain in colic and cramps; "heartburn" (pain in stomach from indigestion) ; backache (from nerves in organs prolapsed by tight clothing pulling upon their attachments at spine) ; hunger ; thirst. The Mind and Health. — A contented or peaceful mind is indispen- sable to soundest health. Worry causes difficult breathing with bated breath. Happiness brings full, easy breathing. Biological study of physiology shows the futility of making health a care or anxiety, and ' teaches " no meddling " with the body, whether by stimulating it, drug- ging it, deforming it, overheating it, half smothering it in close rooms, cultivating artificial instincts, etc. If the body degenerates through wrong living, and disease ensues, a new way of living is needed, not some quick and wonderful remedy. The new life will renew the body and nothing else can. Hygiene of the Nervous System Necessity of Food, Fresh Air, and Rest for Sound Nerves. — The health of the nerves depends upon a free supply of K I30 HUMAN BIOLOGY pure, nutritious blood. Nearly one fifth of the blood goes to the brain. It is clear that the brain cannot give out energy until it has first received it ; the blood supplies energy to the brain. The blood in turn receives the nour- ishment from food and pure air. A rested cell is full of nourishment; a tired cell is shriveled (see Fig. 117). Sleep. — During waking hours energy is used up faster than it is stored in the cells, and protoplasm is o.xidized faster than the cells can replace it. Dur- ing sleep the opposite is true ; repair is more rapid than waste. During sleep the muscles are strength- ened, the breathing is less, the heart beats more slowly, less heat is produced, diges- tion is slower, less blood goes to the brain. Why is it necessary to be more warmly protected by clothing or bed covering when asleep than when awake .-' Above all, the nervous system has an opportunity to recuperate from the constant activity of waking hours. The eye and the ear are rested by darkness and silence. Sleep caused by morphine or other drug is not normal sleep and brings little refreshment. Fig. 117. -Effects of Fatigue on Nerve Cells. A, resting cell, B, fatigued cell, with its body and nucleus shrunken. Practical Suggestions. — Sleep is deepest during the second hour after going to sleep, and a greater shock is given to the nervous system by waking a sleeper during that hour than at another time. An alarm clock is a very unhealthful device. One who cannot trust to nature THE NERVOUS SYSTEM 131 even to awaken has great presumption. If one does not rise promptly upon waking naturally, the instinct to awake when enough sleep has been taken will be lost, and the habit of sleeping too much will be formed, and the brain, like the muscles, will become weak from inactivity. Infants sleep most of the time, and it is injurious to them to be waked. Adults usually require about eight hours of sleep. There is a risk in going to sleep in a warm room, for the bed covering which is comfortable then may not be enough to prevent taking cold when the fire goes out. Sleep usually comes more promptly to one who goes to bed at the same hour each night. The muscles are relaxed in sleep, and relaxing them perfectly upon lying down and breathing slowly, tends to bring sleep. One who is sleepless usually finds that he is breathing fast and is holding the head stiff on the shoulders, the teeth clenched, and the muscles contracted, even though he is lying down. Excitement and worry during the day, but especially just before retiring, tend to produce sleeplessness. One who overworks his mind by too great attention to business is inviting ruin. A student who loses sleep while preparing for an examination will probably fail. Rested brain cells and pure blood are needed for good work. Rules for Preventing Sleepiness. — (i) Do not sit close to stove or especially a fireplace or in very warm room, and do not wear very warm clothing in the house. (2) Let in fresh air freely. (3) Do not sit in rocking chair nor with chest flattened. (4) Make the last meal a very light one. Habits. — Our habits of doing and thinking and feeling really constitute our characters. This shows the impor- tance of right habits. By gradually changing our habits we can strengthen our characters and form them somewhat as we wish. When a muscle contracts in a certain way, this act makes it easier for the muscle to contract in that way the next time ; thus great muscular strength may be developed. When a nerve cell acts, .the circulation around the cell is increased, the fibers develop by use, and the act is easier the next time. We cannot entirely get rid of our habits, because we cannot get rid of our brains. Healthy fatigue is caused by the accumulation of waste products resulting from the oxidation of substances in nerve, muscle, and gland cells. The presence of waste in 132 HUM AX BIOLOGY the tissues affects the nerves. We are rested and strong when these wastes are removed and the tissues are sup- plied with fresh food and oxygen. Work causes the ac- cumulation of iiiiboti dioxid, ivliich is riatitrcs narcotic} The drowsy feeling that ensues is more plea.sant than the drowsy feeling from alcohol or opium. Those who do not employ nature's narcotic but free themselves of it by hurried, anxious breathing become restless and crave arti- ficial narcotics. Fatigue without work occurs with people who are idle. The oxidation in their cells is not complete, and poisonous products of the incomplete burning result. This is known as self-poisoning (auto-toxemia). The poisons are taken by the blood to the nerves and brain, and give a tired feel- ing as effectually as does hard work ; or the food may fer- ment in the food tube and form poi- sons which increase the tired feeling. Such persons are usually irritable, while persons who are fatigued by use- ful labor are likely to be dull and drowsy. Headaches are caused by poisons in the blood or by pressure of blood congested in the head. Like all other pains they should be a source of benefit in ' It has been found that it is injurious to rebreathe expired air containing one per cent of carbon dioxid, but a far greater percentage is harmless if intro- duced into fresh air, thus indicating that the injury from poor ventilation comes chiefly from the " crowd poison," or organic particles thrown off. EYE 5TPAIN.,:., 0Y5PEP5I4.^ COHiTlPAVON OiSTUPBANCES OP hOie, tAR, ANO OCiAY£0 TEtTH . -//Sfit'OUS ETf/AL'STfaV -iPJNAL miTAmn Fig. ii8. — The Situation of Headaches with reference to their causes. THE NERVOUS SYSTEM 1 33 that they show us ways of living to be shunned in the future. Many persons, however, not only derive no profit from a headache, but by unwise efforts to cure the pain, bring permanent injury to themselves in addition to the suffering of the headache. Bromides, opiuDi, and o'Ca^x poisons deaden and weaken the nervous system while preventing the headache from being felt. Headache powders, phenacetin, acetanelid, an- tikamnia, and other vile poisons made from coal tar, shock and weaken the heart and reduce the vital activities so that the headache is no longer felt. In consequence of shocks from repeated doses of such drugs, the heart will not work so well, and may give way some time in the future when an effort or strain makes unusual demands upon it. Their use has made heart disease more preva- lent. The liver and kidney cells and the white corpuscles have to destroy and remove the drugs. Many people are foolish enough to injure their bodies and risk death rather than suffer pain or avoid pain by prudent living. Sick headacJies are foretold by a dull feeling, sleepiness after eating, a coated tongue, and constipation. It would be better to remove the undigested, spoiled food from the stomach (four glasses of water will cause v^omiting) than to take a drug. At the first indication of trouble, ab- stain from eating, or use a fruit diet for twenty-four hours, and drink water freely. This will enable the body to dispose of the excess of waste matter. The Highest Living Medical Authority on Drugs. — Dr. Osier, formerly of Johns Hopkins University and now of Oxford University, says : " But the new school does not feel itself under obligation to give any medicines whatever, while a generation ago not only could few phy- sicians have held their practice unless they did, but few would have 134 Ili'MAX BIOLOGY thouiiht it safe or scientific. Of course there are still manv cases where tile patient or the patient's friends must be humored by administering medicine, or alleged medicine, where it is not really needed, and indeed often where the buoyancy of mind, which is the real curative agent, can only be created by making him wait hopefully for the expected action of medicine; and some physicians still cannot unlearn their old train- ing. But the change is great. The modern treatment of disease relies very greatly on the old so-called natural methods, diet and exer- cise, bathing and massage, in other words giving the natural forces the fullest scope by easy and thorough nutrition, increased flow of blood, and removal of obstructions to the excretory systems or the circulation in the tissues. One notable example is typhoid fever. At the outset of the nineteenth century it was treated with " remedies'" of the extremest violence, — bleeding and blistering, vomiting and purging, antimony and cUomel, and other heroic remedies. Now the patient is bathed and nursed and carefully tended, but rarely given medicine. This is there- suit partly of the remarkable experiments of the Paris and Vienna schools into the action of drugs which have shaken the stoutest faiths ; and partly of the constant and reproachful object lesson of homeopathy. No regular physician would ever admit that the homeopathic " infini- tesimals '■ could do any good as direct curative agents ; and yet it was perfectly certain that hoineopaths lost no more of their patients than others. There was but one conclusion to draw, that most drugs had no effect whatever on the diseases for which they were administered." — '* Encyclopaedia Americana," Vol. X. (Munn & Co., New York.) Applying Hygienic Tests Systematically. — The cause of ill health {e._i[. a headache) should be sought with system and thoroughness, ap- plying the tests in rotation to every function of the body : Lungs. Is the air habitually breathed fresh and free from dust? Is the body held up, and is the chest or waist cramped by clothing? Muscles. Is enough physical exertion made to cause deep breaths to be drawn? Food. Is it simple, digestible, and eaten properly? Drink. Is the water pure? Cleanliness, H'ork and Rest, Clothing, Ventilation, and Mental State may be inquired into until the source of trouble is found and the cause of ill health removed. To give drugs and leave the cause of ill health untouched, is to fail. There are signs of coming weakness or illness which, if heeded and the ways of living improved, will usually prevent illness. Among these signs are headaches, paleness, sensi- tiveness to cold, heavy feeling or pain after meals, constipation. Huxley says that young people should so learn physiology and so understand their bodies that they will heed the first sign of nature's displeasure, and not wait for a box on the ear. THE NERVOUS SYSTEM 1 35 Nervous Children. — A report on the health of the school children in one of our large cities shows that one third of the children in those schools have some disorder of the nerves. Nervousness (weakened control of the nerves) may show itself by sluggishness of mind, great irritability of temper, frequent spells of the " blues,'''' or by involuntary movements of a. Jerky or fidgety kind. Sound development of city children's nerves is hindered because of the constant noise in cities both day and night ; by short enittg of the hours of sleep ; by excessive use of sugar for food ; by living much among people with 710 chance to be alone and let the nerves rest, and among boys by the use of cigarettes. How to Prevent the School from injuring Children. — (i) Ventilation is of first importance. Breathing the breath of fifty other children does far more harm than overstudy. (2) TJic time devoted to zuork should not be long, especially in the lower grades (no study out of school). (3) The zvork should be diversified ; not only printed words, but pictures, natural objects, and the out- door world should be studied. (4) The teacher and parent should see that tJie habitual poise of the child is favorable to health. (5) The children should be encoiwaged to play. Running games at recess are of the greatest value, and are as indispensable to the health of a boy or girl as of a colt. (6) Physical exercise should be provided at short intervals between lessons, especially stretching exercises and movements that straighten the spine and hips and ele- vate the chest. The Effect of Alcohol upon Nerve Function. — In attack- ing the nerve centers, alcohol begins with the cerebrum, the highest, and proceeds toward the lowest. Hence as a man becomes drunk he first talks foolishly (cerebrum affected), then he staggers (cerebellum affected), and he finally goes to sleep and breathes very hard (medulla affected) in a drunken stupor. It rarely happens that the breathing center is completely disabled and the man dies from the strong poison. The greatest evil of alcohol is 136 HUMAN BIOLOGY seen in the case of steady drinking. This gradually de- troys the soundness of the nervous system and weakens self-control. The tendency with nearly all drinkers is to increase the amount taken. Not Total Abstainers, but the Advocates of Universal Moderation are the Visionaries. — The evil results from alcohol are so great as to be almost incredible. The plainest statements of its effects are sometimes denounced as unscientific by persons prejudiced in its favor. A part of the two billion dollars annually paid for liquors is used in influencing public opinion through the press. Practical Questions. — 1. Why does travel often cure a sick person when all else fails .•* 2. Why is working more healthful than "taking e.xercise"? (p. 47.) 3. Is it better for children to play or to take exercise ? 4. Why can one walk and carry on a conversation at the same time ? (p. 127.) 5. How does indigestion cause a headache? (p. 133.) 6. Does perfectly comfortable clothing from head to foot help to make one at ease in company ? Does uncomfortable clothing tend to make one awkward ? 7. Why is it as important to have the shoes and clothes perfectly comfortable when going out as when stay- ing at home ? 8. When one's finger is cut, where is the pain ? 9. In what two ways may opening a window when a student is becom- ing dull and drowsy at his books enable him to wake up and study with ease? 10. What kinds of cells shrivel like a baked apple when they become fatigued? (Fig. 117.) 11. A nerve or nerve fiber can hardly become tired or fatigued, for the nerve cell supplies the energy. What do we mean when we say the nerves are worn out? (Fig. 117.) 12. Why do you throw cold water upon a fainting person ? 13. Why does constant, moderate drinking undermine the health more than occasional intoxication ? 14. Why does stoppage of the circulation cause one to faint? (See Chap. VI.) 15. Why is grazing the skin often more pain- ful than cutting it ? (Colored Fig. i . ) 16. Why do the lower ani- mals always act upon sudden impulse ? What part of the brain enables man to retain sensations and not act upon them until later ? 17. Does '• nervousness " more probably indicate a bright mind or a high temper ? 18. What is the effect of a cold bath upon the nerves ? (Chap. II.) 19. Did you ever know a cigarette smoker whose hand trembled ? 20. Need there be any fear of a sobbing child holding its breath until it dies ? 21. Why is muscle tone greater in cold weather ? THE NERVOUS SYSTEM 1 37 The True Function of Stimulants. — One whose heart has nearly given out because of exposure to severe weather may be temporarily revived by alcohol. It will not be wise to do so 7inless it is certain that a warm fire and protection ivill be reached before the reaction comes. Much less would be necessary to revive an abstainer than a drunkard. Ha- bitually disturbing the body with stimulants makes them ineffective in a time of emergency. A cup of coffee will not keep a watcher awake if he is used to coffee. Definitions : Stimulant, Narcotic, Poison. — A stimulant is anytJiing that excites the body to activity, but is of no help or of insignificant help, in replacing the strength used up. A narcotic is anything that deadens or dulls the nervous systejn. It comes from a word meaning " to benumb." Poisons are active substances, which, taken in quantities, as man takes food, destroy life ; in smaller quantities they injure the body and may destroy Hfe. Alcohol is a poison. Wine, beer, whisky, contain varying quantities of it. The Narcotic and Stimulant Effects of Poisons. — Ex- amples of poisons are alcohol, nicotin, opium, arsenic, strychnin. Poisons excite the body when taken in small doses, while in large doses they produce paralysis and death. The irritating or stimulating effect is due to de- rangement of the functions or to the efforts of the cells to free the body of the destructive substance. The narcotic effect is due to the poison having so benumbed the nerves and injured the cells that their activities cease, or become less for a time. You readily see how the same poison can be both a stimulant and a narcotic : the stimulating effect always comes first , follozued by the stupefyijig effect. If the dose is very small, the stimulating effect will last longer ; if it is large, the narcotic effect is greater and felt more quickly. A habit of using stimulants is an invariable sign 138 HUMAN BIOLOGY of weakness. The first dose of morphine or cocaine may be the first step in a lifelong blij^ht of strength and happi- ness. If physicians whose treatment of a case results in leaving a patient with a drug or alcohol habit were sued for malpractice, they would be less reckless. The annual consumption of morphine is estimated at twenty-seven grains per capita in China, and fifty grains in the United States. Reaction. — This is the depressed and exhausted condition that couus oil after a period of unnatural activity. It fol- lows the exciting effects of a stimulant. Natural Stimulants. — If there were nothing to arouse activitv, life would be impossible. A cold wind is a natural stimulant. The activity aroused by a cold zuind is just enough to help the body zvitlistand the cold ; artificial stimulants cause an expenditure having no relation to the needs of the body. Hence there is a great waste of energy. Feelings may stimulate, as love for his family may stimu- late a man to labor. The desire for knowledge may stimu- late a boy to study. Hunger may stimulate a man to eat. Hunger is a natural stimulant, and is not likely to make him eat to e.xcess ; tea, coffee, pepper, etc., arouse a false appetite. These things are used chiefly for their stimu- lant effect, for they contain little or no nourishment. We will now study about artificial stimulants. Such stimulants ahvays cause an unregulated and unhealthy action, and are always followed by fraction. How much Strength is stored in the Body? — Dr. Tanner of Minnesota believed that most people eat too much. Another physician said that no humaii being could go forty days without food. Dr. Tanner made the experiment. He lost thirty-six pounds in weight, but he weighed \2\\ pounds and had considerable strength at the end of the THE NERVOUS SYSTEM 1 39 forty days. The first thing he ate at the close of his fast was the juice of a ripe watermelon. Once some miners were shut in by the caving of a part of a mine. But, unlike the case just described, they were without zvatcr as ivell as food. When, by digging, the rescuers reached them seven days after, several were still found alive, although most of them had died. The miners, no doubt, had nourishment in their bodies for some weeks more of life, but the body lacked water to dissolve it and bring it within the reach of the cells most needing it. A Stupendous Fact. — These incidents show how wisely the body is made, and prove that the cells store up nourish- ment for weeks ahead. The large amount of jiojcrishment stored in the Jinman body is one of the most striking and important facts with which the science of physiology has to deal, and it should be borne in mind, or we may make great mistakes about some very simple matters and espe- cially in regard to the effects of stimulants. Foolish Rashness. — Did you ever get so tired that you had to give up and stop, however much you would have liked to continue at work or play .'' To rest was the wise tJmig to do. Because you know there is much energy stored in the body, this need not tempt you to go on until you almost break down. Probably you y.r\o^ people who are conceited about their bodies and say they are "made of cast iron " ; that nothing can hurt them. Such conceit will be almost sure to get its possessor into trouble. How a Safeguard may be broken down. — It is a very wise arrangement that, tinder ordinary conditions^ we can- not get at the s?uplus energy we have. Carbon dioxid and other wastes accumulate in the tissues and paralyze the nerves. Fatigue and other feelings compel us to be provi- dent, as it were ; yet stimulants and narcotics, by irritating 140 Hi'MA.V BIOLOGY the nerve cells, arouse them and cause us to expend some of this reserve energy. Thus man is enabled to get at this precious store which he should save for emergencies, when he is sick and cannot digest food, or when he is making some mighty effort. A weak, ill man who has eaten very little for weeks, when delirious is sometimes so powerful that it takes several strong men to hold him in bed. But the delirious mania often uses up the little energy left, and costs the man his life. The only source of energy for man's body is the union of food and oxygen ; he must get his energy from the same source that the engine does ; and this is from his food, which serves as fuel, and the oxygen which burns it. If one has been working hard preparing for examinations, or gathering hay, or in attending to some important busi- ness, or has been under the excitement of some pleasure trip, and feels '^ blue'' and worn out, thcjt let him bear the result like a man, or like a true boy or girl, as the case may be. Giving up for a while, or " toughing it out " with the blues, or losing a little time from business, will not hurt, but will restore strength, while a stimulant will leave him less of a man than before. Nervousness. — The attempt to divide the race into brain workers, muscle workers, and loafers, whether men or women, is a powerful factor in race degeneration. Leonard Hill says : •' Hysteria and nervous exhaustion are the fruits not of overwork, but of lack of varied and interesting employment. The absurd opinion that hard work is menial and low, leads to most pernicious consequences. The girl who, turning from brain work to manual labor, can cook, scrub, wash, and garden, invites the bloom of health to her cheeks; while the fine do-nothing lady loses her good looks, suffers from the blues, and is a nuisance to her friends and a misery to herself." A Japanese lady holds views similar to those of Dr. Hill. Read footnote.^ ^ Statement by Madame Toyi Niku <>f Veddo, Japan, after a six months' visit to the United States. — " Worry and inactivity, it seems to me, sharply THE NERVOUS SYSTEM I41 Subjects for Debate. — (i) Does the Chinese woman deform her body less than the Caucasian woman and suffer less from it ? (2) Does as much disease originate in the dining room as the barroom ? (3) Are drugs a necessary evil ? (4) Does pride cause as much illness as ignorance ? (5) Is it ever right to neglect the health ? (6) Does the mind or the way of living have more effect upon the health ? Disuse and Degeneration. — Many persons in civilized countries cherish a vain hope of having sound muscles without habitual use of them, pure blood without deep breathing, a strong circulation in an inactive body, a fresh skin without keeping the body sound, a hearty appetite without enough physical labor to use the food already eaten, steady nerves with a part of the body overworked and a part stagnating from disuse. Their flabby muscles, pale skins, highly seasoned food to arouse appetite, narcotics to deaden irritable nerv^es, and the wide use of drugs as a fancied substitute for right living all show the attempt to be a miserable failure. If the parents leading such a life escape with fairly good health and average length of life, they leave a few unhealthy chil- dren in whom physical degeneration is plain. Complete, balanced liv- ing only prevents degeneration. Although there are cases of illness which are not necessarily a disgrace, disease usually originates in weak- ness of character or lack of common sense. The snob who thinks him- self above physical labor, the dupes who at the bidding of avaricious fashion mongers think more of clothes than of a free body, the narrow, unbalanced man, who concentrates all his energies on one ambition, the short-sighted one who worries, all grow into a diseased state. mark the women of your middle classes. I did not attempt to study your leaders of society, for they are much alike the world over — • the same fuss, the same display of jewels and finery, the same scandals, the same uselessness. Your women do not diversify enough. If they are good cooks, they stop there ; perhaps another is a good housekeeper, another can sew finely; but doing one thing makes narrow-mindedness. In Japan we strive to do many things. The worry troubles of your women, it seems to me, come largely from improper eating and overeating. I have sat at many of your tables and there is too much fnod on them and too much variety. First, women overeat, then they doctor, then they starve, and then they become nervous. A woman's diet, especially a mother's, should always be simple. Cut down eating and increase variety of labor and exercise. My own people live that way with a result that we have better feminine bodies, better skins, and better tempers than your women. I like the brightness of your young women. Perhaps you will take the hideous hats off them some day, find a substitute for the bad corset, and let them wear clothes that are loose, yet are soft and clinging. They are bound up in their clothes too much now and their judgment of colors and combina- tions is nut good. Their clothing is either garish or very dull in hue. The simplest girl in Japan knows how to harmonize color with herself, — Mother'' s Magazine, November, 1907. CHAPTER IX THE SENSES Experiment i. Where are the Nerves of Touch most Abundant? — Open a pair of scissors so that the points are one eighth of an inch apart, and touch both points to the tip of the finger. Are they felt as one or as two points ? Find how far they must be separated to be felt as two points when applied to the back of the neck. Record results. Caution : The person should be blindfolded, or should look away while the tests are being made. Two pins stuck in a coik will be more con- venient to use than scissors. Experiment 2. Nerves of Temperature, or Thermic Nerves. — Draw the end of a cold wire along the skin. Does the wire feel cold all the time ? Repeat with a hot wire. Do you conclude that temperature is felt only in spots ? Muscular Sense. — Experiment 3. Make tests of the ability to distin- guish the weight of objects weighing nearly the same, when laid by another in outstretched hand : also by laying them in the hand while it rests upon a table. Which test showed more delicate distinctions ? In which were muscles brought into use ? Experi- ment 4. Close the eyes and let some one move your left arm to a new position : then see if you can with the forefinger of the right hand touch the forefinger of the left hand in its new position at the first attempt. Experiment 5. Functions of the Several Parts of the Tongue. — Test the tip, edges, and back of the tongue with sugar, vinegar, qui- nine, and salt. Where is the taste of each most acute ? Record results. Flavors. — Experiment 6. Blindfold a member of the class, and while he holds his nostrils firmly closed by pinching them, have him place successively upon his tongue a bit of potato and of onion. Can he distinguish them ? Experiment 7. Mark /-'after each of the following 142 1 i«j. 119. — " Cold" Srois (light shading). " HOT" SPOTS (dark), skin of thigh. THE SENSES 1 43 foods that have a flavor (see text) : vanilla, apple, lemon, beef, peaches, grapes, coffee, onion. potato, cinnamon. Expert}?ient 8. A Smelling Contest. — Place the following and other things having taste in vials around which paper has been pasted to con- ceal their contents : pepper sauce, vinegar, kerosene, flavoring extracts (diluted), several perfumes, iodine, bits of banana, lemon, apple, etc. Number the vials and have pupils test and write results in a list. Correct the lists and announce pupil having keenest sense of smell. Experiment 9. A tasting contest may be arranged in a similar way. Smelling and tasting tests should be made quickly as these senses are soon dulled by repeating a sensation. Experiment 10. Advantage of Two Eyes over One. — Try to touch forefinger to something held by another at arm's length from you, bringing the finger in from the side: (i) with one eye closed; (2) with both eyes open. Result ? Conclusion ? We tell the dis- tance of an object by the amount of convergence of the eyeballs needed to look at it. Experiment 11. Duration of Impression. — Whirl a stick with a glowing coal on one end (see Fig. 123). Experiment 12. Color Blindness. — Provide a number of yarns of diiTerent tints, and the same tints. Test color blindness by having each pupil match tints and assort the yarns. Experiment 13. Fatigue of Optic Nerve. — Gaze long and steadily at a moderately bright object, then close the eyes. Kesult ? Conclusion ? Experiment 14. Dissection of Eye. — The eye of an ox is an in- teresting subject for dissection. The lens is like a clear crystal. Make out all parts named in the text (see Fig. 122). Experiment 15. Image formed by a Convex Lens. — For a few cents obtain from a jeweler a convex lens, or use a strong pair of spectacles worn by an old person. Hold the lens a few feet from a window (darken any other windows near). A little beyond the lens hold a white card or book open at a blank page to catch the image. Have some one walk before the window. Experiment 16. Work of Iris. — Notice the size of the pupils. Cover one eye with the hand for a few minutes. Uncover and look in a mirror. Gaze at bright window and look again in the mirror. Con- clusion ? Do the two pupils still keep the same size when one eye is shaded ? Experiment 17. Accommodation. — By holding your finger or a pencil in line with writing on the blackboard, you find that you cannot see both finger and blackboard distinctly at the same time — first one and then the other is distinct. Explain (see text). 144 HUM AX BIOLOGY Experiment i8. Astigmatism (efTect of unequal curvature of cornea or lens along certain lines). Willi end of crayon draw about twelve straight, even lines crossing at one point on the blackboard. Have the lines of equal distinctness. How many pupils rejjort that the lines in certain directions are blurred? Inquire whether these pupils have frequent headaches from tyr strain. Expcriincnt 19. Can Sound reach the Ear through the Bones? — Hold a watch between the lips and notice its ticking. Close the teeth down upon it and notice any change in the sound. Cover one, then both ears, and note the result. Experiment 20. Test keenness of hearing by having pupils walk awav from a ticking watch until it becomes inaudible. Test each ear. A " stop " watch is preferable. Experiment 21. Advantage of Two Ears over One. — Have the class stand in a circle. Blindfold some one and place him in the middle of the circle. Let various pupils clap the hands as the teacher points to each. Can the blindfolded one point in the direction whence the sound comes? Stop one ear with a handkerchief and repeat. Result? Con- clusion? From what two points in the circle does the sound fall upon both ears alike ? Experiment 22. The Cause of Nasal Tones. — Let a pupil go to the back of the room and read a paragraph, and hold his nose until partly through the reading. Or the teacher may read with his face and hand hidden by a large book. Let the other pupils raise their hands when they notice a change in the quality of the reader's voice. Does the experiment show that a " nasal " tone comes partly through the nose or through the mouth only? Does stoppage of the nostrils by catarrh cause a nasal tone? Five Differences between Special and General Sensation. — First, the nerves of special sense all end in special organs at the surface; for instance, the touch corpuscles are for touch, the eye is for sight, etc. There are many nerves in the body that do not end in special organs ; these nerves give what is called general sensation. A second difference is that general sensation te//s of the condition of the interior of the body, while special sensations tell us of the condition of the surface of the body and of the outside world. Third, general sensations are not so exact as the reports of the special senses. One can locate a point on the skin that has been touched much more accurately tlian he can locate an internal pain. A fourth difference is that the meaning of each special sensation must be learned (usually in infancy) ; but the meaning of gen- eral sensations is inherited. This inherited knowledge of what general sensations mean is also called instinct. Fifth, the sympathetic nerves THE SENSES 1 45 usually bring general sensations \ the spinal and cranial nerves usually bring special sensations. Examples of general sensations are hunger, thirst, satiety, nausea, faintness, giddiness, fatigue, weight, aching, shuddering, restlessness, blues, creepy feeling, tingling, sleepiness, pain, illness. Any nerve can convey the general sensation of pain, if injured along its course. If a nerve of touch is cut, there is no sensation of touch, but of pain. Touch sensations come only from the ends of the nerves. General sensations are of many kinds. We are only half conscious of some of them ; many of them are hard even to describe. Hygiene of the General Sensations. — General sensation is an invalu- able aid to the health. Without it as a guide, the body could not remain alive a single day. Pain should be heeded as our best friend, and not killed with poisonous drugs as if it were our worst enemy. We should not deaden the stomach ache with an after-dinner cigar. If we do not go to bed when sleepy, the desire for sleep may leave us, and we will undergo untold suffering from sleeplessness. Thirst should be satisfied with cool water, which quenches it the best ; he who makes his teeth ache with ice water will inflame his stomach and be continually thirsty. He who does not stop eating when his hunger is satisfied,-will distend his stomach with food, and the stretched organ will be harder to satisfy thereafter; in fact, eating after a feeling of satiety may cause indigestion so that the cells will not get the food. A d3'speptic is always hungry, for the cells are starving. Fatigue of body or mind gives us wise counsel ; but this feeling may be deadened by alcohol or tobacco, and work continued until the body is injured. We should heed the warning of pain or fatigue or restlessness as promptly as an engineer heeds a red flag on the railway track. One who uses narcotics acts Hke a reckless engineer who removes the danger signal and goes ahead, hoping by good luck to escape an accident. Most of the nerves of touch end in papillae of the dermis as microscopic, egg-shaped bodies (Fig. 120). There are also many in the interior of the mouth, especially on the tongue. On the palms they are arranged in curved lines, and on the tips of the fingers they are in circular lines, with one papilla in the center. The delicacy of the sense of touch varies very much in different parts of the skin. This delicacy refers to tivo things : the ability to feel the slightest pressure and the ability to tell the exact point of 146 Hr.yfAX B/OfOGY Fit;. 120. — DiFFEkF.NT Kinds of Touch Bodies at Ends of Nerves. A , from cornea of the eye ; B, from the tongue of a duck : C, D, E, from the skin of the fingers. (Jegi.) the skin that is touched. A li{;hter pressure can be felt on the forehead and tcni])lcs than with any part of the body. (Why is it best for this to be the case.'') The greatest delicacy in locating the point of the skin touched is found to be located in the tip of the tongue, the lips, and the ends of the fingers (Exp. i). (Why is it best that this is so .'') This deli- cacy is least in the middle of the back. The delicacy varies with the number of touch corpuscles in different parts of the skin. The sense of touch is capable of great cultivation, as in the case of the blind. The temperature sense is given by special nerves called the thermic nerves (Exp. 2). That the thermic nerves are easily fatigued is noticed soon after entering a bath of hot water ; it is also shown by the fact that in cold countries the nose or ears of a person may freeze without his feeling it. The Muscular Sense. — The special sense of touch gives some sense of Tveight. A weight upon the skin must be increased by one third before it feels heavier, but by lifting an object so as to bring into action the muscular sense residing in ner^'es ending in the muscles an increase of only one seventeenth of the original weight can be noticed (Exp. 3). This sense gives us a continual account of the position of the limbs (Exp. 4). The end organs of taste are located in the papillae of the tongue. The tongue has a fuzzy look because of the numerous papillae. THE SENSES 1 47 The principal tastes are only four ; namely, sweet (tasted chiefly by tip of tongue), sour and saline (sides of tongue), bitter (tasted on the back of tongue) (Exp. 5). The nerves of smell end in the mucous membrane of the upper half of the two nasal chambers ; \he. fibers are spread over the upper proportion of the zvalls. The direct current of air does not pass as high as these nerve endings ; hence sniffing aids the perception of odors. This sense is able to bring up the associations of early life more powerfully than any of the senses. The odor of a flower like one that grew in an old garden can almost restore the con- sciousness of the past. We smell gases only ; solids and liquids cannot affect this pair of nerves (Exp. 8). Flavors. — The tastes that we call flavors are really smells. We confuse them with taste, because they accom- pany food that is in the mouth. Name some foods that seem " tasteless " when one has a severe cold in the head. Why is this .-' Some of the most repulsive drugs can be easily swallowed if the nose is held (Exp. 6 and 7). Hygiene of the Senses of Taste and Smell. — A savage or a beast uses the senses of taste and smell to find out whether things are good to eat or not. If a civilized man's senses are not perverted, and he eats only simple foods that have a pleasant taste, they will not injure him or cause him sickness. Things that are poisonous usually have unpleasant tastes and often have unpleasant odors. These senses are naturally of wonderful delicacy. They can be cultivated to a still more remark- able degree, or they can be blunted and almost destroyed. Chronic catarrh dulls or destroys the sense of smell. The loss or even the weakening of the perception of flavors is an injury to the working of the closely related sense of taste. When a person loses the enjoyment of delicate flavors, he wants food to have strong seasoning and more decided taste to prevent it from being insipid. Everything must be either very greasy or very sweet or very salty or very sour, to please his degenerate senses. Wheat, corn, and other grains have each its own pleasant taste, yet such persons must have lard in their bread because they are not capable of appreciating anything with a delicate taste. In 148 HUM AX BIOLOGY England, butter is not salted and its delicate taste is enjoyed ; in America, salt is added to preserve it, and most people have come to prefer the strong taste of salty butter to the delicate taste of pure butter, and do not like it unless its true taste is partly hidden by the taste of salt (Exp. 9). Deceiving the Sense of Taste. — The habit of using narcotics like till and lojf'et- is usually begun by concealing the repulsive bitter taste of the substance by mixing sugar, cream, and other agreeable things with it. Licorice is sometimes mixed with tobacco to weaken its biting taste. Pure alcohol would never be drunk by any one who had the least respect for the sense of taste, but the agreeable flavor of grapes, apples, and other fruit which still remains in wine, cider, and brandy, conceals the repulsive taste of the alcohol. Beer has the insipid taste of grain which has undergone decomposition or partial rotting, and hops are added because the strong bitter taste of hops is needed to hide the stale, rancid taste of the rotted grain, i^.^i^nog is made of eggs, a nourishing food ; sugar, which has an agreeable taste ; water, a refreshing drink, and alcohol, a fiery poison. A very good eggnog is often made without alcohol, but a good one could hardly be made with any of the pleasant ingredients left out. The best eggnog is made by using the fresh juice of lemon, orange, or grape, instead of alcohol. Effect of Narcotics. — Tobacco, alcohol, opium, and other narcotics dull the senses of taste and smell and prevent the enjoyment of delicate flavors. They accomplish this as much by their effect upon the brain as upon the nerves themselves. It is Wrong to eat Food that is not Relished. — Unpalatable food is not likely to be well digested. It is a law of the body that the food which is enjoyed the most is digested the best. This ajjplies to a hungr\' person eating food with its own honest taste, not to food disguised by the taste of something else. The rule does not apply to a taste per- verted by having been forced to become accustomed to poisonous things. People who munch their food slowly enjoy the pleasures of taste the most, and digest their food the best. The nerves of taste and smell easily become fatigued. The first whiff from a cologne bottle is the strongest. Highly flavored foods should be eaten moderately, if we would obtain the greatest enjoyment from them. Thought Questions. — 1. Interfering with the Body. What is the natural direction of growth of the big toe? 2. Think of six evil results, direct or indirect, which will follow from displacing it by tight shoes (p. 48). 3. Which part of the spinal column, designed in infinite wisdom to be most flexible, do some people try to make the most inflexible? 4. The mobility of the false and floating ribs was THE SENSES 149 A pressure upon the eye- intended as a blessing. Some people interpret the blessing as an opportunity to do what ? 5. Name six articles which warn us to avoid them by their bitter, burning, or nauseating tastes, yet which are used by man. 6. Name six feelings which are intended as warnings for our guidance, but which are commonly disregarded. The eyes on the rays of the starfish are mere spots of pigment. Insects have lenses in their eyes. The eyes of vertebrates are all formed on the same general plan as the human eye. The eyeballs are globes about an inch in diameter. They are placed in deep, bony sockets, called orbits, in the front part of the skull. The optic nerve, other nerves, and several large blood vessels pass to the eye through a hole in the back, of the orbit. A soft cushion of fat is in the orbit behind the eyeball, ball causes the eye to sink into the socket, for the fat yields to the pressure. This is a protection to the eye. The eyelids protect the eyes from dust, and at times from the light. They are aided in this by the eyelashes. The tears are formed by tear glands situated above the eyeball in the portion of the orbit farthest from the nose, just beneath the bony brow where it feels the sharpest (Fig. 121). They are about the size of almonds. A salt- ish liquid is continually oozing from the tear glands and passing over the eyeball ; it is carried into the nose through the nasal duct (Fig. 121). The tears reach this duct through tivo small canals, which open into the eye in the little fleshy elevation at the inner corners of the Fig. 121. — Tear Glands and Ducts of right eye. (Jegi.) I50 HUMAN BIOLOGY eye (Fig. 121). The opening of one of the canals may be seen by looking into a mirror. Sometimes these canals are stopped up, and what is called a " \vce])ing eye " results. A temporary stoppage may occur during a cold in the head. Tears prevent friction between eye and lid. Winking applies the tears to the ball. Small glands along the edges of the lids form a kind of oil which usually prevents the tears from flowing over the lids. Sometimes this oily secretion is so abundant, especially during sleep, as to cause the lids to stick together. The mucous membrane of the eyelids continues as a transparent membrane (the conjunctiva) which passes over the front of the ball. The globe of the eye consists of its outer wall and the soft con- tents (Fig. 122). The wall has three layers or coats. The outer coat is the tough sclerotic (Greek, skleros, hard), composed of dense connective tissue (Exp. 14). It gives strength and firm- ness to the eyeball. It shows between the lids as the "white of the eye." It is white and opaque except in front; there it bulges out to form the transparent cornea. This clear portion of the wall may be seen by looking at the eye of another from the side. The second coat, called the choroid, consists of blood ■Retina Choroid 'erotic coat Fig. 122. — Thk A.natomy uk thk Kvk. THE SENSES 151 vessels and a loose connective tissue containing many dark brown or black pigment granules. The choroid absorbs superfluous light. Cats' eyes shine at night because this coat in their eyes reflects some light. The choroid separates from the sclerotic toward the front of the eye and forms the colored iris. The iris makes the eyes beautiful, and it also serves the useful purpose of regulating the amount of light. The hole in the iris is called the pupil (Exp. 15). The third and innermost coat, the sensitive pinkish layer called the ret'in-a, is the most important and characteristic tissue in the eye. It re- ceives the light rays, and retains the image for a fraction of a second (Exp. II). Hence the pictures in a kinetoscope (Fig. 123) appear as one moving pic- ture. The retina is made chiefly of the fibers of the optic nerve. This nerve contains about five hundred thousand fibers, and enters at the back of the ball. The spot where it enters contains no nerve endings and is not sensitive to light. It is called the blind spot. The spot where the light most often falls is most sensitive to light. It is tht yellow spot (Fig. 122). Test for the Blind Spot. — In this experiment shut the right eye and be careful not to let the left eye waver. Fig. 123. — Stroboscope, the original of the kinetoscope. The observer looks through the sHts of a rapidly revolving disk and a new image falls on the retina before the last image has faded. Com- pare the pictures in the figure. 152 HUM AX BIOLOGY * Read this line slowly. Can you see the star all the time ? (If so, hold the book farther or closer and repeat.) Within the coats of the ball, like the pulp within the rind of an orange, are the soft contents, divided into three parts. The first is a watery liquid in front, which serves to keep the cornea bulged out (Fig. 122). It is called the a'quc-oits huvior. The main cavity of the ball is occupied by a clear, jellyhke substance called the I'it're-ous /iii»ior, which serves to keep the ball distended. Back of the iris, and separating the two humors just named, is the cr)'s'tal- line lens, a. beautiful clear lens, convex or rounded out on both sides (Exp. 14). It serves to bring the light to a focus on the retina, thereby forming images of outside objects. The eye, like a camera, has a dark lining, the choroid; the retina corresponds to the sensitive plate, and the lens brings the rays to a focus on it and forms the image. The Path of Light in the Eye. — The light enters through the transparent cornea and passes through the aqueous humor. As it goes through the pupil, the iris shuts off all the light that is not needed. The crystalline lens receives the light that has been al- lowed to pass, and so bends the rays that by the time they have passed through the vit- reous humor they fall upon the retina in just the right way to form a tiny image of anything outside (Exp. 11). The choroid absorbs any light that passes the retina. The iris and choroid of albinos have no pigment; hence albinos squint their eyes to shut out some of the light. Fig. 124. — Crossing of Optic Nerves showing that one nerve reaches same half of both eyes. THE SENSES 153 Fig. 125. — Change of lens in accom- modation. (Jegi.) Accommodation. — In order to focus the light upon the retina, the lens must change shape for every change in the distance of the object looked at {see Fig. 125). The shape of the lens can be readily- changed, for it is elastic and has muscular fibers around its edges (Exp. 17). Defects in the Eye. — Some eyeballs are too long, and the lens brings the rays to a focus before they reach the retina. Such eyes are near- sighted (Fig. 126) and require glasses that round inward (con- cave). Some eyeballs are too flat, and the rays are not brought to a focus soon enough. Such eyes arefarsighted and require oflasses that round outward (convex). See Fig. 127. (Re- peat Exp. 15.) Care of the Eyes. — Because the eyes can do a large amount of work without giving pain, they are often abused. When reading or doing intricate work, turn the eyes from the work occasionally and look at some distant object ; stop work before the eyes are tired. Twilight of early evening has ruined many good eyes. You should FIG. 127.-FARSIGHTED EYE (ball ^^^ ^Qj.j^ bgf^^g too short) which needs convex lens ^ '■ to focus rays upon retina. the twilight begins, for the Fig. 126. — (i) Nearsighted Eye (ball too long), which only focuses rays for near objects (2) when concave glasses are used (3). 154 Hi MAX BIOLOGY light fades so gradually that you will surely be straining the eyes before you know it. Do not work with the light in front ; the glare of the light makes objects appear dim. The light should come from above, and (for right-handed people) from the left. Do not read papers or books printed in fine t)pe. We should not read when convales- cing from illness ; with the head bent down ; when the eyes are sore; in jolting cars. Heating the eyes by a burner, or drying the eyeballs in a dry, stove-heated at- mosphere, using a light without a shade, cause trouble with students' eyes. Of what are blood-shot eyes often a sign."* Our eyes are best suited for seeing at a distance because primitive man had no houses, books, sewed clothes. Effort is required to shape the lens for seeing near objects. Most cases of nearsightedness begin when children are taught to read under eight years old. The eyes are sometimes injured by the use of tobacco. Thought Questions. The Eye. — 1. The eye is shielded from blows by bony projections of , , and . 2. The hairs of the eyebrows lie inclined toward . in order to turn from the . 3. 1 find by trying it that I (can or cannot?) see the position of a window with my eyes closed. 4. The pupil appears to be black, because no is from the interior wall of the eye. I know that the iris is partly muscle, because it the size of the . Sound. — Anything that is sending off sound does so by vibrating, or shaking to and fro, very rapidly. For instance, a vibrating violin string sets every particle of air near it swinging to and fro. The near- est particles of air strike the next ones and bounce back, these in turn strike against others, and thus vibrations called sound waves are sent through space in all directions from the sounding body. We feel these waves with the ear. The ear consists of three portions : the external ear, the middle ear (or drum), and the internal ear (or labyrinth, see Fig. 128). The cranial nerve connecting the ear with the brain is called the auditory nerve. The outer and THE SENSES 155 middle ear pass on the vibrations of air to the ends of the fibers of the auditory nerve in the internal ear. The external ear consists of a large wrinkled cartilage on the exterior of the head and a canal leading from it, called the meatus. This passage is closed at its inner end by the drum membrane or driini skin. It is often called the drum, but this name is properly applied to the whole middle ear. A trial will show that the drum skin cannot The Shell Tube {fioahUa). Fig. 128. Eustachian Tube •Middle and Internal Ear (greatly enlarged). be seen even with the aid of a bright light, for the passage is sHghtly curved (see Fig. 128). Hence a missile or a flying insect cannot go straight against the ear drum. The skin lining this passage contains wax glands, which secrete a bitter sticky wax, which helps to keep the passage flex- ible. This wax catches dust and usually stops insects that may enter. If an insect enters the ear, it may often be coaxed out by a bright light held close to the ear. The ear wax in a healthy ear dries with dust and scales of epi- dermis and falls out in flakes, thus cleansing the ear. It 156 J/LMAX BIOLOGY is unwise to probe into the ear with a hard object or even with the corner of a towel. It is not necessary to insert the finger in the meatus to cleanse it; it is one inch long, but only about one fourth inch across. (How large is the little finger?) The cartilaginous ears on the sides of the head should be carefully washed because of their many crevices. If ear wax is deposited too fast, it will cause temporary deafness and earache. It may be syringed out with warm water. I^arache is usually caused by a small boil which requires -time to relieve itself by bursting. Warm water poured into the upturned ear, or hot flannels or compresses applied to the side of the head will lessen the suffering. Each ear has three muscles for moving it. Once they were doubtless useful to all, but like the scalp muscle they have become so weakened by disuse as to be useless to most people. They are vestigial organs. The middle ear, or drum chamber, contains air (Fig. 128). It is separated from the outer ear by the drum membrane. It contains three bones which stretch across it and conduct the sound waves from the drum membrane to the inner ear. State the order in which they are placed (see Fig. 128). The middle ear is connected with the pharyn.x by a tube (the Eustachian tube ; pronounced yoo-stake'e-an, see Fig. 128). This tube is opened every time we swallow. It allows the air from the throat to enter the middle ear and keep the air pressure equal on each side of the drum skin. This tube and the middle ear are lined with mucous membrane. A co/d in tJic Jicad or a sore throat may extend through this tube to the middle ear and affect the hearing. This occurs because the tube is closed by congestion of its lin- ing ; the air of the middle ear may be partly absorbed, and the pressure of the outside air may cause the drum ^ THE SENSES 1 5/ membrane to bulge inward, and to be stretched so tight that it cannot vibrate freely. The inner ear is called the labyrititJi, because of its wind- ing passages. There is a spiral passage called the snail j-//^// and three simpler passages called the loops {Y\^. 128). The inner ear is filled with a limpid liquid which conveys the vibrations to the ends of the auditory nerve found in the snail shell. If the auditory nerve or labyrinth becomes diseased, the deafness is probably incurable. Quinine and other drugs may cause deafness. Sense of Equilibrium. — Some fibers of the auditory nerve end in the loops and are not believed to be used in hearing. It is believed that each loop acts like a carpenter's level, and the varying pressure of the fluid upon the nerves in the loops tells us the position of the body and constitutes the sense of equilibrium. There are how^ many of these loops in each ear ? (Fig. 128.) CHAPTER X BACTERIA AND SANITATION Experiment i. Yeast Plants. — With a microscope examine a drop from a glass of water in which you have washed grapes or apples (Fig. 129). Experiment 2. Fermentation. — Put a tablespoonful of sugar into this water and set the glass in a warm place for a day or two. Do you see any bubbles of gas ? Have the odor and taste changed ? Does the micro- scope show that the yeast plants are now more abun- dant ? By fermentation, or the growth of yeast in sugar, ^ugar is changed into carbon dio.xid, a gas, and alcohol, a liquid. Experiment 3. A Sani- tary Map. — Construct a sanitary map of the com- munity. Indicate houses where consumption, typhoid fever, or other transmissible di-seases have occurred, with number of cases. Mark loca- tion of stagnant waters where mosquitoes breed, mark garbage dumps, unclean streets. Suggest where improvements may be made in drainage, dust, noises, sunshine, shade, etc. Bacteria, or microbes, the smallest living things, are visible only under a microscope of high power. (See "Plant Biology," p. 182.) They obtain food either from dead tissue or from degenerate tissue of living plants and 158 Fig. 129. — Ykast Ckli.s magnified 200 diameters, or 4o,o(X) areas). Yeast plants multiply by budding. Notice small cells growing on larger and older ones. BACTERIA AND SANITATION 1 59 animals. The green plants and the animals now upon the earth have proved their fitness to survive by successfully- resisting these one-celled vegetable germs, or bacteria. Microbe diseases attack only the weaker individuals of the human species, or those who have gone to regions where there are microbes which their bodies have not yet ac- quired the power of resisting. Usefulness of Bacteria. — Their chief work is to destroy dead tissue and return it to the soil and air for the use of green plants again, otherwise the earth would be filled with carcasses, etc. They are indispensable in soil forma- tion. They give the agreeable flavors to butter and cheese, and cause milk to sour. A rod-shaped bacterium is called a bacillus (Fig. 130); a spherical one is a coccus. Multiplication of Bacteria. — This is by division or fis- sion. Sometimes, instead of dividing, a little rounded mass known as a spore appears. The spore breaks out and the bacterium itself perishes. Species which do not produce spores are readily destroyed, but spores have a hard, tough shell, and they may be dried or heated even to boiling with- out being killed. Spores float through the air and start new colonies. Most common bacteria grow best between 70° ajid 95° F. They render it difficult to preserve foods, espe- cially proteid foods (cheese, lean meat, eggs, etc.). Food decays slowly if at all below 70° and above 125°. Direct sunlight, or the temperature of boiling water (212" F.) kills bacteria but not spores. Pantries, kitchen, and sick- rooms should have bright walls and all the light possible. Boiling water should be poured into the sink, and dish cloths should be thoroughly washed in boiling water. Diseases due to Bacteria. — A germ disease is usually due partly or wholly to substances called toxins produced by the bacteria. Most disease germs attack a single organ l60 HVMAiX BIOLOGY CI % It germ produces a powerful toxii ^^% g<^rms of typhoid fever {¥\g. i; L// . 11' -^ \."' phoid patient all suspicious material . • '^\\'^^*7''v should be disinfected or burned. '*t.- •^^^ ^ Germs of tuberculosis (called coji- I'h;. 131.- bacillus of ^ Typhoid Fever. suviption if the disease is in the lungs) may float through the air. Recent investigations indicate, however, that infection usually occurs through the alimentary canal, the germs being swallowed, then absorbed and taken to the lungs in the blood or lymph. To prevent a patient from reinfecting himself in new parts of the lungs or elsewhere, he should carefully cleanse his teeth, mouth, and throat (by gargling with formal or lysol) before eating. Mosquito Fevers. — Malaria, yellow fever, and probably detigue are transmitted each by a different genus of mosquito (Fig. 132). A mosquito of the malarial genus may bite a patient and suck into its body blood-corpuscles containing spores of the malarial parasite (a protozoan BACTERIA AND SANITATION i6i animal, see "Animal Biology," p. 7). Afterwards a spore (in another stage) may be transmitted by this mosquito when it bites another person. The germ enters a red corpuscle, grows, and finally divides into many little spores. At this moment the cor- puscle itself breaks up, setting free in the blood the spores and toxin formed. This causes the chill and fever. This develop- ment usually takes forty-eight hours, hence the fever occurs every other day. These mos- quitoes begin to fly at dusk. How are they recognized.'' (Fig. 132.) They should be kept out of houses fig. 132.— Culex or Com , r ^1 T. J i_ MON Mosquito, above (pos- by screens or from the beds by netting. Kerosene should be poured on breeding places at the rate of one ounce for fifteen square feet of standing water. "This should be repeated twice a month. Cactus macer- sibly carries dengue fever). Anopheles or Malarial Mosquito, below (not always infected). Body of malarial mosquito is never held paral- lel to the supporting surface (unless a leg is missing) ; it has five long appendages to the head, the culex (above) has only three. (Draw.) ated in water may be used, and forms a permanent film on the water. Stagnant pools may be filled or drained (Exp. 4). Fig. 133. — Protective t, t 1 ■ , ■ i 11 1 1 7 White Corpuscle MalariaL patients slioulet themselves be (phagocyte) digesting screened, as the ckief sojirce of danger to a microbe. j r ^ • ^ ^ Others ; for only mosquitoes who suck the blood of malarial patients will transmit the disease. Even then it is only transmitted to those whose white blood corpuscles are unable to protect them (Fig. 133). l62 Hi'AfAX BIOLOGY Further Means of Protection against Disease Germs. — The best protection is physical vigor. There are certain substances called opsonins which exist in the plasma of the blood of disease-resisting persons ; these opsonins give the white corpuscles the power to devour disease germs. The serum of the blood also develops antitoxins which neutral- ize the toxins formed in disease. Not only can the white corpuscles and serum kill bacteria, but most of the secre- tions of the healthy body (gastric juice, nasal secretions, etc.) are bacteria-killing as well. Persons in a low state of health most readily succumb to disease. Excess in eat- ing may lessen the germicidal power of gastric juice and inactivity that of the lymph. The same germ disease does not usually attack the same person twice, as the body becomes immune; that is, an opsonin, or an anti- toxin, is developed which cures the first attack and remains to protect the body in future. The periods of quarantine or isolation for several com- mon germ diseases are given in the following table : — Name of Disease From Exposire TILL First Symptoms Patient is Infectious to Others Diphtheria 2 davs 14 days after membrane disappears. Mumps IO-22 davs 14 days from commencement. Scarlet fever 4 davs Until all scaling has ceased. Smallpox 12-17 days Until all scabs have fallen. Measles 14 days 3 days before eruption till scaling and cough cease. Typhoid fever II davs Until diarrhoea ceases. Whooping cough 14 days 3 weeks before until 3 weeks after beginning to whoop. Water Supply. — Bacteria are more abundant in flowing streams than in water standing in lakes or reservoirs (con- BACTERIA AND SANITATION 1 63 trary to the usual belief). They are most abundant in rivers that flow through populous regions. They are com- paratively scarce in dry, sandy soils, and very numerous in moist, loamy soils. The water of cities should never be taken from a stream or lake into which sewerage flows unless it is thoroughly filtered. Filters are constructed thus : first a layer of small stones, next a layer of coarse sand, lastly a layer of very fine sand on top, the total thick- ness being four or five feet. Beneficial microbes live upon the grains of sand and destroy all, or nearly all, of the dangerous microbes as the water slowly soaks through. The construction of such waterworks is left to sanitary engineers, of course, and the average citizen does not need to know the details. The department of street cleaning should receive the willing cooperation of all citizens. Banana peeHngs, paper, etc., should not be thrown upon the street or school grounds. Garbage, ashes, and rubbish should be placed in separate cans, as the rules provide. Garbage cans, if not thoroughly cleaned, acquire unpleasant odors and breed flies and bacteria. They should be thoroughly washed with very hot water and sal soda and scalded with boiling water and scrubbed with an old broom. ^ The chief duties of the Health Department are : quar- antine isolation and disinfection, with the purpose of pre- venting or controlling contagious and infectious diseases ; ^ The chief Disinfectants are : fresh air, sunshine, heat, formaldehyde, etc. Airing and sunning will destroy some germs in bedding and clotliing as effec- tually as chemicals. Boiling and steaming are the best ways of applying heat. Formaldehyde is a volatile liquid. After room is sealed and strips of paper pasted all over cracks, a specially constructed generator is applied to keyhole, and room kept closed for 12 hours. Mercuric chloride (corrosive sublimate) is used I part to 1000 parts of water for disinfecting soiled clothing, towels, utensils, surgeon's instruments, and wounds. In place of this, carbolic acid, 5 per cent solution, may be used, but it is not so good a germicide. 164 II UMAX BIOLOGY inspection of dairies, slaugiiterhouses, and other sanitary work; inspection of miliv' and other food stuffs; the de- partment gathers vital statistics ; it enforces the rules for disinfection of jjublic buildings. Importance of Cooperation with the Health Department. — Only an ignorant and short-sighted person would fail to cooperate promptly and cheerfully with local or state health officers. It is for the benefit and protection of every one that the truth concerning contagious diseases be reported promptly. Only in this way may outbreaks of disease be prevented and many lives saved. He is a bad citizen and a public enemy who will conceal a case of disease dangerous to the community. Outbreaks of fatal diseases may be easily prevented or stamped out if the health officer is sustained and his directions carried out. ^ Milk may be sterilized by boiling, but boiled milk is not digestible nor nutritious. Milk may be Pasteurized by immersing bottles of milk in water which is kept nearly (but not quite) at boiling point (160° F.) for five min- utes. But this makes the milk less valuable than fresh milk, and destroys beneficent microbes. Buttermilk has many such microbes, which kill injurious microbes and purify the stomach. Cleanliness, or an aseptic condition, is far preferable to antiseptics. INDEX I, V, X, etc. = Introduction : P = Plant Biology : A- = Animal Biology H = Human Biology. Aboral surface, A 35. Aborted seeds, P 166. Absorption, H 106. Abutilon, p 156. Accessory fruit, p 164, 169. Accommodation in eye, h 143, 153. Acephala, A 107. Acid, ix. Adaptation to environment, p 6, A 148, 185, 201, 205, 207, H 19, 108, 109, no. Adenoid growths, H 86. Adipose tissue, H 12. Adulteration of food, h 93. Adventitious roots, p 36; buds, p 114. Aerial roots, p 34. Aggregate fruit, p 168. Air cells, H 75. Air plants, p 35. Akenes, p 165. Albinism, H 16, 18. Albumen, H 92. Albumin, H 92. Alcohol and circulation, H 67; and fermentation, H 158; and food, H 113; and muscles, H 50; and nerves, H 135 ; and skin, h 20. Algae, p 179, 183, 195. Alkaline, ix. Alternation of generation, p 179, a 30, 31- Ambulacral, A 36. Ameba, A 10. Americans, H i. Anadon, a 98. Anatomy, H 9. Anemophilous, p 149. Animal food, H 95, no. Annual plant, p 17. Antelope, A 215. Antennae, A 68, 87. Anther, p 135, 144, 180. Antheridium, p 178, 186, 198, 200, 202, 203. Ant-eater, giant, A 199; spiny, a 196. Ant-lion, A 91. Ape, A 220. Apical dehiscence, p 166. Appendicitis, h 106. Appendix, vermiform, H 106. Appetite, H 94, no. Aptera, A 82. Apteryx, A 174. Aquarium, A 17. Archegonium, p 178, 198, 200, 202, 203. Argonaut, paper, A 107. Arm, H 2^. Armadillo, A 200. Arrowhead, h 2. Arteries, h 51, 53, 54, 61. Arthropoda, A 9, 125. Arum family, P 140. Ash, p 92. Asiatic cholera, H 160. Assimilation, p 97, h 90. Association fibers, H 123, 126. Asthma, H 86. Astigmatism, h 144. Athletics, H 46, 47. Atwater's experiments, H 113. Auricle, H 53. Automatic action, h 123. Axil, P 112. Axis, plant, P 15. Axon, H 119. Bacillus, H 158, 159. Bacteria, p 39, 109, 182, H 158, 159, 160, 161. Bandage, H 62. Barberry, P 157, 193. Bark, p 54, 66, 67. Bark-bound trees, p 54. Bast, p 61, 66. Bat, A 202. Baths, H^3, 24. Batrachia, A 126. Bean, p 20, 28, 39, 194, h 95, 96, 112. Beaver, A 204. INDEX Bedbug, A 92, 93. Bet', bumble, A 89; honey, A 88. Beebe's experiments. Dr., H 1 13. Beef, II 111; tea, H 1 1 1. Beetle, A 90, 91. Berry, p 167. BicnnuU plant, P 17. Big-headed turtle, a 1^9. Bilateral, a 34, 49, 98. Bile, H 105. Bill of bird, A 151. Biology defined, A i, H 9. Birds, A 150. Blind spot, H 151. Blood, H 58; quantity of, H 55; of insects, A 78. Blood vessels, H 52; control of, H 58. Board of Health, H 163. Boll weevil, a 95, 96. Boll worm, A 95, 96. Bones, H 29; composition of, H 31; growth of, H 14, 36; forms of, H 28, 29, 34; structure of, H 30. Bony tissue, H 13. Borax, H 93. Brace cells, p 67. Bracts, p 134. Brain, H 122; coverings of, h 125; of fish, A 118. Branch, p iii, A 9. Breathing, forms of, H 80; of bird, A 161; of insect, a 76; through mouth, H 85. Breeding, plant, p 7, 8. Bronchial tubes, H 75. Bruises, H 62. Bryophytes, p 181. Bud propagation, p 121. Budding, p 127, 128. Buds, p 72, 82, 87, in; flower, p 115; fruit, p 115. Bureau of entomology, a 95. Burns, H 24. Burs, P 172, 174. Bushes, P 191, A 171. Butterfly, A 83. Cabbage, p 113, h 95. Cabbage butterfly, A 84, 86, 87. Callus, p 56. Calyx, p 133. Cambium, p 63, 65. Camel, A 214. « Candle, xv, a 5. Cane sugar, h 92, 104. Capillaries, H 52, 53, 56. Capsule, p 165. Carbohydrate, p 95, H 91, 95. Carlxjn, vii, .xviii, p 92. C";irl)on, dioxid, A 24, p 22, 93, 106, 11 Oo, 76, 81, 132; monoxid, H 85. Carnivorous, p 99, u in. Carp, A 112, 117, 123. Carpel, p 136. Cartilage, H 13, 35. Castor bean, p 24^ Cat, A 184. Caterpillar, tent, A 84. Catkin, p 158. Caucasian, H 1, 2. Caulicle, P 20, 22, 25. Cedar apple, p 194. Cell, p 42, 63, 145, 176, A 6, 7, H 5.6. Celom, A 46. Cephalopod, a 106. Cerebellum, H 122, 124. Ccrcbro-spinal system, H laS, 129. Cerebrum, H 122, 125, 126. Chclonia, a 143. Chemistry, xv. Chemical symbols, xv. Chest, H 32. Chewing, H 90, 10 1. Chimpanzee, A 219, 221. Chirping, A 66. Chitin, A 77. Chlorophyll, p 86, 94, loi, 183, 186. Cholera, H 160. Choroid, H 150, 152. Chyme, H 103. Cigarettes, H 67, 86. Cilia, A 14, 20, loi, 103, H 76. Ciliated chamber, A 17. Cion, p 125. Circulation, H 51 ; and breathing, H 58; and exercise, H 67; hygiene of, H 68; in ameba, a 12; in insect, A 77; in fish, A 117; portal, H 60, 105; pul- monary, H 60; renal, H 60. City, H 4. Cladophylla, p 100. Clam, hardshell, A 104; softshell, A 104. Class, A 9. Classification, of animals, A 8, 125; of birds, A 177; insects, a 82; mammals, A 193. Cleft graft, p 126. Cleft leaf, p 75. Clcistogamous, p 151. Click-beetle, A 91. INDEX m Climate, and clothing, H 25; and brain work, H 68; and early man, h 2. Climbing plants, p 129. Clitellum, A 43, 47. Cloaca, A 18. Clot, H 61. Clothes moth, a 84, 92, 93. Clothing, H 16, 25. Clover, p 39. Club mosses, p 203. Cluster, flower, p 155, 159; centrif- ugal, p 156, 159; centripetal, p 156; indeterminate, p 156. Coagulation, h 61. Cockroach, A 71. Cocoon, A 84. Codling moth, A 84, 86, 87, 95. Ccelenterata, A 28. Colds, care of, H 69, 86. Coleoptera, A 82. Collecting insects, A 72. Colon, H 106, III. Colonies, plant, p 11. Colorado beetle, \ 90, 91. Coloration, warning, A 84, 146; pro- tective, A 34, 37, 49. Colors of flowers, A 85. Comparative study, A 85, 108, 122, 223; moth and butterfly, A 85. Composite flowers, p 140. Compositions, subjects for, H 15, 50, 116, 141. Compound substance, vii. Congestion, H 68. Conjugation, p 185. Conjunctiva, H 150. Connective tissue, H 11, 54, 120. Consumption, H 159. Convolution, H 126. Cooking, H 114. Coordination, h 124. Copper head, .\ 145. Coral, .A 31. Coralline, A 31. Coral snake, A 145, 146. Cork, p 66, 67. Corn, p 3, 25, 26. Cornea, H 150. Corolla, P 133; funnel form, p 138; labiate, p 138; jjersonate, P 139; rotate, P 138 ; salver form, P 138. Corpuscles, origin of, H 30; red, H 59; white, H 59, 60, 65, 68. Corset, H 58, 80, 87. Cortex, p 44. Corymb, p 159. Cotton plant, P 7, A 95. Cotyledon, p 20. Cricket, A 71. Cross-fertilization, A 25. Crowd poison, h 82. Cryptogam, P 176, 180, 183-204. Cuckoo, A 179. Currant, p 157. Cuttings, p 121, 123, 124. Cuttlefish, A 107. Cyme, p 159, 160. Cypraea, a 104. Cysts, A 13. Cytoplasm, h 6. Darwin, .\ 48, 148. Debates, subjects for, H 141. Deciduous, p 82. Decumbent, p 50. Degeneration, H 3, 4, 141. Dehiscence, p 144, 164. Deliquescent, p 51. Dendron, h 115. Dependent plants, p 106. Dermis, H 17. Devil's horse, A 71. De Vries, a 148, 224. De.xtrin, H 112. Diaphragm, H 77, 78. Dichogamy, p 144. Dicotyledon, p 20. Dicotyledonous stems, p 61. Digestion, p 95, H 89, 96, 100. Digitate, p 74. Digits, \ 222, H III. Dimorphous, p 144. Dioecious, p 138, 170. Diphtheria, H 160. Diptera, A 82. Disease, defined, h 5. Disinfection, H 163. Dispersal of seeds, p 172. Dissection, p 30. Di%'ision of labor, A 27, 29, H 8. Dodder, p 35, 106. Dog, 224. Dolphin, A 209. Doodle bug, A 91. Dorsal, A 43. Dove, A 179. Dragon fly, a 93. Drainage, h 158, 161. Dropsy, H 64. Drugs, H 60, 130, 133. Drupe, p 168. Drupelet, p 168. IV INDEX Duckbill, A 196. Dust, H 8a, 158. Ear, of bird, a 151; of frog, A ij?i; of fish, A 112; of man, h 154. Earthworm, A 42. Echinodcrms, A 9, 34, 125. Ecolog}', p 14, H q. Economic importance of birds, A 167; insects, A q^; mollusks, A 105; rodents, A 206. Ectoderm, A 26, S7. Ectoplasm, A 11, 14. Egg, of insect, A 81 ; of hen, H 95, 96, 1 12. Elaters, p 198. Element, viii. Embrjo, p 26, 180. Embryo sac, p 180. Enamel, H 98. Endoderm, A 26, 27, 37. Endodermis, p 44- Endoplasm, A 11, 14. Endosperm, p 21, 24. Energy, H 96, 140; in ameba, A 12; organic, A 2, 3 ; plant, A 2, 3, 5. Entomophilous, p 148. Environment, p 6, A 148, H a, 3, 4, 48. Enzyme, H 100. Epicotj'l, p 23, 25. Epidermis, of leaf, p 86, 87; of man, H 17; of mussel, a 98. Epigeal, p 23. Epiphyte, p 35, no. Epithelial, H 12, 54. Equisetums, p 201. Erect posture, H 3. Esophagus, H 74, loi. Essays, subjects for, H 15, 25, 50, 116. Essential organs, p 135. Ethiopian, H 12, 18. Evaporation, viii. Excretion, A 12. Excurrent, P 51. Exercise, h 45, 48, 49, 57, 67. Expiration, H 79. Explosive seeds, p 172. Eye, H 149; of bird, a 150; of frog, A 30; of grasshopper, a 67, 79; of fish, A III. Fainting, H 57. Family, A 8. Fangs, venomous, A 145. Farmers' bulletins, A 95. Fatigue, of muscles, h 45; of nerves, H 130, 131, 136. Fats, test for, xi. Fatty tissue, H 12, 103. Feather, A 155. Fehling's solution, xi. Ferment, H 100, 103, 104. 158. Fermentation, p 190, H 158. Fern, p 176. Fertilization, p 144; cross, p 144, 146 A 85; self, P 145, 147, 188. Fiber, H 2.. Fibrin, H 61. Fibro- vascular bundles, P 61, 90. Field study, p 3, 6, 8, 14, 19, 27, 46, 57, 71, 84, 91, loi, no, 118, ia8, 132, 143, :S2, 163, 170, 174, 181, A 10, 2a, 42, 71, 72, 97, 127, 165, 166, 167, 184. Filament, p 135. Filter, H 163. Fins, A no, 113. Flagellum, A 21, 27. Flatworm, A 49. Flavors, H 142, 147. Flea, A 92, 93. Flight, of bird, A 157, 175; of moth, A 84. Floral envelopes, p 133. Florets, p 140. Flower, p 133, 180, A 85; apetalous, P 136; clusters, p 155; complete, p 136; diclinous, P 137; double, p 142; imperfect, p 137; incom- plete, P 136; lateral, P 136; naked, p 136; perfect, p 137; pistillate, P 137; regular, p 138; staminate, p 137; sterile, p 137; solitary, p 156; terminal, p 156. Fly, horse, A 81 ; house, A 92, 93. Foliage, p 16. Follicle, p 165. Food, H 88; defined, h 114; of birds, A 177. Food stuffs, H 91. Food tube, of bird, A 163; of fish, A 116; of insect, A 76; of man, H 97; of mussel, A 102. Foot, H 29. Foraminifera, A 15, 18. Forestry, p 68. Formaldehyde, H 163. Formalin, H 93. Framework of plant, p 15. Frog, A 128. Frond, p 176, 178, 181. Fruit, p 163, H 95. Fucus, P 186. INDEX Funaria, p 201. Function, A i, H 9. P'ungi, p 187. Fungus, p 107, 108, 184, 187, 195. Gametophyte, P 179. Gamopetalous, p 134. Gamosepalous, p 134. Ganglion, A 45, H 120. Ganglionic system, h 127. Garbage, h 163. Gasteropod, a 108. Gastric juice, h 103. Gastrula, A 7. General sensation, H 144, 145. Generation of plants, p 16. Genus, a 8. Geographical barriers, A 148. Geotropism, p 44, 47. Germination, p 22, 23, 27. Gila monster, a 147. GUIs, of mussel, a 100; of fish, A 115- Glands, lymphatic, H 65. Gland tissue, h 13. Glomerule, P 160. Gnawing mammals, A 203. Gopher, pouched, A 204. Gorilla, A 221. Grafting, p 125. Grain, H 95, 112. Grantia, A 18. Grape sugar, x, H 88, 92. Grasshopper, a 70. Grit cells, p 67. Guard cells, p 88. Gullet, H 74, 94, loi. Gymnastics, H 47. Gymnosperm, p 26, 170. Gypsy moth, a 95. Habit, H 131. Hairs, p 87, H 19. Hands, h 4; defined, A 220. Headaches, h 132, 133. Heart, human, h 51, 52; insect, A 77; sound of, H 60. Heating, h 84. Hemiptera, a 82. Hemoglobin, h 59, Si. Herb, p 17. Heredity, a 147, 153, h 4. Hessian fly, a 95. Hill, Dr. L. H., quoted, h 140. Hilum, p 21, 26. Hip, H 4, p 168. Hollyhock, p 147. Homology, p 135. Horned toad, A 140. Host, P 107. House fly, A 92, 93. Houstonia, p 107. Human species, H i, A 220. Hydra, A 22. Hydranth, a 29. Hydrochloric acid, H 103. Hydroid, A 28, 29, 30. Hygiene, h 49, 66, 80, 107, 129, 141. Hymenoptera, A 82. Hyphs, p 107, i88. Hypocotyl, P 22. Hypogeal, p 23. Hypostome, a 23. Ichneumon fly, A 89. Imago, A 81. Immunity, h 158, 160. Indehiscent, p 164. Indian, H 2. Indusium, p 177. Inflammation, h 68, 86. Inflorescence, P 155, 160. Infusoria, a 16. Inhibit, H 68. Inorganic, a i. Insecticides, a 95. Insects, A 73, 75; biting, a 82; classi- fied, A 82; sucking, A 82. Inspiration, h 77. Instinct, A 80, 121; H 49. Intercostal, H 77. Internode, p 52. Intestinal gland, H 104. Intestine, H 98, 103, io6. Involucre, P 34, 141, 163, 164. Iodine test for starch, x. Iris, H 143, 151. Iron, vii, p 39. Iron tonics, H 90. Isoetes, P 203. Ivory, H 98. Jacana, Mexican, a 178. Jay, blue, a 181. Jelly fish, a 29, 30. Joints, H 29, 35, 36. Kangaroo, A 198. Key fruit, p 164. Kidneys, of fish, a 117; of insects, A 76; of man, H 26, 27; of mussel, A 102; of worm, A 45. VI INDEX Kinctoscopc, H 151. Lahi;d palpi, A (jS, 74, loi. Labium, A 68, 74. Laboratory, p 3. Labrum, A 68, 74. Labyrinth, H 157. Lacteal, H 64, 65, 104, 105. Lady bug, A 91. Larrifllihranch, A 107. Landscape, p 13. Lark, meadow, a 182; sky, A 179. Larkspur, p 148, 149. Larva, A 81. Larynx, h 72. Lasso cell, a 34. Lateral spinal curvature, H 37. Latex tubes, p 67. Leaf, apex of, p 80; base of, p 80; function of, p 92; margin of, p 80; structure, p 86. Leaf scar, p 90. Leaves, arrangement of, p 82; shapes of, P 78, 85. Leg, of bird, a 152; of horse, a 210; of insect, A 74; of man, H 33. Legume, p 165, H 95. Legume family, p 35, 169. Lemur, A 220. Lenticel, p 89. Lepidoptera, a 82, 87. Lichens, p 195. Ligneous, p 17. Lime water, xx, H 70. Liver.H 105. Liverworts, p 196. Lobes of leaf, p 75. Lobule of lung, h 75. Locule, p 136, 163, 166. Loculicidal dehiscence, p 166. Louse, A 92, 93. Lumber, p 68. Lungs, of bird, a 165 ; of man, H 76. Lycopodium, p 204. Lymph, H 52, 62, 63. Lymphatics, h 62, 63. Lymph spaces, H 63. Macrospore, p 203, 204. Madreporite, a 35. Malaria, H 160. Malay, H i. Mammal, a 184, H 11 1; classified, A 193; defined, a 189. Manatee, a 209. Mandibles, A 68, 74. Mantis, praying, A 3, Mantle, A 99. Marchantia, p 196. Maxilla-, A 68, 74. Maxillary palpi, A 68, 74. May beetle, A 90, 91. May fly, a 83. Me;isuring worm, A 81, 84. Medulla, h 122, 123. Medullary ray, P 64. Medusa, A 31. Mcsoglea, a 26. Mesophyll, p 86. Metamorphosis of insect, A 80, 81 82. Metazoan, a i. Micropyle, p 21, 26. Microscope, p 21, 26. Microspore, p 203. Midrib, p 77. Migration of birds, a 171, 173. Milk, H 91, 95, 96, 112. Mimicry, A 146. Mind and health, h 129. Minerals, xiv, h 90, 91, 93, 95. Mint family, p 139. Mistletoe, p 109. Moccasin, A 145. Mold, p 188. Mole, A 201. Mollusk, A 9, 97, 125. Molting, A 69, 174. Mongolian, H i. Monkey, A 220. Monocotyledons, P 20, 25, 63. Monoecious, p 138, 150, 170. Morphine, H 105. Morula, a 7. Mosquito, A 92, 93, 96, H 160, 161. Mosses, p 199. Moss, Spanish, p no. Moth, A 83. Mother-of-pearl, A 99. Motor, cell, H 120; fiber, h 120. Mullein, p 87. Municipal sanitation, h 162, 163. Muscadine, p 36. Muscles, H 39; arrangement of, H 41; control of, H 39, 44; function of, H 39, 43; growth, H 42; kinds of, H 39; structure of, H 39. Muscles and health, H 45. Muscular sense, H 142, 146. Muscular ti.ssue, H 1 1. Mushroom, p 107, 194. Mussel, A 96, 103. INDEX Vll Mycelium, P 107, 108, 188. Mychorrhiza, P 108. Nails, H ig. Narcotic, H 137, 148. Nasal tone, H 144. Natural selection, P 8, A 148. Nautilus, chambered, A 107. Nectar, A 8, P 148. Nephridium, A 45. Nerve, h 119; spinal, H 127; cranial, H 127. Nerve cell, h 119; fatigue of, H 130. Nerve center, h 117, 120. Nerve fiber, H iiq. Nerve tissue, h 1 1 . Nerves, vaso- motor, h 23. Nervous children, H 135. Nervous system, of bee, A 78; of man, H 117; of mussel, a 102. Nest building, a 166, 182. Neuron, h 118. Neuroptera, a 82. Neutral substances, ix. Nitella, p 187. Nitric acid test for proteid, xi. Nitrogen, viii, p 39, 40, h 81. Nitrogenous compounds, xi. Nodes, p 20, 52. Nodules, p 39, 40. Nose bleed, h 52. Nostoc, p 1 84. Nostril, of bird, A 151; of fish, A 112. Notebooks, p 3. Nucleolus, A 6, H 6. Nucleoplasm, h 7. Nucleus, p 144, 185, A 6, II, 14, H 6, 18. Nutrients, H gi. Nuts, p 164, H 95. Octopus, A 106. Oil gland, H 20. Oils, test for, xi. Okapi, A 214. Oleander, p 86. Omnivorous, A 47, H iii. One-celled animals, A 7. Oogonia, p 1S6. Opossum, A 197; H 4. Opsonin, H 162. Optic nerve, H 151, 152. Oral surface, A 35. Orang, A 227. Orbit, H 149. Orchid, P 35, no. Order, A g. Organ, A i, H g. Organic, xiv, A i. Organism, A i. Orthoptera, A 82. Oscillatoria, P 184. Osculum, A 18. Osier, Dr. William, quoted, h 133. Osmosis, p 42, 48. Outdoor life, h 5, 22. Ovary, P 135, 144, 163, 170, A 25, 37. 117- Overgrowth, P 12. Oviduct, A 46. Ovule, P 144, 186. Oxidation, xii, A 3, 4, 5, H 14, 90, 91, 120. • Oxygen, viii, A 4, 5, H 4, 76, 81, 140. Oyster, A 104. Palisade cells, p 86. Palmate, p 74. Pancreas, h 104. Panicle, P 158. Papilla, H 17. Pappus, P 141. Paramecium, A 13. Parasites, p 107, a 49, 93. Parenchyma, p 60, 86. Partridge, A 178. Pearls, a 105. Peccary, A 217. Pedicel, p 162. Peduncle, P 62. Peltate, P 77. Pelvis, H 33. Pepsin, H 103. Perch, a 109, no, 123. Perennial, P 17. Pericarp, P 164, 165, 169. Peristalsis, H 102, 106, 127. Peritoneum, H 106. Pests, insect, A g3. Petals, p 134. Petiole, P 76 Phagocyte, h 161. Pharynx, H 73, 85, loi. Pheasant, A 174. Phenogam, p 177, 180. Phosphorus, vi. Photo-synthesis, P g4, loi. Phyllotaxy, P 84. Physics, xiv. Physiology, H g. Pigment, h 18. Pine cone, p 27, 170, VIM INDEX Pinna, p i8i. Pinnate, P 74. Pinnatifid, p 76. Pistil, P 135. Plantain, P 157. Plant societies, P 9. Plants, unlikeness of, P 9. Plastron, a 141. Pleura, H 76. Plexus, H 128. Plumule, p 20, 23, 25. Plur-annual, P 18. Pod, p 164. Poison, H 137. Pollen, p 135, 144, 180, A 85. Pollen basket, A 88. Pollination, p 144, 145; artificial, p 153. Polyp, A 9, 22, 125. Polypetalous, P 134. Polysepalous, p 134. Polytrichum, p 199. Pome, P 169. Portal vein, H 105. Portuguese man-o'-war, a 28. Posterior curvature of spine, H 37. Potato, H 92, 95, 112; bug, a 90. Practical questions, H 50, 69, 87, 112, 136. Primates, A 220. Primitive man, H 3. Primrose, P 149. Proboscis, of butterfly, A 83, 87; elephant, A 207. Prolegs. A 84, 87. Propagation by buds, P 121. Prop-roots, p 36. Protection of birds, A 171. Protective resemblance, A 34, 146. Proteid, xi, H 88, 91, 92, 94, 95, 96, 104. Proterandrous, P 146. Proterogynous, p 146. Prothallus, p 178, 202. Protoplasm, xiv, p 42, 94. 97, 185, A 6, II, H 5, 6, 59, 106, 118. Protozoa, A 7, 9, 11, 125. Pruning, p 105. Pseud-annual, p 17. Pseudoneuroptera, a 82. Pseudopod, a 11. Pteridophytes, p 181, 201, 203. Ptyalin, H 100. Puflball, p 194- Pulse, H 55. Pure food law, H 93. Pylorus, H 103. Pyxis, P 166. Quarantine, H 163. Quarter-sawed, p 70. Quill, A 156. Rabbit, A 205, 223. Radial symmetry, A 34, 125. Ration, daily, H 94, 96. Rattlesnake, a 145. Reaction, H 151, 152. Receptacle, p 134, 163. Rectum, A 134, H 97. Reflex action, H 121. Regeneration of lost parts, A 37. Rennin, H 103. Reproduction, a 12, 15, 20, 35, 37, 46, 120. Reptiles, a 139. Respiration, cellular, H 81; human, H 70; hygiene of, H 80; in plants, p 97, 103. Resting spore, p 184, 185, 189, 191, 192. Retina, H 151, 152. Rhizome, p 52, 202. RhizofKjda, A 16. Road runner, A 169. Robin, A 183. Root cap, p 44. Root climber, p 129. Root hairs, P 41, 42, 46. Rootlet, P41. Root pressure, p 99, 104. Roots, and air, p 41; forms of, p 32; function, p 38; structure, P 38, 43; systems, P 32. Rotifer, a 49. Round worm, A 49. Ruminant, A 213. Rust, P 192. Salamander, A 134. 138, 139. Saliva, H 96, 100, 112. Salt, X, H 93. Samara, P 164. Sand, xiii. Sandworm, A 49. Sanitary map, H 158. San Jose scale, A 95. Sap, p 67. Saprophyte, P 107, 108. Scab in sheep, A 95. Scales, of bird, A 161; fish, A no; moth, A 89. Scallops, A 104. Scape, p 161. Scarab, A 90, 91. INDEX IX School and health, H 135. Sclerotic, H 150. Scouring rush, p 203. Scramblers, p 129. Sea anemone, A t^j,. Sea fan, A 32. Sea horse, A 124. Sea urchin, A 38. Seed, p 20, 163, 180; coat, p 21. Selaginella, P 204. Selection, natural, p 8; artificial, p 8. Sense, muscular, H 143; thermic, H 142. Senses of insects, A 76. Sensory, cell, H 120; fiber, H 120, 121. Sepal, p 133, 169. Septicidal capsule, P 166. Serum, H 61. Sessile, P 77. Setae, A 43, 48. Sexual selection, a 174. Shark, A 121. Shelf fungus, p 194. Shoes, H 48. Shoulder, H 32. Shrub, p 19. Sick headache, H 133. Sieve tubes, p 66. SUicle, p 167. Silique, p 167. Silkworm, A 84, 86, 95. Silver scale, A 83. Siphon, A loi. Siphonoptera, a 82. Skeleton, of bird, a 152; cat, a 188; frog, A 131; of fish, A 113; man, H 28; chart of, A 218. Skin, H 16. Skull, H 63 ; mammalian, A 194. Sleep, H 130. Slipper animalcule, A 13. Sloth, A 199. Slug, A 105. Smell, H 147. Snail, A 105. Societies, p 9. Soil, p 40, 47, A 48. Soredia, p 196. Sori, p 177, 192. Souring of milk, H 158. Spadix, p 140. Sparrow, a 182; English, A 170. Spathe, p 138, 140. Specialization, a 20, 27, 66, 210, Species, A 8. Spermary, A 25, 27. Spermatophytes, P 180. Spicule, A 18. Spider, A 94. Spike, P 157. Spinal cord, H 120, 121. Spinal deformities, H 37. Spine, H 31. Spiracle, A 77, 87. Spirogyra, P 184. Sponges, A 17, 125; glass, A 19; horny, A 19; limy, A 19. Spontaneous combustion, xiii. Sporangium, p 177, 186, 188, 201, 203, 204. Spore, p 176, 178, 181, 184, H 159. Sporophyll, p 180, 201. Sporophyte, p 177. Sports, A 148, 224. Sprain, H 38. Squash bug, a 93, 95. Squid, A 106. Stamen, p 135. Starch, x, p 95, loi, H 88, 91. Starvation, H 138. Stem, p 49; endogenous, p 59; exoge- nous, P 61; kinds of, P 49. Sterilizing wounds, H 163. Stickleback, A 119. Stigma, P 135, 144, 145- Stimulant defined, h 137. Stipule, p 76, 84. Stock, p 125. Stomate, P 87. Stone age, H 2. Stone fruit, p 168. Storage of food, p 99. Street cleaning, H 163. Struggle to live, p 4, 6, A 147, h 4 Study, comparative, a 82, 149, 223. Style, p 13s, 163. Sugar, H 91, 100. Sulphur, vii. Summer-spore, P 191. Sun energy, p 95, A 2, H 91. Sunlight, A 2, H 18. Survival of fittest, p 7, A 147, H 4, 141. Sutures, H 35. Swarm-spores, p 186. Sweat gland, H 20. Symbiosis, P 196. Sympathetic system, h 137, 129. Syngenesious, p 141. Synovial fluid, H 36. INDEX Tadpole, A ia6, 134. TiiimiT, Dr., H 13S. Tapeworm, A 40. Tarantula, A 04. Taste, H no, 143, 140. Tear gland, H i4(>. Teeth, H 88, y8, qc), i i i ; of fro^;, A 1 30. Teleutospores, P 192. Temperature, n 21; nerves of, H 142, 146. Tendon, h 41. Tendril, p 101. Terrapin, A 143, 144. Thallophytc, p iSi, 184. Thallus, p 184, iq;. Thompson, Sir Henry, on smoking, H 87. Thoracic duct, h 64, 65, 105. Thorns, p loi. Thought questions, H 20, 27, 7q, 107, 109, 116. Thyrse, P 160. Thyroid gland, H 97. Tillandsia, p no. Timber, decay of, p 195. Tissue, H 7, 10, p 60, 62. Toad, A 137. Toadstool, p 194. Tobacco, and heart, H 67; and lungs, H 86; and taste, H 148; when enjoy- able, H 87. Tortoise, A 140, 143, 144. Torus, p 134, i6q. Touch, H 145, A 119. Toxin, H 160, 161. Toyi Niku, Madame, quoted, H 141. Trachea, H 74. Tracheid, p 65. Transpiration, p 98, 103. Trap-door spider, A 94. Tube feet, A 35. Tuberculosis, H 5, 160. Tumble bug, a 90, 91. Turtle, A 140, 143, 144. Twiners, p 129, 131. Typhoid fever, H 159. Umljcl, p 159. Umbo, A 98. Undergrowth, P 12. Ungulate, A 212. Urea, H 94. Uric acid, H 114. Urinary tufcrule, H 27. Vacuole, A 11, la, 14. Valve, p 164, H 51, 53, 57. \'ampire, A 203. \'ariation, A 147, p 2. \ariety, A 8. \'aso- motor nerves, n 23, 68. N'aucheria, p 186. \'i-getal)k'S, II 9S, 112. X'cnomous snakes, A 143. \'cnt, A 42. X'entilation, H 71, 82, 83. Ventral, a 43. Ventricle, 11 53. Vermes, A 9, 125. Vermiform appendix, h 4, 106. Vertcljra, H 71, 82, 83. X'ertcijrates, A 9, 125. Vertebrate skeletons, A 218. Verticellate, p 84. Vestigial organs, H 106. Villi, n 104. Vinegar, H 94. Viscera, H 127; of bird, A 163. X'itreous humor, H 152. Voluntary act, u 122, 124. Warning sound, a 147. Wasps, digging, A 89. Water-pore, p 88. Waterworks, H 163. Weevil, A 90, 91, 96. Whale, A 208. Wheat rust, p iq2. White corpuscles, H 50; origin of, H 61 ; work of, n 60, 161, 162. White weed, or ox-eye daisy, p 155. Whorled, p 84. Willow mildew, p 190. Wind travelers, p 173. Wings, of grasshopper, A 67; of bird, A 153. 158- Woodpecker, A 180. Woody fiber, P 17. Worms, A 42. Wounds of plants, P 56. Written exercises, H 15, 50, 116. Yeast plants, p 190, H 158. Yellow fever, H 160. Yellow spot, H 151. Zoology defined, A i. Zoophytes, A 33. Zygnema, P 185. Zygospore, p 185, 189, 181, 189. LESSONS IN HYGIENIC PHYSIOLOGY By W. M. Coleman, x + 271 pages. 198 illustrations (16 colored, 13 full-page plates). 60 cents net. In Lessons in Hygienic Physiology the study of physiology is simphfied without weakening the presentation of its three essential principles — the biological principle of environment, the chemical principle of oxidation, and the physical principle of energy. The subject is approached throughout from the standpoint of health, because this is the most useful as well as the most interesting point of view. The question of temper- ance is treated fully, but at the same time in a conservative manner. The book is fully illustrated, one hundred and ninety- eight figures being furnished, sixteen of which are colored. The Lessons is suited to the needs of teachers who may find the Elements somewhat too advanced for their classes. ELEMENTS OF PHYSIOLOGY By W. M. Coleman, xii + 364 pages. 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