GIFT OF j-xXS^X C f 1 BIOLOGY LIBRARY THE PLANT, Illustration OEGANIC LIFE OF THE ANIMAL. BY HARLAND COULTAS, AUTHOR OF "THE PRINCIPLES OF BOTANY AS EXEMPLIFIED IN THE CRYPTOQAMIA, ETC., ETC. PHILADELPHIA: PERKY AND ERETY, PUBLISHERS, S. W. CORNER FOURTH AND RACE STSr 1850. BIOLOGY Entered according to the Act of Congress, in the year 1855, by HARLAND COULTAS, in the Office of the Clerk of the District Court of the United States, in and for the Eastern District of Pennsylvania. PRINTED BY HENRY B. ASHMEAD, GEORGE ST. AB. ELEVENTH. TO SAMUEL JACKSON, M. D., PROFESSOR OP THE INSTITUTES OF MEDICINE IN THE UNIVERSITY OF PENNSYLVANIA. DEAR SIR, — Knowing the enlarged and liberal views which you'' take of medical education, and your willingness to encourage your stu- dents in all inquiries tending to render them skilled and accom- plished in their profession, — allow me to lay before you this humble attempt to show the uniformity of the organic laws in plants and animals. I remain, With sentiments of respect, Yours truly, HARLAND COULTAS. 284310 CONTENTS. INTRODUCTION. GENERAL CONSIDERATIONS ON ANIMAL AND VEGETABLE LIFE, - ---13 PART I, HISTOLOGY OF PLANTS AND ANIMALS. CHAPTER I. ON THE INDIVIDUALITY OF THE CELLS, - .;- - - 31 On the Chemical Composition of the Vegetable and Animal Tissues, - - - - - 47 CHAPTER II. ON THE DEVELOPMENT AND PROPAGATION OF CELLS, - 51 1. Formation of Cells from Nuclei, - - - 51 2. Formation of Cells by Division, - . . » - 55 3. Formation of Cells by Gemmation, - - - 59 CHAPTER III. ON THE TRANSFORMATION OF CELLS INTO TISSUES, - - 62 CHAPTER IV. Ox THE CONTRACTILITY OF THE TISSUES, - - - - 73 i CONTENTS. PART II, NUTRITION IN PLANTS AND ANIMALS. CHAPTER Y. ON THE ABSORPTION AND CIRCULATION OF FOOD IN PLANTS AND ANIMALS, --------85 CHAPTER VI. ON THE NlJTRITIYE PROCESSES OF RESPIRATION AND AsSIM- 1LATION, ________ 104 PART 111. REPRODUCTION IN PLANTS AND ANIMALS. CHAPTER VII. GENERAL CONSIDERATIONS ON REPRODUCTION IN PLANTS AND ANIMALS, 123 Hybridization, 131 CHAPTER VIII. ON THE ESSENTIAL AND CONSECUTIVE PHENOMENA OF RE- PRODUCTION, ----____ 135 PART IV. ON THE GEOGRAPHICAL DISTRIBUTION 0? PLANTS AND ANIMALS. CHAPTER IX. ON THE LAWS, ACCORDING TO WHICH PLANTS AND ANIMALS ARE DISTRIBUTED ON THE SURFACE OF THE GLOBE, - 153 CHAPTER X. ON THE GEOLOGICAL SUCCESSION OF PLANTS AND ANIMALS, OR THEIR DISTRIBUTION IN TIME, - -168 ' PREFACE. THE two volumes on Cryptogamous and Phanerogamous plants already published by the author, were written with an " especial reference to the wants of medical students and phy- sicians." Botany has not yet obtained that position to which it is deservedly entitled, as a preparatory study to the organo- graphy and physiology of animals. It is still excluded from the most important medical schools ; and this state of things will continue despite of all the efforts of botanists, so long as the plant is regarded as if it were isolated from the rest of organic nature. The functions of animal life appear to be gradually super- added to those which are strictly vegetative. As we pass from the plant through the coral and sponge to the higher order of animals, bones, blood-vessels and nerves, gradually appear ; the organs of the senses become more perfect, and the motions more complicated, until at length in man, the nervo- muscular system, which has thus been gradually, superadded to the vegetative, manifests itself most perfectly in all that infinite variety of movement and sensation peculiar to rational beings. On the other hand, as we descend from man to ani- mals still lower in the scale of creation, in proportion as the -8 PREFACE. functions of animal life are suppressed, the vegetative life of the organism gradually predominates, until life becomes wholly vegetative. Life in plants is therefore limited to the two functions of "nutrition and reproduction ; and nutrition and reproduction in animals are necessarily illustrated by the flowers and forest trees with which the earth is beautified and adorned. Such appears to me to be the way in which organic nature ought to be regarded, such the relative positions of the vegetable and animal creation. Few, we believe, recognize as they ought to do, the benefits which have already resulted to animal physiology and the science of medicine, from the study of a few humble plants, The great cell-doctrine of physiology, which is now admitted to be the basis of all sound scientific investigations into the phenomena of organized beings, originated in the study of vegetable matter. M. Mirbel, in a most admirable memoir on the development of Marchantia polymorpha, a little acotyle- donous plant belonging to. the family of the Hepaticae, was the first to show the cellular origin of every other form of vegetable tissue. He proved that the fibre cells of plants are only attenuated utricles, and that the different varieties of vasiform tissue and ducts, by which the interior of the plant is aerated, originate in a row of utricles ; these gradually elon- gate, and the various secondary deposits characteristic of the different forms of spiral vessels, appear on their internal sur- face ; the septa or partition walls between the several cellules are then absorbed, and the transformation of the utricles into vessels is completed. These observations were confirmed by the researches of Schleiden and other distinguished botanists, PREFACE. 9 and thus a flood of light was thrown on the organization of plants. But how do the cells of plants and animals originate ? How do they multiply and extend themselves so as to produce the growth or enlargement of the organs ? These are difficult but interesting questions, and botanical researches have enabled us to reply to them satisfactorily. A German naturalist, Mohl, selected for observation one of the fresh water algae, which had been previously figured and described as Conferva glomerata. This simple, thread-like plant was placed beneath the microscope, and the develop- ment of the row of utricles of which its entire organization consists, watched. Very soon, Mohl observed that the inte- rior face of the cavity of one of the utricles presented towards its middle part a fold, which increased almost imperceptibly until it ended by forming a complete wall dividing the cavity of the utricle into two parts. Each of these then dilated itself into a new utricle. Thus in the place of one cell there were two cells, which again divided in the same way, and so on. It is in this way that a single cell gives rise to a row of connect- ed cells, when the division takes place in one direction, and to a plane or solid mass when it takes place in two or more di- rections. There are other modes of increase which we shall notice in the ensuing pages ; suffice it for the present to say, that their discovery originated in the investigation of crypto- gamous plants of extreme simplicity of organization. Up to this period it was believed .by the most eminent phy- siologists, that animal and vegetable tissues differed widely in their development, and that cells existed only in plants. Such was the condition of things in 1838, when Schwann, taking up 10 PREFACE. the beautiful investigations that Schleiden had just published upon the structure and growth of vegetable cells, came to the conclusion that animal tissue consisted equally of cells, and that whatever may be the character of the tissues^ whether they assume the form of muscle, bone, or blood-vessels, all ori- ginate in cells, of which they are but modifications. Let it be remembered that these grand discoveries, which have given such an impulse to animal physiology within the last twenty years, originated in botanical investigations. After such fruits have been reaped, the study of the physiology of plants ought to be encouraged. Where would have been our knowledge of the histology of animals, but for the botanical researches of Mohl, Schleiden, Mirbel and other distinguished physiologists? Incalculable, then, has been the amount of good which has resulted to animal physiology, from the study of the simple and beautiful organization of plants, and in the face of these facts, there is no excuse for the coldness and ne- glect with which this department of Natural History still con- tinues to be treated. It is not the mere collecting of species, the technical description of their several peculiarities, and their proper classification and arrangement which is here ad- vocated, so much as the study of their vital phenomena and the laws of their development. No extensive acquaintance, either with rare exotics or the choicer native species, is at all necessary for such researches, for these laws may be studied in the commonest weeds growing around our dwellings. The views on vegetable respiration in this work are jiot my own peculiarities ; for they were held by Dr. Gilbert Burnett, an eminent English physician and physiologist. I have also been very favorably impressed with the opinions advanced by PREFACE. 11 Dr. Draper, in reference to the exciting causes of the motion of the nutritive fluids in the organism of plants and animals, notwithstanding the attempts which have been made to con- trovert them. Let it be considered that there is the same suc- cessive degrees of attenuation in the conduits of both the sap and blood, resulting fro'm lateral ramifications ; the same beau- tiful anastomoses amongst the capillaries in which these con- duits finally terminate. By these means the nutritive fluids are diffused in all directions, and brought into immediate com- munication with the cellular tissue of the organs. Let the structure of any exogenous leaf be examined even superficially, without the microscope. The successive attenuations of the fibrous system by lateral ramifications into a network of capil- laries, which develop horizontally in a series of closely approx- imated planes, through the parenchyma of the leaf, show that the same laws predominate in the distribution and elaboration of fluids in vegetable as in animal matter. At least it is not unphilosophical to infer some analogy, if not absolute identity of function, where there is so manifest a similarity in organic structure. I cannot conclude my Preface without acknowledging my obligations to my numerous friends and patrons through whose assistance I have been enabled to produce this volume. In the preparation of Part I. an excellent Chevalier micro- scope was employed. This instrument was kindly lent me by Dr. Francis Lewis. It gives me pleasure also to mention the services of Dr. Samuel Jackson, Dr. Samuel Lewis, Dr. Francis West, Dr. S. Tucker, the Hon. W. D. Kelly, and Professor Saunders of the French Collegiate Institute, West Philadelphia. INTRODUCTION. GENERAL CONSIDERATIONS ON ANIMAL AND VEGETABLE * LIFE. IF we cast a glance at the immense quantity of animals and plants which live on the surface of our globe, we are at first struck with the variety of forms under which they present themselves, with their colors so diversified and sometimes so brilliant, and with the collossal proportions of some, as compared with the diminutiveness of others. But when, after this superficial examination, we study them more attentively ; when we examine with care the structure of each being, we at once see the perfection which exists in its organs, and how well they are adapted to its peculiar habits and mode of life — from the enor- mous whale, which requires an ocean to swim in, to those minute and myriad forms which find ample room for all their evolutions in a single drop of its waters; from the lofty tree which has stood for centuries, an ornament in the midst of the landscape, to the lowly flower which attracts us by its beauty and fragrance — all form a collection of objects whose framework is constructed in the most admirable manner, and whose vital manifesta- tions are in the highest degree instructive and interesting. At first sight, nothing would seem to be more widely 14 INTRODUCTION. different from each other, than an animal and a plant. How different is the tree from the bird singing on its branches, or the traveller resting beneath its shade. In the one instance, the organism is immovably fixed to the soil which gave it birth, and has neither the faculty of moving itself, nor that of manifesting pleasure or pain. The hatchet penetrates its tissues, and it falls without any external signs of suffering. But in the other cases, the organic beings are far more highly complicated. They are endowed with the power of moving from place to place, have a will and desires, senses to apprise them of the character and qualities of external bodies, and introduce food into their interior, where a special cavity is provided for its elaboration before it is employed in the nutrition of their organism. Plants have no such special receptacle in their interior. They live, as it were, in the midst of their food. It is furnished to them by nature in a condition fit for assi- milation and circulation. They draw it at once from the earth by their roots, and from the atmosphere by their leaves. They therefore possess no special organs for its preparation. It would seem impossible that there could be anything in common between bodies so strikingly dis- similar in their organization and habits. But if we consider the vital phenomena manifested by animals and plants, we shall very soon see that there is abundant reason for believing that the difference between these organic productions of nature is not so great as we at first thought. In the first place, both the animal and plant spring in- variably from a being perfectly similar to themselves, to which they adhere during a space of time more or less long, and from which they are finally separated at a deter- minate epoch, under the form of an egg or .a seed, which, INTRODUCTION. ,15 under envelopes more or less resisting, encloses a germ. In this germ, all the organs of the adult animal and plant exist in a rudimentary undeveloped condition. Germina- tion, or the act by which these organs disengage themselves from their envelopes, does not increase their number, but only augments their size or modifies their form. The seed contains the plant, and the egg the animal. Thus, they are alike at the commencement of their being. In the second place, the organs of plants and animals, — the root, stem, and leaves of the former, the bones, muscles, and limbs of the latter, — will not grow without a plentiful sup- ply of food and air. In both instances it is absolutely necessary that the nutritive aliment should be introduced into the interior of the plant or the animal, and be dis- tributed to all the parts of their organization. Now the absorption, circulation, and assimilation of food and air, by animals and plants, is in principle precisely the same process. Abundant proof of this position will be given in the succeeding pages. Well-marked and obvious distinctions between animals and plants exist only in the more highly organized forms of animal and vegetable life. As we descend to beings of a lower rank in creation, these distinctions become gra- dually effaced, and we see successively disappear the most important organs of animal life. The organs of the senses become rudimentary, bones, blood vessels, and nerves to- tally disappear, and in proportion as the powers of animal life are suppressed, those which are truly vegetative gain the ascendancy. Thus, the lower orders of the cold- blooded vertebrata, whose bodily temperature is regulated by that of the medium in which they live, become torpid and inactive in common with plants in winter. So also many vertebrated and crustaceous animals change their 16, INTRODUCTION. epidermal appendages. The serpent casts its skin, the bird its feathers, crabs and lobsters their claws, just as the leaves and bark fall from the branches and stems of trees. Moreover, the exercise of the reproductive function which in man is not limited to any particular time, is periodical in inferior animals, precisely as plants flower and fruit at certain seasons of the year. At length, in the lowest orders of the animal creation, the animal and plant ap- proach each other so closely that it is hardly possible to draw any line of demarcation between them. This is the case, for example, with that order of animals which have been very properly called by naturalists, zo- ophytes, of which the coral and the sponge are familiar examples. These creatures, which show undoubted signs of animality, present also at the same time many striking Fig. 1. Fig. 1. Hydra, or polype attached to a piece of stick, with its arms extended in quest of prey. a. The mouth of the animal, surrounded by the tentacula. &. The tendril-like grasp of an aquatic insect, c. Foot or base of the animal with its suctorial disc. The figure shows also the natural size of the animal. INTRODUCTION. 17 indications of a vegetable nature. They are not only fixed to the ground like plants, but they have also a plant-like method of growing and propagating. It is extremely difficult to convey any general idea of a zoophyte, because there is no order of creatures of which the different individuals bear so little resemblance to each other. The organization of the corallines, flustras, sertu- larias, and other orders of marine zoophytes may, however, be illustrated by that of the Hydra, or common fresh-water polype. These animals, which resemble little pieces of jelly, are found in ponds or slowly running streams, attached to the under surface of the leaves of aquatic plants, or to any floating substance, such as a stick or a straw. They are remarkable for the extreme simplicity of their organiza- tion, which consists of nothing but a digestive cavity or stomach, surrounded by a fringe of long thread-like arms or movable tentacula, by means of which the animal pro- cures its food — generally some minute insect or worm, which it seizes with a tendril-like grasp and instantly con- veys into its stomach by a contractile effort. The contrac- tility* of the tentacula of the Hydra is truly wonderful, When the animal is hungry and in search of prey, the ten- tacula are extended to a distance of not less than six or seven feet from the mouth of the stomach ; but when the digestive -cavity is filled with food and the wants of the animal are appeased, they are so contracted as to appear only like tubercles around its entrance. The different species of corallines, flustras, and sertu- larias, usually found attached to, or more frequently intermingled with, the sea-weed cast upon our shores, con- sist of an association of polypes having individually a simi- lar organization to the Hydra, but united together about a common axis of growth like the buds and branches of 18 INTRODUCTION. a plant. It is interesting to trace the analogies between the members of the animal and vegetable kingdom in the lower orders of animated nature. The sertularian polypes Fig. 2. Fig. 2. a. Sertularia or compound polype. &. Magnified view of a portion of its branches, showing the polype buds. with their common stalk bearing numerous individuals, have in every instance been produced by continuous growth from a single individual. Here we have a repe- tition of similar parts precisely as in plants. There can be no mistake as to the vegetative nature of these actions. Each of these associated polypes has an independent vi- tality of its own, and yet all depend on the general life diffused through the entire community. They individually capture and digest their prey like the Hydra, and yet the products of their individual digestion are applied not only to their own support but to that of the general axis ; for the stomachs of the several polypes, communicate with each other by means of a tube which proceeds from the base of each into the common digestive cavity of the stem. Some of these polype buds periodically die and are cast off like the leaves of a tree j whilst others, retaining their INTRODUCTION. 19 vitality, spontaneously detach themselves and evolve into similar fabrics elsewhere. It is, however, amongst .the algae that vegetable and animal life appear to be the most completely blended to- gether. It is well known to naturalists that the spores of some of our common fresh water algae, as for instance, con- ferva glomerata and prolifera rivularis, when first dis- charged into the water, move about by means of certain ciliary appendages during a certain period of their life. At this stage of development they were observed by Ehren- berg, and were actually figured by him as infusoria. After awhile, however, their cilias are absorbed, their motions cease, they become attached to some substance in the stream, and develop into plants fixed and immovable ex- cept from the influence of the current. It would appear from this, that these simple unicellular organisms are animals during the first period of their life and vegetables towards its close. All organized matter, whether animal or vegetable, con- sists of cells, and life is only known to us as manifested through their agency. Not only may every animal and plant be traced to a simple cell, but organic nature is evi- dently only a series of forms which exhibit the successive stages of its development. The animal and plant seem to be blended together in this the primitive form of all organized being. It is here that the last signs of animality disappear, after which, life becomes wholly vegetative. It is not then among vegetables and animals the most highly organized, that we find the most striking analogies between the animal and vegetable kingdoms, but it is those which possess the greatest amount of structural simplicity, that approximate the most closely to an identity of function. The assemblage of organized beings denominated animals 20 INTRODUCTION. and plants, may be collectively represented, in reference to their mutual relationship, by two cones, one of which is in- verted on the other, so that their summits are brought into mutual contact. For there is a point of departure common to both of these grand divisions of living nature, — THE ORGANIC CELL, — which animated, commences the animal series, and remaining immovable, serves as the basis of the vegetable creation. This organic cell may be imagined to be situated at the apex of the cones, the lower cone repre- senting the vegetable and the upper one the animal creation. Plants and animals increase in organic simplicity and the analogies between them multiply and become more striking in proportion to their approach to this point ; while, on the contrary, the differences which separate them increase and their organization becomes more complicated, as they elon- gate from it. All that variety of form which marks the external organs both of plants and animals, is clearly traceable to the same organic laws. Thus, the same organ which attains a high degree of development in one plant or animal, is for certain physiological reasons in another, either suppressed altogether or reduced to a rudimentary condition. But these changes take place almost imperceptibly. We never see an important organ disappear all at once in any of the classes of the animal and vegetable kingdom. It is by de- grees that the organ loses in succession the several parts which complicated it ; these become rudimentary, and the organ is finally reduced to the utmost degree of structural simplicity, those parts alone remaining which are absolutely essential to enable it to perform its function. What are called varieties by naturalists are, in fact, only different phases in the organic development of the same specific form j and a truly scientific classification can only be INTRODUCTION. 21 achieved in proportion to the accuracy of our perceptions of the natural relationship subsisting among the organs thus modified. The anterior organs of the different order of vertebrated animals, for instance, are organically modified to the degree of their intelligence, their powers of locomotion, and their peculiar habits. In some quadrupeds they are adapted for the prehension of food and for locomotion ; in the bird they are organized for flight ; in the fish, for balancing the body and assisting its progress through the water. The twisted arm of the tortoise can be applied to no other purpose than that of creeping, and the enormous hand of the mole can be used only for burrowing. Yet the anterior members in the different orders of the vertebrata consist essentially of the same parts as those which exist in the same members in man. We find in each the same bones, muscles, nerves, and vessels. Yet how different their appearance ! how varied their functions ! All these ends are attained by a modification in the development of the different parts, one bone being largely developed, a contiguous one less so, some being evolved to a maximum, whilst others are left rudimentary. We have a manifestation of the same organic law in the vegetable world. Thus the leaves of plants are variously modified so as to be rendered subservient to the exercise of the different vegetative functions. The different organs appended to the vegetable axis and designated as scales, stipules, bracts, sepals, petals, stamens, and pistils, are only a series of leaves in a state of progressive or retrograde de- velopment, which have assumed this peculiarity of form in consequence of the peculiar and distinct functions assigned them. A fully developed leaf consists of two parts, a little stalk or support called a petiole, and a flat expanded por- 22 INTRODUCTION. tion called the blade or limb. In the scale, stipule, and bract, the petiole and lamina of the leaf are reduced to rudi- mentary condition ; in the sepal the former is wholly sup- pressed and the latter more or less developed. In the petal both lamina and petiole are sometimes present, as in the pink and wall-flower. The petals of these flowers which are broad and expanded at their summit gradually taper into a narrow stalk or petiole, which in this instance is called an unguis, or claw. In the stamen, the petiole is represented by the filament, the lamina by the anther, whilst the repro- ductive matter called pollen, which is contained in the anther-cells, is only a peculiar transformation of the paren- chyma of the leaf. In the pistil, there appears to be the greatest departure from the primitive type ; yet it is not difficult to trace it even in this instance. The pistil is nothing but a folded leaf, the margins of which have united to form a placenta or point of attachment for the ovules, or young germs, which develop along its edge. Other in- stances might be brought forward illustrative of the fact that the same laws of development and adaptation, govern the organization of both plants and animals. It is only by viewing nature as a whole that any part of nature can be properly understood. It is to the study of comparative anatomy and physiology, that we are indebted for our knowledge of this identity and unity of organization. The organism of one species has been compared with that of another, and the transitions forms of the several organs have been traced, so that organs are now recognized as the same which were formerly thought to be altogether different. It is to the contributions which they mutually afford each other that we are indebted for the advance of the physical sciences, and the same principle applies to natural history. Almost every part of the human frame has its homologue INTRODUCTION. 23 in some inferior animal. Hence "the advantage — the necessity, rather — of combining a general knowledge of the organization of the lower animals with that of man, which ought always to claim the first attention of the medical student, is now universally recognized. A great part, of the best part, of the proofs of the most important physio- logical doctrines are derived from comparative anatomy. The increasing taste for the natural sciences, and the rapidly diffusing knowledge of zoology and geology render it scarcely pardonable in a member of a liberal profession to be wholly unversed in them, and almost discreditable to a medical man to be unable to offer any sound opinion on a fossil coral, shell, or bone, which may be submitted to his inspec- tion."* So also, the great cell doctrine which is now the basis of animal physiology, had its origin in microscopical investigations into the organization of plants. " Since it has been ascertained that the animal tissues are in their fundamental structure identical with the vegetable tissues, we may expect that botanical investigations may throw as much light upon the animal kingdom, as the study of ani- mals may throw on the vegetable kingdom. Easy as it has been to study the structure of vegetable tissues, so difficult has it been to ascertain their functions, and the work of the various organs in plants, that the most contradictory opi- nions are entertained upon vegetable functions, upon the circulation of their sap, upon their respiration, and the action of respiration on their fluids. On the contrary, in animal structures the functions are easily traced. The com- bined action of the various functions upon each other can be easily ascertained. It was the structure, the intimate * Lectures on the Comparative Anatomy and Physiology of the Invertebrate Animals, delivered at the Royal College of Surgeons : by Richard Owen, F. R. S. 24 INTRODUCTION. structure which it was difficult to investigate. And now by referring the result from one kingdom to the other, it is to be hoped that much more rapid progress will be obtained than before."* Many problems connected with nutrition and reproduction in animals will probably be solved by a more careful observation of these functions in vegetables. A knowledge of cell-life, now universally admitted to be the basis of all scientific physiology, can be best acquired by examining the cells of plants which are much larger than those of animals, and visible to ordinary microscopes at every epoch of their development. The differences which exist among the organic productions are not so great as is commonly thought. There is a oneness in nature which has yet to be understood and appreciated. One of the most striking differences of organization be- tween the higher orders of animals and plants consists in the presence of a nervo-muscular system in the former of which the latter are totally deprived. This nervo-muscular system, which is essential to animality, appears to be gradu- ally developed in vegetable life, which thus becomes in- separably bound up with the exercise of the animal func- tions. It is gradually developed in the inferior orders of animated being, and is manifested most perfectly in man, and those animals the most closely allied to him in organi- zation. Now comparative anatomy shows that the animal func- tions of sensation and voluntary motion, manifest themselves in proportion to the more or less perfect condition of the organs appropriated to their exercise. In man, the highest vertebral animal, the organs of the senses and the muscular * Lectures on Comparative Embryology, delivered before the Lowell Institute in Boston, by Louis Agassiz. INTRODUCTION. 25 system are the most highly developed, and prove successive degrees of simplification as we descend in the scale. The muscles in the human body are more than five hundred in number, and almost every movement is produced, not by the action of one, but of several of them. The muscular system in man not only moves the body but expresses thought and emotion, and is capable of a very high degree of education. The accomplished tragedian and musician manifest in their performances, the degree to which the muscles of expression and voluntary motion may be educated. The body of man is capable, through the agency of his highly developed nervo-muscular system, of an infinite variety of movement and expression. In man, the muscles of expres- sion are chiefly in the face. In conversation, all persons to a greater or less extent communicate thought by the expres- sion of their countenance. In some, however, the muscles of expression respond more readily to the emotions of the mind than in others, every shade of thought and feeling being beautifully depicted in their faces.* In the inferior animals, the expression of which they are capable is much more limited, and is confined to other parts of the body. The dog wags his tail, the cat elevates her back, the horse erects his ears, and the game-cock spreads out his ruff of feathers on his head. The countenance of the inferior ani- mals is in general devoid of expression. Kage and fear are almost the only passions which are expressed in their faces. Their muscular movements are susceptible of education, as is evident from the performances of dancing dogs and bears, # Human Physiology designed for Colleges and the Higher Classes in Schools, and for General Reading, by Worthington Hooker, M. D., Professor of the Theory and Practice of Medicine in Yale College. Chapter xiii. page 222. 3 26 INTRODUCTION. but not to the same extent as those of man, owing to the low degree of their intelligence. The organs of the anterior and posterior extremities connected with the trunk or spinal column in the higher vertebrata, are gradually absorbed in the lower, until at length in the serpent tribe, these locomotive appendages are suppressed altogether, and the body of the animal consists of little else but the spinal column itself, which is very long and extremely flexible, owing to the immense num- ber of vertebra, and their connection with each other by a ball and. socket joint. The perceptions of the animal are now obtuse, and all its movements sluggish, — a mere trailing of the body along the ground. The same gradual simplification of the nervo-muscular ap- paratus, may be traced throughout the descending series of invertebrated animals. Insects may be truly regarded as the most highly developed of the invertebrata. In them the ani- mal functions are decidedly more developed than the vegeta- tive. Their rapidity of motion, and extraordinary display of intelligence, entitle them to this position. The tegumentary skeleton of insects is composed of a number of movable pieces articulated to each other, and is of a horny texture. This integument becomes progressively hardened, and the pieces fewer in number, and more consolidated in the different orders of the Crustacea, so that the movements are necessarily much more restricted and confined. In the testaceous mollusca, the integument is finally reduced to a pair of valves, and the muscular movements of the animal are of the simplest character. Most of the bivalve muscles, such as the cardium, move along by means of a fleshy organ called a foot. The movements of the oyster are restricted to the single act of opening and closing its shell, and those of serpulae and limpets, to the alternate protrusion and INTRODUCTION. 27 withdrawal of their tentacula within their testaceous cove- ring. What a contrast do the simple motions of these animals present to the complicated motor machinery of the human frame ! How immense the chasm of separation between these creatures and man ! The laws of phenomena really constitute science, and facts ought ever to be made subservient to their discovery. The zoologists and botanists who devote all their time and attention to the mere business of collecting species, of de- fining their external characters, and of forming systematic arrangements of them, undoubtedly perform a great and valuable service ; but this after all, is but a coarse outline of the natural history of any country. It is not sufficient to obtain specimens of natural history for the cabinet, to group plants and animals according to their outward appearance ; we must look more deeply into the mysteries of their organization, we must study their physiology and the laws of their development. It is true that little pro- gress can be made in these investigations without we avail ourselves of the labors of the systematist ; but after all, the technical description of the external organs of plants and animals, is only the infancy of science. It is not sufficient that we make ourselves acquainted with facts we must study their philosophy. For example, it is well known to botanists that the calyx of the bloodroot (Sanguinaria Canadensis,) drops from the flower stem as soon as the petals open and expand, whilst in the blackberry (Rubus villosus;,) it survives the decay and removal of the other parts. Why do the cells of the calyx perish at so early period in the one instance, and remain persistent about the fruit in the other ? What is it that pro- duces their early decay or the prolongation of their vitality ? This is a very simple question, and yet in the present state 28 INTRODUCTION. of science, it is impossible to give the reader a satisfactory answer. All botanists are acquainted with the fact, its philosophy is unknown. Every branch of natural history is more or less in this imperfect condition. Botany is perhaps the most defective. It is in truth very little better than an accumulation of sterile facts. He who studies botany or any other branch of natural history in this, the true philosophical spirit, will not fail of becoming an origi- nal contributor to the department which he undertakes. In the place of a narrow circumscribed science, he will find an immense field, in which the commonest and most insig- nificant weed or animal, will furnish him with innumerable subjects for reflection and study. PART I. HISTOLOGY OF PLANTS AND ANIMALS. CHAPTER I. ON THE INDIVIDUALITY OF THE CELLS. EVERY plant, germinating from the seed or spore, is sub- ject from the commencement of germination to the close of its allotted period of life, to certain definite laws of develop- ment which are impressed on the cells of which that seed or spore consists. If we consider the cells collectively as associated together in masses, constituting definite organs, the regularity and fixity of form assumed by those organs, shows that a certain definite number of cells must be developed to form them, and that these cells must attain a determinate amount of expansion; for growth, or the enlargement of the organs of plants, certainly appears to be as much the result of the expansion of cells already existing, as of the formation of new cells. But the cells themselves, regarded individually, exhibit a series of phenomena which prove that they are subject to laws of development as rigid and invariable as those which govern them collectively. The primitive form of all cells, whether animal or vegetable, is that of a closed spherical vesicle or utricle. There is no plant, or organ of a plant, which is not at the commencement of its growth, fabricated exclusively of cells which approach more or less to that of a sphere in form. If we examine a bud, a young leaf or rootlet, with the microscope, in the first stages of growth, we shall find that cells which retain in a great measure their primitive sphericity, and present the same uniform 32 THE TISSUES OF PLANTS appearance in their external configuration, constitute the substance of each of these organs. At this stage of growth the cells are all apparently the same, and endowed with similar functions; but that this is not really the case, is shown by their subsequent behavior in their after develop- ment. It is only in plants which are very low in organi- zation, such as algae and lichens, that the cells permanently retain this primitive and uniform appearance; in vegetation of a higher grade, this uniformity speedily disappears, and the individuality of the cells becomes manifest as growth progresses. Whilst some of them continue spherical, others take a much higher degree of development, and be- come gradually transformed into woody fibre, vascular tissue, and spiral vessels. We say that certain determinate cells only, thus change their character. This is apparent on the cross section of the stem of any herbaceous exogen, which has just begun to grow, and to unfold its first sets of leaves. It will be seen that the cells in the centre and towards the circum- ference of the stem, which form collectively the pith and the bark, together with those of the medullary rays, are only slightly altered by mutual pressure from the spherical form. Those, on the contrary, which constitute the wood, and which occupy an intermediate position between the bark and the pith, are so changed in appearance that it seems at first impossible to refer them to the same common type. If we examine a longitudinal section of the stem, the nature and extent of the transformation which the wood cells have undergone, will be rendered more apparent. It will be seen that the fibrous portion of the wood consists of elongated, and extremely attenuated cells, which taper to either extremity and lie together in bundles, and that there are intermingled with these fibres several varieties of COMPARED WITH THOSE OF ANIMALS. 33 vasiform tissue and spiral vessels, the last being particularly abundant in the neighborhood of the pith. Fig. 3. Longitudinal section of Italian reed, a, Cells of the pith ; b, annular ducts ; e, spiral duct ; d, dotted duct ; e, woody fibre ; /, cells of the herbaceous integu- ment, one of the epidermal layers. It is not difficult to follow this transformation through its successive stages, and thus to arrive satisfactorily at the im- portant physiological fact of the individuality of the cells. It is only necessary first to examine the stem or any other organ in the embryonic condition, and then at intervals, soon after active life has begun to manifest itself in the germ. If we observe the fibrous portion of the wood, for instance, when germination commences, we shall see that at first the fibre cells consist of a row of utricles somewhat more elongated than the neighboring cells ; gradually these 34 THE TISSUES OF PLANTS elongated utricles become lengthened into tubes, and the septa or partitions which separate them, and which in this instance are not absorbed, assume an oblique position with reference to their interior. The different varieties of vasiform tissue or ducts will be seen to originate like the woody fibre from a row of elongated utricles; but the membrane which forms the walls of the fibre cells appears to be more susceptible of ex- tension than that of the duct cells. Both the transverse and lateral walls of the row of utricles which form the fibre cells are elongated, and this takes place owing to the great tenacity and extensibility of ..the walls of the several cellules, without any rupture or open communication be- tween them being effected. Hence it is that the fibre cells overlap each other at their extremities, or are as it were spliced together, and their calibre or bore must necessarily diminish in proportion to the degree of their attenuation. It is in fact reduced to the very finest degree of capillarity, so that the tubular character of the fibre cells can only be verified by employing the very highest powers of the best microscopes. The parietes of the row of utricles which originate the several varieties of vasiform tissue or duct cells, on the other hand, will not submit to a similar degree of tension ; on the contrary, a very slight degree of elonga- tion is sufficient to rupture the cross walls of the several cells, so as to form a continuous communication between them. An uninterrupted tube with a conspicuous calibre or bore, is the natural result. These ducts are generally situated on the inner side of the circle of fibre cells, and their open mouths are not unfrcquently visible on the cross section without the aid of the microscope in the form of rounded openings or pores. In their earliest condition, the cells of animals, like those COMPARED WITH THOSE OF ANIMALS. 35 of plants, present the same uniformity of appearance in their external configuration. Some of them maintain this condition throughout the life of the animal, and are the in- struments by which the strictly vital operations are carried on ; others rapidly undergo a change of form in accordance with those laws of growth to which they are individually subject. In this respect precisely, the same laws govern both the animal and vegetable world. " A globular mass," says Carpenter, " containing a large number of cells is formed before any diversity of parts shows itself ; and it is by the subsequent development from this mass of different sets of cells, of which some are changed into cartilage, others into nerve, others into muscle, others into vessels, and so on, that the several parts of the body are ultimately formed." There is, however, one distinction between the cells of plants and animals which must not be overlooked. It con- sists in the fact that the cells of plants are rnu^h larger than those of animals, and retain all the characteristics of cells throughout the life of the plant, so that a cross section of any part of the vegetable fabric will at any time show them. But the cells of animals rapidly undergo a development into tissues in which the cellular form wholly disappears. Hence it is that the cellular origin of many of the .animal tissues can only be detected in the ovum ; in the fully developed embryo all appearance of cell and nucleus has vanished. Thus whilst the cellular origin and structure of plants has been long known, that of animals is to be enumerated amongst the discoveries of modern times. As an instance of this gradual obliteration of the nucleus and cell wall, we refer to those cells which originate the more permanent and solid parts of the animal body ; such, for example, as the teeth of man, or the shells of the mol- 36 THE TISSUES OF PLANTS lusca. At first these parts consist of cells more or less closely connected together, either by a general enveloping membrane, or by an intercellular substance which holds them together by its adhesive properties. Fig. 4. Fig. 4 represents a portion of one of the animal layers included between the calcareous laminse of a bivalve shell ; in which are |>etual snow, the vegetation becomes wholly cryptogamous, and similar to that of the arctic regions. M. Mirbel has therefore very properly compared the terrestrial globe to two immense mountains, whose bases are united at the equator, and whose summits are the arctic regions around its northern and southern poles. . . 168 THE GEOLOGICAL SUCCESSION CHAPTER X. ON THE GEOLOGICAL SUCCESSION OF PLANTS AND ANIMALS, OR THEIR DISTRIBUTION IN TIME. In the preceding chapters we have endeavored to show that the operations of organic law are the same in plants and animals. In order to render the argument complete, it is necessary to consider them in the order of their ap- pearance on the earth's surface ; and for this purpose we must examine their fossil remains and their position in the rocks. The study of these remains constitutes the science of Paleontology — one of the most essential branches of Botany and Zoology. By this science we are taught that the present arrange- ments of land and water, and the forms of animal and vege- table life on the earth's surface, are the result of a long succession of antecedent changes of which the earth's crust has preserved the memorial. The History of the Earth has been written in its strata, which have been very properly termed " the leaves of the stone book." But the language left on these stony pages can only be interpreted by a care- ful and accurate knowledge of the living creation, and of the laws which now govern the distribution and development of species. Natural History is the alphabet of geology. The highest attainments in the natural sciences are re- quired for these researches. The knowledge of Botany which is required to throw light on fossil plants, must be both varied and extensive. It is obvious that the Linnaean system is of no use in deter- OF PLANTS AND ANIMALS. 169 mining genera and species, because it is founded on charac- ters which have not been preserved, viz., the different parts of the flower. Fossil plants are not so easily determined as recent species, because their parts are usually separated from each other. It is very seldom that any traces of their reproductive organs are left. Fragments of stems, leaves, and occasionally seeds, are the only data by which the plant can be determined. We have to fall back, therefore, on our knowledge of the natural system. There must be a thorough acquaintance with the different natural orders, and a familiarity with vegetable anatomy. There must be a competent knowledge of the minute structure of all the organs of plants, such as their root, stem, leaves, bark, and fruit, and of the markings which they exhibit on their exterior surface, together with some general ideas of the vegetation of tropical climates as well as of cooler latitudes, before the living affinities of the fossil plant can be deter- mined. As fossil plants are generally found in detached frag- ments, it is necessary to reconstruct the plant as completely as possible, and to determine the relations of its several portions to each other. It is evident that this must be a very difficult task -, but it is a very necessary one, for the neglect of it has led to a needless multiplication of fossil species, portions of the same plant having been described as sepa- rate species or genera. A knowledge of Comparative Anatomy is also necessary. To a person unacquainted with this science it may appear impossible, that from a single fragment of a fossil bone or tooth, Naturalists are able to determine the general character of its skeleton, and from thence to infer its appearance and mode of life. Yet all this is true. If we find, for example, a single fossil tooth, if it be a molar, it is sufficient to indi- 15 170 THE GEOLOGICAL SUCCESSION cate the mode of life of the animal to which it belonged, and to show that it fed on vegetables, as the other organs of the body constantly correspond in structural adaptation to the same function. There is the utmost harmony and adaptation of parts to each other amongst the several bones of the skeleton, and hence each, taken by itself, indicates and gives form, to all the others. This has been shown by the acute and laborious researches of Cuvier and Owen. There is every reason to believe that the history of the development of vegetation on any barren rock, or newly formed coral island, illustrates those stages by which the earth itself became covered with verdure. The first vege- table denizens of the rocky surface in modern times, are usually cryptogamous plants, such as crustaceous lichens, these are succeeded by the foliaceous species, and by such mosses as Polytrichum commune, Hedwigia ciliata, and the different varieties of Leskia and Hypnum, plants which are of very humble growth, and of exceedingly simple structure, consisting, comparatively speaking, of only a few cells. The oxalic acid contained in the thalli of the lichens, to- gether with the oxygen of the atmosphere, slowly disin- tegrate the rocky surface, and successive generations of these lowly protophytes finally create a humus which gives birth to a more highly organized vegetation. The higher cryptogamia now make their appearance, Polypodium vul- gare, Asplenium trichomanes, Asplenium ebeneum, together with the Saxifrages, Arenarias, Aquilegia Canadensis and other phanerogamous plants. Such appears to be the order of nature — the cellular Cryptogamia preparing the way for ferns and flowering plants — the simple preceding the com- plex. That cryptogamous plants are the most ancient inhabi- tants of the earth ; that they existed anterior to the Pha- OF PLANTS AND ANIMALS. 171 nerogamia, and formed for a long succession of ages a lead- ing feature in the flora of the antediluvian world, is evident, if we consult the pages of geological history. It is true that the cellular Cryptogamia, such as lichens and mosses, are very seldom found in a fossil state ; but this is not to be wondered at, when we remember that the preservation of plants in this condition necessarily depends on their structure. The fossil Cryptogamia, which have a woody and vascular structure, have however, been preserved in the greatest abundance. The absence of organic remains in rocks is not always sufficient to enable us to state that these rocks were formed before animals or vegetables existed, since the late Prof. Forbes has shown that, even in the present day, there are depths in the ocean which are destitute of organic life. Hence rocks deposited at such depths might contain no organic remains. Fossil plants are found in the aqueous and stratified for- mations, which have been divided into three great groups, the Paleozoic, the Secondary, and the Tertiary. The Paleo- zoic rocks include the Silurian, Cambrian, and Old Red Sandstone and Carboniferous formations. In the Silurian, Cambrian, and Old Red Sandstone we meet with the remains of marine plants, and also a few terrestrial species. In the Old Red Sandstone of Scotland, Miller has detected fucoid ferns, and in the same formation at Oporto, Bunbury has found Pecopteris cyathea, P. muricata, and Neuropteris tenuifolia, ferns which are closely allied to those of the car- boniferous period. There was land, therefore, as well as water at this remote epoch, although the abundance of fishes and marine plants seems to indicate that the sea covered the greater part of the earth's surface. Towards the close of the paleozoic period, however, land 172 THE GEOLOGICAL SUCCESSION plants appear to have been developed on an enlarged scale. Coal owes its origin to the abundant vegetation of this era; for it is now universally admitted that this substance is of vegetable origin. This the microscope has fully de- monstrated. In some kinds of coal, punctuated woody fibre has been detected, in others dotted and scalariform tissue, as well as cells of various kinds. The occurrence of dotted and scalariform vessels indicates the presence of ferns and their allied forms, such, as Sigillaria, Stigmaria and Lepi- dodendra, whilst true punctuated wood implies the pre- sence of Coniferae. Impressions of these plants are abundant amongst the argillaceous and sandy beds of the carboniferous system. About one hundred and fifty species of fossil ferns have been distinguished by Botanists in the coal system of Eng- land, and many of the fronds of these ferns have been clearly ascertained to have fallen from the stems of tree- ferns, which grew at the time that the coal was deposited. The Lepidodendrons were gigantic Lycopodiums, or club mosses, which rose to the height of sixty feet, although the representatives of these plants are now mere herbs. In the Secondary formations we meet with a greater num- ber of Coniferse and Cicadacese, whilst ferns and Lycopo- diacese are not so abundant, and less gigantic in their growth. The Tertiary period is characterized by an abundance of Dicotyledonous and Monocotyledonous plants, especially palms. Many of the fossil plants of these deposits, such as pines, elms, beeches, and maples, may be referred to genera at present existing, and merely present specific differences. The general result of all researches in fossil botany tends to prove that the early vegetation of the globe consisted of OF PLANTS AND ANIMALS. 173 plants of extreme simplicity of organization. The more ancient the geological formation the greater is the differ- ence between its fossil plants and those now living; whilst on the other hand, the Tertiary deposits which are, com- paratively speaking, recent in the history of creation, con- tain in addition to species now extinct, botanical remains which are identical with species now living. There has therefore been a gradual approximation of vegetation to its present condition. There appears to have been a similar progression in the animal creation. All naturalists admit that the animal re- mains found in the Primary or Paleozoic rocks are charac- terized by great simplicity of organization, and that the animals of this period present the least resemblance to those now living. The articulata are mostly trilobites — animals which evidently belong to the lower order of the Crus- taceans. There is an incompleteness and want of develop- ment in the form of their body, that strongly reminds us of the embryo among the crabs. The class of insects is entirely wanting. The radiata are represented by the Crino- idea, or lily-like zoophytes, animals remarkable for the sim- plicity of their organization, and the peculiarly complicated structure of their skeleton. The body of these Crinoids was supported on a long and flexible column, which was attached to a rock or some other hard substance, at the* bottom of the sea. This column was composed of an im- mense number of joints, through which an aperture de- scended from the stomach to the base or support. The bodies of the Crinoidea, like that of the Hydra, were sim- ple digestive cavities surrounded with jointed tentaculse of the same structure as the stem, which the animal had the power of spreading abroad for the purpose of grasping its prey. These animals belonged to the class of Echinoderms, 15* 174 T^HE GEOLOGICAL SUCCESSION represented at present by the star fishes and sea-urchins, a far more highly organized race. Numerous brachiopod molluscs, the lowest of the class, have been discovered in the Paleozoic rocks. The class of worms is represented by a few serpulse. But the most convincing proof of the organic inferiority of the first animal inhabitants of our globe is afforded by the remains of the fossil vcrtebrata of this epoch which are those of a low order of fishes. These were then the most highly organized animals. Hence the period has been called by Agassiz, the AGE or FISHES. There was as yet neither reptiles, birds, nor mammals. The sea appears to have covered the greater portion of the earth — an ocean without, a shore. The animals were all aquatic, and the vegetation marine; and " among the aqua- tic population no sound was heard. All creation was then silent/7* Towards the close of the paleozoic period, the earth ap- pears to have presented the aspect of a vast ocean studded with an immense number of islands, which were covered with a luxuriant vegetation, consisting principally of arbor- escent ferns, Equisetacese, Calamites, Lycopodiacese, and Coniferae — plants of very simple structure, but of gigantic size. It was during this geological era that the coal was deposited. The animals of the carboniferous formation resemble, in many respects, those of the paleozoic epoch. The crus- taceans, however, have evidently improved. In addition to the trilobites, we have the horse-shoe crabs, and other gigantic forms. We also meet with traces of insects and scorpions. We come now to that immense period in the natural history of the earth, which geologists have called The Secondary Age, or the AGE OF REPTILES. The * Louis Agassiz. OF PLANTS AND ANIMALS. 175 carboniferous rocks have been included within the geologi- cal formations of this period by some geologists, because they contain the remains of the first land animals ; whereas in the paleozoic age, the animals were altogether marine, breathing by gills. Reptiles, however, are not found in the coal measures, and do not make their appearance until about the time of the deposition of the New Red Sandstone, which took place immediately after the formation of the carboniferous rocks. The tracks of a gigantic Batrachian animal, a creature allied to the frog, have been left on the New Red Sandstone of Pennsylvania and Germany ; enor- mous aquatic birds have also left the impression of their footsteps on the same rocks in Connecticut. The reptiles seem to have attained their maximum de- velopment during the Oolitic period. We find in this for- mation those enormous amphibia known by the names Ichthyosaurus, Plesiosaurus, Megalosaurus and Iguanodon, animals somewhat allied to the lizard and crocodile in structure. But the most wonderful relic of the age of reptiles, is the Pterodactylus, which resembled a gigantic bat, and is thought to have been capable of flying. The trilobites are now extinct ; but in the upper stages of the Oolitic, we meet with tortoises and also the impressions of several families of insects, among which dragon flies and beetles are conspicuous. All the invertebrated animals, including the mollusca, the articulata, and the radiata, are largely represented. The peculiar forms of the paleozoic age have nearly all disap- peared, and are replaced by creatures whose organization is adapted to the new conditions. Of the brachiopod mol- luscs, only one type is abundant, that of the Terebratula. The G-asteropods display a great variety of species, and also the Cephalopods, among which the Ammonites are the 176 THE GEOLOGICAL SUCCESSION most prominent. The Belemnites also abound, creatures resembling the cuttle fish. The polyparia were very abun- dant in the seas of the Oolitic period. Whole rocks are entirely formed out of the remains of these animals. The crinoids are not quite so numerous as in former ages; but star-fishes abound, and an extraordinary and beautiful va- riety of sea urchin with large spines, the Cidaris coronata. The animals of the Cretaceous period bear the same gene- ral characters as those of the Oolitic, but with a more marked tendency towards existing forms. It is true that there is some evidence of the existence of mammalia, but they are few and insignificant. The only traces of mam- malia consist of two or three marsupial animals — creatures allied to the opossum. Throughout the whole of this im- mense period of time, the class reptilia was the preponde- rating form. The lower forms of both animal and vege- table life attained a gigantic development. " With flocks of pterodactyles flying in the air, and shoals of no less mon- strous ichthyosauri and plesiosauri swarming in the ocean, and gigantic crocodiles and tortoises crawling on the shores of the primeval lakes and rivers ; air, sea, and land must have been strangely tenanted in these early periods of our infant world/'* In those geological periods immediately following the deposition of the chalk, the last formation of the secondary age, the marine or amphibian reptiles are replaced by nu- merous mamm/dia of enormous size. These periods com- prise the different tertiary formations. This era has, therefore, been called the AGE or MAMMALS. The animal remains contained in these formations, strikingly approxi- mate in organic development to the species now living. « Dr. Buckland. OP PLANTS AND ANIMALS. 177 Many of the animals peculiar to former eras have passed away. The two great families of Ammonites and Belem- nites are no more. A multitude of species of molluscs are however found, which more or less resemble those of the present era, some of them being in fact identical with those in the adjacent seas. The most ancient of the tertiary deposits is characterized by the presence of great pachyderms, or thick-skinned ani- mals, among which we may mention the Paleotherium and Anoplotherium, creatures which approached the rhinoceros and tapir in the peculiarities of their organization. These fossil mammalia were first found in the gypsum beds of the Paris basin. Their bones were brought to Cuvier, who re-constructed them, and thus laid the foundations of the science of Paleontology. In these ancient tertiary deposits the earliest remains of monkeys have also been detected. The animals of the most recent tertiary formations re- semble, still more closely, those of the present epoch. The fossil remains represent all the terrestrial and aquatic spe- cies now living around us, and besides these, many -types now extinct, some of them of monstrous size, such as the mastodon, or fossil elephant, which is probably the last large animal which became extinct prior to the creation of man. By these revolutions of organic and inorganic nature was the world finally fitted for the abode of man. In the tertiary formations, which preceded the AGE OF MAN, no human remains have been discovered, no skeletons except those of the hitherto irrational denizens of the earth. Man is, therefore, comparatively speaking, a recent creation. If we consider the men of the earliest time as children in intellectual capacity, gradually advancing from a state of the most brutal ignorance, to a clear and rational per- 178 THE GEOLOGICAL SUCCESSION ception of their own capabilities, and their power of under- standing and controlling nature, we shall probably enter- tain an opinion which approximates to the truth. Whilst an untutored savage, man must have lived on the spontaneous -productions of the earth which he was unable at this period of his history to cultivate. Slowly did he arrive at a consciousness of his power over the other ani- mals, which at first disputed his dominion, but ultimately fled before him. This- stimulated pursuit. He became a hunter; especially as he found the skins of the wild inhabitant of the woods useful as an article of clothing, and the flesh of some of them nutritious. He chose for his dwelling the margin of rivers and lakes, or the sea shore, whose banks were more or less covered with plants, and whose waters abounded in fish. These he sought by force or craft to obtain. Even now the red Indians, in those portions of this con- tinent yet uncivilized, subsist in this manner; and such appears to have been originally the condition of the ances- tors of all civilized nations. To avoid the trouble of hunting perpetually, such ani- mals as he found useful for the supply of his wants, he endeavored to tame them. But the animals most readily subjugated were ruminants or plant-eaters, for which pas- ture ground must be provided. As a herdsman with his flock, from one place to another, he now wandered, dwelling in huts, until experience finally taught him to select those spots which produced the plants most useful for his animals, and sufficient in quantity to give them continuous support. He now erected for himself settled habitations, and re- sorted to stones and metals to give them greater durability and strength. United he put forth mightier efforts, he OP PLANTS AND ANIMALS. 179 built cities and founded empires. We have arrived now at the historical era. From the written accounts which have been transmitted to us, it is clear that the long reign of instinct is giving place to that of reason, and that the pre- sent period of the world's history is characterized by its slow development. The occurrence of human skeletons, and of coins and works of art, in modern fluviatile and marine deposits ; the preservation of the bones of the existing species of ani- mals, and of the leaves and branches of plants now grow- ing on the earth's surface, in the various geological forma- tions now in progress, shows the immutability of nature, and proves that the same enduring monuments of the pre- sent state of things will be transmitted to future ages. When the beds now forming in the existing seas shall be elevated above the waters and covered with woods and forests; when the deltas of our rivers shall be converted into fertile tracts, and become the sites of towns and cities ; in excavating the earth thus newly created, there is little doubt that the then existing races of men will discover the same indelible records of the physical history of our times, as we have now of that of former ages. The Linnsean maxim, "Natures mirandaest maxime in minimis," nature is chiefly to be admired in the least things, is as yet only partially appreciated by a few distin- guished minds, although it should never be lost sight of in the investigation of vital phenomena. If it be philoso- phical to pursue researches in the physical sciences by ex- periments and observations on the properties of inorganic matter ; it would seem to be equally in accordance with the principles of science, in the study of organic nature, to adhere as closely as possible to the plan of nature, and trace her operations in the simpler forms of life before we 180 THE GEOLOGICAL SUCCESSION, ETC. attempt the study of those that are more complicated. The development of the simple before the complex, appears to have ever been the plan of nature, whether her operations be traced in time or through the dark geological periods of the past; and whether we contemplate the successive phases through which life has already passed, or the organic phe- nomena of the present living races of plants and animals, we see everywhere evidence of the immutability of nature, and the uniformity of her organic laws. THE END. 14 DAY USE RETURN TO DESK FROM WHICH BORROWED BIOLOGY LIBRARY TEL. 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