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TEXT BOOK 
 
 OF 
 
 atural History. 
 
 by ADRIAN J. EBELL, Bli.B., M.D. 
 
 PART x. 
 
 ENDING TO THE STRUCTURAL FEATURES OF CLASSES IN TH 
 ANIMAL KINGDOM. 
 
 ebell & CO . 
 
 Publishers of School and Popular Scientific Works, 
 Room 18, Cooper Union Building, 
 
 NEW YORK. 
 
Entered according to Act of Congress in the year 1870, by Adrian J Isbell, 
 in the Office of the Librarian of Congress, at Washington. 
 
 Stereotyped and printed by 
 ^olhemus <Sc Pearson, 139 Pulton St., N. V. 
 
*=? 
 
 590 
 
 Fir3t 
 
 I 
 
 J 
 
 PREFACE. 
 
 ThIe following pages were published by the author for 
 se i.|n the classes and schools to which he lectures on 
 Natu ral History. Meeting that end, they will have an- 
 weredi the special purpose for which they were prepared. 
 If, hoyvever, the plan he has adopted for his own system 
 of ins/truction, may chance to please his co-laborers in the 
 work, \ it will rejoice him to share with them in its results. 
 
 He would beg, in this connection, the privilege of ex¬ 
 pressing his most heartfelt thanks to his many patrons— 
 j principals of schools and seminaries in all parts of the 
 land , especially in the cities of Philadelphia, New York, 
 Balt imore and Troy—for the kind support and counten- 
 ^Incetf with which they have encouraged his labors for the 
 past J five years ; for if any merit exist in this effort, it is 
 ^_,the Jresult of their fostering, and has been drawn forth by 
 —them words of encouragement and approval. 
 
 3 f 
 
 ^ In this number the department of Zoology has been con- 
 -sideried only as far as the Classes, but it is hoped that by 
 ‘^th ' 
 
 /jjf‘ Tc 
 pres 
 
 CM 
 
 G) 
 
 CM 
 
 summer of ’71 the major part, if not the whole, of the 
 xt Books of Natural History” may be ready for the 
 s. 
 
 N] £w York, December 1st, 1870. 
 
CONTENTS 
 
 w 
 
 ChaiK 
 
 3? AH, T I. 
 
 Page 
 
 Preface . 4 
 
 Introduction—General Review of Natural Science 5 
 
 Plan of N atural History.8 
 
 Organic and Inorganic Matter.12 
 
 Divisions of Inorganic Matter.16 
 
 Divisions of Organic Matter.18 
 
 Methods of Study—Zoology.22 
 
 Generation—Methods and Organs of.25 
 
 Digestion.28 
 
 Respiration.30 
 
 Organs of Respiration.32 
 
 Circulation.33 
 
 Sensation and Nervous Systems ... ... 35 
 
 The Five Senses .37 
 
 Motion.40 
 
 Systems of Classification.41 
 
 Methods of Study—Classification and Natural His¬ 
 tory .43 
 
11 
 
 CONTENTS. 
 
 Chap. 
 
 XVII. 
 
 XVIII. 
 
 XIX. 
 
 XX. 
 
 XXI. 
 
 XXII. 
 
 XXIII. 
 
 XXIV. 
 
 XXV. 
 
 XXVI. 
 
 XXVII. 
 
 XXVIII. 
 
 XXIX 
 
 XXX. 
 
 XXXI. 
 
 Page 
 
 46 
 
 OH* 
 
 v 
 
 
 Type of Protozoa. 
 
 Protozoa—Nervous System and Organs 
 
 Sense. 
 
 Protozoa—Natural History. 
 
 Type of Kadiates. 
 
 Radiates—Nervous System and Organs d k £ 
 
 Sense. 
 
 Type of Mollusks. 
 
 Mollusks—Respiration and Circulation—Nei,_ 
 
 vous System. 
 
 Mollusks—Integument or Shell of ... . 
 
 Articulates—Arrangement of Rings . . . 
 
 Articulates—Nutritive Organs. 
 
 Articulates—The Nervous System—Organs of 
 
 Sense and Natural History. 
 
 T)pe of Vertebrates. 
 
 Vertebrates—Circulation. 
 
 Vertebrates — Nervous System — Organs of 
 
 Sense . 
 
 Vertebrates—Organs of Motion—Bony System 
 —Engravings of Typical Vertebrse and 
 Skeleton. $7 
 
 49 
 
 51 
 
 53 
 
 56 
 
 59 
 
 61 
 
 64 
 
 68 
 
 70 
 
 72 
 
 76 
 
 79 
 
 82 
 
 92 
 
 95 
 
 XXXII. Vertebrates—Muscular System 
 XXXIII. Table of Classes ... 
 
TEXT BOOK 
 
 OF 
 
 NATURAL HISTORY. 
 
 CHAPTEE I. 
 
 INTRODUCTION. 
 
 Natural History, in the wider meaning of the term, 
 teats of the appearances and connections of nature as a 
 whole, or of its several departments by themselves. It is 
 us Tally, however, understood to mean the study of plants 
 and animals. 
 
 Before we enter into the specific study of the animal 
 ki lgdom, we shall review its relations with the other de- 
 pi rtments of nature. 
 
 The book shall be divided into three parts : 1st. The 
 0 Ejects ; 2nd. The Plan ; and 3rd. The Methods of 
 Si tdy of Natural History. 
 
 The first of these, though of most importance, will oc- 
 
 *py much the least space and time in consideration, 
 
6 
 
 INTRODUCTION. 
 
 1st.—O bjects oe Study. 
 
 The chief objects to be sought after in the study of 
 nature, especially in the first general perusal of the sub- £ 
 ject, are two: First, The Development of our observing 
 powers / end Second, An acquaintance with the prime \ 
 laws and divisions of Nature. Besides these, are all the 
 more special aims and ends of subsequent study; but our 
 attention in this work shall be confined to the furthering, 
 chiefly, if not alone, of the ends mentioned. 
 
 The observing powers , through the medium of the five 
 senses, are the first faculties put forth in the development 
 of the mind, the first educators of our reflective faculties, 
 and the only methods we have of gathering facts of na¬ 
 ture from which to educe the laws and principles of 
 science. 
 
 A. — The training of the observing powers is attained 
 only by means of thinking as we perceive. 
 
 The various objects in nature and art may present them¬ 
 selves to our senses without producing any greater effect 
 in our mind, or on our powers of observation, than they 
 do upon the horse or ox, until we learn by thought to 
 group and associate them in their various divisions. 
 
 This is the chief advantage to be gained by fixing! in 
 our minds the general tables and outlines of Nature mat 
 will be given throughout this work ; and it cannot be too 
 urgently pressed upon the learner, that the first tallies 
 (I, II, Y, VI) be clearly memorized. 
 
 B. —The prime laws of nature are the methods of ac- ^ 
 tion of forces around us, and the relations of objects to 
 
 J 
 
 4 
 
INTRODUCTION. 
 
 7 
 
 each other. While a complete acquaintance with these 
 would require a review of all departments of Nature, we 
 have, as it were, a compendium of all departments in the 
 Structure and Life of the Animal Kingdom . 
 
 Therefore Zoology, treating (1st) of the structure and 
 life , (2nd) the classification , and (3rd) the distribution , 
 relations and uses of the animal kingdom , is the depart¬ 
 ment of Natural Science chosen, in preference to any 
 other, to be the channel through which to attain these two 
 chief ends. 
 
8 
 
 PLAN OP NATURAL HISTORY. 
 
 CHAPTER II. 
 
 PLAN OF NATURAL HISTORY. 
 
 • 
 
 The plan or arrangement of Natural History comprises 
 a review of the relations and connections of the different 
 departments of nature considered as a unit. 
 
 Nature in its great variety of forms and appearances, is 
 most intimately connected throughout; and the different 
 sciences and departments of human knowledge are but so 
 many points of sight of a single creation. 
 
 This unity in nature extends, not merely to its different 
 departments on this earth, but, as far as our observations 
 have been able to reach, throughout the infinity of space. 
 The laws of physical, and even of chemical science, as 
 lately revealed by the spectroscope, are the same in bodies 
 remote in space as on our planet. 
 
 Reasoning from analogy, we might bespeak a similarity 
 also for the laws of vital force. We propose in this con¬ 
 nection to give merely an outline of this plan ; comme nc¬ 
 ing with nature as a unit, and tracing out its prime, or 
 chief divisions. 
 
 Although, an infinite variety of forms and appearances 
 surround us, and nature seems inexhaustible in her shapes 
 and phenomena, yet all may be so classified, that we dan 
 review the whole in its larger divisions and groups, ass a 
 single creation: hence before we commence the study of 
 any special department we shall review the comprehens ive 
 plan of the field, first in the following table, and aft*er- 
 
 0 
 
PLAN OF NATURAL HISTORY. 
 
 9 
 
 : 
 
 wards in the chief points of relation and difference be¬ 
 tween its several parts; that we may entertain a clear con¬ 
 ception of the whole of nature as a unit, designed and 
 created by a single God. 
 
 All that our senses can perceive of nature may be sepa¬ 
 rated into the two divisions of Matter and Force, wholly 
 different in their character, though inseparable in their 
 existence. 
 
 Each of these are still further distinguished by their 
 kind or character, viz., Force, into physical, chemical, and 
 vital; and Matter, into organic and inorganic. 
 
 Table I. 
 
 Nature 
 
 Force . . 
 
 f Physical, 
 
 i 
 
 <( Chemical, 
 
 L Vital. 
 Organic . 
 
 ( Plants, 
 
 ^ Animals. 
 
 Matter 
 
 < 
 
 Inorganic . 
 
 'Elements, 
 
 Metals, 
 
 Minerals, 
 
 Pocks. 
 
 We do not propose here to enter into any abstract 
 metaphysical discussion about the difference between 
 Matter and Force. 
 
 Whatever occupies space, and is tangible to our senses, 
 we call Matter; and any agent or power that is capable 
 of changing the condition of, or moving matter—Force. 
 We know this definition is incomplete, but if any one 
 will present a better, we shall gladly accept it. 
 
10 
 
 PLAN OF NATURAL HISTORY. 
 
 It is not within the province of Natural Science, nor 
 indeed, within the capability of man, to answer the 
 What and Why , in relation to the character and appear¬ 
 ances of Matter and Force. They are the embodiment, 
 or expression of an Infinite Creative Mind, beyond the 
 reach of human intellect; and so are themselves incom¬ 
 prehensible. We would request any one who questions 
 this to give us an exhaustive definition of physical, 
 chemical or vital force, or any one of their various 
 evincements, as gravitation, electricity, magnetism, or 
 of any particle of organic or inorganic matter, beyond 
 a description of their appearances to our senses. 
 
 It is of these appearances to our senses of Matter 
 arid Force alone that we can speak. 
 
 The entire field of Natural Science , then, contracts 
 itself into an observance of the appearances of Matter 
 and Force, and of their various relations ; or, in other 
 words, of the how objects and forces appear to our 
 senses and influence each other. The reasonings and 
 theories, which are not directly supported by observation, 
 belong to the metaphysical and speculative sciences. 
 
 Physical Force evinces itself at all times from objects 
 that are alone, and unassociated with others, as well as 
 in their combined conditions, £//., a piece of wood 
 or stone ever evinces the power of gravitation, cohesion, 
 etc., while they have to be brought into favorable rela¬ 
 tions and under favorable circumstances, to show forth 
 the chemical forces they are capable of, ey., an acid and 
 a base or alkali have an affinity for each other, but will 
 not evince it, except under the condition of solutions. 
 
 Physical and chemical forces may be, and doubtless are, 
 correllated forms of each other ; but Vital force is not as 
 
PLAN OF NATURAL HISTORY. 
 
 11 
 
 easily disposed of in that way ; else, we might produce 
 organic forms in our laboratories. Vital Force is the 
 power that produces and constitutes what we call the 
 life or living force of plants and animals, and by no 
 means merely another form of electricity or magnetism. 
 Names that of late have been made the scape-goats of 
 all our ignorance and every power or force that has 
 been thought inexplicable (though indeed no one is more 
 so than another), has been called electrical or magnetic. 
 
 In review, we might, then, distinguish these three 
 forces by their different conditions of action, thus— 
 
 Physical Force , existing in all nature and through¬ 
 out all space, evincing itself from all objects, at all 
 times, and under all conditions, as gravitation, electri¬ 
 city, magnetism, cohesion, repulsion, etc. 
 
 Chemical Force , requiring for its evincement a cer¬ 
 tain favorable relation of objects called chemical affin¬ 
 ity, and certain circumstances or conditions, as heat or 
 moisture, under wdiich alone the force will show itself, 
 or act, eg , salt and sand have no chemical affinity 
 and will not set up chemical action under any circum¬ 
 stance, but tartaric acid and soda have; yet, brought 
 together dry, will not affect each other ; if moistened, 
 however, tiny at once set up chemical action. So, also, 
 there is a chemical affinity between the organic struc¬ 
 ture of a piece of wood and the oxygen of the air, 
 but a certain degree of heat is necessary to commence 
 this action, and then we say the wood burns. 
 
 Regarding Vital Force, we can merely say that it is 
 the living force of the plant, or the animal / always 
 associating with itself, in its action, both physical and 
 chemical force, but itself different from either. 
 
12 
 
 ORGANIC AND INORGANIC MATTER. 
 
 CHAPTEE III. 
 
 ORGANIC AND INORGANIC MATTER. 
 
 Matter, we found, divided into the two great divisions, 
 Organic and Inorganic ; differing from each other chiefly 
 in four respects: 
 
 1st. Structure. 
 
 2d. Origin. 
 
 3d. Food, or material of which it is built. 
 
 4th. Life, or manner of existence. 
 
 1st. Structure.— Organisms (Plants and Animals) are 
 composed of cells, eg., if a thin slice of animal or vegetable 
 structure be examined with the microscope it would appear 
 to be composed of a great number of- small bags, which 
 in their earlier stages of growth are spherical, but assume 
 all varieties of shape, as they are pressed out of form by 
 being crowded together. A cell is composed mainly of 
 the four elements : Carbon, Oxygen, Hydrogen and Nitro¬ 
 gen. The first three of these—Carbon, Oxygen and Hy¬ 
 drogen—exist in all organic cells, while the fourth—Nitro¬ 
 gen—is found only in animal structure and the seed and 
 coloring matter of plants. Although the form and ap¬ 
 pearance of cells admit of no distinction, there is a special 
 life peculiar to each species of plant and animal, that 
 governs their arrangement and invariably produces a 
 structure similar to that from which they originated. 
 
 The living is different from the dead cell. The mate¬ 
 rial of the dead cell can be taken up by the animal and 
 worked over into the living cell, but the plant requires its 
 
ORGANIC AND INORGANIC MATTER. 
 
 13 
 
 partial separation before it can take it up. This we shall 
 hereafter find to be a chief point of difference between 
 plants and animals. Every organism, that we call alive, 
 is composed of both living and dead cells. The living 
 cells are those that are in a formative state, and are em¬ 
 ployed in building the various parts of the structure; 
 while all parts that are finished, and are not in the process 
 of formation, are composed of what we may call dead 
 cells. 
 
 In the resolution of these into simpler compounds, or 
 the elements of which they are made, the force that held 
 them together is given forth in the form of physical or 
 chemical force ; but these forces are unable to reconstruct 
 the cell; hence vital force, the only one capable of build¬ 
 ing an organic structure, exists in the living cell alone. 
 
 Inorganic matter , on the other hand, is not composed of 
 cells, and hence does not evince the results of vital action. 
 It is made up of the accretion of infinitesimal particles, 
 called atoms , in three degrees of familiarity,*?*, e.: 
 
 1. In a positive attraction for each other—forming a 
 Solid—the degree of attraction of the particles determining 
 the hardness of the solid. Every kind of inorganic matter 
 permitted freely to solidify without restraint, will assume 
 a definite form peculiar to itself called a Crystal. 
 
 2. The atoms being in a negative state to each other, 
 and so freely yielding to every influence as a Liquid. 
 
 3. In which the atoms repel each other, as a Gas or 
 Vapor, the latter (vapor) capable of being reduced to a 
 liquid or solid by cold or pressure, as carbonic acid gas, 
 the vapor of water, &c., and the former (fixed gas) not 
 
14 
 
 ORGANIC AND INORGANIC MATTER. 
 
 reducible to a liquid by any degree of cold we are ac¬ 
 quainted with. 
 
 2d. Origin.— Organisms commence their existence as a 
 single cell, which (except among the lowest forms of plants 
 and animals) bear no resemblance whatever to the struc¬ 
 tures they are to build, and arranged by the special vital 
 force of each kind, construct the countless forms of plant 
 and animal structure according to the fixed and definite 
 patterns of beings from which they sprang. 
 
 This vitality is transmitted down from parent to off¬ 
 spring in an unremitted chain, and creative power alone is 
 capable of calling forth a new organism from inorganic 
 matter, or of relighting the flame when once totally ex¬ 
 tinguished. Inorganic forms are neither built of cells nor 
 commenced from a single cell; but are constructed by the 
 accretion of homogeneous particles from without. 
 
 The minutest microscopic crystal may be of the same 
 form as the largest one of the same material. 
 
 3d. Food, or Material of Construction. —Organisms 
 are capable of taking and working into their own struc¬ 
 ture materials of different kinds. In other words they are 
 heterogeneous in their composition; while inorganic mat¬ 
 ter, in assuming the forms of crystals, is homogeneous, or 
 makes use of one kind alone, though several others may 
 be imbedded in it, <?//., a crystal of salt or quartz may 
 imbed in itself, or have commingled with it, several other 
 substances by mechanical union ; but nothing but salt or 
 quartz can be of avail in the forma ion of a crystal of 
 either one : while a plant or an animal will take to itself 
 as food and incorporate into its own being a variety of 
 
ORGANIC AND INORGANIC MATTER. 
 
 15 
 
 substances united together by the three-fold power of 
 physical, chemical and vital force. 
 
 The plant will take from the atmosphere carbonic acid 
 gas, and from the soil, water, with various minerals dis¬ 
 solved in it, and from these, construct its numerous cells 
 and organs. 
 
 The animal will take these elements, already bound to¬ 
 gether by the plant, and reconvert them into its own 
 structure. 
 
 The manner of arrangement of the material of growth 
 of the organic and inorganic is different The organism 
 grows from within , the inorganic mass from without. 
 
 In the interior of the plant or animal, the food is 
 prepared for the building of the structure, and thence 
 distributed to the several parts. But it is on the out¬ 
 side, and that directly from without, that the particles 
 are added for the construction of the crystal or concre¬ 
 tion of inorganic matter. 
 
 4th. Life, or Manner of Existence.— The inorganic 
 mass is stable , or, in other words, does not readily tend 
 to change or decomposition, while the organic structure 
 is continually changing during its life, and is ever on 
 the point of breaking up its combinations and return¬ 
 ing to its original elements. 
 
16 
 
 DIVISIONS OF INORGANIC MATTER. 
 
 CHAPTER IV. 
 
 DIVISIONS OF INORGANIC MATTER. 
 
 Inorganic matter may, for convenience, be considered 
 under the divisions of Elements, Metals , Minerals and 
 Rocks. 
 
 This grouping is, in a manner, arbitrary ; established 
 more for convenience than from natural differences. 
 We call an element that which, by either chemical or 
 mechanical means, we are unable to resolve into any 
 simpler materials; but future efforts may be able to 
 separate some that we now call elements, into yet others, 
 or show that several that we term such are but differ¬ 
 ent forms of the same element. 
 
 Elements combine with each other in two ways, i.e., 
 1st, mechanical mixture and 2d, chemical union; pro¬ 
 ducing in each an entirely different product. 
 
 Mechanical mixture consists of a mere commingling 
 of the elements, each element continuing unaltered in 
 the mixture, the same as a measure of corn and beans 
 may be mixed together, and the grains of each remain 
 whole and unchanged. 
 
 Such is the mixture of the elements oxygen and 
 nitrogen, in the formation of the atmosphere. 
 
 Chemical union is an intimate combining of the ele¬ 
 ments in such a way that the product is totally different 
 from either. While mechanical mixture may be insti- 
 
DIVISIONS OF INORGANIC MATTER. 
 
 17 
 
 tuted between any and all elements, chemical union 
 will take place only when there is a special attraction 
 between the elements, called chemical affinity, and that, 
 as stated above, only under certain favoring circumstan¬ 
 ces, as moisture or heat, eg., hydrogen and oxygen, 
 though commingled together in the right proportions, at 
 a low temperature, furnish merely a mechanical mix¬ 
 ture ; if the temperature be, however, raised to a cer¬ 
 tain point, they will immediately and violently combine 
 with each other chemically, and form a product, water, 
 wholly different in all its characters from either. 
 
 Pure metals are, indeed, also elements, and cannot be 
 resolved by chemical or mechanical means into simpler 
 ingredients. Yet few are obtained unassociated in some 
 slight degree with other elements. 
 
 Minerals are produced by the chemical association of 
 elements, as quartz from silicon and oxygen; water from 
 hydrogen and oxygen. 
 
 Rocks, in the full signification of the term, include any 
 and all masses of elements, metals or minerals, mechani¬ 
 cally commingled together, whether in the solid, liquid or 
 gaseous condition, as granite, the sand heap, the soft mud 
 of the river bank, or the atmosphere. 
 
18 
 
 DIVISIONS OF ORGANIC MATTER. 
 
 CHAPTER V. 
 
 DIVISIONS OF ORGANIC MATTER. 
 
 Organisms are divided into the two kingdoms of Plants 
 and Animals ; and the first question that occurs to us in 
 relation to them is : What is the difference between the 
 plant and the animal ? 
 
 The points of resemblance we have observed as consti¬ 
 tuting the characteristic features of organic structure. 
 
 It is often stated that the distinguishing feature is, that 
 animals are endowed with the powers of motion and feel¬ 
 ing, or sensation, while plants are destitute of both. 
 These differences exist only in the higher grades of each 
 kingdom ; but as we descend to the lower ranks we find 
 this rule wholly at fault, or even misleading us ;—a large 
 proportion of the lower animals are partially or wholly 
 destitute of feeling, while many microscopic plants sustain 
 a rapid and energetic motion ; as the Volvox-globator, and 
 some, as the Sensitive Plant and Venus Ely-trap, evince a 
 spasmodic action, resulting from a kind of a sensitiveness, 
 which, though not the same, is seemingly akin to that of 
 the lower animals. The fundamental difference between 
 the plant and the animal consists in— 
 
 1. Their respective kind of work / and 
 2 Their food. 
 
 It is the work of the plant in the economy of nature 
 to store up force, It is the province of the animal to 
 spend it. 
 
Divisions or organic matter. 
 
 19 
 
 The physical and chemical force expended in the living 
 and moving of the animal, are first laid up in the growing 
 plant. 
 
 In the living cell, vital, physical and chemical forces 
 are conjointly at work ; the vital force of the plant is 
 capable of la)ing up or storing away the physical and 
 chemical force, and the life of the animal is dependent on 
 this force, bound up by the plant, for its forces of motion. 
 
 Thus plants are the conservators of the force that all 
 animals are ever expending in the functions of life and 
 motion. 
 
 From this it is evident that there must be, as indeed 
 there is, a difference in the kind of food required and 
 taken by each kingdom. 
 
 Plants require and can take only that as food which is 
 inorganic, while every animal, from the microscopic ani¬ 
 malcule to the human system, requires and can subsist 
 only on food that has first passed through the construc¬ 
 tive agency of vegetable life and been made into a plant. 
 
 By this definition of food, we designate that from which 
 can be evolved motion in the living animal; inorganic 
 substances are necessary in large proportions as auxiliaries 
 to food, as water and other minerals, but from these the 
 living and moving powers of the animal cannot be ob¬ 
 tained. 
 
 While the plant can assimilate only inorganic food, it 
 cannot take any of it in its simplest elemental state, eg., 
 carbon, though the chief constituent of plant structure can¬ 
 not be taken up by the plant in its simple state, but has 
 
20 
 
 DIVISIONS OF ORGANIC MATTER. 
 
 to be first chemically combined with oxygen in the forma¬ 
 tion of carbonic acid gas : and so also nitrogen, though 
 ever bathing the plant in its free state in the ocean of 
 atmosphere that it lives in, cannot be taken up by the 
 leaf, and the plant will wither and die for the want of it, 
 unless presented to the roots dissolved in the water in its 
 binary condition of ammonia. 
 
 Oxygen and hydrogen are, also, ever present elements 
 of plant structure, but are received chiefly in their 
 chemically combined condition of water. 
 
 There is also a difference in the way in which plants 
 and animals take up their food. The plant receives it 
 into its system through the skin wall of its cells by 
 osmose / while the animal invariably first takes the 
 food into an interior cavity, permanently located or ex¬ 
 temporized at the time, as in some animalcules, and 
 then subjects it to a chemico-vital process of solution 
 called digestion, before it is fit to be absorbed by the 
 system. 
 
 We have thus reviewed the plan on which the dif¬ 
 ferent departments of nature are arranged, and observed 
 that throughout the whole there is an intimate con¬ 
 nection . 
 
 While this general review of the entire field, gives us, 
 as it were, a bird’s-eye view of nature, and is indispens¬ 
 able for an introduction to the proper study of any of 
 its special departments, each one of its branches has 
 methods of study peculiar to itself. 
 
 The numberless facts of nature are beyond the capa¬ 
 city of any mortal mind; but these methods of study, 
 
DIVISIONS OF ORGANIC MATTER. 
 
 21 
 
 to a certain degree, are easily and quickly attainable 
 by all. 
 
 To carry out this to the extent of the foundation we 
 have laid, would require a separate treatise on each of 
 the special sciences ; but we shall choose that branch in 
 which are evinced most of the laws and phenomena of 
 nature. 
 
 Zoology, or the study of the structure and life, classi¬ 
 fication, and distribution and relations of the animal 
 kingdom, is the only science that presents a compen¬ 
 dium of all departments of nature—of physical, chemi¬ 
 cal and vital force, and of organic and inorganic 
 matter. 
 
 We shall, therefore, next proceed to an observance of the 
 Methods of Study of the department of natural history 
 pertaining to animals. 
 
22 
 
 METHODS OF STUDY-SCIENCE OF ZOOLOGY. 
 
 CHAPTEE YI. 
 
 METHODS OF STUDY-SCIENCE OF ZOOLOGY. 
 
 The animal kingdom may be studied in relation— 
 
 1st. To its functions and structure. 
 
 2d. Its Classification and Natural History. 
 
 3d. Its Distribution and Eelations in Time, or Geologi¬ 
 cal History. 
 
 Any one of these departments, as evinced in even a 
 small order or family of animals, would furnish field and 
 material enough to occupy a lifetime of patient labor; but 
 
 the object of this volume is to present an Outline Sketch 
 of the methods by which the study of these departments 
 may be commenced. 
 
 The specialist would not find here what he may need to 
 aid him in furthering his research; but it is hoped the 
 general student or reader may have as it were a bird’s-eye 
 view of the entire field, with its prominent outlines mapped 
 out clearly before him: on any special portion of which, 
 having first scanned the whole realm, he may afterwards 
 alight and view its wonders and beauties with a closer 
 ken. 
 
 We shall now proceed to a consideration of each of 
 these three departments separately. 
 
 1st Functions and Structure . 
 
 The structure of an animal is always arranged according 
 to the requirements of its functions. In the principles of 
 
METHODS OF STUDY-—SCIENCE OF ZOOLOGY. 
 
 23 
 
 of animal mechanics, the simplest mechanism is employed 
 in performing any work, and hence we find the anatomy 
 of an animal made according to its physiology or work. 
 
 The place an animal lives in, its methods of locomotion, 
 the climate it must endure, its kind of food, and the way 
 it will have to procure it, the medium it will have to 
 breathe, whether water or air, the amount of pressure it 
 was intended to sustain, its duration of life, and the spe¬ 
 cial part in the economy of nature it was intended to fill 
 all separately and conjointly, determine not only the ex¬ 
 ternal appearance of an animal, but also the entire ana¬ 
 tomy of the interior. 
 
 The structure of animals is not according to a number 
 of patterns, but though there exist hundreds of thousands 
 of different forms, apparently in no way connected, yet all 
 these are variations of a single plan, or model system. 
 
 All animals have their organs developed out of this 
 model plan, according to the requirements of their life ; 
 even the microscopic animalcule, whose shapeless body 
 seems destitute of organs, has enough of this plan deve¬ 
 loped in itself to meet the wants of its plant-like life. 
 
 The following is a table of the organs of a model 
 animal, arranged according to its functions : 
 
24 
 
 METHODS OP STUDY—SCIENCE OP ZOOLOGY* 
 Table II. 
 
 Animal ^ 
 Functions 
 
 Motion. 
 
 ’ 1 . Skeleton for 
 Protection, 
 Leverage, 
 and 
 
 Support, 
 
 as Bones , 
 Shell , or 
 Skin, 
 
 2. Muscles. 
 
 Vegetative 
 
 Functions 
 
 , Y . C Nervous System, 
 sensation . < < 
 
 ' Organs ol Sense. 
 
 Organs of the 
 Digestive 
 System ; 
 Respiratory, or 
 Breathing 
 System ; 
 Circulatory 
 System. 
 
 Touch, 
 
 Taste, 
 
 Smell, 
 
 Hearing, 
 
 Smht. 
 
 " Nutrition . < 
 
 j' Organs of Generation ; 
 
 - Generation A Methods of Generation ; 
 
 [_ Development of Embryo. 
 
 It belongs to the province of Comparative Anatomy to 
 trace out these organs in their relations to the above model 
 plan; but we shall make a brief review of each function 
 and its special organs. 
 
GENERATION. 
 
 25 
 
 CHAPTER VII. 
 
 GENERATION. 
 
 1st. Generation is the function by which the young 
 of animals are produced and the species continued. 
 
 As the classification and history of animals depends 
 very largely upon their methods of reproduction, it is 
 essential that we should get a clear conception of this 
 subject before we proceed. 
 
 We would consider in this connection— 
 
 1st. The Methods of Generation. 
 
 2d. The Generative Product and its Development. 
 
 1st. Methods of Generation .—All animals are pro¬ 
 duced from parents like themselves, and so continue 
 their own kind in unvarying succession. 
 
 The next table gives us an outline of the differences 
 in this function : 
 
GENERATION on REPRODUCTION. 
 
 TABLE OF METHODS OF GENERATION. 
 
 Non-Sexual < 
 
 Table III. 
 
 Fissiparous. . . <{ 
 
 Gemmiparous 
 
 Sexual 
 
 Hermaphrodite . 
 
 Dioecious. 
 
 Parent splits — Each 
 part a new animal: 
 
 1. Transverse. 
 
 2. Longitudinal. 
 
 3. Irregular. 
 
 Parent splits and dis¬ 
 charges the young. 
 
 Budding upon the 
 parent stock. 
 
 Separated buds. 
 Gemmae or Sporules. 
 
 1. On all parts of 
 the body. 
 
 2. On one part or 
 organ only. 
 
 Both sexual organs on 
 one individual. 
 
 1. Self impregna¬ 
 tion. 
 
 2. Mutual impreg¬ 
 nation. 
 
 Sexes Distinct. 
 
 Laying eggs which are 
 hatched. 
 
 1. internal fecun¬ 
 dation. 
 
 2. Internal fecun¬ 
 dation. 
 
 Eggs hatched within 
 the maternal body. 
 Mammiferous, 
 
 Suckling the young. 
 Ovo- Viviparous 1 . Monotrematous. 
 
 2. Marsupial. 
 
 3. Placental, or 
 strictly Vivipa- 
 
GENERATION. 
 
 27 
 
 2d. The germ, is produced from the parent animal in 
 three ways, i.e. : 
 
 1. By the spontaneous division of one individual into 
 two or more parts, each of which may form a distinct 
 animal exactly resembling the parent—called Fissiparous 
 reproduction. 
 
 2. By the production of bitcls, either on the surface or 
 within the parent —Gemmiparous reproduction. 
 
 8. By the production of eggs, which may be matured 
 within or without the body of the parent —Oviparous re¬ 
 production. 
 
 The study of the development of the germ or embryo 
 is called Embryology. 
 
 Much that would be of value under this head the 
 size of this volume compels us to omit. More of it will, 
 however, l e brought on with the descriptions of the 
 types and classes of animals. 
 
28 
 
 DIGESTION. 
 
 CHAPTER VIII. 
 
 DIGESTION. 
 
 Digestion consists of the process by which the indi¬ 
 vidual animal is built up, and its waste of life and 
 motion repaired. 
 
 The digestive apparatus, unlike that of plants, where it 
 is always on the surface, among animals, is always in the 
 interior, and called the Alimentary Canal or Cavity. 
 
 It is of a great variety of forms and sizes, from a mere 
 sack or bag, made at the moment of use, and then again 
 closed up to give place to others in different parts of the 
 body; as among numbers of the animalculae (Amoeba, 
 sponge animals, &c.,) to the elaborate and complete system 
 of mouth-organs, such as tongue, teeth, salivary glands, 
 pharynx, oesophagus, stomachs, intestines, excretory or¬ 
 gans, absorbents, glands of secretion and excretion, as 
 liver, pancreas, spleen, &c. 
 
 The structure and condition of the digestive system indi¬ 
 cate, more than any other part, the habits and requirements 
 of life of an animal. The structure of the tongue and 
 teeth, the size and muscular strength of the alimentary 
 canal, especially the stomach, and the power of the attend¬ 
 ant organs to make their special secretions, indicate defi¬ 
 nitely the kind of food an animal requires, and hence the 
 kind of life it leads, for these organs are ever constructed 
 with special reference to these conditions of life. 
 
DIGESTION. 
 
 29 
 
 To a study of this system, then, we are indebted, not only 
 for an acquaintance with much of the greatest importance 
 and interest in relation to modern animal life, but also for 
 our entire sum of knowledge, of the life and habits of the 
 countless number of animals, that lived on the earth before 
 the appearance of man. 
 
30 
 
 RESPIRATION. 
 
 CHAPTER IX. 
 
 RESPIRATION. 
 
 Respiration or Breathing consists of the two-fold func¬ 
 tions : 
 
 1st. The evolution or giving off of carbonic acid gas ; 
 and 
 
 2nd. The absorption of oxygen. 
 
 The causes of these are, that in the economy or life of 
 the animal, there are continually disintegrating changes 
 going on, that produce carbonic acid gas; which is poisonous 
 to animal life, and is gotten rid of chiefly through the 
 medium of respiration ; and in the next place, oxygen is an 
 indispensable element for the construction, motion and 
 warmth of the being, and in the degree that the animal 
 is active and energetic in its motions, warm in its tempera¬ 
 ture, and delicate and subtle in its structure, will it require 
 the functions of respiration. 
 
 The animal structure is continually decaying during life, 
 as well as in death; and breathing is the act by which 
 most of the product of this decay is removed from the sys¬ 
 tem. “ Every development of muscular force, or of nervous 
 power, is accompanied by a destructive change in a certain 
 amount of tissue, to which change the presence of oxygen 
 is essential, and one of the products of the union of oxygen 
 with the elements of the nervous and muscular substances 
 is carbonic acid.” 
 
RESPIRATION. 
 
 31 
 
 Respiration is the only function,- through which this sup¬ 
 ply of oxygen, as well as the removal of carbonic acid gas, 
 is effected; and though the higher warm-blooded animals 
 are much more dependent on it than the lower, no ani¬ 
 mal life, whether of the land or water, can be supported 
 without it for any length of time. 
 
32 
 
 ORGANS OF RESPIRATION. 
 
 CHAPTER X. 
 
 ORGANS OF RESPIRATION. 
 
 The Respiratory Organs consist fundamentally of a 
 permeable or porous membrane , through which the free 
 oxygen of the air, whether from the atmosphere, or dis¬ 
 solved in water, and the gasses of the animal fluid may 
 change places with each other, by the mechanical law of 
 the interchange of gasses and liquids, called Osmose. 
 
 In some of the lower animals this is accomplished solely 
 by the delicate skin of the entire body, on the inner side 
 of which are the animal fluids, on the outer the air dis¬ 
 solved in the water in which the animal lives. But as we 
 ascend in rank in the animal kingdom, we find this deli¬ 
 cate expanded membrane confined to special parts of the 
 body, and two systems of organs added auxiliary to it, 
 i . e.: 
 
 1st. A set of organs for circulating the animal fluid along 
 the inner surface of the membrane. 
 
 This alone is added in those water animals that have the 
 power of free motion. 
 
 2d. All air breathing animals, and some stationary 
 aquatic animals, have a set of organs for changing the 
 material they breathe, either air or water. 
 
 These three sets of respiratory organs exist in all stages 
 of development, and adaptation to the different kinds of 
 animal life—as ciliary appendages, branchiae, gills, lungs, 
 etc, 
 
CIRCULATION* 
 
 33 
 
 CHAPTER XI. 
 
 CIRCULATION. 
 
 Circulation in the animal is the function by which the 
 fluids of the body are moved about, for the purposes of pu¬ 
 rification, or of building up the structure and repairing 
 waste. 
 
 This may be either directly through the thin walls of 
 the bags and organs, or along sets of tubes for exporta¬ 
 tion called Arteries , and importation called Veins, from a 
 central propelling organ called the Heart . 
 
 The degree and kind of circulation indicates markedly 
 the character of the animal, and is one of the chief fea¬ 
 tures on which zoological classification is founded. 
 
 While digestion and respiration prepare the nutriment 
 for the body, circulation bears it to all parts of the system, 
 and supplies it to all the organs and their tissues as need¬ 
 ed, and removes away from them the refuse product of 
 their decay, and the waste of heat and motion. 
 
 The structure of animals in relation to the circulation 
 may be arranged according to the following table : 
 
34 
 
 CIHCTTLATTON* 
 
 Table of Methods of Circulation. 
 
 Table IY. 
 
 ]. Animals without hearts or circulating tubes. 
 
 2. Animals with 
 a single set 
 of circula t - 
 ing tubes . . 
 
 f Without heart 
 
 J ! Cold-blooded, or 
 
 ] With heart of a single f Hfematocrya. 
 lobe or valve. . . . J 
 
 3. 
 
 Circulating 
 tubes in the 
 two distinct 
 sets of arte¬ 
 ries and 
 veins .... 
 
 ” Heart of two lobes or-> 
 valves . 
 
 Heart of two or three 
 *4 lobes or valves. . . - 
 
 Cold-blooded, or 
 Haematocrya. 
 
 Heart of four lobrs 
 or valves. 
 
 '] Wann-blooded, 
 [> or 
 
 J Haematotlierma. 
 
 These four functions of Generation , Digestion , Respi¬ 
 ration and Circulation , are called vegetative, because 
 they are essential alike for the life of both plants and 
 animals. Those of sensation and motion are peculiar to 
 animals alone, and hence are called Animal Functions. 
 
SENSATION, 
 
 35 
 
 CHAPTEK XII. 
 
 SENSATION. 
 
 The special functions of sensation are those of— 
 
 1. Nervous Action, 
 
 2. Touch, 
 
 3. Taste, 
 
 4. Smell, 
 
 5. Hearing, 
 
 6. Sight. 
 
 Nervous Action is the means by which the organs, or 
 parts of the animal body, reciprocate with each other in 
 the relations of sensation, or feeling and motion, whether 
 voluntary or involuntary. In the lowest members of the 
 animal kingdom this nerve, or vital power, is equally dis¬ 
 tributed through all ..parts of the body, and is transmitted 
 from one portion to another by the direct contact of the 
 cells and organs, there existing no distinct sets of nervous 
 organs. As we ascend in rank, however, distinct systems 
 of nervous organs are found with increasing perfection, 
 forming the chief basis of zoological classification , and 
 the ladder on which the rank of the animal kingdom is 
 arranged. 
 
 The nerve systems of animals are arranged according 
 to five plans, which, we shall hereafter find, give rise to 
 the five great types or branches. 
 
36 
 
 SENSATION. 
 
 Table V. 
 
 1. Nervous system, without any distinct nerve organs. 
 
 2. Nervous system, consisting of a nerve thread around 
 the stomach, with branching nerve filaments. 
 
 3. Nervous system of nerve bunches, called Ganglia, 
 arranged chiefly about the stomach, and their connecting 
 and branching nerves. 
 
 4. Nerve system of a row of nerve bunches, or Gang¬ 
 lia, extending from one extremity of the body to the 
 other, with their connecting and branching system of 
 nerves, called the Ganglionic or Sympathetic System. 
 
 5. Nerve system, consisting of a governing nerve mass, 
 of two parts (Cerebrum and Cerebellum), located in the 
 head, from which extends the entire length of the trunk a 
 nerve chain , called the Spinal Cord, with its branching sets 
 of nerves / with which is associated the Ganglionic or 
 Sympathetic System. 
 
 The nervous systems may act independently, as in feel¬ 
 ing, or in a special way peculiar to themselves, called Elec¬ 
 trical or Magnetic, in connection with the Muscular Sys¬ 
 tems, in motion, whether voluntary or involuntary, and 
 in the several functions of life peculiar to the animal, and 
 as agents in the higher faculties of volition, instinct, 
 thought, and roason. 
 
FIVE SENSES. 
 
 37 
 
 CHAPTER XIII. 
 
 ^ FI YE SENSES. 
 
 The organs of special sense are those of 
 Touch, 
 
 Taste, 
 
 Smell, 
 
 Hearing, 
 
 Sight. 
 
 These are found by no means equally distributed through¬ 
 out the animal kingdom; indeed, most of the lowest types 
 of animals are almost, if not quite, destitute of them ; but 
 as we ascend in rank, and find the nervous systems more 
 developed, so also these organs of special sense keep pace 
 with them in their development and perfect action. 
 
 Touch 
 
 Is the sense by which animals, through their surfaces, gain 
 a knowledge of the bodies surrounding them, or the con¬ 
 ditions in which they may exist. 
 
 It is the physiological parent of the other senses, being 
 not only the first educator of them in man, but the first 
 one evinced among the lower animals. Thus, while of all 
 the senses, it is the simplest and the least confined to any 
 one part of the animal, and the most general in its action, 
 V* it is at the same time the most direct, positive and certain 
 of them all. 
 
38 
 
 FIVE SENSES. 
 
 It might be considered under the heads of Tactile Dis¬ 
 crimination, Temperature and Muscular Sense. 
 
 The first two, Tactile Discrimination and Temperature, 
 are exercised through the surface of the body, and the 
 third, Muscular Sense, through the action of the muscles. 
 
 Taste 
 
 Is the sense by which animals are enabled to perceive the 
 differences of flavor in their food, and make a proper 
 selection thereof. It is invariably located in the mouth, 
 in the organ called the tongue, though the tongue is by no 
 means always possessed of the function of taste. 
 
 Among most of the lower animals the tongue is merely 
 a prehensile organ for catching and holding the food, and 
 is wholly destitute of the powers of taste. Among great 
 numbers of the lowest members of the animal kingdom 
 there is an entire want of any organ that may be called a 
 tongue, and, in many cases indeed, of any mouth-organs 
 whatever. 
 
 Smell 
 
 Is the sense by which animals are capable of taking 
 knowledge of odors, and is chiefly a guide, as well as taste, 
 in the selection of food. Most of the lower animals seem 
 either to be destitute of it, or to have it merged with the 
 functions of touch. 
 
 Among the higher animals the nose and the nostrils are 
 the organs of smell, and greatly vary in their form and 
 development. 
 
 Hearing 
 
 Is the sense by which animals are enabled to receive and 
 distinguish sounds. The organ of hearing consists funda- 
 
FIVE SENSES. 
 
 39 
 
 mentally of an elastic membrane to receive the vibrations 
 of the air, and a set of nerves to impart a knowledge of 
 those vibrations to the chief nerve centres. 
 
 The lowest members of the animal kingdom are desti¬ 
 tute of any organs of hearing whatever; and the highest 
 members have a wonderful and delicate mechanism in the 
 ear, comprised in three chambers, i.e., the anterior , middle , 
 and posterior chambers. Between these two extremes 
 exist organs of all degrees of complexity and perfection. 
 
 Sight , 
 
 Or vision, is the sense by which animals are enabled to re¬ 
 ceive impressions from light. The organs of vision con¬ 
 sist fundamentally of one or more transparent refractive 
 membranes for lenses, to collect together the rays of light 
 and form the image, together with an expanded nerve to 
 receive it. In the lowest animals—when it exists at all, the 
 entire eye consists of a mere speck, capable only of receiv¬ 
 ing light, but not form or color. From this elementary 
 form upward, we find all stages and degrees of develop¬ 
 ment, to the wonderful visual organs of the birds and 
 mammals. 
 
 We do not propose to take up, at length, in this connec¬ 
 tion the development of the organs of sense ; that would 
 be the special work of a treatise on comparative anatomy 
 and physiology. We would merely, in our methods of 
 study, outline as it were, the several functions and organs 
 to be taken into consideration in a review of animal me¬ 
 chanism. 
 
 Proceeding from the Organs of Sensation we would next 
 sketch, in brief, those of Motion , 
 
40 
 
 MOTION. 
 
 CHAPTER XIV. 
 
 MOTION. 
 
 Motion , or movement in the animal mechanism, is of 
 two kinds, Voluntary and Involuntary; and quite dif¬ 
 ferent in its character from the movement of plants. It is 
 executed through two sets of organs, first, Muscles , and 
 second, Endo , or Exo- Skeleton, for leverage, protection 
 and support; but in many of the lower animals, a muscu¬ 
 lar system alone exists, and even that, indeed, often of a 
 very weak and loose texture. 
 
 The skeleton is either external, as the shell of the crab 
 or lobster, or the hard skin of the insect, and is called 
 Exo-Skeleton; or is internal, having the muscles attached 
 to its exterior, as the bony skeleton of the vertebrae, and 
 is called Endo-Skeleton. 
 
 An outline of the model or Archetype Endo-Skeleton 
 will be given in connection with the characteristic features 
 of vertebrates. 
 
 As has already been said, the structure of the animal 
 is the basis of the classification adopted by this volume. 
 
CLASSIFICATION. 
 
 41 
 
 CHAPTEE XV. 
 
 CLASSIFICATION. 
 
 Thor© are two systems according to which plants and 
 animals are classified: one called the Natural, and the 
 other the Artificial system. 
 
 The artificial system arranges plants and animals ac¬ 
 cording to their appearance and external conditions, with¬ 
 out reference to their structural relations, hut it is one of 
 great uncertainty and ever subject to changes and varia¬ 
 tions. It was adopted by the older zoologists, and hence 
 we find their systems ever conflicting with each other. 
 
 The end sought after by the artificial system, is merely 
 to name objects, for which oftentimes the commonest points 
 of external appearance are alone observed; and animals 
 and plants that are, according to their structure, wide apart, 
 are grouped together, and those that may be closely related 
 are placed far asunder; thus answering the purposes of a 
 dictionary or table of reference. 
 
 The natural system, on the other hand, is founded 
 wholly on points of structural resemblance and difference. 
 
 Those animals that are alike in the most prominent fea¬ 
 tures of structure, though they may differ in a number of 
 lesser ones, it groups together in the great departments of 
 Branches and Types, differing from each other in the most 
 important features of their anatomy. Those of each of 
 these types that resemble one another in some other lesser 
 points of structure, but differ from a number of other 
 
42 
 
 CLASSIFICATION. 
 
 groups of the same type on those very points, it still further 
 divides into classes, and these, by other successive grada¬ 
 tions of resemblance and difference, into Orders, Families, 
 Genera, and Species. 
 
 This gradation of 
 
 Types, 
 
 Classes, 
 
 Orders, 
 
 Genera, and 
 
 Species, 
 
 Forms the nomenclature of the natural system of classi¬ 
 fication. 
 
 The last two (Genus and Species) combined together 
 forms the specific name of an animal. The Generic pre¬ 
 ceding the Specific name, as Smith John, instead of John 
 Smith, e.g ., canis familiar is, the common or familiar dog, 
 instead of familiaris cards. This method is one that 
 greatly economises the number of words used in naming 
 the animal, as comparatively a few names, variously com¬ 
 bined and interchanged with each other, furnish distinctive 
 terms for the hundreds of thousands of animals of which, 
 if each were possessed of an entirely distinct name, the 
 vocabulary would be far beyond the reach of any human 
 intellect, and an acquaintance with the members of even 
 an order or family an utterly hopeless task ; while now, a 
 few names, that soon become familiar, are used over and 
 over m different combinations, under the several larger 
 groups, and so combine the utmost definiteness with the 
 greatest simplicity. With these introductory remarks we 
 will now enter upon the second head or department. 
 
METHODS OF STUDY. 
 
 43 
 
 CHAPTER XVI. 
 
 METHODS OF STUDY, l.e ., CLASSIFICATION AND NATURAL HISTORY. 
 
 Classification of the animal kingdom, or systematic 
 zoology , relates to the arrangement of animals in their 
 several groups of types, classes, orders, etc., according to 
 their resemblance and difference of structure. Natural 
 History is the science of descriptions relating to the 
 appearances, methods of life, and habits of animals. 
 
 Our methods of study shall be, first, to get a clear idea 
 of the types and their points of distinction; next, of the 
 classes they include; then, of the orders, and so on, noticing 
 merely a few genera and species in connection with each 
 of these divisions, to illustrate the structural peculiarities 
 we may have under consideration. 
 
 The learner would make much easier and quicker pro¬ 
 gress in the attainment of an acquaintance, even with the 
 details of classification of any special part of the animal 
 kingdom, by first thoroughly mastering the distinctive fea¬ 
 tures of the larger division of types, classes and orders, 
 and this method, certainly, is of the first importance, if 
 the two chief objects in the study of Natural History, 
 spoken of in the first section of this volume, i.e., the de¬ 
 velopment of our observing powers and learning the 
 laws of nature, are the ends in view. 
 
 We must, then, concisely review— 
 
 1. The special and distinctive features of all the types; 
 
44 
 
 METHODS OF STUDY. 
 
 2. The classes of each type ; and 
 
 3. The order of each class. The compass of this 
 volume will not, except in a few special cases, permit us to 
 proceed beyond the sub-orders and families, and, indeed, 
 not in all cases even beyond the orders. 
 
 The animal kingdom, according to its structure, divides 
 itself into five great types, or branches, i. e., beginning 
 with the lowest, as we shall, in all cases: 
 
 Protozoa, 
 
 Radiates, 
 
 Mollusks, 
 
 Articulates, 
 
 Vertebrates. 
 
 € 
 
 We have chosen to arrange our tables from the lowest 
 upward, because we are thus enabled to study the struc¬ 
 ture of the higher groups as taught synthetically, by the 
 lower ones. 
 
 These types are all constructed according to the same 
 plan; though in the highest alone do we find the entire 
 system brought out as given in our review of Structural 
 Zoology. 
 
 Each of these types, however, expresses a distinctive 
 arrangement of the organs of the body, and is built on 
 an idea or method exclusively peculiar to itself. 
 
 That we may have clearly before us the method in which 
 our studies of each of these divisions will be conducted, t 
 we would again call to the mind of the student the table 
 
METHODS OE STUDY. 
 
 45 
 
 of functions and organs, as our studies of the divisions 
 shall be conducted in relation to each of these, i. e.: 
 
 Generation, 
 
 Digestion, 
 
 Eespiration, 
 
 Circulation, 
 
 Nerve Action, 
 
 Organs of Sense, 
 
 Organs of Movement, 
 
 And also as regards their general appearance, habits, and 
 places of residence. 
 
 > 
 
46 
 
 PROTOZOA. 
 
 CHAPTER XVII. 
 
 PROTOZOA.-GENERATION. 
 
 The Type of Protozoa comprises the lowest and sim¬ 
 plest organisms in the animal kingdom. In the lower 
 orders, no definite organs exist, but the animals present, 
 under the microscope, formless and shapeless masses of 
 jelly, in which the various organs of the body are made 
 for the occasion at the tim3 they are needed for use. 
 
 Reproductio?i is non-sexual. No distinct sexes have 
 been discovered among the Protozoa. They multiply ex¬ 
 clusively by dividings (fissiparous), and by budding (gem- 
 miparous). They comprise all the methods of fissiparous 
 multiplication, i. e ., by the parent splitting transversely, 
 longitudinally, or irregularly, or splitting open and dis¬ 
 charging the young. 
 
 Some of the Protozoa pass through several genera¬ 
 tions in a few hours, and their spores or buds survive 
 almost any exposure of heat or cold, and may be even sub¬ 
 jected to chemical action, or be pulverised, without losing 
 their vitality. 
 
 Digestion among the Protozoa is of the lowest grade, 
 and enacted by organs of the very simplest structure, con¬ 
 sisting, among the greater number of them, of a mere 
 cavity, or depression in the soft shapeless body, endowed 
 with the vital power to dissolve the food taken into it. 
 
 The entire alimentary canal consists of a mere sack, with 
 
PROTOZOA.-DIGESTION. 
 
 47 
 
 the same opening for entrance and outlet, and even this 
 simple organ has to be made at the time of use among 
 many of the lower orders; as the amoeba, sponge animals, 
 etc., where, on the contact of the food, a bag or cavity is 
 sunk into the body, or little filaments are projected as arms 
 that encircle it, and so a stomach is formed of the part of 
 the body where the food is floating. 
 
 Several of these stomachs may be formed on different 
 parts of the body at the same time, which, after having 
 performed the special work for which they were extempo¬ 
 rized, may again be merged and lost in the soft plastic 
 tissue of the body, called Sarcode. This feature led Ehren- 
 berg, the great microscopist of Berlin, to call this type 
 Polygastria, or many-stomached. 
 
 Some others of this type have even a simpler process of 
 digestion ; subsisting entirely on liquid food, they have need 
 of neither stomach nor digestive fluid, and so absorb their 
 nutriment directly through the skin wall of the body. 
 
 Others, again, are supplied with a more elaborate system, 
 consisting of a permanent stomach, with tubes of inlet and 
 exit. 
 
 The existence and courses of these organs in such 
 minute jelly-like animals, have been traced under the 
 microscope, after they had been fed on colored liquids. 
 
 Many of them—as the Stentor, Yorticella, Potifera— 
 have numerous vibrating hairs or cilia around their mouth 
 openings, that keep up a rapid vibration, and so sustain 
 the circulation of a current of water through their stom¬ 
 achs, and are thus supplied with the particles of decaying 
 matter floating in the water that furnish their food. 
 
48 
 
 PROTOZOA.-RESPIRATION-CIRCULATION. 
 
 Distinct Respiratory and Circulatory Organs are 
 usually wanting. 
 
 The oxygen is absorbed from air, dissolved in the water, 
 directly through the entire skin wall of the body. 
 
 It is presumed that, in some of the higher orders, the 
 vibratile cilia around the mouth answer, in a greater 
 degree than the rest of the body, the functions of respira¬ 
 tion. 
 
 The circulating fluids are conducted in the lowest orders 
 directly from cell to cell, through their partition walk ; 
 though, in the higher, there are a few branching, circulat¬ 
 ing tubes, through which, the fluids are conducted by the 
 contraction and expansion of the body. 
 
PROTOZOA.-NERVOUS SYSTEM-ORGANS OF SENSE. 49 
 
 CHAPTER XVIII. 
 
 PROTOZOA.-THE NERVOUS SYSTEM AND ORGANS OF SENSE. 
 
 Among the Protozoa no distinct nervous organs have 
 been found, although they are evidently possessed of a 
 distinct nervous action and the functions of some of the 
 organs of sense. 
 
 The vital power is equally distributed through all parts 
 of the body, to such an extent that the animals will con¬ 
 tinue ther existence, unharmed, even if cut into a number 
 of pieces ; each piece readily fashioning itself into and 
 taking up the life of a distinct animal. All the organs of 
 sense among them are wanting, yet they evidently are 
 capable of the sense of touch ; but the entire lining of 
 the body is equally capable of it, except among the higher 
 orders, which have many hairs or cilia around the mouth, 
 that seem to be possessed of a greater degree of tactile or 
 sensitive power than the rest of the body. 
 
 Some of the higher members of the type seem to be 
 sensitive to light, but their powers of vision extend no 
 further. Ehrenberg describes some red spots on the lin¬ 
 ing of their bodies as rudimentary eyes, but this is not yet 
 established as a fact. They evince a choice in the selection 
 of their food, but this cannot be attributed to anything like 
 a sense of taste, but rather to a vital principle, the same as 
 that which guides the plant to a selection of its food. 
 
 That they are possessed, in any degree, of the functions 
 of smell and hearing we have no evidence. 
 
50 
 
 PROTOZOA.-MOTION 
 
 Motion , among a great many of this type, is active and 
 constant, although only a few of them are possessed of even 
 a rudimentary locomotive apparatus. They are all of them 
 devoid of anything like a skeleton, either external or in¬ 
 ternal ; although many of them secrete hard shells, or cases 
 of lime or flint, on the exterior of their bodies, which 
 aggregate and form masses, often of great extent. Yet 
 this hard covering is merely a protective envelope, and 
 those occupying it are usually fastened to one spot. 
 
 Except among some of the higher orders, which have 
 those vibratile cilia we spoke of, even distinct muscles are 
 wanting, and the little animal moves by a contraction and 
 expansion of its entire jelly-like mass, or the incessant 
 vibration of many little hairs on all parts of the body. 
 
PROTOZOA.-NATURAL HISTORY. 
 
 51 
 
 CHAPTEK XIX. 
 
 PROTOZOA-NATURAL HISTORY. 
 
 The type of Protozoa includes countless numbers of 
 microscopic animals, most of which are quite invisible to 
 the naked eye. Their numbers, however, exceed all com¬ 
 putation. 
 
 Of the hard shells, of those that secrete limy or flinty 
 coverings, immense strata of rock have been formed, tens 
 and hundreds of feet in thickness, and thousands of square 
 miles in extent; which, by subsequent wrinkling, have 
 formed lofty mountains. The ocean, in its broad expanse 
 and depth, and all its branches and streams ; the lakes and 
 rivers of the land; the ponds and little runnels and ruts, 
 and even the mud-puddle or little pocket contained in the 
 hollow of the rock or a decaying log, or, indeed, any place 
 where we may find a drop of water, if there is the least 
 decaying organic matter in it, is found to contain countless 
 hosts of these Protozoa. 
 
 They are the first animals that were created on the sur¬ 
 face of the earth, for we find their remains in the lower¬ 
 most strata that contains animal fossils. 
 
 Although of insignificant size, they are of immense 
 importance in the life or economy of the earth ; not only do 
 the shells of the hard covered ones form great layers of rocks, 
 but the myriads of formless, organless, jelly-like atoms that 
 swarm in all waters that contain the least decaying organic 
 matter, act as scavengers, ridding the waters of the little 
 
52 
 
 PROTOZOA.-NATURAL HISTORY. 
 
 putrid masses, that else would render them unfit for sustain¬ 
 ing higher kinds of life. 
 
 The Protozoa all live, only in the water, although their 
 bodies will sustain an indefinite amount of injury without 
 loss of life. 
 
 The ponds in which they swarm may be dried up, and 
 the dust made up of their bodies blown abroad over the 
 land, and subjected to a hundred various changes, yet, on 
 the first application of sufficient moisture, they will again 
 come to life and be as active as ever. 
 
 The type of Protozoa includes such animals as the vari¬ 
 ous kind of Sponges, Chalk Animals, Flint Animals, 
 Amoeba, Vorticella, etc., which we shall consider hereafter. 
 
TYPE OF RADIATES.-GENERATION. 
 
 53 
 
 CHAPTEE XX. 
 
 TYPE OF RADIATES. 
 
 The type of Eadiates is characterized from all others, 
 by having the organs arranged around a common centre, 
 from which the branches or segments of the body radiate, 
 usually in multiples of five. They are all of them inhabi¬ 
 tants of the water, and nearly all of the ocean or salt and 
 brackish waters. The vital organs of the animals are all 
 soft, but many orders of them secrete and deposit struc¬ 
 tures of lime within their bodies, forming masses called 
 corals, or build either a scaffolding or frame-work, amid 
 which the animal lives, as the star fishes ; or else constructs 
 a shell or case around their bodies, composed either of lime, 
 and studded with pencil-like spines, as in the Sea Urchin, 
 or as in the Sea Cucumber, or Synapta, a cartilagenous 
 shell, sometimes even garnished with hooks. 
 
 We may now proceed to a review of the structure of the 
 type of Eadiates, commencing with that of the organs of 
 generation. 
 
 Generation. 
 
 The Eadiates increase in three ways : 
 
 1st By dividing into segments or parts. 
 
 2d. By budding. 
 
 3d. By emission from their bodies at certain times of the 
 year of great numbers of spores, or ciliated round masses, 
 resembling eggs. 
 
54 TYPE OF RADIATES.-DIGESTION-RESPIRATION. 
 
 The last two are the most prevalent methods of multi¬ 
 plication, and are of extreme importance m the life and 
 economy of the animals in the ocean. The little spores, or 
 detached buds, float freely in the water, and so reach the 
 places most conducive to their life and growth, and then, 
 as they develop, either continue moving about in that 
 region or else fix themselves permanently to the rock, and 
 increase to an indefinite extent by buds from all parts of 
 their surface. Multiplication by division is comparatively 
 rare among them. 
 
 Those that increase by spores or eggs are always bi¬ 
 sexual, though both sexes may be either united in the 
 same individual, or exist on separate ones. 
 
 Digestion. 
 
 The digestive apparatus of the Radiates is extremely 
 simple in all except the highest class. It usually consists 
 of a mere sack, with but one opening, into which the food 
 is drawn by numerous arms or tentacles placed around it. 
 
 These tentacles are endowed with great contractile 
 power, so that they can be drawn back into the body 
 or projected out to great length, at the option of the 
 animal. They are also often armed with a powerful sting, 
 and an acrid liquid that is capable of producing, even on 
 the human surface, a smarting, and in some cases a severe 
 inflammation ; but, among the animals on which they feed, 
 it acts as a paralyzing or deadening agent. The bodies of 
 some appear as mere sacks or stomachs, with the few 
 soft radiating organs of the body arranged around. 
 
 Respiration among the Radiates is altogether and invari¬ 
 ably aquatic. None of them are capable of breathing in 
 
type: op radiates.— a iiteuLATiotf. 
 
 55 
 
 the atmosphere. The oxygen is taken from the dissolved 
 air in the water either by the entire skin wall of the body 
 or by the numerous tentacles that surround the mouth. 
 
 Circulation is carried on by a scarcely more complex sys¬ 
 tem than among the Protozoa. There are tubes that branch 
 out from around the stomach and convey the chyle or digest¬ 
 ed food to all parts of the body, but there is no distinct sys¬ 
 tem of arteries and veins, nor is the fluid propelled through 
 its tubes by means of a muscular heart. 
 
56 RADIATES.-NERVOUS SYSTEM-ORGANS Of SENSE. 
 
 CHAPTER XXI. 
 
 RADIATES-NERVOUS SYSTEM AND ORGANS OF SENSE. 
 
 A delicate nerve filament surrounding the mouth or 
 stomach, opening and sending off branches into the several 
 parts of the body, especially where the tentacles or arms 
 are fastened, is the only rudimentary set of nervous organs 
 found among the Radiates. 
 
 And the Organs of Sense are in a similar state of devel¬ 
 opment. The sense of touch apparently is equally distri¬ 
 buted over the body. Among the members of the highest 
 class, at the ends of certain nerve-lines, are organs which 
 are capable of taking knowledge of light, but not of form 
 or color. The remaining functions and organs of sens'; 
 seem to be entirely wanting. 
 
 The Organs of Locomotion are distributed under a wide 
 variety of forms. Many of them, as the coral animals, 
 are anchored to one spot during the whole of their ex¬ 
 istence, and only such of their numbers as are thrown off 
 from the parent animals in the form of spores, are capable 
 of swimming around and changing their habitation, and 
 that, only during the earliest stages of their lives. 
 
 Others, as the Star Fishes and Sea Urchins, are only 
 capable of crawling along, slowly and deliberately, at the 
 bottom of the water, over the rocks and rubbish, amid 
 which they live ; while yet others again, as the Jelly Fishes, 
 dance along through the waters or float lightly upon its 
 surface. 
 
RADIATES.-NATURAL HISTORY. 
 
 57 
 
 The special set of organs requisite for each of these will 
 be taken into consideration in connection with the several 
 classes of Radiates 
 
 The solid formation within the coral animals can 
 scarcely be called a skeleton, as it is more properly a 
 deposit in the body as it grows old. 
 
 In the highest kind of Radiates alone do we find what 
 may be classed as a skeleton, in which the growing walls 
 of the Sea Urchin and Star Fish, furnish the first instance 
 of a growing skeleton. Among most of the Jelly Fishes, 
 however, neither a growing skeleton or even a living de¬ 
 posit is found ; but the body consists of a mere mass of 
 jelly, in which not even muscular fibres are visible, and 
 which perform their motions by a simultaneous contrac¬ 
 tion and expansion of their entire body or disk. 
 
 The higher classes, however, which have distinct arms, 
 are possessed of delicate masses of muscular fibres. 
 
 The natural history of the Radiates, as we have already 
 observed, pertains entirely to the water. Countless 
 myriads of them have inhabited the ocean, ever since the 
 first appearance of animal life on the earth ; they swarm 
 in the seas of all latitudes, and fill the two important parts 
 in the economy of the ocean life, of purifying the waters 
 and of furnishing food for hosts of higher animals. 
 
58 
 
 TYPE OF MOLLUSKS.-GENERATION. 
 
 CHAPTER XXII. 
 
 TYPE OF MOLLUSKS.-GENERATION AND NUTRITION. 
 
 Members of the type of Mollusks are distinguished 
 from the two preceding types, by the greater distinctness 
 of their nervous system and organs of sense, by the per¬ 
 fection of the circulatory and breathing systems, and the 
 first introduction and simplest evincement in the animal 
 kingdom, of the dual or double arrangement of the struc¬ 
 ture, called the “ bilateral system ,” in which all the chief 
 organs of the body are arranged in pairs. 
 
 Their general structure will present itself in the follow¬ 
 ing review of Molluscan organization. 
 
 Generation is bi-sexual, although both sexes are, among 
 many species, combined in the same individual. 
 
 In passing up to the Mollusca, we lose sight altogether 
 of every trace of Gemmiparous and Fissiparous reproduc¬ 
 tion. 
 
 We have no illustrations of their increase by divi¬ 
 sion into segments, or by budding. They are produced 
 wholly by eggs, which, in a few cases, however, are de¬ 
 posited within the body of the parent and retained within 
 the shell until hatched, and thus living young are given 
 forth. The eggs of some are distinct, and protected by a 
 shell that is either albuminous and flexible, or calcareous 
 and brittle. 
 
 Others again connect their eggs into masses, or spread 
 
'.TYPE OF MOLLUSKS.—-NUTRITION. 
 
 59 
 
 them out in the form of a strap or ribbon, coiled up spirally 
 like a watch-spring, attached by one of its edges. Some 
 enclose their eggs in numbers together, within little tough 
 capsules, which they string together on a chain, or cluster 
 around a stem, like bunches of grapes, or arrange in radi¬ 
 ating masses. 
 
 Most usually, the young are passed from the egg in a 
 form not in the least resembling the parent, and, after a 
 series of changes, in the adult state alone are like their 
 parents in all points. 
 
 Such immature changes, through which the young of 
 many animals pass, is called the larval state , and the 
 young themselves the Larva 
 
 Digestion , and its attendant functions of respiration 
 and circulation, especially the last, are in a much higher 
 degree of development among the Mollusca than in any of 
 the preceding types. Among some, the mouth is unarmed, 
 except by soft feelers, but among others, powerful and 
 sharp jaws flank it on either side. We would observe, 
 before speaking of what is called the lingual tube of some 
 of these Mollusks, that among the invertebrates, the word 
 tongue is used to designate any prehensile organ of the 
 mouth, without reference to its being the organ of taste. 
 Among many of the Mollusks, a tube extending back from 
 the mouth, and lined its whole length with teeth, number¬ 
 ing in some instances several thousands, is called the lin¬ 
 gual-tube. 
 
 These teeth assume all varieties of forms as well as 
 numbers. 
 
 ►Sometimes the tongue forms a short semicircular ridge 
 
60 
 
 TYPE OE MOLLTTSXS.-NUTRITION. 
 
 contained between the jaws, at others it is extremely elon¬ 
 gated, and its folds extend backward to the stomach, 
 while yet in others its folds are longer than the whole body. 
 
 Some Mollusks are possessed of organs resembling the 
 gizzard of a fowl, in which the food is received and ground. 
 Others are yet further supplied with a crop, in which the 
 food is received and held as it is swallowed until subjected 
 to digestion. The liver is always large in the Mollusca; 
 its secretion is derived from arterial blood, and is poured 
 either into the stomach or the intestines. Many are even 
 furnished with developed salivary glands, and some have 
 a rudimentary pancreas, and also special glands for the 
 secretion of colored liquids of the most delicate tints. 
 
MOLLUSKS.-RESPIRATION AND CIRCULATION. 
 
 61 
 
 CHAPTER XXIII. 
 
 MOLLUSKS.-RESPIRATION AND CIRCULATION. 
 
 Respiration among the Mollusks is of both kinds— 
 aquatic and aerial; among those that live in the water it is 
 accompanied by pairs of gills, called branchiae, which are 
 exposed to the changing water, either by merely floating 
 in it, or by having the water led in and out through a 
 special pair of tubes, called siphons, which are drawn out 
 to considerable length in those that live in the sand. 
 Others breathe directly through their mantle or covering. 
 
 The depth of water in which the Mollusks live is fixed 
 partly by the amount of oxygen they need, and partly by 
 the adaptation of the body to endure pressure. 
 
 The air-breathing Mollusks are possessed of lungs, or 
 air chambers, formed by the folding back of the mantle, 
 in the interior of which are arranged the breathing organs, 
 consisting of merely a permeable set of air bags, and a 
 circulatory system to supply and remove the blood, the air 
 being renewed with sufficient rapidity merely by the law 
 of diffusion. 
 
 The respiratory system is of very great importance in 
 the economy of the Mollusks, and a fundamental point in 
 their classification. 
 
 Circulation is carried on among the Mollusks by a sys¬ 
 tem of organs of much greater development than among 
 either of the lower types. 
 
62 
 
 MOLLUSKS.-NERVOUS SYSTEM. 
 
 This type is not possessed of any distinct absorbent sys¬ 
 tem, but the product of digestion (chyle), passes into the 
 general abdominal cavity, and thence into the numerous 
 veins of the body. They are possessed of a distinct heart 
 of two chambers, arteries and veins, and so have a circula¬ 
 tory system of much greater development than the Protozoa 
 and Padiates, and, indeed, than even the larger number of 
 the Articulates. 
 
 The Nervous System. 
 
 Among the Mollusca, the chief portion of the nervous 
 system consists of a ring of nervous matter surrounding 
 the throat, thickened out in places into nervous bunches, 
 called ganglia, and from which proceed nerve-cords to all 
 parts of the body. 
 
 Organs of Sense. 
 
 Every one of the organs of sense exist among some of 
 the Mollusks, though in various degrees of perfection. 
 Their eyes vary from mere spots on the sides of the mantle, 
 that are scarcely capable of taking knowledge of light, as 
 among such as the Oyster, to the most elaborate visual 
 organs of the Cuttle Fish. The lowest of the type do not 
 evince any organs of hearing, but among the higher orders 
 the middle chamber chiefly is developed. 
 
 The sense of Smell is evidently possessed by the Cuttle 
 Fishes, and by the class to which the Snails and other uni¬ 
 valve shells belong. Snails seek and select their food by 
 this sense. Slugs are attracted by special odors, and many 
 of the ocean Mollusks may be taken with animal baits. 
 
 The sense of Taste is also indicated rather by the habits 
 of the animal, and their choice of food, than by the struc¬ 
 ture of a special organ, for, as we have already observed, 
 
MOLLUSKS.—OKGANS OF SENSE. 63 
 
 that which is called the tongue, is an organ intended for 
 the seizing and preparing of the food, and not for the 
 functions of taste. 
 
 The sense of Touch , in the lowest class, is equally, dis¬ 
 tributed over the entire covering of the body, called the 
 mantle. 
 
 Such is the case among the Clams, Oysters, and other 
 bivalves; but, among the higher classes of the type, special 
 organs, called tentacles, are appropriated to it. Thus all the 
 Snails and other univalves have flexible feelers, or arms, 
 from the head; two of which are for the purposes of 
 touch, while the other pair support the eyes. Among 
 members of the highest class there exist several arms 
 around the head, which are endowed with organs of touch. 
 
 Thus we find the special organs of sense, as well as the 
 general structure of the nervous system, among the type 
 of Mollusks is altogether on a higher plan than that of 
 either of the two lower types, the Protozoa or Padiates. 
 
64 
 
 MOLLUSKS.-INTEGUMENT. 
 
 CHAPTEE XXIY. 
 
 MOLLUSKS.-INTEGUMENT OR SHELL OF. 
 
 We next proceed to consider the organs of locomotion 
 and of protection, among the type of Mollusks. 
 
 The muscles are mostly attached directly to the skin, 
 or mantle, of the body, and are of rather a flaccid char¬ 
 acter. 
 
 A few muscles, however, are always of a more solid and 
 compact character. Such are the strong muscles that, 
 among the Oysters and Clams, connect together the two 
 valves of the shell, and open and close them at will, and 
 the projecting foot of the Snail, or the powerful prehensile 
 arms of the Cuttle Fish and Nautilus. 
 
 All the Mollusks are devoid of an endo-skeleton, except 
 the Cuttle Fishes, where is found the first appearance of 
 anything like an internal organ, of support and protection 
 in the Cuttle Fish bone. 
 
 Most of the Mollusks manufacture, however, an exo- 
 skeleton , or shell, as it is called, which is constructed in a 
 wonderful and delicate manner on the outside of the body, 
 as it enlarges. 
 
 The mantle, or skin covering of the body, is the organ 
 that builds the shell. Its structure is commenced around, 
 the young animal before it is passed from the egg-case 
 
MOLLUSKS.-INTEGUMENT. 
 
 65 
 
 and is enlarged and thickened as the animal grows larger. 
 Molluscan shells are composed of three layers or parts : 
 
 1. Limy layer. 
 
 2. Nacreous layer. 
 
 3. Periostracum. 
 
 The limy layer is the greater part of most shells. It is 
 composed of carbonate of lime, and built along the outer 
 side and edge as the animal increases in size. These layers 
 are added one to the other, as may be seen in a transverse 
 section of an onion, and each of these layers are composed 
 of a series of closely fitting columns, usually hexagonal, 
 which, themselves, are again composed of a series or pile 
 of plates. 
 
 The nacreous layer is deposited on the inside of the 
 living shell by a liquid secreted by the body. It is com¬ 
 posed of very delicate plates, laid partly over each other, 
 and presenting sometimes the appearance of a coat of por¬ 
 celain varnish, at others that of a sheet of burnished silvery 
 metal, while yet others are ire descent, with a beautiful play 
 of colors. 
 
 This layer answers as a protecting cushion for the soft 
 body that lies within it, and forms what we are so exten¬ 
 sively acquainted with in the arts, under the name of 
 mother-of-pearl, and is also used as a lining for any 
 foreign object, as a grain of sand ; or a wound that 
 may happen within the body of the animal, and this 
 forms, by the addition of layer above layer, what we call 
 a Pearl. 
 
 The periostracum or epidermis is an outer coat of 
 animal matter of various appearances; on some it is 
 
66 
 
 MOLLUSKS.-INTEGUMENT. 
 
 thin and transparent, on others again, quite thick and 
 opaque. 
 
 It is thick, leathery and olive-colored in all fresh water 
 shells, and all Arctic sea shells. It gives color to a number 
 of land shells. 
 
 On some shells it is silky, or fringed with hairs ; on 
 others it is thick and rough, like coarse cloth ; and on yet 
 others, drawn out into long beard-like filaments. 
 
 The periostracum is a living part of the shell, and protects 
 it against the injury of water-wear and chemical action. 
 
 After death, however, it soon cracks and crumbles away, 
 often exposing beneath it a most exquisitely colored and 
 variegated surface. 
 
 This coloring of the shell is effected by little paint bags 
 placed along the edge, from which the patches and lines 
 of pigment are interwoven into the shell as it is built. 
 Those shells, particularly of the tropics, that live nearer the 
 surface of the water, are the most beautifully colored. 
 
 Having thus reviewed the chief structural peculiarities 
 of the type of Mollusks, we shall now proceed to say a few 
 words in relation to their Natural History , or general 
 economy. 
 
 They are the first air-breathing animals we have yet, in 
 our studies, reviewed. They have existed in the oceans 
 from the earliest zoological ages, and have continued in 
 immense numbers ever since, forming in some places, of 
 their shells alone, layers of rocks hundreds of feet thick 
 and scores and hundreds of miles in extent. 
 
MOLLUSKS.-INTEGUMENT. 
 
 67 
 
 They are more intimately connected with the economy 
 of human life than either the Radiates or Protozoa. 
 
 Their bodies are extensively used as food, and their 
 shells for the manufacture of articles of use and orna¬ 
 ment. 
 
68 
 
 ARTICULATES.-ARRANGEMENT OF RINGS. 
 
 CHAPTEE XXY. 
 
 ARTICULATES-ARRANGEMENT OF RINGS. 
 
 We will next proceed to consider the distinctive features 
 of the type of Articulates. 
 
 The type of which we are now to speak comprises by 
 far the greatest number of species in the entire animal 
 kingdom. They swarm in countless myriads in the ocean, 
 on the land, under its waters, and in the air; and in 
 places that seem absolutely untenable, even to the lowest 
 kinds of animal life, as the interior of the bodies of other 
 living animals, and the springs of boiling water. Nor 
 is their structure less varied and interesting; according to 
 their diverse habits and habitations, their forms assume an 
 infinite variety of modifications, though all are built, as 
 the other types, on one general plan. It is of this model, 
 or general structure, that we will now proceed to speak. 
 
 The Articulates are distinguished by the body being 
 composed of a chain of rings. 
 
 There are three plans, or methods, of arrangements of 
 these rings: 
 
 1st. A uniform chain of rings, as among the worms. 
 
 2d. Eings arranged in cephalo-thorax and abdomen, as 
 in Lobsters and Spiders. 
 
 3d. Eings arranged as among insects, in 
 Head, 
 
 Thorax, 
 
 Abdomen. 
 
ARTICULATES.-ARRANGEMENT OF RINGS. 
 
 69 
 
 1. Those of the first plan merely have the rings of the 
 body attached to each other, as a string of beads ; and, 
 among the lowest of these, all the rings are possessed of an 
 equal amount of vitality, so that, if they be severed into as 
 many pieces as there are rings in the body, each piece 
 might reproduce itself, or grow into a complete animal, 
 such as the Tape Worm. 
 
 2. Those in which the rings are arranged into a ceph- 
 alo-thorax and abdomen , have the rings of the front 
 welded more or less together, into one piece, on vdiich are 
 located the organs of the mouth, of the senses, and of 
 locomotion. 
 
 3. The arrangements of the rings into the head, thorax 
 and abdomen exists among the highest members cf the 
 Articulates. The head is possessed of the largest nerve 
 mass of the body, the organs of the senses and of the 
 
 mouth. 
 
 The thorax is axis of the body, composed usually of 
 three rings, joined closely together, and to it are fastened 
 the organs of locomotion, both wings and legs. 
 
 And the abdomen is composed of rings, connected 
 together with a flexible skin, or membrane, and possessed 
 of the chief organs of digestion, respiration, circulation, 
 generation and oviposition. 
 
 t 
 
70 
 
 ARTICULATES.-NUTRITIVE GROANS. 
 
 CHAPTEE XXVI. 
 
 ARTICULATES-NUTRITIVE ORGANS. 
 
 We will now proceed to study the Articulates in relation 
 to their structure. Reproduction is chiefly by means of 
 eggs; the sexes in most cases are distinct; the young is 
 passed from the egg usually in an immature condition, 
 called larva, which often passes through many stages of 
 transformation before reaching the adult state. Some will 
 multiply themselves by breaking or dividing into parts— 
 fissiparations. 
 
 Such is the case with the Entozoa or intestinal worms. 
 The Articulates multiply with extreme rapidity. 
 
 Digestion among the Articulates has a wider range of 
 action than among any other animals. As members of 
 this type are found in nearly every place, they are also 
 capable of taking and digesting every kind of food that 
 any animal can live on. 
 
 There is, accordingly, a great variation in the structure 
 of the digestive organs; from a mere sack, without any 
 special openings of entrance or exit—absorbing its nutri¬ 
 ment like a plant cell from its entire surface, as in the 
 intestinal worms—to an elaborate alimentary canal, con¬ 
 sisting of mouth and prehensile organs, oesophagus, stom¬ 
 ach, intestines, liver and other auxiliary organs, as among 
 the insects, which we shall consider at length when we 
 come to a reviewal of that class. 
 
 Respiration among the Articulates is both aquatic and 
 aerial. Myriads of them spend their entire brief existence 
 
ARTICULATES.-NUTRITIVE ORGANS. 
 
 71 
 
 in the water; as many others again, are exclusively deniznes 
 of the air ; while yet others live in, and breathe water dur¬ 
 ing their earlier life or larval condition, and are exclusively 
 air-breathing during their adult state, as certain insects, 
 such as the Dragon Fly, Mosquito, Gnat, etc. 
 
 The respiratory organs are essentially of three kinds : 
 
 1st. Among the lower orders of the worms, the entire 
 surface of the body acts the part of a breathing organ ; 
 such are always inhabitants of the water, or of moist places. 
 
 2d. The body is provided with tubes, which are either— 
 as among some of the higher worms—turned outward, and 
 fastened about the body in tufts, or are turned inward, and 
 branch as spiracles, through the rings of the body. Such 
 we find to be the case among the insects. 
 
 3d. In the abdomen exist air-bags called lungs, as 
 among the Spiders ; these are, however, different from the 
 lungs of Vertebrates, in that they are simple sacks, and 
 not collections of air and blood cells. 
 
 Circidation is less complete in this type than among the 
 Mollusks. The muscles and organs of the body are con¬ 
 stantly bathed in blood, and even the insects have not any 
 definite circulating tubes, as arteries and veins. 
 
 A contractile tube along the back of the body answers to 
 a heart, and moves the blood from one part of the system 
 to another. The blood, however, among some of the active 
 insects, as the Bee, is of a warmer temperature than among 
 any of the lower types, and, indeed, even than among 
 many of the higher types, as Fishes, and other cold¬ 
 blooded Vertebrates. 
 
72 
 
 ARTICULATES.-THE NERVOUS SYSTEM. 
 
 CHAPTER XXYII. 
 
 ARTICULATES-THE NERVOUS SYSTEM. 
 
 Although the organs of circulation, among the Articu¬ 
 lates, are of a lower grade than among the Mollusca, 
 the greater development of their nervous system entitles 
 them to a higher rank in the animal kingdom. 
 
 The nervous system consists of a nerve cord or chain, 
 extending the entire length of the body, along which, at 
 regular distances, are fastened nerve-centres, or masses, 
 called ganglia, and about each ganglionic mass is con¬ 
 structed a ring or segment of the body, through which the 
 nerves of feeling and motion branch from the centre gang¬ 
 lion. The nerves of feeling, however, even among the 
 Articulates, are but in a rudimentary condition. These 
 animals, as well as all the other Invertebrates, seem almost 
 destitute of the sensations of pain. 
 
 It is true that in poetry we are told, “ The poor beetle 
 “ that we tread upon, in corporeal sufferance, feels a pang 
 “ as great as when a giant diesbut anatomy and true 
 philosophy tell us differently: “ Pain, nature’s kind har- 
 “ binger of mischief, is only inflicted for wise and import- 
 “ ant purposes; either to give warning of the existence 
 “ of disease, or as a powerful stimulus, prompting to 
 “ escape from danger.” 
 
 These animals, incapable of remedying the one or avoid¬ 
 ing the other, not only ever exposed to destruction and 
 death, but created for the purpose of preying on each other 
 
ARTICULATES.-ORGANS OF SENSE. 73 
 
 by tlie myriad, are kindly denied the feeling of acute pain. 
 Their nervous organization still further denies the existence 
 of it, save in a low degree. 
 
 The central chain of ganglia, among the Articulates, can 
 perceive external impressions and originate motion, bat not 
 feel pain ; that is, a perception of the brain , and may be 
 acute, as the body is under a special nerve mass located in 
 the head, as among the Vertebrates. 
 
 How far the feeling of pain is actively developed in 
 these animals may be deduced from every-day observation. 
 The Fly, seized by the leg, will leave its limb behind and 
 alight, with apparent unconcern, to regale upon the nearest 
 sweets within its reach ; the Caterpillar seems to enjoy a 
 tranquil existence while the larvae of the Ichneumon 
 hatched in its body devours its very viscera; and in the 
 Crustacea, of so little importance is the loss of a leg, that 
 the Lobster will throw off its claws if alarmed by the 
 report of a cannon. The arrangement of the nervous sys¬ 
 tem among the Articulates is the reverse of that among 
 Man and the other Vertebrates. 
 
 Organs of Sense. 
 
 Organs of Sense , though of a lower grade than among 
 the Vertebrates, are, in the highest orders, of a more 
 elaborate and delicate structure than among any of the 
 preceding types. There is, however, a great range in the 
 development of these organs, from the lower worms to the 
 insects; and as we shall treat of each of these, somewhat 
 in detail, in connection with the classes of Articulates, our 
 remarks in relation to them here shall be brief. 
 
 The sense of Touch among the two higher classes is seated 
 chiefly in feelers from the head, called Autense, Among 
 
74 
 
 ARTICULATES.-ORGANS OF MOTION. 
 
 the lowest class of worms, what there is of the sense is 
 distributed over the entire surface of the body. 
 
 Taste evidently exists among many of this type, for they 
 evince a choice and selection in their food ; but, as among 
 the Mollusks, the tongue is not usually invested with the 
 sense of taste, but is moie generally a prehensile organ 
 for the purpose of catching and retaining the food. 
 
 The senses of Smell and Hearing are both in a rudi¬ 
 mentary condition, and the organs, through which they 
 act, undetermined, though usually referred to the antense 
 or palpi of the head. Smell, however, seems to be more 
 generally active than hearing, as it is active in the search 
 and selection of food. 
 
 The sense of Sight among the Articulates varies from 
 the eye speck, scarcely capable of perceiving light, to elab¬ 
 orate systems of simple and compound eyes, as in the heads 
 of insects, while such as the Intestinal Worms are wholly 
 destitute of organs of vision. Simple eyes, are single eyes 
 placed on the back of the head, in numbers from one to 
 about twenty; such are the eyes of Spiders, Lobsters and 
 the young or larvae of insects; and they are also possessed, 
 in connection with compound eyes, by many insects. 
 
 Compound eyes consist of a pair of globes, one on each 
 side of the head, composed on the surface of facets, or 
 lenses, like a multiplying glass, varying in number from 
 about fifty to ten or twenty thousand in each globe. The 
 internal structure of these shall be observed in connection 
 with the study of insects. 
 
 ( )rgiins of Moti<n i „ 
 
 None of the Articulates are possessed of an endo - 
 skeleton , and many of them are destitute of even a shell 
 
ARTICULATES.-NATURAL HISTORY. 
 
 -75 
 
 or exo-skeleton. The Worms and the larvrn, or young, of 
 all the higher orders are wholly devoid of anything that 
 may be called a shell or skeleton. 
 
 The exterior skeleton of the Lobster, the Crab, and the 
 Insects shall be taken up in connection with a study of 
 those orders. 
 
 Their muscular system is arranged with reference to 
 the ring division of the body; loose among the Worms 
 and larvae, or young, of the higher classes, but extremely 
 well knit and powerful among the insects. 
 
 The force evinced in the motions of a Leetle, or a Ilea, 
 in proportion to their relative sizes, is many fold greater 
 than that of the human frame, or the ()x or Horse. 
 
 The Natural History of the Articulates is the most 
 varied and interesting of the entire animal kingdom. 
 
 IS ot only are they in the greatest numbers on all parts 
 of the earth’s surface—land, air and water—but their 
 habits and appearances also furnish the greatest variety. 
 
 They have been almost coeval, in their zoological exist¬ 
 ence, with the Molusca and lladiata, and they are of great 
 importance in the general economy of life, both as scaven¬ 
 gers of the land, air and w^ater, destroying the immense 
 mass of decaying material that otherwise w T ould render 
 these regions uninhabitable for the higher kinds of life ; 
 and serve also as food for myriads of animals that prey 
 upon them, and, indeed, many of them furnish excellent 
 and abundant food for Man himself, as the Crab, Lobster, 
 Shrimp, and even numbers of the insects themselves. 
 
 Their uses in the arts and in medicine are also very ex¬ 
 tensive and important. 
 
76 TYPE OF VERTEBRATES.-GENERATION-DIGESTION. 
 
 CHAPTER XXVIII. 
 
 TYPE OF VERTEBRATES. 
 
 This type takes its name from the chief bones of the in¬ 
 ternal, or endo-skeleton, i.e., the spinal column or chain of 
 Vertebrae. It comprises all the higher animals—as 
 Fishes, Birds, Reptiles, and Mammals—including all those 
 that are intimately connected with human life under the 
 term of domestic animals, and of all the highest—Man 
 himself. An acquaintance with the special anatomy of 
 this type is of extreme importance, as it comprises that of 
 the human frame; but, as we are not especially on the 
 study of anatomy and physiology, we shall be obliged to 
 confine our remarks, in this important department, to the 
 barest outline that will answer our purposes. 
 
 Generation among the Vertebrates is sexual, and either 
 oviparous or ovo-viviparous. The young, in many orders, 
 pass through marked transformations after birth. 
 
 Digestion .—The organs of digestion may be arranged 
 under three divisions. 
 
 1. The first, that hg tvhich the food is prepared for, and 
 conveyed into the stomach. This is chiefly of a mechanical 
 nature, and is executed by the organs of the mouth and 
 the oesophagus or gullet. 
 
 The mouth, among the Fishes, Reptiles, and Mammals, 
 is most usually armed with teeth, but among the Birds we 
 always find, instead of teeth, a hard, horny skin, extend¬ 
 ing beyond the jaws, forming a bill. 
 
TYPE OP VERTEBRATES.-DIGESTION. 
 
 77 
 
 The teeth of Vertebrates furnish a most interesting 
 range of variation, by which, not only the kind of food, 
 but the character and habits of life of the animals may be 
 read. 
 
 The study of teeth constitutes the science of Odontogra¬ 
 phy . A tooth consists of three parts or materials, as 
 cementum or crusta-petrosa, that part set inside of the 
 tooth cavity in the jaw; the dentine, the softer ivory, 
 forming the greater mass of the upper part; enamel, 
 the hard limy covering of the upper part of the tooth. 
 The tongue is an all-important organ in the work of seiz¬ 
 ing, preparing, and swallowing the food, and is possessed 
 of a wide range of structure and activity. 
 
 The oesophagus is a muscular tube leading from the 
 mouth to the stomach, at the back of the wind-pipe or 
 trachea. It is widest among snakes or such animals as 
 swallow their food whole. There is, perhaps, no act of the 
 system that exhibits a more perfect specimen of animal 
 mechanism than the process of deglutition. It consists of 
 the successive action of a series of muscles that effect their 
 end in the most complete manner. 
 
 2. Those that have been exclusively termed the proper 
 digestive organs , where the food receives its appropriate 
 chemical change, i.e., the stomach, a bag of an irregular 
 oval form, occupying the upper part of the abdomen, for 
 the solution of tne food, provided with as much or more 
 vitality than any other part of the system, and hence fur¬ 
 nished with a large supply of blood vessels and nerves; 
 
 3. That part of the canal that removes the residue of 
 the food, after the nutritive part has been absorbed, and 
 a part of the waste of the system— i.e., the intestines. 
 
78 
 
 TVPE OE VERTEBRATES.-RESPIRATION. 
 
 Digestion among the Vertebrates is essentially of three 
 kinds: 
 
 Herbiverous—plant eating; 
 
 Carniverous—flesh eating; 
 
 Omniverous—eating all kinds of food ; 
 
 And their organs are constructed with special reference to 
 their different methods of life. 
 
 Respiration among the Vertebrates is both aerial and 
 aquatic. A large proportion of the lower orders of the 
 type, as all the Fishes and many of the Rep tiles, breathe 
 only water; a few are capable of both aquatic and aerial 
 respiration, being furnished with breathing organs appro¬ 
 priate for both; while others, as the Frogs, breathe fresh 
 water during the earlier stages of their existence, and only 
 air after reaching the stages of maturity. The respiratory 
 organs, among the air-breathing Vertebrates, invariably 
 take the form of lungs, and among those that breathe 
 water the form of gills, or branchiae. 
 
 { 
 
VERTEBRATES-CIRCULATION. 
 
 79 
 
 CHAPTER XXIX. 
 
 V ERTEBRATES-CIRC U L ATIOX. 
 
 The organs of circulation among the Vertebrates consist 
 of the: 
 
 Heart. 
 
 Arteries, 
 
 Veins, and 
 
 Capillary Vessels. 
 
 These organs, though ever present in this type, are in 
 different degrees of development in the several classes. 
 This variation we shall speak of when we come to the 
 study of the classes, for, as we have observed, the structure 
 and action of the circulatory organs constitute one of the 
 principle bases, upon which the modern classification of 
 animals is founded. At present, however, we will take a 
 general view of each of these four circulatory organs: 
 
 The Heart , among the Vertebrates, consists of two por¬ 
 tions—of a stronger and more muscular cavity, called a 
 cent ride, for propelling the blood through the system, or 
 the breathing organs; and a weaker and less muscular 
 cavity, called an auricle , for receiving the blood on its re¬ 
 turn, and passing it back into the ventricle, again to be 
 propelled forward. 
 
 Around the heart is a tough membranous sac, called the 
 Pericardium, which both restrains and protects it in its 
 action. Within it are a series of valves that prevent the 
 flowing back of the blood from its course, either into the 
 
80 
 
 VERTEBRATES-CIRCULATION. 
 
 arteries and veins or into the chambers of the heart. Such 
 a heart, consisting of but one auricle and one ventricle, is 
 called a single heart, and is found among all the Fishes, 
 and essentially, also, among the reptiles, though here 
 (Beptilia) the heart is variously modified, and brought very 
 near to the double heart of Birds and Mammals. 
 
 Among the higher or warm-blooded Vertebrates (Birds 
 and Mammals), the heart is always double, and possessed 
 of two auricles and two ventricles ; one set for receiving 
 and sending bach the blood through the system, and the 
 other for receiving and sending it through the lungs. 
 
 The Arteries are the tubes that convey the blood front 
 the heart, and distribute it throughout the body. 
 
 The ancients first called these tubes “ arteries,” because 
 they supposed them filled with a vapor, or a spirit, as they 
 are always found empty after death. 
 
 In the complete system there are two great trunks, one 
 of which conveys the blood through the system, and the 
 other through the breathing organs. 
 
 The Veins are tubes, that gather up the blood from all 
 parts of the system, and return it to the auricles of the 
 heart; to be thence again sent by the ventricles, through 
 the arteries, into the breathing organs to all parts of the 
 body. 
 
 The capi/aries form the intermediate blood channels be¬ 
 tween the finest arteries and veins When looked at 
 under the microscope, in tbe thin, transparent membrane 
 of an animal—as the web of a Frog’s foot or the thin part 
 of a Salamander’s tail—they are found to be of different 
 
VERTEBRATES-CIRCULATION. 
 
 81 
 
 sizes, some conveying two or more rows, and others only a 
 single row of blood corpuscles. 
 
 The same tubes are, however, found at different times 
 alternately to contract and d'diKO, An important addition 
 to the circulatory system of Vertebrates, not found among 
 any of the types yet spoken of (the Invertebrates), is an 
 entirely new system of vessels, destined to absorb from the 
 intestines the nutritious products of the digestive process, 
 and convey them into the veins, to be mixed with the cir¬ 
 culatory blood. These are called Lymphatics or Lacteals. 
 
 The blood of all the Vertebrates is red, and is composed 
 of microscopic globules of variable form and dimension in 
 different animals. 
 
 The bile among the Invertebrates, that are possessed of 
 a liver, is secreted from the arterial blood; but among the 
 Vertebrates, from out the venous blood. And hence we here 
 find another new system of vessels, distinct from the general 
 circulation, called the portal system ; in connection with 
 which we also find another remarkable organ, the Spleen. 
 
 The peculiarities of cold and warm blood among the 
 Vertebrates shall be taken up hereafter, in connection with 
 the divisions of the types. 
 
82 
 
 VERTEBRATES- NERVOUS SYSTEM. 
 
 CHAPTER XXX. 
 
 VERTEBRATES-NERVOUS SYSTEM. 
 
 The Nervous System of the Vertebrates is organized on 
 a much more complex and elaborate plan than that of any 
 of the four preceding types. 
 
 It consists, in fact, of several distinct systems, differently 
 disposed and appropriated to different offices. 
 
 A few largely developed masses of nervous matter, or 
 ganglia, bound together by tendonous bands and mem¬ 
 branes, and protected by a bony skull, constitute the brain , 
 which presides over all acts of voluntary motion, feeling 
 and sensation. 
 
 From the brain proceeds a long chain of nervous 
 centres, or ganglia, joined closely together, into what 
 is called the Spinal Cord , protected by a chain of 
 bones called Vertebrae, which form, with arches, along 
 their upper or back surface a continuous canal, and suc¬ 
 cession of rings from the head to the end of the trunk, 
 and among many into the tail, if one exist. 
 
 From the two sides of the Spinal Cord, between the 
 different bones of the Spinal Column, pass out pairs of 
 Nerves ; one filament being the Nerve of Motion, and the 
 other the Nerve of Feeling ; and these distribute them¬ 
 selves, by successive branchings, to the voluntary muscles 
 and integuments of the two sides of the body. 
 
VERTEBRATES.-ORGANS OF SENSE 
 
 83 
 
 In addition to the above, which is called the Cerebro¬ 
 spinal System , there exists in the Vertebrate a distinc- 
 system of nervous centres, or ganglia, placed amid the 
 organs of digestion, respiration, etc., and connected to¬ 
 gether by another set of branching nerves, called the 
 Sympathetic System , which presides over the organic life, 
 or involuntary motions of the animal, as those of circula¬ 
 tion, digestion, respiration, and the like. 
 
 Five Senses. 
 
 The Organs of Sense are developed in a proportionate 
 degree with the nervous system, and have a much greater 
 perfection of structure and regularity of arrangement than 
 in any of the Invertebrates. 
 
 The sense of Touch among the Vertebrates has a wide 
 range of variation. Among the higher members of the 
 type, tactile discrimination is exercised more or less from 
 the entire surface of the body, but is always keenest in 
 special parts, as, in the human system, in the ends of the 
 fingers and tongue, the lips, the palms of the hands and 
 the soles of the feet; among some Monkeys, even at the 
 end of the tail; among the Bats, in the wings ; in the flesh¬ 
 eating quadrupeds, in the whiskers or vibrissee; among the 
 Ant-eaters, Moles, Hogs and Elephants, at the end of the 
 nose. Others, again, from the structure of their covering, 
 are incapable of the sense over their entire surface, and 
 can exercise it only through particular organs or parts. 
 
 Of such are the Birds, with their covering of feathers 
 and scales, only capable in any degree whatever of the 
 sense of touch in their toes and beak; the Reptiles, with 
 their slimy or scaly covering, feel by the tongue, and per¬ 
 haps some what in the lips. And the Fishes have the same 
 
84 
 
 VERTEBKATES-ORGANS OF SENSE. 
 
 in the side fins, and also, sometimes, in projecting feelers 
 from the head, called Barbules. In all cases, however, this 
 sense (tactile discrimination) is due to exceedingly delicate 
 pimples, called Tactile Papillae, in which the nerve of 
 sense is spread. Wherever these papillae are arranged 
 most abundantly, the sense is keenest. 
 
 The Vertebrates are capable of enduring the widest 
 range of climatic temperature existing on the entire surface 
 of the globe, and in the remote geological ages survived 
 probably yet greater extremes. 
 
 Among them we find the utmost development of the 
 muscular sense, both in accuracy and agility. 
 
 Taste , among the Vertebrates, is developed chiefly in 
 the highest type—that of Mammalia. It is here an import¬ 
 ant guide in the selection of food; but among the lower 
 classes—Birds, Peptiles, and Fishes—which swallow their 
 food whole, it scarcely, if at all, exists. 
 
 The sense of Smell , however, is more widely distributed 
 throughout the type, and among many of the lower Ver¬ 
 tebrates is much more keenly developed than in the human 
 system. 
 
 Hearing, among the Vertebrates, reaches the highest 
 development. The Ear, in its complete condition, as in 
 Man, consists of three portions: the external, the middle, 
 and the internal Ear. 
 
 The external consists of the outside ear-trumpet, and the 
 ear-tube for the purpose of collecting $nd leading the 
 sound. 
 
VERTEBRATES.-ORGANS OP SENSE. 
 
 85 
 
 The middle ear is a chamber containing a tense mem¬ 
 brane, called the ear-drum, and certain bones, for the pur¬ 
 pose of collecting and conducting the vibrations of sound; 
 and the internal ear, or labyrinth, in which are spread out, 
 in tubes called semi-circular canals and cochlea, or shell, 
 the auditory nerve, or nerve of hearing. 
 
 All these parts, in their complete state, are found by no 
 means among all the Vertebrates. The Fishes have but 
 the middle ear, and from these we find all degrees of vari¬ 
 ation, till we reach the complete condition in Man, and the 
 animals associated with him in structure. 
 
 Sight is attained among the Vertebrates by eyes con¬ 
 structed on the same plan as in the human system, invari¬ 
 ably two in number, lodged in cavities formed for their re¬ 
 ception in the bony frame-work of the face, and ex 1 libit 
 in the simplicity and completeness of their structure a 
 higher plan of organization than any we have yet ex¬ 
 amined. 
 
 There are in the Vertebrate eye three coats, or tunics : 
 
 1st. Sclerotic and Cornea ; 
 
 2d. Choroid, Iris, and Ciliary process; 
 
 3d. Retina ; 
 
 And three Lenses, consisting of refracting membranes and 
 
 humors: 
 
 Aqueous Humor, 
 
 Crystaline Lens, 
 
 Vitreous Humor. 
 
 The Sclerotic is the outside coat, or layer, and the Cornea 
 the frontal transparent part of it. The Choroid and Oil - 
 
86 
 
 VERTEBRATES.-ORGANS OF SENSE. 
 
 iary process form the second coat or membrane, and the 
 Iris the front curtain of the eye, the centre of which is the 
 pupil, and the Retina is the interior colored layer, on 
 which the optic nerve is spread. 
 
 ■ * 
 
 The Aqueous Humor is the front lens of the eye, it is a 
 liquid, filling the Cornea above and below the Iris. The 
 Crystaline Lens is a beautiful double convex lens, of a 
 semi-solid substance, and presents some of the most 
 wonderful mechanism in the whole animal kingdom. The 
 Vitreous Humor is the inner lens, and fills the globe or 
 body of the eye ; it is formed of a liquid contained in bags, 
 or chambers, formed of a delicate transparent membrane. 
 
 This optical instrument is adapted, among the different 
 Vertebrates, to the various kinds of life they lead; among 
 the Fishes, for aquatic vision; among the Birds, for a teles¬ 
 copic range, as they soar aloft in the sky, or microscopic 
 distinctness as they bring their eyes within a few inches of 
 their prey, in seizing it; and in the human system for the 
 wide and wonderful capabilities of the eye of Man. 
 
 It is protected and moved by systems of muscles, glands 
 and protective membranes, and hairs, peculiar to the vari¬ 
 ous necessities of life. 
 
Vertebrates—organs of motion. 
 
 87 
 
 CHAPTER XXXI. 
 
 VERTEBRATES-ORGANS OF MOTION. 
 
 Vertebrate motion comprises the widest range and most 
 delicate combination of mechanical structures that can be 
 found within the entire realm of nature or art. 
 
 All Vertebrates are possessed of an internal or enclo- 
 skeleton , formed of bones, arranged on the same model or 
 arche-type plan. 
 
 The skeleton answers a three-fold purpose : 
 
 1. It forms a frame-work to give shape and support to 
 the body. 
 
 2. It protects the more delicate organs of the system by 
 a series of cases and cages. 
 
 3. For the movements of the body, and the exertion of 
 force, it furnishes a system of levers, joints, hinges, etc., 
 constructed on the most complete accordance with the laws 
 of mechanics and motion. 
 
 Bones are composed chiefly of animal cartilage and 
 phosphate of lime. In the young of all Vertebrates and 
 in Fishes—especially in such orders as the Shark and Stur¬ 
 geon—the animal cartilage exists in greater abundance. In 
 the aged, and the bones of Snakes and Birds, exist the 
 greater proportion of mineral matter. 
 
 Bones are constructed of delicate plates or layers, through 
 which traverse, in all directions, tubes of various sizes, 
 
88 
 
 VERTEBRATES-OROAKS OE MOTION. 
 
 which distribute the blood-vessels and nerves which give 
 them life and growth. 
 
 These tubes, or lacunae, vary to a considerable extent in 
 form and size in the several classes of Vertebrates, and also 
 among the orders, in several cases, so that by examination 
 of them under the microscope the tribe to which the bone 
 belongs may be determined. 
 
 This is of the greatest importance in the study of the 
 extinct animals of past geologic ages. 
 
 The skeletons of Vertebrates are constructed from a 
 model or archetype plan, consisting of a succession of 
 bones, called vertebrae, and two arches with a pair of limbs 
 on each. 
 
 This model plan exists within no one animal, as in each, 
 those parts that are needed for the special kind of life 
 the animal was intended to lead, are the most developed. 
 Many parts are thus in one order of Vertebrates greatly 
 enlarged, and in others are rudimentary or altogether want¬ 
 ing ; while in another order of Vertebrates, these same parts 
 may exist in the opposite extreme of development. For ex¬ 
 ample, the Snake, to accommodate its methods of locomo¬ 
 tion, has an entire want of a breast-bone, while the Bird, 
 for the same purpose, has a large, strong, keel-shaped 
 breast-bone. 
 
 The Vertebrae themselves, are made of model or elemen¬ 
 tal parts, which vary greatly in their size and development 
 in different portions, even of the same animal, as in those 
 of the head, neck, chest, trunk, and tail. 
 
 An elemental Vertebra—that is, one in which all the 
 
VERTEBRATES-ORGANS OF MOTION. 
 
 89 
 
 parts are equally developed—would be constructed as fol¬ 
 lows : 
 
 a. Centre or body of the bone. 
 
 b. Two processes called the nerve or Neural processes, 
 which enclose the spinal cord or the great nerve masses 
 forming the brain. 
 
 ('. The upper or Neural Spine. 
 
 (/. The two transverse or side processes. 
 
 e . The two lower processes, enclosing the chief blood 
 vessels, and called the Haemal processes. 
 
 f. The lower or Haemal Spine. 
 
 The upper arch (g), is called the Neural Arch, and the 
 lower arch (A), the Haemal Arch. 
 
90 
 
 VERTEBRATES-ORGANS OF MOTION. 
 
 The archetype or model skeleton is constructed as fol¬ 
 lows : 
 
 Fig. 2. 
 
 Metatarsus 
 // i i i Phalanges 
 
VERTEBRATES-ORGANS OE MOTION. 
 
 91 
 
 EXPLANATION OF FIGURES ON MODEL VERTEBRATE 
 SKELETON. 
 
 Chain of Vertebra ?. 
 
 1. Cranial Vertebrae. 
 
 2. Cervical Vertebrae. 
 
 3. Dorsal Vertebrae. 
 
 4. Lumbar Vertebrae. 
 
 5. Sacral Vertebrae. 
 
 6. Coccygeal or Caudal Vertebrae. 
 
 Upper Arch. 
 
 1. Clavicle. 
 
 2. Caiacoid. 
 
 3. Scapula. 
 
 Lower Arch. 
 
 1. Ilium. 
 
 2. Ischium. 
 
 3. Pubes. 
 
 From this model plan there has been no deviation since 
 the first creation of Vertebrates in the remote ages of the 
 past, though from the modifications of it, have been 
 formed the great number of shapes that appear among 
 Fishes, Reptiles, Birds and Mammals. 
 
92 
 
 VERTEBHATES-MUSCULAR SYSTEM. 
 
 OH AFTER XXXII. 
 
 VERTEBRATES-MUSCULAR SYSTEM. 
 
 Muscles, among all animals, are the direct agents or 
 organs of motion. 
 
 If we compare the bony skeleton of the animal to the 
 masts, yards and hulk of the ship, we might liken the 
 muscular system to the ropes and sails, that give motion 
 and life to the mass. 
 
 Among Vertebrates, muscles attain their most complete 
 condition and highest development. 
 
 A muscle consists of bundles of fibres, bound together 
 by a silvery sheath; and by the alternate contraction and 
 relaxation of this bundle of little threads or fibres the 
 motions of the animal are attained. 
 
 The varied arrangement of these bundles of muscles, on 
 the different parts of the body, secure the symmetry and 
 beauty of form, that characterizes most members of this 
 type, especially among the classes of Birds and Mammals. 
 
 This is what artists term Surface or Superficial An¬ 
 atomy. 
 
 The muscular tissue of Vertebrates presents two con¬ 
 ditions—the striped and the unstriped. All the muscles 
 of voluntary motion, together with those of the heart, are 
 striped and of a red color; the muscles of involuntary 
 motion are unstriped and of a light color. 
 
VERTEBRATES-MUSCULAR SYSTEM. 
 
 93 
 
 The muscles of an animal are arranged in accordance 
 with the special structure of its skeleton ; either one being 
 given, the other may be accurately deduced from it. Hence, 
 by the discovery of bones of animals, long since extinct, 
 their muscular structure, and entire form, may be, and in 
 many cases has been, entirely rebuilt in what is called a 
 Hestoration. 
 
 The individual muscles are named : 
 
 1st. From their situation. 
 
 2d. From their direction. 
 
 3d. From their uses. 
 
 4th. From their shape. 
 
 5th. From the number of their divisions. 
 
 6th. From their points of attachment. 
 
 All Vertebrates are clothed, or cased, in an integument, 
 consisting of a true or deep skin, called the Derma , in 
 which are placed the surface glands and the nerves of 
 feeling; and the upper, or surface layer, called the Epi¬ 
 dermis, which assumes, in the several orders, a very wide 
 range of variation, such as the delicate skin of the human 
 system, or the thick hide of the Elephant or Hippopota¬ 
 mus, or is developed out into hair, wool, nails, claws, 
 hoofs, scales, horns, feathers, etc. 
 
 The Natural History of Vertebrates is, of all, the most 
 important and intimately connected with the economy of 
 human life, as it includes all those animals that are daily 
 associated with Man, on all parts of the earth, where he 
 himself resides; furnishing him food of their flesh, raiment 
 of their covering, and sharing with him his toils, privations 
 and dangers ; and, furthermore, indeed, it includes the 
 
94 
 
 VERTEBRATES-MUSCULAR SYSTEM. 
 
 history of Man himself, as being the highest member of 
 the entire animal kingdom. 
 
 The geological history of the type is one replete with 
 interest. 
 
 Among its members have been included animals of 
 most gigantic size, both in the water and on the land; but 
 a consideration of these points must be reserved for a 
 future part of this work. 
 
 We have thus reviewed the chief structural peculiarity 
 of the five types of the Animal Kingdom, and we shall next 
 proceed to the Methods of Study of the Classes of Each 
 Type. 
 
 But in doing this, we shall not trouble the learner with 
 a full review of all their structural peculiarities, but merely 
 make a brief review of those that are most important and 
 characteristic. 
 
CLASSES OF ANIMALS-TABLE OF CLASSES. 
 
 95 
 
 OHAPTEE XXXIII. 
 
 CLASSES OF ANIMALS-TABLE OF CLASSES. 
 
 Table VI. 
 
 'Sponges, ok Pobifeba, 
 PEOTOZOA. . . . ^ Ehtzopods, 
 
 Inftjsobia. 
 
 ' Polyps, 
 
 EADIATES. . . J Acalephs, 
 
 Echinodebms. 
 f Acephala, 
 
 MOLLUSKS. . . . <| Gastebopods, 
 i 
 
 l_ Cephalopods. 
 
 FWoBMS, OB VeBMES, 
 
 AETICULATES \ Cbtjstacea, 
 1_Insectians. 
 
 'Fishes, 
 
 VEETEBEATES. 
 
 Batbachians, 
 
 Eeptiles, 
 
 Bibds, 
 
 Mammals. 
 
 A description of these classes will be given, with illus¬ 
 trations, in Part II. 
 
 Ettd ol Jfart l. 
 
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