Animal body

“ Part 8 We have now to consider the remaining homogeneous parts, and will begin with flesh, and with the substance that, in animals that have no flesh, takes its place. The reason for so beginning is that flesh forms the very basis of animals, and is the essential constituent of their body. Its right to this precedence can also be demonstrated logically. For an animal is by our definition something that has sensibility and chief of all the primary sensibility, which is that of Touch; and it is the flesh, or analogous substance, which is the organ of this sense. ”

“ Nor is hearing, nor is leaping, nor are many of the things which the toad can do; and animals can exist, and do exist, without any of those organs which enable the toad to see and hear and leap. But the body of any animal must be capable of performing the few essential processes which are necessary to animal life. How surprisingly simple such a body can be will be later discovered. But in most animals the body is a complicated object, and is able to do many things which are accessory to the really essential life-processes, and which make its life complex and elaborate. ”

“ Let us note, in conclusion, that it is through the blood-system, ramifying to all parts of the body, and the nerve-system, the ramifications of which are not less perfect, that the larger and higher organisms are knit together into an organic whole. ”

“ But let it not be supposed while I thus object to the reputed vitality of the blood, I wish either directly or indirectly to detract from the importance of its use in the animal system. Conveying the principles, which acted on [21] by living organs form the various parts, and presuming it the most general and applicable stimulus of the body, I can still conceive its importance, and appreciate its value though itself be dependent on external agents for its essential qualities. ”

“ All animals therefore, I contend, have a similar cause of their organization, originating from a single living filament, endued indeed with different kinds of irritabilities and sensibilities, or of animal appetencies; which exist in every gland, and in every moving organ of the body, and are as essential to living organization as chemical affinities are to certain combinations of inanimate matter. ”

“ It is continually taking in water from the body, or the outside, and driving it out again, and thus aids in respiration and excretion. The animal has no organs in the proper sense of the word, and yet it has the rudiments of all the functions which we possess. ”

“ I feel as if I were nearer to the vitals of the globe, for this sandy overflow is something such a foliaceous mass as the vitals of the animal body. ”

“ As we read his views, one cardinal axiom seems always prominent: "It is not the organs—that is to say, the nature and form of the parts of the body of an animal—which have given rise to its habits and its special faculties ”

“ Our first object must be to study the structure of the animal. The whole of his body is inclosed within a hide, a skin covered with hair; and if that hide or skin be taken off, we find a great mass of flesh, or what is technically called muscle, being the substance which by its power of contraction enables the animal to move. ”

“ Such animals—little more than masses of living animal jelly—now abound in the waters, and protect themselves by secreting calcareous skeletons, often complex and beautiful, and penetrated by pores, through which the soft animal within can send forth minute thread-like extensions of its body, which serve instead of limbs. ”

“ I have described, in the second chapter, the gait and appearance of a dog when cheerful, and the marked antithesis presented by the same animal when dejected and disappointed, with his head, ears, body, tail, and chops drooping, and eyes dull. ”

“ In the higher animals we are accustomed to speak of certain organs as vital and necessary for the further existence of the animal; these are essentially the central nervous system, the respiratory system, the circulatory system, and the digestive system. ”

“ Fishes, birds, quadrupeds, all manifest a divergence from each other in the first action of the respirating organs—in the nervous system—and in all the apparatus connected with the movements of the heart and blood-vessels. There is no structural interchange, in the minutest part, that distinguishes the orders of the perfect animal in any of the antecedent fœtal conditions ”

“ In proportion as the animal grows, this organ is filled with a liquid which, in passing through the spinners, the orifice of which you see, dries in the air, and forms a thread. This thread constitutes the silk.
The nervous system of the animal, placed below the digestive tube is with insects, as with all animals, of the highest importance. It is the nervous system which seems to animate all the other organs, and particularly the muscles. The latter are what we call flesh or meat. They are in reality the organs of movement, with our caterpillar as with man himself. ”

“ The active waking life of the animal, that part of its life which distinguishes it from the plant, involves the external parts—the sense-organs and the extremities. An animal is, as it were, made up of a complex of organs performing the vegetative functions, assimilation, growth, and reproduction, surrounded by an envelope formed by the limbs, the sense-organs, the nerves and the brain, which is the centre of this "envelope." ”

“ Are all animals similarly complex in structure, and capable of doing such a great variety of things? We shall find that the answer to this question is No. There are many animals in which the body is composed of but a few parts, and whose life includes the performance of fewer functions or processes than in the case of the toad. There are many animals which have no eyes nor ears nor other organs of special sense. There are animals without legs or other special organs of locomotion; some animals have no blood and hence no heart nor arteries and veins. ”

“ Gradually the busy little cells arrange themselves to build up heart, lungs, brain, stomach, and limbs, for which the yelk and white furnish nutriment. There is a small bag of air fastened to one end inside of the shell; and when the animal is complete, this air is taken into its lungs, life begins, and out walks little chick, all its powers prepared, and ready to run, eat, and enjoy existence. ”

“ The fact that in all animals, down almost to the very beginnings of life, sense organs exist, suggests that sensation may be almost, if not quite, coextensive with animal life. All mammals, birds, reptiles, amphibians, and fishes have the same special sense organs as man, and the organs of sight, sound, taste, and smell occupy in all vertebrates the same relative positions in the head. Birds see better than any other animals, and carnivora smell better. ”

“ All animals are provided with two distinct sets of organs: 1. The master tissues, the nervous and muscular tissues, the voluntary muscular tissues, which are the organs of animal life, the voluntary, the active organs that do the work, consume the food, and throw off the waste material ”

“ Seeking, then, for the features likely to distinguish the most highly developed animal, we may safely say that they will appear in that animal exposed to the most complex conditions, adapted to the greatest variety of food, possessed of the most fully specialized organs, capable of using its innate forces to the best advantage, and commencing its individual existence with the best start in life. ”

“ Why there are more than those already mentioned, and what they are, and whence they arise, I will now proceed to consider, starting from the principle already admitted, which is that every state consists, not of one, but of many parts. If we were going to speak of the different species of animals, we should first of all determine the organs which are indispensable to every animal, as for example some organs of sense and the instruments of receiving and digesting food, such as the mouth and the stomach, besides organs of locomotion. ”

“ But both of these animals agree in possessing in common the capability of performing those processes such as taking food, breathing, reproducing, etc., to which attention has been called as being indispensable to all animal life. ”

“ The animal, in addition to these vegetative functions, has another set of powers, by the use of which he becomes conscious of a world external to himself, and brings {149}himself into active relations with it. By means of the vegetative processes, his life and species are maintained; while, by means of certain animal functions, he feels, acts, and thinks. ”

“ The appendages to the trunk, like the arrangement of the nervous system, furnish also a leading peculiarity of structure, and they may be selected as the basis of a classification founded upon outward form. For the most part, destined either for the purposes of locomotion, or to assist in the procuring of food, they must of necessity be in perfect accordance with the nervous and nutritive systems. Hence the capacities, powers, and general habits of an animal, must be in correspondence with this part of its organisation ”

“ Each animal is provided with an organ, which it is difficult to designate by any name, since it performs the office of so many members, and is the only indicator of the existence of vital powers in the creature. ”

“ To put this question in an arbitrary sense would

be like asking if a mammal is the product of its lungs, or its heart, or its stomach, or of vegetable constituents, or of the atmosphere; whereas each of these conditions, internal and external, is necessary to the life of the animal. ”

“ One of the most interesting occupations which the wide field of Zoology offers to the naturalist, is the investigation of those remarkable adaptations of organs to functions, and of these again to the necessities and well-being of the entire animal. ”

“ These functions, among which are sensation, motion, and volition, not only distinguish the animal from the plant, but, in proportion to their development, elevate one creature above another; and it is by virtue of his pre-eminent endowment, in these respects, that man holds his position at the head of the animal creation.
3. Animals whose structure is simple? As we approach man? Dependence of the animal functions of man?
3. Among animals whose structure is very simple, the hydra, or fresh-water polyp, being an example, no special organs are empowered to perform separate functions ”

“ Accordingly, zoologists have so arranged the animal kingdom that warm-blooded animals, including man, the birds, and the quadrupeds, are classified together; while the cold-blooded animals, such as the fish, tortoise, frog, and all that have no vertebral column, are classed by themselves. ”

“ The arrangement of animals, according to the organs of sense, coincides consequently with that derived from the anatomical systems, and each animal division is therefore determined by two principal organs, by a vegetative and an animal. ”

“ When we ascend to the somewhat higher plane of physiology we find in a general way the same relationship to animals. Of the four grand leading functions of the animal, nutrition, reproduction, voluntary motion, and sensation, all are performed by man as by other animals. Here, however, there are some marked divergences connected with special anatomical structures, on the one hand, and with his higher endowments on the « 485 » other. With regard to food, for example, man might be supposed to be limited by his masticatory and digestive apparatus to succulent vegetable substances. ”

“ But there is so close a solidarity between ourselves and our poor relations of the animal world, that our inaccessible inward parts may be supplemented by theirs. A comparative anatomist knows that a sheep’s heart and lungs, or eye, must not be confounded with those of a man; but, so far as the comprehension of the elementary facts of the physiology of circulation, of respiration, and of vision goes, the one furnishes the needful anatomical data as well as the other. ”

“ I. All those internal motions of animal bodies, which contribute to digest their aliment, produce their secretions, repair their injuries, or increase their growth, are performed without our attention or consciousness. They exist as well in our sleep, as in our waking hours, as well in the fœtus during the time of gestation, as in the infant after nativity, and proceed with equal regularity in the vegetable as in the animal system. ”

“ But all animals have and hold a principle in their interior. Wherefore the heart is seen as the first distinct part in animals that have blood; for it is the origin of all the parts, whether similar or dissimilar; and the creature that begins to feel the necessity of nourishment, must already be possessed by the principle of an animal and a full-grown fœtus. ”

“ All the actions which are common to us and the lower animals depend only on the conformation of our organs, and the course which the animal spirits take in the brain, the nerves, and the muscles; in the same way as the movement of a watch is produced by nothing but the force of its spring and the figure of its wheels and other parts. ”

“ The general circulating fluid of animals, and that on which the nourishment and growth of their bodies depend, and from which all the secretions are formed. It is warm and red in vertebrated animals; and, for the most part, cold and white in the invertebrata. In man and all other mammals, and in birds—the two highest classes of the animal kingdom—the blood, though collectively forming but one circulating stream, varies considerably in appearance according to the part or vessels in which it is found. ”

“ Animals become nobler in rank, the greater the number of organs which are collectively liberated or severed from the Grand animal, and which enter into combination. An animal, which e. g. lived only as intestine, would be, doubtless, inferior to one which with the intestine were to combine a skin; and that animal again must be regarded as higher than the latter, which should present, in addition to these organs, vessels, liver, branchiæ, tracheæ, and lastly bones, &c. ”