Skeleton (biology)

“ This exoskeleton differs from the main or axial skeleton of the higher animals, the latter being inside of the body. The exoskeleton is dead, being secreted by the cells lining the body, while the endoskeleton is, in part at least, alive and is capable of growth, e.g. a broken arm or leg bone will grow together. [Pg 186] But a man has certain parts of the skeleton, as nails or hair, formed by the skin and in addition possesses inside bones to which the muscles are attached. Some of the bones are arranged in a flexible column in the dorsal (the back) side of the body. ”

“ This is more especially the case with respect to the skeleton, which forms the foundation of all the other mechanisms within the body, and is of the highest importance in the history of fossil animals, of which we rarely find any other remains besides the bones, and teeth, and the scaly or osseous integuments. ”

“ A. Up to a certain point, the evidence is strikingly favourable to the hypothesis of human evolution. By this is meant the gradual development of the modern type of skeleton found in association with a large and active brain, capable of manifesting its activity in a great variety of ways. Most of the oldest human skeletons just described, differ from this type. Although a difference cannot be demonstrated in respect of cranial capacity, yet those older skeletons are usually distinguished by the heavier jaw and by stout curved limb-bones of such length as to indicate an almost dwarf stature. ”

“ The skeleton is far from being merely the mechanical frame-work of the animal. Such a frame-work it is, of course, but it is much more than that; it is the living and growing expression of the entire organism and is modified, not only by age, but by the conditions of the environment and accidental circumstances [43] as well. The bones of the same individual differ very materially in early youth, maturity and old age; so long as the animal lives, its bones are perpetually changing, slowly it is true, but with ready response to needs. ”

“ In animals the skeleton is usually, and in higher animals always, rendered more rigid and permanent by the deposit in it of lime salts, thus leading to the formation of bone. Sometimes, as in most of the lower or invertebrate animals, the skeleton is on the surface and thus acts as a protection as well as a framework. ”

“ In general, it may be said that the higher the geological antiquity of a skeleton is, the greater is the chemical alteration which it has undergone. Bones of Pleistocene or later date have, as a rule, suffered little change beyond the loss of more or less of their animal matter, the amount of such loss depending chiefly upon exposure to the air. Bones which, for thousands or tens of thousands of years, have been buried in dense cave-earth, in an antiseptic peat-bog, or in asphalt, are often perfectly sound and fresh when taken up. ”

“ Very clearly it had not been covered by the limestone talus upon the floor of the cave. Portions of the encrusting matrix enabled one to determine that the bones had been in large part, if not wholly, articulated when discovered. Every collector of vertebrate fossils knows how rarely so large a skeleton as that of a man is found preserved entire and with the bones in position. ”

“ Corresponding bones of a recent human skeleton accompanied the exhumed remains. The following is Dr. Flight’s "Report":—
"The bone is considerably altered in appearance and character; it is of a fine dark brown colour, and is readily reduced to a powder in an iron mortar. When heated, water and only oily matter are evolved, and it turns black or nearly so; treated with soda-lime, a large quantity of ammonia is given off. The density of the bone is 2⋅138, that of the recent tibia was found to be 1⋅985. ”

“ The skeleton is formed by small crystals and long threads of vitreous silica, cemented together, during life, by protoplasm. They are arranged in longitudinal and annular bands so as to form a long curved cylinder, about nine to twelve inches long, the walls of which are about one inch in thickness. The threads and bands are interwoven with the greatest regularity, and when the skeleton is freed from the adhering organic matter, it looks extremely beautiful. ”

“ With one consent, though in silence, every one gathered nearer, and looked in—they saw a human skeleton. The action of the elements, which the sands had not been able to impede, had destroyed every vestige of a human frame, except those discoloured bones, and long tresses of dark hair, which were wound around the scull. ”

“ The skeleton of the Mammalia consists almost solely of the endoskeleton. It is only among the Edentata that an exoskeleton of bony plates in the skin is met with. As in other Vertebrates, the skeleton is divisible into an axial portion, the skull and vertebral column, and an appendicular skeleton, that of the limbs. The bones of mammals are well ossified, and in the adult there are but few and small tracts of cartilage left. ”

“ It is very seldom that the entire skeleton of an animal is found in a fossil state: in most instances the bones have been separated and scattered before they were entombed, and a tusk, a jaw, or a single joint of the back-bone is very often all that is met with, and frequently too in a mutilated state. ”

“ Had the osseous system been merely intended to give shape to animals, and preserve the relative position of their parts, it might, for any useful purpose, have been as well formed of one piece; and accordingly, when almost all the bones of the body have been anchylosed, or immoveably united to each other by disease, the functions of life have gone on uniformly to an advanced age. There is a remarkable skeleton of this kind preserved at Trinity College, Dublin; where all the large bones of the body are immoveably united together, except the lower jaw, and the joints of the fingers ”

“ This skeleton is that of a large and powerfully built man, the bones being very heavy and strong with marked impressions and prominences for muscular attachment. The skeleton, with the exception of some of the small bones of the hands and feet is complete.
The skull is large and massive, and the lower jaw very strong and heavy. ”

“ Several small copper awls in bone handles, and the shells of box-turtles, were also found with the skeletons. Many fragments of pottery and broken bones of animals were scattered through the mass of stones and human bones. At the feet of the skeleton, in the center of the mound, there was an upright slab of limestone 2 feet long by 20 inches wide, and with this skeleton were the following objects: Resting on the chest was a large ornament made from the apex of a conch shell, with a hole at one edge for suspension ”

“ It is so very rare an instance to meet in fossile remains with a real human bone, skull, jaw-bone or entire human skeleton (as in one particular instance was found enclosed in a lime-stone, mixed with some few utensils and instruments of the primitive world, such as a stone-knife, a copper axe, an iron club, and a dagger of a very ancient form, together with some human bones) ; that the very rareness of the exception serves only to confirm the general rule. ”

“ The geologist finds a fossil skeleton. His acquaintance with anatomy enables him to pronounce that the objects found are bones. He sees cylinders, condyles, cavities for the marrow, scars of attachment of muscles and tendons, foramina for the passage of nerves and blood-vessels; he finds the internal structure, no less than the form and surface, such as to leave not a doubt that these are real bones. Now universal experience has taught him that bones imply the existence of flesh; that flesh implies blood; that blood implies life; that life implies time. ”

“ The embryological and phylogenetic histories are in complete unison to show that the cranial skeleton is older than the spinal, and this primitive branchial skeleton is also in harmony with the laws of evolution, in that its structure, even in the adult lamprey (Petromyzon) , never gets beyond the stage characteristic of embryonic cartilage in the higher vertebrates.
The simplest and most primitive skeleton is that found in Ammocœtes and consists of two parts: (1) a prosomatic, (2) a mesosomatic skeleton. ”

“ It must not be supposed that no successful restoration of missing bones is practicable; on the contrary, this can often be done very easily, but only when all the essential parts of the skeleton are known.
Even if an unlimited number of perfect skeletons were available, of what use would they be? A skeleton is a very different looking object from a living animal, and how is it possible to infer the latter from the former? Do the many restorations of extinct mammals which this book owes to the skill of Mr. ”

“ Yet in these same formations there is no want of bones of mammalia belonging to extinct and living species. In the course of the last quarter of a century, thousands of them have been submitted to the examination of skilful osteologists, and they have been unable to detect among them one fragment of a human skeleton, not even a tooth. ”

“ In the Carnivora the skeleton, or bony framework of the body, attains its utmost perfection, both as a tissue and as machinery. Its tissue is dense, white, and ivory-like, every bone is exquisitely moulded and polished, so that there are few more beautiful objects of study than a well-prepared Cat’s skeleton, and almost none more instructive or better calculated to give an idea of the perfection of “animal mechanics.” ”

“ Candid comparison of these five skeletons shows that they are not only very like each other generally, but are identical in the structure, arrangement, and connection of all the parts. The same 200 bones compose the skeleton in man and in the four tailless anthropoid apes, our nearest relatives. The same 300 muscles serve to move the various parts of the skeleton. The same hair covers the skin; the same mammary glands provide food for the young. ”

“ So far we have considered merely the mode of development of the most important organs of the body, but we have said nothing of the most important supporting structure, namely, the skeleton. The earliest appearance of anything in the shape of a skeleton is the structure known as the notochord, a structure of immense importance and interest in the embryology of all vertebrate animals, in which it is a temporary thing only. ”

“ THE SKELETON OF REPTILES
The bony framework, or skeleton, that which gives form and stature to the body, and which serves for the support of the soft parts and the attachment of muscles, is, with rare exceptions, all that is ever preserved of fossil animals. Because, therefore, students of extinct animals must rely so much, if not exclusively, upon the skeleton much attention has been given to the study of comparative osteology, the science of bones. ”

“ No other complete skeleton was found in the mound, though pieces of human bones representing nearly all parts of the skeleton were scattered through different parts of the structure, together with the bones of other animals. ”

“ The vertebrata, too, all have their hard skeletons, easily capable of preservation, whether it be in the form of the massive exo-skeleton of bone that characterized the older ganoidal fishes, or the compact endo-skeleton of the reptiles and mammals. ”

“ After skulls, vertebræ are the most useful parts of the skeleton, then limb bones. If complete skeletons are found, they are usually well worth some trouble in transporting. If fossil bones are found abundantly in any locality, and the traveller has no sufficient means of transport, he will do well to carry away a few skulls, or even teeth, and carefully note the locality for the benefit of future geologists and explorers. ”

“ In making the division of Vertebrate animals into classes the skeleton is often almost ignored. Its value is entirely empirical and based upon the observed association of the various forms of bones with the more important characters of the brain and other vital organs. What is understood as a Mammalian or Avian character in the skeleton is the form of bone which is found in association with the soft vital organs which constitute an animal a Mammal or a Bird. ”

“ Myriads, perhaps millions of skeletons of animals like this one have come at different times under human observation, which have been obviously referrible to creatures that, within the same sphere of observation, had been alive. No similar skeleton has ever come within the range of recorded observation that could be referred to any other source than that of a quondam living animal. On these premises you build the conclusion that a skeleton must, at some time or other, have belonged to a living animal. ”

“ It is well known that a competent naturalist needs but a single fossil bone to describe the animal itself, and tell us its habits. So also anthropologists need but fragments of the human skeleton, especially of the skull, to describe characteristics of the race to which the individual belonged.
This cut, though an ideal restoration, is a restoration made in accordance with the results of careful study of fragmentary skulls found in various localities in Europe. The head and the face present a savage aspect; the body harmonized with the head; the height was not more than five feet and a half ”

“ The skeleton begins as a continuum, and a continuum it remains all life long. The things that link bone with bone, {713} cartilage, ligaments, membranes, are fashioned out of the same primordial tissue, and come into being pari passu, with the bones themselves. The entire fabric has its soft parts and its hard, its rigid and its flexible parts; but until we disrupt and dismember its bony, gristly and fibrous parts, one from another, it exists simply as a “skeleton,” as one integral and individual whole. ”

“ The ‘sub-boulder-clay’ skeleton, discovered near Ipswich in 1911, was in an extraordinarily contracted attitude. Many parts are absent or imperfect, owing to the solvent action of the surroundings, but what remains is sufficient to reveal several features of importance (cf. fig. 29) .
Save in one respect, the skeleton is not essentially different from those of the existing representatives of humanity. The exception is provided by the shin-bone. ”