Spine (zoology)

“ The long curved spines (s, s, s) , are a very curious feature of the appendage and the most marked character of the genus and species. They are articulated to the posterior margin of the joints, as the latter rest flattened out in the slate or shale, and there is no evidence but that they form a single series as shown in the specimen and in the drawing, figure 2. Each spine is constricted a little near its base, forming a rounded end or point of articulation; from this well out toward their pointed termination they retain an average width curving gently backward and inward. ”

“ The vertebræ, or joints of the spine, are excavated at each end in a conical cavity; the hollow thus formed between every joint and its neighbour is filled with a jelly-like substance, which is continuous through the whole spine, by means of a hole pierced through the centre of each vertebra. There is no true spinal marrow. ”

“ The external form of birds is modified so as to be subservient to aërial progression. The vertebral column, or spine, along the centre of which runs the spinal cord, is divided into three regions—the cervical, dorsal, and sacral regions—terminating in the caudal extremities, the number of vertebræ, or pieces, varying much in different genera. The body consists of the dorsal, sacral, and caudal parts of the column; laterally, of the ribs and pelvis; and beneath, of the sternum and the soft parts contained in it. Its anterior part, containing heart, lungs, and liver, is named the thorax ”

“ Simple rays are also sometimes articulate. Rays thus jointed are known as soft rays, while those rays which are neither jointed nor branched are called spines. A spine is usually stiff and sharp-pointed, but it may be neither, and some spines are very slender and flexible, the lack of branches or joints being the feature which distinguishes spine from soft ray.
The anterior rays of the dorsal and anal fins are spinous in most fishes with thoracic ventrals. The dorsal fin has usually about ten spines, the anal three, but as to this there is much variation in different groups. ”

“ If, originally, the spine in vertebrate animals consisted from head to tail of separate movable segments, as it does still in fishes and some reptiles—if, in the evolution of the higher vertebrata, certain of these movable segments were rendered less movable with respect to each other, by the mechanical conditions to which they were exposed, and at length became relatively immovable—it is comprehensible why the sacrum formed out of them should continue ever after to show more or less clearly its originally segmented structure. ”

“ Some of these spines bear little pincer-like organs called pedicellariæ, which are capable of considerable movement. Many of these little organs are arranged in groups about the spines, which swell at the point of attachment to the surface of the starfish, thus forming a shelf or base, around which these organs arrange themselves in the form of a wreath, the spine projecting high above the center. The exact function of these little organs is not known, although they have been seen to catch small animals, such as crustacea, and this is probably one of their duties. ”

“ The habitual rigidity of the spine, as compared with its possible freedom, is more noticeable in training, of course, than is that of any other part of the body. Each vertebra should be so distinctly independent of every other, as to make the spine as smoothly jointed as the toy snakes, which, when we hold the tip of the tail in our fingers, curve in all directions. Most of us have spinal columns that more or less resemble ramrods. It is a surprise and delight to find what can be accomplished, when the muscles of the spine and back are free and under control. ”

“ The scales of the underside of the body are of the same form as those of the back, and are furnished with similar but smaller and less produced spines. The back of the neck of the two specimens I have seen is furnished with a large rounded protuberance like a cherry, covered with large granular spinous scales, and armed on each side with a large conical spine; but I do not know if this is common to the species or merely accidental in these individuals ”

“ It is an interesting fact that the spine is the central and fundamental structure of all the higher organisms on this earth. In the course of the evolution of life on this planet there developed from the very simplest forms of animal organisms two different higher forms of life- on the one hand the vertebrate animals, possessing an internal skeleton, and on the other hand the insects, clams, crustaceans and other creatures that have their skeletons on the outside, as one may say, in the form of shells. ”

“ But some snakes have hundreds of these vertebræ. The boas, for example, have no less than three hundred and four!
In the next place, remember that all these vertebræ are fastened together by what we call ball-and-socket joints. That is, there is a round knob at the back of each vertebra which fits into a socket in front of the vertebra behind it. This gives to the spine of a snake great strength, for a vertebra cannot be forced out of its place without breaking the vertebra behind it. And it also allows the spine to be curled and twisted about in almost any direction ”

“ A neck-swing, and lying down in the day, should be occasionally used to prevent or remove any curvature of the spine. The rest as in Species 13 and 15 of this genus.
18. Spina protuberans. Protuberant spine. One of the bones of the spine swells, and rises above the rest. This is not an uncommon disease, and belongs to the innutrition of the bones, as the bone must become soft before it swells; which softness is owing to defect of the secretion of phosphorated calcareous earth. The swelling of the bone compresses a part of the brain, called the spinal marrow, within the cavity of the back-bones ”

“ The shoulder-blade of mammals is as a rule a much-flattened bone with a ridge on the outer surface known as the spine; this ridge ends in a freely-projecting process, the acromion, from which a branch often arises known as the metacromion. This gives a bifurcate appearance to the end of the ridge. The spine is less developed and the scapula is narrower in such animals as the Dog and the Deer which simply run, and whose fore-limbs therefore are not endowed with the complexity of movement seen, for instance, in the Apes. ”

“ The spine system is grouped and spreading, with four to seven central spines sometimes three inches in length, often crooked or twisted, and surrounded by smaller radials scattered along the stem ridges, not more than a fourth-inch to an inch long, all thorns of a beautiful golden or light translucent yellow. The spines often vary in their general characteristics, long and short, twisted and bulbous, straight and bent and twisted, flat and grooved, tough and easily broken. ”

“ Just as the muscular arm has been the determining factor in the structure of the Ophiuroidea, so the movable spine has been {506}the leading factor in the evolution of Echinoidea. The spines have cup-shaped basal ends, which are inserted on special projections of the plates of the skeleton called tubercles. The tubercle is much larger than the cup, and hence the spine has a great range of possible motion. ”

“ The surface of the neural spine is sometimes marked with a shallow groove. The spines are longer and more slender in the genera Œstocephalus, Urocordylus, and Ctenerpeton than they are in the species of the genus Ptyonius, where they are short, although the usual pectinations are present. ”

“ If, on the contrary, the spine is a terminal tail-spine, then, as far as the fossilized remains indicate, the animal consisted of a dorsal shield, a ventral shield, and a tail-spine, to which must be added two apparently lateral pieces and a few scales. If the animal did not possess a flexible body with a tail-fin, but terminated in a rigid spike after the fashion of a Limulus-like animal, then it must have moved by means of appendages. ”

“ In the animal, nature makes a vertebra, or a spine of vertebræ, and helps herself still by a new spine, with a limited power of modifying its form,—spine on spine, to the end of the world. A poetic anatomist, in our own day, teaches that a snake being a horizontal line, and man being an erect line, constitute a right angle; and between the lines of this mystical quadrant, all animated beings find their place: and he assumes the hair-worm, the span-worm, or the snake, as the type or prediction of the spine. Manifestly, at the end of the spine, nature puts out smaller spines, as arms ”

“ In accord with this fact it will be observed that9 the foramen or hole in the base of the skull through which the spinal cord passes is adjusted closer and closer to the centre of the base of the skull as the spine becomes erect. In man, whose spinal column is erect, the hole is in the centre of the base; in the reptile, whose spine is horizontal, the hole is at the extreme end of the base. In the ape the spinal axis is at an angle with the vertical line, and the plane of the face conforms to a similar one. ”

“ Spines equal, straight, three-sided prismatic, thorny, connected by three convex bows, the meeting branches of lateral spines arising in one pair from the middle part of each spine. Therefore the skeleton exhibits three large ovate meshes only. ”

“ In front the transverse wedge is flattened and compressed, so as to look forward and outward, and in the middle shows a large ovate pneumatic foramen. Behind, the wedge is compressed so as to look backward and downward.
The neural spine is massive and forms rather more than half the height of the vertebra. It is flattened with a ridge rising near its base in front and ascending in a concave curve obliquely backward and upward. ”

“ It is not invariable in a long series of female examples; occasionally one is found with four spines on one of these genual joints, in others there is occasionally but one spine and sometimes (but rarely) none; perhaps in this case broken off? I am inclined to attach some importance as a specific character to the number, presence, or absence of these spines on the outer side of the genual joint of the third pair of legs ”

“ I was able to distinguish that the two lower pair of spines on the ventral surface, are seated a little way one below and within the other, as in S. vulgare. The abdominal spines altogether form quite a brush, and there are certainly several more than in S. vulgare, and those on the two sides are much longer.
Antennæ.—The disc is hoof-like, with the upper surface forming a straight line with the upper edge of the basal segment; the apex is pointed and clothed with some fine down; there is a single spine pointing backwards, which rises from the lower flat surface. ”

“ The first of the three dorsal spines is very strong, roughened in front like a file, and hollowed out behind to receive the second much smaller spine, which, besides, has a projection in front, at its base, fitting into a notch of the first. Thus these two spines can only be raised or depressed simultaneously, in such a manner that the first cannot be forced down unless the second has been previously depressed. ”

“ The structure of the dorsal spines is similar. There are no secretory glands imbedded in the membranes of the sacs and the fluid must be secreted by their mucous membrane. The sacs are without an external muscular layer and situated immediately below the thick, loose skin which envelops the spines at their extremity. The ejection of the poison into a living animal, therefore, can only be effected as in Synanceia, by the pressure to which the sac is subjected the moment the spine enters another body. ”

“ Comparing this form with the more spinose species of Tuzoia, we note first the extraordinary extension of the dorsal line into long, upturned spines such as we find in some living Crustacea. Assuming that the longer spines occur on the rear margin and that the outer edge extends only to the keel, we note the very long spine in the usual position between the dorsal extension and the keel. If this is only the inner part of the test one or more marginal spines should occur beyond the keel. At least five spines edge the anterior margin exclusive of the dorsal extension. ”

“ The cavity of the interior of the limb bones is usually filled with calc-spar stained with organic matter, but showing no structure; and the inner side of the bony wall is smooth without any indication of cartilaginous matter lining it.
The vertebræ, in the external aspect of their bodies, remind one of those of fishes, expanding toward the extremities, and « 274 » being deeply hollowed by conical cavities, which appear even to meet in the centre. There is, however, a large and flattened neural spine. ”

“ Manifestly, at the end of the spine, nature puts out smaller spines, as arms; at the end of the arms, new spines, as hands; at the other end, she repeats the process, as legs and feet. At the top of the column, she puts out another spine, which doubles or loops itself over, as a span-worm, into a ball, and forms the skull, with extremities again ”

“ It seems rather constant in each species, so that all the pieces of the skeleton of one specimen possess either four or six or eight lateral meshes, &c. But sometimes individual irregularities occur. In the majority of species each skeleton-piece is armed with spines. Usually a radial horizontal spine starts centrifugally from each corner of the basal ring, and on the side of this a small tooth or thorn often starts centripetally or downwards. ”

“ The neural arch is very broad (in an antero-posterior direction) and is extended dorsally as a wide neural spine (1) . The neural spines of the following thoracic and the first two or three lumbar vertebræ are increasingly broad and truncated. The transverse processes are very broad, long and thin, and in the third to eighth vertebræ they have [56] two articular surfaces, an anterior and more medial one for articulation with the head of the rib (3) and a posterior and more distal one for articulation with the tubercle of the rib. ”