BONASSUS. 



BONE. 



670 



than half au inch longer than the outer ones ; the individual feathers 

 nearly aquare at the end. Tarsus feathered more than halfway down 

 anteriorly, and about half an inch lower posteriorly. All the toes 

 strongly pectinated." 



The dimensions on an average may bo taken as 18 inches in length, 

 and 23 or 24 inches in extent. 



Sir John Kichardson states, that after a careful comparison of the 

 specimens of Mr. Douglas's Tetrao Sabini, deposited in the Edinburgh 

 Museum, they appeared to differ in no respect from the young of 

 Tetrao Umbellus (Bonasia), and that the characters by which Mr. 

 Douglas distinguishes his bird are equally applicable to the latter. 



Douglas also found in the valleys of the Kocky Mountains, 54 N. 

 lat., and a few miles northward, near the sources of Peace River, a 

 bird which he regarded as a variety of B. Umbellus. 



BONASSUS. [BISON.] 



BONE, the organ which in higher animals forms the basis of the 

 fabric of the body. Many of the creatures placed at the bottom 

 of the animal scale, composed of soft gelatinous matter, and 

 buoyant in water, need no solid support ; but all animals that 

 possess solid organs, and whose body rests upon particular points, 

 must have some substance of a dense and inflexible nature to afford 

 to their various tissues and structures the requisite resistance and 

 support. The substances that serve this purpose are various, but the 

 most common are the salts of lime, sometimes the carbonate, some- 

 tunes the phosphate, and at other times both combined in different 

 proportions. Carbonate of lime constitutes the solid basis of many 

 of the compound zoophytes and the corals. It also constitutes the 

 principal part of the fabric of the shells of Molluca. It is found 

 also in the external skeleton of the Cruxtacea, aa the crabs and lobsters, 

 but in this instance the phosphate of lime is also present, and 

 predominates. It is in the skeletons of the Vertebrate animals that we 

 find the phosphate of lime greatly preponderating. This is 

 characteristic of bone. 



When an animal possesses bone as the solid support of its fabric 

 it indicates a high degree in the scale of organisation. Bone is an 

 elaborate structure found in no class below the Vertebrata. Even the 

 lowest order of this, which is the highest class of animals, is wholly 

 destitute of it ; for it is not found in large tribes of fishes, the shark, 

 the sturgeon, the ray, &c. In these the less highly-organised substance 

 called cartilage is substituted, and accordingly these fishes are called 

 cartilaginous in contradistinction to the osseous; and in all classes below 

 the cartilaginous fishes the dense and inflexible substance which sus- 

 tains the soft parts of the body, and which affords points of resistance 

 for the action of those parts, consists either of shells or of some 

 modification, and not of true organised bone. 



In general the structure which performs the office of bone in the 

 lower animals is placed on the exterior of the body, and often indeed 

 forms its external envelope; true bone, on the contrary, is always 

 placed in the interior. Even when it approaches the surface bone is 

 always covered by some soft part, as muscle, membrane, skin, Ac. 

 Crust, shell, bora the substances which form the skeleton of the 

 inferior animals are thus external, the soft parts being internal; but 

 in the higher animals the skeleton is always internal, and the soft parts, 

 which are sustained by it and which re-act upon it, are external. 



The office of bone in the animal economy is chiefly mechanical, and 

 the mechanical purposes to which it is subservient require that it 

 should be of different sizes and forms. In the human skeleton there 

 are commonly enumerated 260 different bones, which present every 

 variety of size and figure. But all these varieties may be reduced to 

 three classes : the long and round, as the bones of the upper and lower 

 extremities ; the broad and flat, as the bones of the skull ; or the short 

 and square, as the separate bones that compose the vertebral column. 

 The long bones are adapted for motion, the flat for protection, and the 

 square for motion combined with strength. Accordingly the long 

 bones, which are adapted to communicate a free range of motion, are 

 moulded into lengthened cylinders, and form so many levers, consti- 

 tuting organs of locomotion exquisitely constructed and combined for 

 the accomplishment of their office, aa is seen in the fin of the firth, in 

 the wing of the bird, and in the limb of the quadruped. In the 

 employment of the flat bones for the covering of some of the more 

 tender and delicate organs, aa the brain and spinal cord, the form of 

 these bones is such aa to add to their strength, as is manifest in the 

 vaulted roof of the skull ; while in the construction of the vertebral 

 column, composed of the short and square bones, which are so adjusted 

 as to afford a limited range of motion with a great degree of strength, 

 many and opposite purposes are effected. 



The structure, disposition, and connection of the individual bones 

 accomplish in the most perfect manner the following mechanical 

 uses : 1. By.their hardness and firmness they afford a support to the 

 soft parts, forming pillars to which the more delicate and flexible 

 organs are attached, and kept in their relative positions. 2. By the 

 same properties of hardness and firmness they defend the soft and 

 tender organs, by forming solid and strong cases in which such organs 

 are lodged and protected ; aa the case formed by the bones of the 

 cranium for the lodgment and protection of the brain ; by the bones 

 of the vertebral column for the lodgment and protection of the spinal 

 cord ; and by the bones of the thorax for the lodgment and protection 

 of the lungs, the heart, and the great vessels connected with it. 3. By 



affording fixed points for the action of the muscles, and by assisting 

 in the formation of joints, they aid and are indeed indispensable 

 adjuncts to the muscles in accomplishing the function of locomotion. 



Bone is a complex organ, and the arrangement and combination of 

 its constituent parts are highly curious. It is composed essentially of 

 two distinct substances, an animal and an earthy matter. The animal 

 matter is composed of gelatine ; the earthy matter consists principally 

 of phosphoric acid combined with lime, forming phosphate of lime. 



This structure of bone is rendered manifest by subjecting it to 

 certain chemical processes. If a bone be placed in a charcoal fire, and 

 the heat be gradually raised to whiteness, it appears on cooling as 

 white as chalk ; it is extremely brittle ; it has lost very much of its 

 weight, yet its bulk and shape are little changed. In this case the 

 membranous matter is wholly consumed by the fire, while the earth 

 is left unaltered. Over the surface of a bone so treated are visible a 

 number of minute crevices, the spaces which were filled in the natural 

 state of the bone with the animal matter ; and on breaking the bone 

 across, the size and shape of the cavities which contained the marrow 

 become manifest. If on the other hand the same bone be placed in 

 an acid sufficiently diluted to prevent its injuring the animal mem- 

 brane, and yet strong enough to dissolve the phosphate of lime if 

 for this purpose it be macerated in diluted nitric or hydrochloric acid 

 every particle of the phosphate of lime may be removed, and the 

 animal matter alone will remain perfectly uninjured and unaltered. 

 Accordingly the remaining substance retains the exact figure and 

 dimensions of the original bone, but it has lost all its other mechanical 

 properties. It is so soft and flexible that if either of the long bones 

 of the human arm that, for example, called the radius be treated in 

 this manner, it can with the utmost ease be tied in a knot. By the 

 first process the earth is obtained, deprived of its animal constituent ; 

 by the second, the membranous matter free from the earth. In the 

 bone both are combined ; in every constituent atom of it there is au 

 earthy in intimate combination with an animal matter. The first 

 gives it hardness, the second tenacity ; and thus by the intimate 

 combination of these elements two qualities which in unorganised 

 matter are scarcely compatible are combined. By increasing the pro- 

 portion of phosphate of lime any degree of hardness can be obtained : 

 the bony portions of the ear, the bony portions of the teeth, for 

 example, are as hard as marble, or even flint ; but substances so hard 

 would not do for the ordinary purposes of bone, because they would 

 be brittle in proportion to their hardness, and would be productive of 

 fatal mischief whenever they were subject to any sudden and violent 

 concussion. 



In certain diaeased states of the human system the earthy matter 

 preponderates in the whole osseous system, and in this condition per- 

 sons are liable to fracture their bones by the slightest accident. On 

 the other hand, the earthy matter is sometimes deficient ; then the 

 bones give way and become bent, and ultimately the body becomes an 

 immoveable mass. 



Bones not only differ so much from one another in their comparative 

 hardness according to the office which each has to serve that no two 

 bones possess the same degree of rigidity, but no bone is equally hard 

 in ita entire substance. When a section of a bone is made in such a 

 manner as to show its structure throughout, it is seen to consist of two 

 varieties, a hard or compact and an alveolar or spongy substance. 

 In general the compact forms the external and the spongy the internal 

 portion of the bone ; the compactest part of the bone forms a com- 

 pletely solid body, exhibiting scarcely any visible .'.rrangement, without 

 apparent fibres and laminae ; but towards the inner part of the bone 

 the substance becomes less and less dense,' until at length it presents 

 the appearance of minute and delicate fibres, which intersect each 

 other in every direction, forming the cells termed cancelli (lattice- 

 work). The transition from the compact to the spongy or cancellated 

 part is not marked by any distinct boundary ; the one passes into 

 the other by insensible degrees, showing that there is no essential 

 difference between them ; and indeed the evidence is complete that, 

 although in the densest part of the bone there u scarcely any trace of 

 specific organisation, it is made up of fibres and plates perfectly 

 similar to those of the spongy or cancellated part, differing from it 

 principally in its greater degree of condensation. Often in the centre 

 of the bone there is scarcely any even of the spongy matter, but a 

 hollow space is left, which is filled up with a series of membranous 

 cells in which the substance called marrow is lodged. 



In the arrangement of the fibres in different bones, so as to adapt 

 them to the specific offices they have to serve, there is exquisite 

 mechanism. Where the principal object iseither extensive protection, 

 or the provision of broad surfaces for the attachment of muscles, the 

 osseous fibres are so disposed as to form flattened plates, as in the 

 bones of the skull. When on the other hand a system of levers is 

 wanted, as in the limbs which have to sustain the weight of the 

 trunk, and to confer extensive powers of locomotion, the bones are 

 modelled into lengthened cylinders, generally somewhat expanded at 

 the extremities for greater convenience of mutual connection. The 

 shank or body of this hollow cylinder consists principally of compact 

 with but little spongy matter, while the extremity or head of it is 

 principally composed of spongy matter, with only a thin crust of compact 

 substance. The principal mechanical property required in every 

 cylindrical lever is rigidity, and more especially the power of resisting 



