MAMMALIA. 



cords and other working tackle which connect the 

 muscles with that which they move, or give direction 

 and security to the motions. 



The parts moved, and, generally speaking, the 

 fulcra or points which give resistance so as to pro- 

 duce the motion, are the hones ; and as thev are the 

 most permanent part of the animal, those which give 

 stability and consistency to the whole, and which 

 determine its general form and principal modes of 



. action, it is desirable that they should be first under- 

 stood ; because the greater part of the action of an 

 animal may be said to consist in moving or changing 

 the positions of the bones. In doing this we shall 

 first very shortly notice the general structure of bones 

 and their appendages ; and then take a very brief 

 view of their number and arrangment in the human 

 body ; as that body, by not being adapted to any peculiar 

 locality or kind of action, which is the case with the 

 bodies of almost all other animals, is perhaps the best 

 which c-iii be used for this very general purpose. In 

 treating of the bones and other parts of the animal 

 structure whicli have no general English names, a 

 few technical words are unavoidable ; but we shall 

 use them as sparingly as possible, and, generally 

 speaking, accompany them by explanations, when 

 such appear to be necessary. 



BONES AND THEIR APPENDAGES. Bones are very 

 . differently shaped, according to the purposes which 

 they have to answer in the motions of the animal ; 

 and their shapes are often so peculiar, that to us thev 

 are unaccountable. But in every case where the com- 

 . plete use of the bone has been ascertained, it is in variably 

 found that in shape, in strength, and in quantity of 

 matter, the bone and also every individual part of it, 

 are perfect, nor could an improvement be imagined 

 by any device whatever. The bones of the limbs are 

 nearly cylindrical, and they are comparative!}' straight, 

 though those which are most, loaded with muscles 

 have generally a peculiar curvature, which both in- 

 creases their strength, and makes the motions of the 

 joints less jolting or jarring than it would be in the 

 case of perfectly straight bones applied to each other. 

 Others again are long and curved, as in the ribs ; and 

 bones of this form generally support the walls of 

 cavities admitting of a varied capacity, as the chest, 

 which expands and contracts iil the operation of 

 breathing. Some bones are broad and flat, and when 

 these have much fatigue to undergo, they are in 

 general strengthened by a ridge placed longitudinally 

 upon the external face of the flat bone. The blade- 

 bones, which are embedded among the soft parts of 

 the shoulders, aud not articulated or jointed with the 

 spine or back-bone, are of this description. The 

 haunch bones which support the posterior part of the 

 cavity of the body, forming a basin for this purpose, 

 and also having the thigh bones, or first bones of the 

 posterior extremities articidated to them, are irregular 

 in their forms. Bones are also often elongated into 

 a sort of branches at particular places ; and those 

 branches in general serve for giving a more extensive 

 insertion to the muscles, and they also anssver as 

 levers in moving the bones from which they project. 

 Those projecting branches, when they form a con- 

 necting part of the bone, are called processes, or 

 apophyscs, either of which words means that they 

 proceed or project outward from the bone ; but when 

 they are less firmly united, and have the appearance 

 of one bone applied to another, they are called 

 cpiplujscs, which means that they have the appcar- 



103 



ance of being applied or planted on the bone. For 

 the sake of ready distinction, technical names have 

 been given to these processes, according to the par- 

 ticular forms. When round and smooth, as they are 

 in the extremities of bones which have a circular 

 motion as, for example, in the shoulder and hip 

 joints of the human body they are called heads ; and 

 they are received into sockets of greater or less 

 depth ; the head, when the bone is vertical, beinc 



always placed under the socket, in which position it 

 is much less liable to be dislocated than if the position 

 were reversed. When the motion of the joint is in 

 one direction only, with comparatively little lateral 

 play, the extremity is called a condyle ; and it is a 

 portion of a greater or smaller circle fitting into a 

 concavity which is sometimes single and sometimes 

 double, thus forming a hinge. The working extre- 

 mities of bones at their articulations are often, how- 

 ever, far more complicated than this, and by means 

 of variously shaped bones, and the sliding and rolling 

 motions thence produced, a degree of play, still con- 

 sistent with perfect firmness, is given to the limb of 

 the animal, which it is altogether impossible to imi- 

 tate in common mechanics. The human hand and 

 wrist, and indeed the whole bones of the arm, and 

 the mode of their combination, furnish one of the 

 most remarkable instances of this, as we shall after- 

 wards have occasion to notice at greater length. 



Of the permanent processes to the extremities of 

 which other bones are not always united by articula- 

 tion, the following are the principal names and dis- 

 tinctions : Mastoid, or those which have some fan- 

 cied resemblance to a nipple ; Coracoid, or those 

 which are something shaped like the bill of a crow ; 

 Styloid, or those which resemble the style or bodkin 

 used by the ancients in writing ; Spinmis, or those 

 which stand out like a thorn ; Pterygoid, or those 

 which are supposed to be something like a wing ; 

 and Zygomatic, or those which have some resemblance 

 to a yoke. When the irregularities on the bone 

 merely roughen the surface wilh roundish projections, 

 they are called tuberosities. These names are, of 

 course, merely conventional ; but as they are used by 

 every writer who treats of the forms of the bones, and 

 the motions of which they admit, with any thing like 

 precision, it becomes necessary to know them if we 

 are to study the structure or the living action of 

 animals with any thing like the proper advantages. 

 Bones are never, or at least. seldom, in the mammalia 

 of the same consistency throughout their whole sec- 

 lion when divided. The long cylindrical bones have 

 generally a hollow in the middle part which contains 

 marrow or fatty matter in the full-grown animal, but 

 has more of the colour of blood in the young subject. 

 Toward iheir extremities they become cellular, the 

 cells being still filled with fatty matter, and at these 

 parts the central cavity is gradually obliterated. 

 There are also usually openings into the bone for the 

 admission of vessels ; and there are also frequently 

 grooves along their surfaces. The thin bones consist 

 of two plates, which are called tables, with a spongy 

 diploe between them. 



In the working structures of the body, bone never 

 touches bone, and therefore we must attend to the 

 basis of bones, as it were, in seeking to know some- 

 thing about its nature. In the middle part of the 

 bone this basis is composed chiefly of gelatine or ani- 

 rnal glue, which boils soft, and may be extracted from 

 the bone by boiling for a sufficient length of time ; 



