DESCEIPTIVE OE SPECIAL ANATOMY. 



OSTEOLOGY. 



THE SKELETON. 



The Skeleton or solid fi-amework of the body is mainly formed of 

 the bcnes, but is completed in some parts by the addition of cartilages. 

 The bones are bound together by means of ligaments, and are so dis- 

 posed as to support the softer parts, protect delicate organs, and give at- 

 tachment to the muscles by which the different movements are executed. 



In the lower animals the term skeleton has a wider signification than 

 in man, comprehending two sets of parts, viz., 1st, those of the endo- 

 slceleton, or the deeper osseous and cartilaginous framework which 

 corresponds to the human skeleton ; and 2nd, those of the cxo-slccJeton, 

 or dermal-sJceJdon, comprising the integument and various hardened 

 structures connected with it. All vertebrate animals possess an endo- 

 skeleton ; but in some of them the exo-skeleton attains greater pro- 

 portions than in others, and is combined by means of hardened parts 

 more fully with portions of the endo-skeleton. In almost all inverte- 

 brate annuals the dermal or exo-skeleton alone exists. 



In man, as in the higher vertebrates, the greater part of the endo- 

 skeleton is formed of bone, a calcified animal tissue, which, when freed 

 by putrefactive maceration from its fat and various soft adherent parts, 

 and subsequently dried, is capable of remaining unchanged for a very 

 long period of time. It is customary and convenient thus to study the 

 bones chiefly in the macerated and dried state, that is, deprived of their 

 accessory soft parts. 



Certain accessory soft parts are connected with the bones : these con- 

 sist chiefly of the external fibrous and vascular covering iarmGdi periosteum, 

 and of the medulla, marrow or fat, which fills their larger internal cavi- 

 ties. The bones are permeated by blood-vessels, which supply materials 

 for their nourishment, and they are provided also with absorbent 

 vessels and with nerves in small quantity. 



The bony substance or osseous tissue consists of an organised 

 animal basis which is essentially fibrous in its structure, and is inti- 

 mately combined with a large proportion of earthy and saline ingre- 

 dients. The former gives tenacity, the latter hardness and rigidity to 

 the osseous substance. The earthy and saline matter may be obtained 

 separate by burning or calcination of bones in an open fire, and when 

 this is done with sufficient care, these may be preserved in the form of 

 the original bone. It constitutes about two-thirds of the weight of the 

 dried substance of bone, and consists mainly of a tribasic phosphate of 

 lime, or bone earth, together with about a fifth of carbonate of lime 

 and smaller quantities of fluoride of calcium, chloride of sodium, and 

 magnesian salts.'; 



The earthy ingredients and salts of bone may be removed by solu- 

 tion in hydrochloric acid, and there is thus obtained separately the 



