24 



OSTEOLOGY 



A trochlea is a pulley-like articular mass. 



A glenoid cavity (C'avitas glenoidalis) is a shallow articular depression, and a 

 cotyloid cavity or acetabulum is a deeper one. 



Tlie term facet is commonly applied to articular surfaces of small extent, 

 especially when they are not strongly concave or convex. 



The terms fossa, fovea, groove or sulcus, and unpression are applied to various 

 forms of depressions. 



A foramen is a perforation for the transmission of vessels, nerves, etc. 



A sinus or antrum is an air-cavity. 



Other terms, such as canal, fissure, notch, etc., require no explanation/ 



VERTEBRAL COLUMN 



The vertebral column (C'olumna vertebralis) is the fundamental part of the 

 skeleton. It consists of a chain of median, unpaired, irregular bones which 

 extends from the skull to the end of the tail. In the adult certain vertebrae have 



become fused to form a single bony mass 

 with which the pelvic girdle articulates. 

 Vertelirge so fused are termed fixed or 

 "false" vertebrae (Vertebrae immolnles), as 

 distinguished from the movable or "true" 

 vertebrae (Vertebrae mobiles). 



The column is subdivided for descrip- 

 tion into five regions, which are named ac- 

 corchng to the part of the body in which 

 they are placed. Thus the vertebrae are 

 designated as cervical, thoracic (or dorsal), 

 lumbar, sacral, and coccygeal or caudal 

 (Vertebrae cervicales, thoracales, lumbales, 

 sacrales, coccygeae). The number of verte- 

 brae in a given species is fairly constant in 

 each region except the last, so that the ver- 

 tebral formula may be exjjressed (for the 

 horse, for example) as follows: 

 CTTigLgSjCyjs.jj. 

 The vertebrae in a given region have 

 special characters by which they may be 

 distinguished from those of other regions, and individual vertel)ra^ have characters 

 which are more or less clearly recognizable. All typical vertebrae have a common 

 plan of structure, which must first be understood. The parts of which a vertebra 

 consists are the body or centrum, the arch, and the processes. 



The body (Corpus vertebrae) is the more or less cylindrical mass on which the 

 other parts are constructed. The anterior and posterior extremities of the Ijody 

 are attached to the adjacent vertebrae by intervertebral fibro-cartilages, and are 

 usually convex antl concave respectively. The dorsal surface is flattened and enters 

 into the formation of the vertebral canal, while the ventral aspect is rounded 

 hiterally, and is in rehition to various muscles and viscera. In the thoracic region 

 tiie botly presents two jjairs of demifacets (Fovea? costales) at the extremities for 

 articulation with the heads of two pairs of ribs. 



The arch (Arcus vertebra?) is constructed on the dorsal aspect of the body. 

 It consists originally of two lateral halves, each of which is considered to consist 

 of a i^edicle and a lamina. The pedicles form the lateral parts of the arch, and are 



' As mipht be exported from the liistory of anatomy, a good many of tlicse terms are more or 

 less interchangeable; furthermore, a given skeletal feature may differ greatly in various species. 



Transv. 

 jjroa. 



fkeef 



Fig. 4. — Firm I v^- i' \ r.RTF.Bn.E of Horse 



To illustrate plan of structure of vertebrae. 



