VARIOUS KINDS OF MOVEMENT. 151 



loops and retinacula binding down tendons, also belong to the last category. 1 (On this subject 

 see J. B. Button, Journ. Anat., xviii xxii, and " Ligaments, their Nature and Morphology." 

 London, 1887.) 



VARIOUS KINDS OF MOVEMENT. The various movements of the bones in 

 diarthrodial joints are distinguished by different terms, such as angular movement, 

 circumduction, rotation, and gliding ; but it is proper to remark that although 

 different kinds of movement, answering to these several terms, may readily be 

 recognised, yet in many cases several kinds of movement are combined in one joint, 

 and they also run into one another in great variety. 



Angular movement is movement in such a manner as to increase or diminish 

 the angle between two bones, so that they shall lie more or less nearly in a straight 

 line. The different kinds of angular movement are designated by different terms 

 according to the directions in which they take place with reference to the limb or 

 body : thus flexion and extension indicate angular movements about a transverse 

 axis, which have the effect of bending or straightening parts upon one another or 

 upon the trunk ; adduction and dbdmlion indicate angular movement to and from 

 the median plane of the body, or, when fingers and toes are referred to, these 

 terms are generally used to denote movement to and from the middle line of the 

 hand or foot. 



Circumduction is the movement performed when the shaft of a long bone or 

 a part of a limb describes a cone, the apex of which is placed in or near the joint 

 at one extremity of the bone, while the sides and base of the cone are described 

 by the rest of the moving part. 



Rotation signifies movement of a bone round a longitudinal axis without any 

 great change of situation. 



Gliding is applied to that kind of movement in which the surfaces of adjacent 

 bones are displaced without any marked angular or rotatory motion, as in the 

 movement of flat surfaces over each other in some of the carpal and tarsal articula- 

 tions, or in the movement of advance and retreat of the lower jaw. 



Although the term. r/Uding movement is used in the restricted sense indicated above, yet it 

 is to be observed that the movement between opposed articular surfaces is almost always 

 purely of a gliding nature, and that only in one or two instances, such as in the movement 

 of the patella on the femur, is the gliding associated with a limited degree of rolling move- 

 ment, by which different parts of the two surfaces are brought successively into contact in 

 the manner of a wheel rolling on the ground : to this form of movement the name of coap~ 

 tatlon has been given. 



I. THE ARTICULATIONS OF THE TRUNK AND HEAD. 



THE ARTICULATIONS OF THE VERTEBRAL COLUMN. 



The moveable vertebras are connected together by elastic discs interposed 

 between the bodies, by synovial joints between the articular processes, and by 

 ligaments. 



The intervertebral discs are plates of composite structure placed between 

 the bodies of the vertebrae from the axis to the sacrum. Each is composed of a 

 fibro-laminar part externally, and of a pulpy substance in the centre. 



The laminar part forms more than half of the mass. The laminae are arranged 

 concentrically, and consist mainly of parallel bundles of fibres running obliquely 

 between the vertebrae and attached firmly to both, the direction of the fibres being 

 reversed in successive layers : some fibres also run nearly horizontally. The outer- 



1 The name of ligament is also given in descriptive anatomy to various structures in no way connected 

 with the joints or skeleton, such as folds of serous membranes and the remains of obliterated vessels. 



