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form, being in one case comparatively flat and at another elevated; 

 or as forming a j)rotruding head or knob, with a distinct convexity; 

 and again jiresenting a corresponding depression or cavity, accurately 

 adapted to comi)lete, by their coaptation, the ball and socket joint. 

 The articulation of the arm and shoulder is an examj)le of the first 

 kind, while that of the hip with the thigh bone is a perfect exhibition 

 of the latter. 



The structure whose oflice is the retention of the articulation in 

 place, is the ligament. This is a white, inelastic, or yellowish texture, 

 ]x»ssessing in some degree the opposite equality. In some instances it 

 is of a corded or funicular shape, but consists in others of a broad 

 membrane, in the first form serving to bind the bones more firmly 

 together, and in the latter surrounding or inclosing, in whole or in 

 part, the broad articulations, and calculated rather for the i^rotection 

 of tlie cavity from intrusion bj' the air than for other security. These 

 latter are usually found in connection with those of the joints which 

 X>ossess a free and extended movement, but are also found accompa- 

 U3"ing the funicular ligaments either suiTOunding and inclosing the 

 joints or occupjang the interior of their structure, as inter articular, 

 in which situation they secure the union of the several bones more 

 firmly and effectively" than would be possible for the capsular liga- 

 ment unassisted. 



The universal need which pertains to all mechanical contrivances 

 of motion has not been forgotten wliile providing for the perfect work- 

 ing of the interesting piece of living machinery which x^erforms the 

 function of locomotion, as we are contemj)lating it, and nature has con- 

 sequently provided for obviating the evils of attrition and friction, 

 and insuring the easy play and smooth movement of its parts, by the 

 establishment of the secretion of the synovia, tlie vital lubricant of 

 which we have before spoken, as a yellow, oily, or rather glairy secre- 

 tion, which performs the indisx>ensable office of facilitating the play 

 of the tendons over the joints and certain given i^oints of the bones. 

 This fluid, which is deposited in a containing sac, the lining (serous) 

 membrane of which forms the secreting organ, is of an excessivelj'' 

 sensitive nature, and while it lines the inner face of the ligaments, 

 both capsular and fascicular, is attached onlj^ upon the edges of the 

 bones without extending upon their length or between the layers of 

 cartilage which lie between the bones and their articular surfaces. 



Our object in thus partially and concisely reviewing the structure 

 and condition of the essential organs of locomotion has been rather 

 to outline a sketch which may serve as a reference chart of the gen- 

 eral features of the subject than to offer a minute descri^jtion of the 

 parts referred to. Other j^oints of interest will receive due attention 

 as we proceed with the illustration of our subject and examine the 

 matters which it most concerns us to bring under consideration. The 

 foundation of facts wliich we have thus far prepared will be found 

 suflicientl}^ broad, we trust, to include whatever may be necessary to 



