250 



ARTICULATION. 



intended to obviate the ill consequences which 

 must have resulted from the violent application 

 of the neck of the femur against the bony 

 margin of the acetabulum : for, where the 

 margin of that cavity is ligamentous, viz., at 

 the notch on its inner side, this fibro-cartilage 

 does not exist. 



c. The most remarkable and beautiful variety 

 of this structure belongs to the third class. It 

 consists of fibro-cartilaginous laminae, generally 

 of considerable thickness, which intervene be- 

 tween two bones and adhere intimately to each. 

 Examples of it are to be found between the 

 bodies of the vertebrae, (inter vertebral sub- 

 stance) between the pieces of the sacrum in 

 early life between the sacrum and coccyx, 

 and between the pieces of the latter also, be- 

 tween the ossa pubis at the joint called the 

 symphysis pubis. In this class of fibro-car- 

 tilages too, we may place that which is situ- 

 ated between the scaphoid and lunar bones in 

 the carpus. 



It is evident that these fibro-cartilages are 

 useful, not only as very powerful bonds of 

 union, but also as elastic cushions placed be- 

 tween the bones to prevent the concussion 

 which must necessarily result, did the unyield- 

 ing bony surfaces come together with any de- 

 gree of force. No where is this so beautifully 

 exhibited as in that chain of bones which 

 forms the spinal column in the mammiferous 

 vertebrata, the strength and flexibility of 

 which result from the fibro-cartilaginous discs, 

 which, placed between the bodies of the ver- 

 tebrae, are commonly called intervertebral car- 

 tilages. 



As to the structure of articular fibro-cartilage, 

 we can distinctly observe, without any process 

 of dissection, that it is compounded of fibrous 

 tissue as well as of cartilage. As these nbro- 

 cartilages generally assume more or less of the 

 circular form, we find that the fibrous tissue is 

 most abundant towards the circumference, and 

 that the cartilage is most manifest at the centre. 

 In the intervertebral substance, the fibrous 

 tissue is arranged in concentric laminae, placed 

 vertically behind one another. Each lamina is 

 composed of a series of interlacing fibres, which 

 have intervals between them ; these intervals, 

 as well as those between the laminae, are filled 

 by cartilaginous tissue ; towards the centre the 

 fibrous laminae diminish in number, the inter- 

 vals become large, and at length the fibrous 

 tissue disappears in toto ; hence the gradually 

 diminishing density towards the centre, which 

 characterises the intervertebral substance. In 

 fishes, there is such a diminution of density, 

 that the central part is fluid, but here the sur- 

 faces of the vertebras are excavated, not plane 

 as in the mammiferous vertebrata, and the cha- 

 racter of the articulation is thereby materially 

 altered. The incompressible central fluid forms 

 a ball, round which the cup-like excavations of 

 the vertebras play, while the fibro-cartilage at 

 the circumference is made available in the la- 

 teral motions of the spine. 



Of the three varieties of fibro-cartilage above 

 enumerated, the menisci possess the most car- 

 tilage in their structure, and the circumferential 



fibro-cartilages the greatest quantity of fibrous 

 tissue. 



It may be questioned whether that peculiar 

 structure which intervenes between the base of 

 the skull and the condyle of the lower jaw in 

 the whalebone whale, (baltena mysticetus) be- 

 longs to the class of fibro-cartilages, although 

 it seems to bear a nearer resemblance to that 

 than to any of the other structures employed in 

 the composition of joints. The following is 

 Sir Everard Home's description of it.* " Be- 

 tween the condyles of the lower jaw and the 

 basis of the skull is interposed a thick sub- 

 stance, made up of a network of ligamentous 

 fibres, the interstices of which are filled with 

 oil, so that the parts move readily on each other. 

 The condyles have neither a smooth surface 

 nor a cartilaginous covering, but are firmly 

 attached to the intermediate substance, which 

 in this animal is a substitute for the double 

 joint met with in the quadruped, and is cer- 

 tainly a substitute of the most simple kind." 



4. Ligament. The term ligament, as it is 

 used by systematic writers on descriptive ana- 

 tomy, is by no means confined to portions of 

 the " fibrous system" of Bichat, although all 

 the articular ligaments (properly so called) be- 

 long to that system. Weitbrecht comprehends 

 under this term all fibrous structures in and 

 about joints, including the fibrous sheaths of 

 tendons, and also all membranous folds, which 

 are in any way concerned in maintaining soft 

 parts or viscera in proprio situ. I apprehend, 

 however, that a better definition of articular 

 ligament could not be given than the following, 

 which is that of Weitbrecht, the words printed 

 in italics being added," Ligamentum est par- 

 ticula corporis, plerumque albicans, interdum 

 jlava, ex fibris flexilibus, interdum elasticis, 

 plerumque parallele concretis, in substantiam 

 tenacem fibrosam, ruptioni fortiter resistentem, 

 et solidam compacta, eum in finem creata ut 

 duae pluresve partes quaa alias divulsae per se 

 subsisterent, adunentur atque in situ respectivo 

 determinentur."f Most of the articular liga- 

 ments are employed to unite the bones which 

 compose a joint ; they also will be found uniting 

 some of the interarticular cartilages within 

 joints, or passing from one part of a bone to 

 another (forming the " mixed" class of liga- 

 ments of Beclard) ; and such is the vagueness 

 with which names are applied in descriptive 

 anatomy, that folds of the sy no vial membrane 

 often receive this appellation without the least 

 title to it. 



Articular ligaments are divisible as regards 

 their forms into two species, the capsular and 

 the funicular or fascicular.J 



Capsular ligaments are generally cylindrical 

 in shape, or rather barrel-shaped, being wider 

 in the centre than at the extremes. Each ex- 

 tremity envelopes one of the bones that enters 

 into the formation of the joint, so that the arti- 

 cular cavity is completely surrounded by and 

 enclosed within the ligamentous capsule. Liga- 



* Comp. Anat. vol. i. p. 83. 

 t Syndesmologia, 5. 



. T>__1_ -J A __ .. A. /~1 



oynaesmoiogio., y t. 

 Beclard, Anat. Gen. 



