13i 



AETICULATIOXS OF THE TRUNK. 



attached to both ; the direction of the fil)res being reversed in each 

 f;uocessive layer. Some of the fibres also are nearly horizontal. The 

 central part of the fil^ro-cartilage is a pulpy and elastic material wliich, 

 when the pressure which confines it is taken off by cutting through 

 the intervertebral substance, rises up so as to assume a conical form. 

 It is then seen to be of a lobate structure, and, examined under the 

 microscope, exhibits a finely fibrous and homogeneous matrix, with 

 numerous spherical and elliptical cells, some of them resembling carti- 

 lage-corpuscles, others larger and of various appearance. 



It is now generally admitted that the pulp of the intervertebral disc is a per- 

 sistent part of the chorda dorsalis ; homologous, therefore, with those larger 

 vestiges of the chorda dorsalis which occupj- the biconical ca-vaties between the 

 bodies of the vertebrie in fishes. According to Luschka, there is present in each 

 disc a sjTiovial cavity, and the lobes of the pulp are synovial villi, similar to 

 those which are to be found in the knee and shoulder joints, but of larger size, 

 and occupying the whole cavity : and it is worthy of notice that in like manner 

 secondary cavities, developed within the chorda dorsalis, are found in the inter- 

 vertebral substance in many fishes. (Luschka, " Die Halbgelenke des Menschli- 

 chen Korpers," Berlin, 1858, p. 8-1.) 



A thin cartilaginous layer, incomplete towards the circumference, 

 covers the surfaces of the vertebrae and gives attachment to the discs. 

 Excluding from consideration the first two vertebra?, between which it 



Fig. 117. — Vertical Axtero- 

 TosTERioR Section thrdugii 

 TWO Lumbar Vertebrae, show- 



INC, THE arrangement OF THE 

 INTERVERTEBRAL DiSC. § 



1,1, the fibrous oblique bands, 

 wliicli are curved outward ; 2, 

 those which are curved inwards ; 

 3, the central soft cartilaginous or 

 gelatinous substance : the capsule 

 of tbe joint between the articular 

 processes is represented. 



does not exist, the inter- 

 vertebral material forms in 

 length about a fourth of 

 the mov.able part of the column. The dorsal part of the column has, 

 in comparison with its length, a much smaller proportion than the 

 cervical or lumbar parts. 



The discs in the cervical and lumlmr regions are thicker in front than Ijehind. 

 and it has been determined that the convexity of those portions of the column is 

 due to them much more than to the bodies of the vertebraj, while the arching of 

 the dorsal portion, on the contrary, is rather owing to the shape of the bones. 

 (W. and E. Vv'eber, " Mechanik der menschl. Gewerkzeuge,"' p. 'JO, et seq., Got- 

 tingen, 18i)G.) 



The anterior common ligament is a strong band of fibres, which 

 is placed on the front of the bodies of the vertebras, and reaches from 

 the axis to the first bone of the sacrum, becoming broader as it descends. 

 It consists of longitudinal fibres which arc dense, firm, and well marked. 

 The superficial fibres extend from a given vertebi'a to the fourth or fifth 

 below it; the fibres beneath these pass over the bodies of several verte- 



