286 SPECIAL HISTOLOGY. 



may be recognized as dull yellow streaks, which become hard and trans- 

 parent in water. The fibro-cartilage, on microscopic examination, pre- 

 sents minute, elongated cartilage cells, disposed serially in a fibrous 

 tissue, differing from connective tissue in its greater rigidity, the absence 

 of distinct fibrils, its great resistance to alkalies and acetic acid, and the 

 total absence of elastic fibres. 



The whitish layers of the outer laminae, although their fibrils are 

 rather more rigid than those of the common ligaments and tendons, are 

 less easily separated, and present 'but few fusiform cells, and frequently 

 no elastic fibres whatever among them, must nevertheless, at present, be 

 regarded as composed of connective tissue. These laminae are from J 

 to | of a line and more in thickness, and form entire circles or segments 

 of such, which, alternating with the somewhat thinner, and also fre- 

 quently incomplete, rings of fibro-cartilage, with which they are closely 

 connected, together with the latter constitute the larger half of the in- 

 tervertebral ligaments. The general direction of the fibres of both sets 

 of laminae is from above to below. They are, however, invariably 

 oblique, so that those of the different layers cross each other. Besides 

 which, it must be remarked, that the individual layers themselves also 

 exhibit a more or less distinctly foliated structure, constituted in such a 

 manner that the fine lamellae, in the portions composed of connective 

 tissue, observe the same direction as the layers themselves, whilst in the 

 fibro-cartilaginous portions they are disposed more in the direction of 

 the radius of the ligamentous disc. 



The softer central substance of the intervertebral ligaments, or the 

 gelatinous nucleus of authors, does not differ, essentially, from the por- 

 tions above described ; for, even in this situation, layers of connective 

 tissue occur, although they gradually diminish in proportion to the 

 fibro-cartilage, and are less distinctly defined. The nearer we approach 

 the centre, the less evident is any trace of an alternation of different 

 Fio . 122 layers, and of a concentric ar- 



rangement of them ; the whole 

 becomes transparent, soft, and, 

 finally, almost homogeneous. The 

 microscope shows the predomi- 

 nance of fibro-cartilage, with 

 large cells (0-012-0-024 of a 

 line), frequently one within the 

 other (Fig. 122) ; the uniformly thickened walls of which, composed of 



FIG. 122. Cells from the gelatinous nucleus of the lig. intervertebralia : 1, large parent 

 cell, a, with a septum derived from two secondary cells of the first generation, and five 

 secondary cells, 6, of the second generation ; with concentrically thickened walls and 

 shrunken nuclei, c, in the small cell cavities: 2, parent cells, a, with two secondary cells, 

 separated by a delicate septum, 6, and which, with uniformly thickened walls, contain a 

 minute cavity and shrunken nucleus, c. 



