194 CONNECTIVE TISSUE. 



interarticular and intervertebral disks ; in the cartilaginous pro- 

 jections (labra cartilaginosa) of concave articular surfaces, and 

 in those portions of the tendons which glide over bones. In the 

 latter instance, the cartilage corpuscles extend far into the tissue 

 of the tendon. In the intervertebral disks of middle-aged per- 

 sons, the upper and under portions consist of a tissue closely 

 resembling hyaline cartilage, with flat lenticular corpuscles ; from 

 this layer arise the bundles of fibrous cartilage interwoven in 

 oblique direction. The bundles are thinner near the center, and 

 increase in size from within outward. The most central portion 

 of the disk is non-striated, of uniform appearance, and of a gela- 

 tinous consistence, approaching, therefore, the features of myx- 

 omatous basis-substance ; it is abundantly supplied with plastids 

 arranged in nests, like cartilage corpuscles. The lateral portions 

 of the disks consist of a dense fibrous connective tissue, likewise 

 blending with the fibrous cartilage. 



The fibrous tissue which we find within hyaline cartilage, 

 mainly that of the ribs, the tracheal and laryngeal cartilages, 

 but not in normal articular cartilages, is of considerable interest. 

 Histologists claim that this fibrous tissue is a product of second- 

 ary or senile changes, occurring very regularly, some say between 

 the fifth and sixth, others between the tenth and twelfth, year of 

 life. A queer senile metamorphosis, indeed, which is of regular 

 occurrence in childhood. 



L. Elsberg has observed in specimens of the thyroid and 

 cricoid cartilages of human foetus, five to six months old, a deli- 

 cately striated basis-substance in the middle of the cartilaginous 

 plates. This striation becomes more distinct with the age of the 

 individual, and sometimes even in middle life invades nearly all 

 the laryngeal cartilages. The same change has been observed 

 in articular cartilages of so-called arthritic persons. The most 

 peripheral portions of the cartilage, as a rule, remain free of 

 fibrous metamorphosis. The fibers are arranged in either 

 straight or slightly curved bundles, and exhibit features iden- 

 tical with those of the lateral surfaces of the condyles, illustrated 

 in Fig. 73. 



We must abandon the opinion that this fibrous tissue is the 

 result of a senile metamorphosis. The question remains unset- 

 tled, however, whether hyaline basis-substance of cartilage is 

 directly changed into fibrous, or whether this transition goes on 

 through the intermediate stage of medullary tissue, in accord- 

 ance with the general rule of tissue transformation. 



