Histology 



323 



a length of rubber tubing, closed at the ends, and filled with liquid 

 under pressure. 



Cartilage. In development of cartilage, mesenchyme cells become 

 densely massed and then produce an abundant intercellular substance 

 whose accumulation causes the cells to become more or less widely 

 separated from one another (Figs. 234, 266). The intercellular matrix 



Fig. 265. Developing vertebrae of the 

 amphibian. Ambystoma. (I) Earlier. (//) 

 Later. Longitudinal sections. Cartilage and 

 bone are forming around the notochord. (cc) 

 Cartilage in center of vertebra; (ei) epitheli- 

 oid internal elastic sheath of notochord; (i) 

 incisure cutting through (ic) intercentral 

 (intervertebral) cartilage; (n) notochord; 

 (ns) outer notochordal sheath; (») develop- 

 ing bone (black) of centrum of a vertebra. 

 (Courtesy, Kingsley: "Comparative Anat- 

 omy of Vertebrates," Philadelphia, The 

 Blakiston Company.) 



becomes solid and acquires a firm or even hard consistency. Chemi- 

 cally it is a complex of collagenous, albuminoid, and other protein 

 substances. The cartilage-cells remain embedded in the matrix, each 

 occupying a close-fitting space, a lacuna. Some cartilages have been 

 described as containing exceedingly fine canals penetrating the matrix 

 and putting any one lacuna into communication with neighboring 

 lacunas. 



