5 2 



HISTOLOGY. 



it denotes a hyaline cartilage. Hyaline, elastic, and fibre-cartilages 

 require special examination. 



Hyaline cartilage macroscopically is a pale bluish or pearly trans- 

 lucent substance, firm and elastic. It forms some of the cartilages of the 

 larynx, and those of the trachea and bronchi, the nose, ribs and generally 



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FIG. 55. THE THREE TYPES OF CARTILAGE: A, HYALINE; B, ELASTIC; C, FIBROUS. (Radasch.J 

 a, b, Outer and inner layers of perichondrium; c, young cartilage cells; d, older cartilage cells; e, f, cap- 

 sule; g, lacuna. 



the covering of the joint surfaces, together with the cartilaginous skeleton 

 of the embryo. Its matrix, though apparently homogeneous, Fig. 55, A, 

 is actually fibrillar, as shown by its behavior under polarized light, and by 

 its separation into fibers after artificial digestion. Whether its lacunae 

 are connected with each other by small canals as in bone and in the carti- 

 lage of some invertebrates, is very doubtful. Such canals as have been 

 observed are ascribed to shrinkage caused by reagents. Sometimes, as 

 in portions of the laryngeal and costal cartilages, the matrix may develop 

 coarse fibers, neither white nor elastic, which have a luster like asbestos. 

 In old age, and even by the twentieth year in the case of some laryngeal 

 cartilages, lime salts may be deposited in the matrix, first as granules 

 but later combining to form shells enclosing the cartilage cells. Calcified 

 cartilage, together with calcified tendon and other structures, should not, 

 however, be regarded as bone. 



Elastic cartilage is a pale yellowish structure containing in its matrix 



