CARTILAGE. 



[ 135 ] 



CARTILAGE. 



CARTILAGE. Cartilage consists of a 

 firm, but elastic, bluish, milky or yellowish 

 substance, which morphologically forms 

 either a simple parenchyma composed of 

 cells, or a structure consisting of cells 

 immersed in an intermediate basis. 



The cells of cartilage are usually round, 

 oval, elongated or angular, frequently flat- 

 tened and sometimes spindle-shaped. In 

 some cartilage they appear stellate, or ex- 

 hibit distinct radiating processes, as in 

 that of the cuttle-fish, the sharks and rays, 

 and enchondromatous growths. 



In the ossifying pseudo-cartilage of true 

 bone, real stellate cells are however met 

 with. See BONE. 



Pig. 100. 



Magnified 350 diameters. 



Primary (parent-) cells with one and two nuclei, or 

 two and four secondary cells and intervening basis. 

 From the cranial cartilage of a full-grown tadpole. 



The cell-walls are generally thick, and 

 frequently composed of several layers or 

 capsules. The contents consist of a clear 

 liquid and a nucleus ; sometimes the cell 

 and sometimes both the cell and the 

 nucleus contain one or more globules of 

 oil. The cells also frequently constitute 

 parent-cells, i. e. cells containing other or 

 secondary cells within them, these con- 

 taining also nuclei or tertiary cells. 



The secondary and tertiary cells some- 

 times exhibit well the internal layers. 



It is undecided whether these capsular 

 layers are hardened products of secretion of 

 th*e cells, or whether they represent the 

 changed peripheral portions of the cell- 

 bodies themselves. The latter seems most 

 probable. 



The intervening basis is either homoge- 

 neous, finely granular, or fibrous ; sometimes 

 the fibres are distinct and can be isolated. 



The simplest form of cartilage, viz. that 

 composed of cells only, is met with in the 

 chorda dorsalis or notochord of embryos, in 

 the adult skeleton of many fishes, the ten- 

 tacles of the Acalephae, and in the cartilage 

 of the ear of many mammals. The proto- 

 plasm in these cells often exhibits radiating 

 striae in which currents are visible. The 

 structure is beautifully seen in the chorda 

 dorsalis of a young tadpole or Triton, or in 

 the ear of the mouse (PL 49. fig. 38). In 



Fig. 101. 



*-"" 



Magnified 350 diameters. 



Cells from the gelatinous nucleus of the interverte- 

 bral ligaments. 1 a, large primary cell with a septum 

 formed by two secondary cells, and five tertiary cap- 

 sular cells or cells of the second generation with concen- 

 tric walls and shrunk nuclei c in the small cell-cavities. 

 2, primary cell a, with two secondary cells separated 

 by a delicate septum 6, with thickened walls, a small 

 cavity and a shrunk nucleus c. 



the latter instance, each cell is filled with 

 a globule of oil, which must be separated by 

 digestion in ether before the cell -structure 

 can be properly examined ; but boiling on a 

 slide in solution of potash, or the addition 

 of sulphuric acid will liberate the globules 

 of fat from parts of a section. This variety 

 of cartilage exactly resembles in appearance 

 a section of vegetable cellular tissue. 



The second variety of cartilage, in which 

 the basis is more abundant and homo- 

 geneous or finely granular, true or hyaline 

 cartilage as it is called (PI. 49. fig. 39), is 

 met with in the larger cartilages of the 

 respiratory organs, in the articular, costal, 

 ensiform and nasal cartilages. In this the 

 cell- walls are closely adherent to the inter- 

 cellular basis, so that they are rarely visible 

 without the use of reagents. The cells are 

 most numerous in the articular cartilages, 

 and are mostly smaller the further they are 

 from the bone. Their long axes are placed 

 perpendicularly to the axis of the bone, 

 except in a thin layer next the surface of 

 the joints, in which they are parallel to the 

 surface. Both the cells and the nucleus of 

 this cartilage exhibit a fibrous network. 



