CARTILAGE. 



CARTILAGE. 



BONE, p. 93). The cell-walls are generally 

 thick, and frequently composed of several 

 layers. The contents consist of a clear liquid 

 and a nucleus; sometimes the cell and some- 

 times 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 containing also nuclei or tertiary 

 cells. 



Fig. 105. 



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 secondary and tertiary cells sometimes 

 exhibit well the internal layers. 



Fig. 106. 



Magnified 350 diameters. 



Cells from the gelatinous nucleus of the intervertebral 

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

 by two secondary cells, and five tertiary cells or cells of the 

 second generation with concentric walls and shrunk nuclei 

 c in the small cell-cavities. 2, primary cell a, with two 

 secondary cells separated by a delicate septum b, with 

 thickened walls, a small cavity and a shrunk nucleus c. 



The intervening basis, when present, is 

 either homogeneous, 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 of embryos, 



in the adult skeleton of many fishes, and in 

 the cartilage of the ear of many mammals. 

 It is beautifully seen in the chorda dorsalis 

 of a young tadpole or young Triton ; or in 

 the ear of the mouse (PI. 40. fig. 38). In the 

 latter instance, each cell is filled with a 

 globule of oil, which must be separated by 

 digestion in aether 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 homogeneous or finely granular, 

 or true cartilage as it is called (PI. 40. 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. 



The third variety of cartilage or fibro-car- 

 tilage (PI. 40. fig. 40) occurs in the human 

 epiglottis, the external ear, the Eustachian 

 tube, the intervertebral ligaments, &c. It con- 

 sists principally of fibres, single or in bundles, 

 sometimes running parallel, at others inter- 

 lacing, and between them lie the cartilage 

 corpuscles. Sometimes the basis of true 

 cartilage becomes fibrous, and true fibres may 

 be found in it. The chemical composition 

 of the components of cartilage has not been 

 satisfactorily determined. The homogeneous 

 basis usually consists of chondrine. The 

 cell-walls are composed of a substance allied 

 to elastic tissue ; they are not dissolved by 

 boiling in water and are acted upon with diffi- 

 culty by acids and alkalies. The liquid within 

 the cells is probably albuminous ; it is coagu- 

 lated by water and dilute organic acids, and is 

 readily soluble in alkalies. The fibrous 

 elements of the fibro-cartilages sometimes 

 agree in composition with white fibrous 

 tissue, at others with the yellow or elastic 

 tissue. 



When sections of cartilage are subjected 

 to the action of Schultze's test, the cells are 

 coloured red, but not the basis. 



The cartilage of bone is noticed under 



