45 



LESSON XII. 



THE CONNECTIVE TISSUES (continued). 

 COSTAL CARTILAGE. FIBEO-CAETILAGE. 



1. MAKE transverse and tangential sections of a rib-cartilage, stain them with 

 magenta, and mount in dilute glycerine, cementing at once. Sketch a part of 

 a transverse section under a low power and a cell-group from one of the 

 tangential sections under a high power. Notice especially the arrangement 

 of the cells, somewhat concentric near the surface but radial near the centre. 

 The costal cartilages are often ossified near the middle. 



2. Make sections of the cartilage of the external ear. Mount in dilute 

 glycerine faintly coloured with magenta. If from the ox, notice the very 

 large reticulating elastic fibres in the matrix. Notice also the isolated 

 granules of elastin, and around the cartilage-cells the area of clear ground- 

 substance. Draw a small portion of the section. 



3. Mount a section of the epiglottis in the same way. Notice the closer 

 network of much finer fibres. 



4. Cut sections of white fibro- cartilage (intervertebral disk), and stain 

 them with dilute magenta. Mount in dilute glycerine. Observe the wavy 

 fibres in the matrix and the cartilage-cells lying in clear areas often con- 

 centrically striated. Look for branched cartilage-cells. Sketch three or four 

 cells and the adjoining fibrous matrix. 



Costal cartilage. In the costal cartilages the matrix is not always 

 so clear as in the matrix of the joints, for it often happens that fibres 



FIG. 54. SECTION OF RIB-CARTILAGE, SHOWING TWO CELL-GROUPS IN A 

 SOMEWHAT FIBROUS-LOOKING MATRIX. 



become developed in it. The cells are generally larger and more an- 

 gular than those of articular cartilage, and collected into larger groups 



