THE ESSENTIALS OF HISTOLOGY. 



LESSON XII. 



THE CONNECTIVE TISSUES (continued}. 







COSTAL CARTILAGE. FIBRO-CARTILAGE. 



1. MAKE transverse and tangential sections of a rib-cartilage, which may 

 either be fresh, or may have been preserved in spirit. Stain them with 

 haematoxylin (if fresh, after treatment with acetic acid as in Lesson XL, 

 2), and mount in glycerine. 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 con- 

 centric near the surface but radial near the centre. The costal cartilages 

 are often ossified near the middle in animals, but in man when ossification 

 occurs it is the superficial layer which is invaded. 



2. Make sections of the cartilage of the external ear, either fresh or after 

 hardening in alcohol. 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 in its cartilage. 



4. Cut sections of white fibro-cartilage (intervertebral disk), which has 

 been hardened in saturated solution of picric acid, followed by spirit, or in 

 spirit only. Stain the sections with -dilute hsematoxylin. Mount in dilute 

 glycerine. Observe the wavy fibres in the matrix and the cartilage-cells 

 lying in clear areas often concentrically striated. Look for branched carti- 

 lage-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 cartilage of the joints, for it often happens that fibres 

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

 angular than those of articular cartilage, and collected into larger 

 groups (fig. 62). Near the circumference, and under the perichondrium 

 or fibrous covering of the cartilage, they are flattened and parallel to 

 the surface, but in the deeper parts they have a more irregular or a 

 radiated arrangement. They frequently contain fat. The cartilages of 

 the larynx and windpipe and of the nose resemble on the whole the 

 costal cartilages, but the study of them may be deferred until the 

 organs where they occur are dealt with. 



