CARTILAGE. 19 



YELLOW FIBRO-CARTILAGE. 



This may be easily obtained from the epiglottis, the arytenoid cartilages, or the external ear. 



PREPARATION. Place the arytenoid cartilages and the epiglottis of a sheep or ox (if the 

 latter, cut it into two pieces) in a saturated solution of picric acid. Remove it after forty-eight 

 hours and make transverse sections of it in the usual way. Preserve it in methylated spirit. 



Treat the external ear of a cat or rabbit in the same way and make sections. This 

 method is preferable to simple hardening in alcohol. 



Stain a transverse section of an epiglottis hardened as above with picrocarmine. A few 

 minutes suffice to stain the parts. Remove the surplus staining fluid with blotting paper, 

 and mount in Farrant's solution. 



EXAMINATION (L). This specimen contains a section of the mucous membrane covering 

 both surfaces of the epiglottis. This may be neglected at present. The cartilage itself is 

 stained bright yellow (picric acid) with a perichondrium of connective tissue which is of a deep 

 red colour. Lying in the bright yellow fibrous matrix are a number of red spots, which 

 are the nuclei of the cartilage-corpuscles. 



(H). N otice the matrix- - yellow, distinctly fibrous, and the fibres like those of elastic tissue, 

 and branched. If the line of section cuts these fibres transversely they appear as fine yellow 

 granules. Trace these fibres into the red connective-tissue perichondrium, where they become 

 yellow elastic fibres. This continuity can be easily made out in a thin section. Study the 

 corpuscles. Towards the periphery of the cartilage they are flattened ; but near the centre 

 they are rounded, have a distinct capsule, and the nucleus is distinctly stained red. This 

 forms an extremely beautiful preparation. These preparations require a day or two for the 

 colours to become differentiated. 



A section may be double-stained with picrocarmine and logwood, but this method pos- 

 sesses no advantages over the above. 



Stain a section of the ear of a cat with picrocarmine as above. Mount it in Farrant's solution. 



EXAMINATION (L and H). The yellow mass of cartilage stands out beautifully between 

 the red connective tissue (PI. III., Figs. 4 and 5). Sections of muscles, skin, and sebaceous 

 glands may also be seen. The same general characters are seen with a high power as are indi- 

 cated above. 



TRANSITION FROM HYALINE TO YELLOW FIBRO-CARTILAGE. 



Make longitudinal sections of an arytenoid cartilage of an ox, and stain it with picro- 

 carmine. The upper half shows the structure of yellow fibro-cartilage, while the lower half is 

 chiefly hyaline, with a few elastic fibres extending into the matrix. This shows the mode of 

 development of yellow fibro-cartilage from hyaline cartilage. 



CHANNELS IN THE MATRIX OF HYALINE CARTILAGE. 



These are easily seen in a section of a part of the cephalic cartilage of Loligo, which has 

 been hardened in picric acid and stained with picrocarmine. 



