CARTILAGE. 63 



and immersed in a drop of saturated solution of picric 

 acid on a slide, and covered and surrounded at once by 

 a rim of asphalt varnish, before the acid solution com- 

 mences to evaporate. 



In such thin sections, cavities are seen here and there 

 from which the cells have fallen out ; these may be filled 

 with the preservative fluid, or with bubbles of air. 

 Picric acid is one of the best agents for preserving the 

 normal characters of cartilage cells, but even in this 

 they shrink somewhat, and after a time become coarsely 

 granular. 



Fibro cartilage may be studied in thin sections from 

 the intervertebral cartilages of man or any of the domes- 

 tic animals ; or from the head of the femur, through the 

 insertion of the ligamentum teres, parallel with the 

 course of its fibres. The tissues should be laid for a 

 few days in alcohol before cutting. The sections are 

 stained with picro-carmine, and mounted in glycerin. 



Fibro- Elastic Cartilage. This is best studied in the 

 .epiglottis of man or the lower animals, which has been 

 preserved in alcohol. Thin sections are stained with 

 picro-carmine, which colors the cells red and the elastic 

 granules and fibres yellow. They are mounted and pre- 

 served in glycerin. The cells in both fibro and fibro- 

 elastic cartilage are, by the above modes of preparation, 

 more or less shrunken and deformed. 



BONE. 



In studying bone we have to consider: I, the 

 hard substance, or bone-tissue proper ; 2, the connec- 

 tive-tissue envelope which surrounds the bone the 



