TUV. rOXXKCTIVE TISSUES 101 



be transferred directly to glycerin, in which tlicy arc mounted, or the bits of 

 tissue may be first stained with haematoxylin (page i8). In addition to the pig- 

 mented cells should be noted the ordinary fixed connective-tissue cells which lie 

 among them. Only the nuclei of these cells can be seen. 



8. ConneiiLhigr tissue cells to show anastomosing processes. — Stain a cornea 

 with gold( chIori( j/ i^see page 28). Sections are made tangential to the convex 

 surface and are mounted in glycerin. 



9. Connective-tissue cell spaces (lacunae) and their anastomosing canaliculi 

 may be demonstrated by staining a cornea with silver nitrate (see page 28). 

 The silver stains the ground substance of the cornea, leaving the lacuna) and 

 canaliculi unstained. The relation which this picture bears to the preceding 

 should be borne in mind (see Figs. 31 and 32). 



10. Coarse elastic fibres may be obtained from the ligamentum nuchae, which 

 consists almost wholly of elastic tissue. A piece of the ligament is fixed in satu- 

 rated aqueous solution of picric acid and hardened in alcohol. A bit of this 

 tissue is teased apart on a glass slide in a drop of pure glycerin, in which it is also 

 mounted. Before putting into glycerin, the specimen may be stained with picro- 

 acid-fuchsin. This intensifies the yellow of the elastic fibres and brings out in 

 red the fibrillar connective tissue. Pieces of the ligament fixed and hardened 

 in the same manner may be embedded in celloidin and cut into longitudinal and 

 transverse sections. These stained with picro-acid-fuchsin show well the rela- 

 tion of the coarse elastic fibres (yellow) to the more delicate fibrous tissues (red). 



11. Fat Tissue. — Human subcutaneous fat as fresh as possible is fixed in 

 formalin-Miiller's fluid (technic 6, p. 7), hardened in alcohol and embedded in 

 celloidin. Sections are stained with haematoxylin and picro-acid-fuchsin (technic 

 3, p. 21). The alcohol and ether of the celloidin remove the fat from the fat 

 cells, leaving only the cell membranes. The fat gives the celloidin a milky 

 appearance. Such celloidin does not cut well. The celloidin should, there- 

 fore, be changed until it ceases to turn white. The sections are cleared in oil of 

 origanum or carbol-xylol, and mounted in balsam. The fibrillar tissue is stained 

 red by the fuchsin, and the protoplasm of the fat cell yellow by the picric .icid. 

 Fat tissue may also be satisfactorily stained by Sudan III or Scharlack R. F 

 details see p. 31. 



12. Developing Fat Tissue. — Remove bits of tissue from the axilla or groin 

 of a five-inch foetal pig, or other foetus of about the same development. Fix 

 twenty-four hours in a i-per-cent. aqueous solution of osmic acid (technic 10, 

 p. 31), wash thoroughly and mount in glycerin. A part of the tissue mounted 

 should be thoroughly teased, the rest gently pulled apart. The teased portion 

 will show the fat cells in various stages of development. The unteased part will 

 usually show brownish blood-vessels and the grouping of fat cells around them, 

 to form embryonic fat lobules. Note the developing connective tissue between 

 the groups of fat cells. It is from this that the areolar tissue, which envelops 

 and separates the lobules of adult fat, is developed. 



13. Reticular Tissue. — Fix a lymph node in formalin-Miiller's fluid (technic 

 6, p. 7), and stain very thin sections with haematoxylin and picro-acid-fuchsin 

 (technic 3, p. 21). In the lymph sinuses of the medulla the reticulum can 

 usually be plainly seen. 



