DIRECTIONS FOR LABORATORY WORK 773 



tic fibrils. The latter may be arranged in a wide-meshed network. 

 Sketch (56) a bundle of white fibers. Do the bundles anastomose? 

 Sketch (57) also several elastic fibers. Do they branch? Explain the 

 curled character of some of the fibers. Add several drops of a 5 per cent, 

 aqueous solution of acetic acid. Note that the collagen fibrils swell, 

 some of the bundles become beaded, and finally disintegrate. What is 

 the significance of the beaded condition of the bundles of collagen fibrils? 

 Note difference in structural and chemical characteristics of the collagen 

 (white) and elastic (yellow) fibers. Add a drop of a nuclear dye (e.g., 

 methylene blue solution) and examine and sketch (58) the several types 

 of cells: (a) spindle-shaped cell; (b) plasma cell; (c) lamellar cell; 

 (d) clasmatocy te ; (e) granular leukocyte. Wash the preparation in dis- 

 tilled water and add several drops of a 1 per cent, solution of magenta 

 (basic fuchsin) in 70 per cent, alcohol. This will stain the elastic fibers 

 (red). Examine the preparation for final study of the elastic fibers. 



Sketch (59) a small area of subcutaneous tissue from a section of 

 skin stained with Weigert's elastic tissue stain (resorcin-fuchsin), Dela- 

 field's hematoxylin and Van Gieson's stain (picric-acid-fuchsin). Note 

 cells, fibers and intercellular spaces ('tissue spaces', filled with 'tissue 

 fluid'). 



(5) DENSE WHITE FIBROUS TISSUE (e.g., tendon, sclera of eye). 

 Study a longitudinal section of tendon. Sketch (60) a small area 

 under the l.p. noting the fasciculi. Sketch (61) h.p. a small area from 

 a transverse section of tendon. Note shape of cells and nuclei, their 

 arrangement with respect to each other and the bundles (fasciculi) of 

 white fibrils. Tease a fragment of tendon (from tail of rat or leg muscle 

 of rabbit) in salt solution ; add a few drops of a 5 per cent, aqueous solu- 

 tion of acetic acid to destroy some of the collagen fibrils; add a few 

 drops of methylene blue solution; sketch (62) several isolated cells. (A 

 stained macerated preparation of tendon is an equally favorable material 

 for study of tendon cells.) 



(6) DENSE ELASTIC TISSUE. Study a teased or macerated prepa- 

 ration of ligamentum nucha3 of ox, and make drawing (63) of a 

 few fibers. Note transverse markings in portions of some fibers. Sketch 

 (64) small areas of stained (Van Gieson's dye) sections, (a) transverse 

 and (b) longitudinal, of ligamentum nuchae. 



(B) MODIFIED. 



(1) ADIPOSE (Fat} TISSUE. This is modified areolar tissue. Study 

 a cover-glass mount of fresh fat, from the subcutaneous tissue of 



