j^r 



100 v' THE TISSUES 



Place a drop of hycftic acelatc, i-per-cent. aqueous solution, at one side of the 

 cover and a bit of filter paper at the other side. The filter paper absorbs the salt 

 solution, which is replaced by the hydric acetate. The latter causes the white 

 fibres to swell and become indistinct while the elastic fibres show more plainly. 



2. Areolar Tissue, to show Cells and Elastic Fibres. — Prepare second speci- 

 men of areolar tissue in the same manner as the preceding. Instead of mounting 

 in salt solution, allow it to become perfectly dry, then stain in the following 

 solution : 



Gentian violet, saturated aqueous solution, 40 c.c. 



Water, 60 c.c. 



Wash thoroughl}-, dry, and mount in balsam. 



The nuclei of the fixed connective-tissue cells are stained violet. Their deli- 

 cate cell bodies show as an irregular haze around the nuclei. Both nuclei and 

 cell bodies appear cut in all directions by the stretched elastic fibres. Wander- 

 ing cells (leucocytes) may usually be seen. Plasma cells are frequently not 

 demonstrable, and mast cells are only occasionally present. The elastic fibres 

 are stained violet. The white fibres are almost unstained. 



While these methods are most satisfactory for bringing out the different con- 

 nective-tissue elements, they are misleading to the student in that they show a 

 picture of connective tissue after special preparation, rather than as it usually 

 appears in sections. For contrast the student should study carefully the con- 

 nective tissue as it appears in sections through the skin, the mucous membranes 

 and other organs. 



3. Formed Connective Tissue. — Fibrous tissue arranged in the form of a net- 

 work may be seen in the specimen of omentum (technic 7, p. 82). 



4. Densely formed connective tissue may be studied in tendon. Cut through 

 the skin of the tail of a recently killed mouse about half an inch from the tip and 

 break the tail at this point. By pulling on the end of the tail this portion may 

 now be separated from the rest of the tail, carrying with it long delicate tendon 

 fibrils, which have been pulled out of their sheaths. These should be immedi- 

 ately examined in salt solution, using the high power and a small diaphragm. 

 The fibrils are seen arranged in parallel bundles. 



5. Place a drop of hydric acetate (2-per-cent. aqueous solution) at one side 

 of the cover-glass, absorbing the salt solution from the opposite side by means 

 of filter paper. The fibres swell and become almost invisible, while rows of 

 connective-tissue cells (tendon cells) can now be seen. The cells may be stained 

 by allowing a drop of haematoxylin or of carmine solution to run under the cover. 

 After the cells are sufiiciently stained, the excess of stain is removed by washing, 

 and the specimen mounted in glycerin. 



6. Fix a small piece of any good-sized tendon in formalin-Miiller's fluid (page 

 7). After a week, harden in alcohol, embed in celloidin, and make longitudinal 

 and transverse sections. Stain strongly with haematoxylin, followed by picro- 

 acid-fuchsin (page 21). Mount in balsam. 



7. Pigmented connective-tissue cells are most conveniently obtained from 

 the chorioid coat of the eye. Fix an eye in formalin-Miiller's fluid (see page 7), 

 cut in half, remove chorioid and retina and pick ofif the dark shreds which cling 

 to the outer surface of the chorioid and inner surface of the sclera. These may 



