CONNECTIVE TISSUE. 25 



TENDONS IN THE TAIL OF A RAT OR MOUSE. 



PREPARATION. Kill a rat preferably a young one seize the tip of the tail, and for- 

 cibly pull it. This ruptures the caudal vertebrae, and a leash of fine silvery-looking tendons 

 is pulled out. Place several of these tendons in the filtered juice of a lemon. Leave them 

 there for three minutes. They become clear and transparent and swell up considerably. 

 Remove them, wash them thoroughly in water, and place them in several times their bulk of 

 a one per cent, watery solution of chloride of gold (p. xlv), and allow them to remain there 

 for fifteen or twenty minutes. They become of a deep yellow colour, contract somewhat, 

 and are rendered more rigid. Remove them from the gold solution, and wash away the sur- 

 plus gold in water. Place them in an ounce of a twenty-five per cent, watery solution of 

 formic acid. The bottle containing them must be kept in a dark place for twenty-four hours. 

 At the end of this time, the tendons are removed from the formic acid and are thoroughly 

 washed in water. They have now a decided purple colour throughout. The formic acid re- 

 duces the gold on which it is deposited in the tissues, and to a greater extent in the protoplasm 

 of the cells than in the fibres. There are other ways of employing the ' gold method,' but we 

 have found this modification of Ranvier's very successful. [Each student cannot do the entire 

 process ; but he is shown how to do it.] Take a small piece of one of the above tendons, 

 and tease it with needles, in a drop of glycerine, and apply a cover-glass, or what does very 

 well, gently press on the cover-glass until the tendon is flattened. 



EXAMINATION (H). Observe the rows of flattened quadrilateral cells lying between the 

 longitudinally disposed fibres. The central part of each cell which contains the nucleus is 

 of a dark purple colour and finely granular. Thin slightly coloured wings may be seen ex- 

 tending outwards from this. The position of the nucleus is often left unstained and is usually 

 placed at one end of the cell, and the nuclei of adjacent cells in a row are usually so disposed 

 that the two nuclei lie close together. One or more dark lines may be seen running along the 

 centre of the cells (Boll's stripe). These are ridges projecting in a direction vertical to the 

 plane of the rectangular plate of the cells (PI. IV., Fig. 8). It is easy, by teasing out the 

 preparation carefully, to isolate a fibre with some of the cells still adhering to and partly 

 embracing it, so as to indicate the relation of the cells to the fibres. They can be seen to 

 send their thin lamellar or wing-like expansions around the fibre, so as partly to embrace 

 it (PI. IV., Fig. 9). These cells partly occupy the branched interfascicular spaces seen in a 

 transverse section of tendon (p. 24). 



DOUBLE-STAINING OF TENDONS. 



Gold Chloride and an aniline dye. Place an inch of the tail of a rat in gold chloride for an 

 hour, and then treat it as above. After the gold is reduced place the tail in chromic and nitric 

 acid fluid, to remove the lime-salts (p. xxxiii). Make transverse sections, and stain them with 

 iodine green and aniline blue, and mount them in dammar (p. 1). Beautiful sections of tendons 

 stained with gold are obtained, while part of the bone or interstitial cartilage becomes green. 

 These form most instructive preparations. 



CELL-SPACES IN TENDON. 



The above-described cells lie in spaces, which may be demonstrated by a solution of 



E 



