X.] 



CONNECTIVE TISSUE. 



161 



lying in a serous cavity is covered with endothelium. The nuclei on 

 the surface are the nuclei of endothclial cells, and those in the sub- 

 stances of the trabeculffi belong to connective-tissue cells. 



ADDITIONAL EXERCISES. 



10. Martinotti's Reaction for Elastic Fibres ( H ). Harden elastic tissue, 

 e.g., ligamentum nuchse, or an organ containing elastic fibres, e.g., skin, 

 artery, lung, trachea, in .2 per cent, chromic acid for three weeks. Cut 

 sections and place them for twenty-four to forty-eight hours in a saturated 

 alcoholic solution of safranin-0. Wash them in acid alcohol (p. 65), and then 

 in absolute alcohol, to remove the surplus dye ; 



clear in xylol, and mount in xylol-balsam. 



(a.) All the elastic fibres, and they alone, are now 

 either purplish, or, if the fibres be fine, black. 

 This is a most excellent method for differentiating 

 elastic fibres. The one thing of importance is to 

 secure a good sample of safranin ; some samples are 

 quite inactive. 



11. Elastic Fibres (ffcrxheimer's Method). Place 

 the sections containing elastic fibres in an alcoholic 

 solution of hjematoxylin, to which is added a few 

 drops of a saturated solution of lithium carbonate. 

 Stain them for a few minutes. Place them for five 

 to twenty seconds in tincture of perchloride of iron, 

 which rapidly decolorises all except the elastic 

 fibres, which remain bluish or blackish. Wash in 

 water and mount in balsam. This method is admir- 

 ably adapted for demonstrating the longitudinal 

 layer of elastic fibres in the trachea and bronchi. 



12. Violet-B Method. Cut out the hyaloid mem- 

 brane of a frog's eye, or a piece of the omentum of a 

 young rabbit, or the suspensory ligament of the liver 

 of a rabbit. In normal saline pencil away the epi- 

 thelium covering the membrane. Stain the section 

 with violet-B (i gram violet- B in 300 cc. of normal 

 saline). This stains the cells and the elastic fibres. 

 The preparation cannot be mounted in glycerine 

 or Farrant's solution, as these dissolve out the dye, 

 but a strong solution of common salt may be used 

 (,V. Mayer). 



13. Areolar Tissue Permanent Preparations. 

 (i.) By means of a hypodermic syringe (fig. 126) 



make an interstitial injection of silver nitrate 



(i : 1000) into the subcutaneous tissue of a dog or 



rabbit. In this way an artificial cedema is produced 



and the tissues are " fixed." With a pair of scissors 



curved on the flat, snip out a little of the now cedematous connective tissue 



and stain it with picro-carmine. It requires some time to stain, and the 



preparation should be left for ten to twelve hours in a moist chamber 



.^fig. 70), and then the picro-carmine is slowly displaced by acid glycerine, 



i.c., glycerine slightly acidulated with formic acid. In this way the 



FIG. 126. Hypodermic Sy- 

 ringe for making a Sub- 

 cutaneous or Interstitial 

 Injection. 



