128 THE TISSUES. 



Elastic fibers remain unchanged in acetic acid, and even when 

 boiled in a 20% solution they only become slightly brittle. They are, 

 however, rapidly destroyed by concentrated hydrochloric acid, although 

 in a 10% solution at ordinary temperature no change is seen. In a 50% 

 solution the fiber is dissolved in seven days, and in a concentrated solu- 

 tion in two days. The inner substance of the fiber is first attacked, then 

 the membrane. To demonstrate this membrane, the fibers are boiled 

 several times in concentrated hydrochloric acid and the whole then 

 poured into cold water. Occasionally, a longitudinal striation of the 

 membrane is seen, indicating a fibrillar structure. Concentrated solutions 

 of potassium hydrate disintegrate the fibers in a few days ; weak solutions, 

 more slowly. A i % solution of potassium hydrate requires months to 

 produce the effect; a 2% solution, one month; a 5%, three days; a 

 10%, one day; and 20% to 40%, only a few hours. A weak solution 

 of potassium hydrate, even when brought to the boiling-point, does not 

 dissolve elastic fibers, nor does it cause them to become brittle. If, how- 

 ever, they be boiled in a 5% or 10% solution of potassium hydrate, the 

 membranes of the fibers will be isolated. A cold 20% solution has the 

 same effect in one or two days. Pepsin induces a disintegration of the 

 contents of the fiber, leaving the membranes intact. 



To demonstrate the inner substance of elastic fibers and their 

 membranes, magenta red has been recommended (a small granule is 

 added to 50 c.c. glycerin and 50 c.c. water). By this method the 

 internal substance is colored red while the sheath remains colorless. 



Orcein, Unna's Method. Make a solution consisting of Griibler's 

 orcein i part, hydrochloric acid i part, absolute alcohol 100 parts. The 

 sections are stained in a porcelain dish. The stain is heated over a 

 flame or in an oven until the stain becomes quite thick. Rinse thor- 

 oughly in alcohol, clear in xylol, and mount. Elastic fibers stain a dark 

 brown, white fibrous tissue a light brown. 



Fuchsin-resorcin Elastic Fibers Stain (Weigert). A solution 

 containing i % of basic fuchsin and 2 % of resorcin is made and brought 

 to boiling. To 200 c.c. of this solution there is added 25 c.c. of liquor 

 ferri sesquichlorati (Germ. Pharm.). Boil for about five minutes, stir- 

 ring the meanwhile. Filter on cooling, and place the filter paper and 

 the precipitate collected in a porcelain dish and add 200 c.c. of 

 95% alcohol and bring to boiling. Filter on cooling and add to the 

 filtrate 4 c.c. of hydrochloric acid and enough alcohol to bring it up to 

 200 c.c. Stain sections for about one hour. Sections are then washed in 

 alcohol or acidulated alcohol, or, better still, in alcohol to which a few 

 crystals of picric acid have been added'. Clear in xylol and mount. 

 Elastic fibers are stained dark blue or bluish-black if washed in picric 

 alcohol. 



Differential Stain for Connective-tissue Fibrillse and Reticu- 

 lum (Mallory). Fix tissues in corrosive sublimate or in Zenker's so- 

 lution. (Tissues fixed by other methods may also be used, although the 

 results are not quite so satisfactory, if the sections are immersed for fifteen 

 to thirty minutes in a saturated corrosive sublimate solution just before 

 staining. ) The sections, which may be cut in celloidin or paraffin, are 

 stained for one to three minutes in a ^/ aqueous solution of acid fuch- 

 sin, rinsed in water, and placed in a i % aqueous solution of phosphomo- 

 lybdic acid for five to ten minutes, and then washed in two changes of 

 water. They are now stained in the following solution for two to twenty 



