DECALCIFICATION 253 



603. Phosphoric Acid. Ten to lifticn \wr cent. (IIauo. Iqc. cit., in 

 § 590). Somewhat slow, staining not good. According to Schaffer, 

 § 590, it produces swelling. 



604. Lactic Acid. Ten per cent, or more. Fairly rapid, preserves 

 well, and may be recommended (IIaug, loc. cit.). 



605. Chromic Acid is employed in strengths of from 01 per cent, to 

 2 j)er cent, (but see !^ 590), the maceration lasting two or three weeks (in 

 the case of bone). It is better to take the acid weak at first, and increase 

 the strength gradually. Action excessively slow. 



606. Chromic and Nitric Acid. Seilf.r (Fol, Lerh., p. 112) takes 

 70 volumes of 1 per cent, chromic acid, 8 of nitric acid, and 200 of water. 

 The action is still excessively slow, frequently requiring months to be 

 complete. 



607. Chromo-aceto-osmic Acid (Vax der Stricht, Arch. Biol., 

 ix. 1889, p. 29 ; and Schaffer, Zeit. wiss. Mik., x, 1893, p. 179). 

 Objects to be left in it for months, the liquid being changed at 

 first every two days, afterwards less frequently. Structure well 

 preserved. 



608. Arsenic Acid. Four per cent, aqueous solution, used at a 

 temperature of 30° to 40° C. (Squire's Methods and Formulce, etc., 

 p. 11). 



609. Phloroglucin with Acids (Andeer, Centralb. med. Wiss., xii, 

 xxxiii, pp. 193, 579 ; Intern. Monatsschr., i, p. 350 ; Haug, Zeit. zviss. 

 Mik., viii, 1891, p. 8 ; Ferreri, ibid., ix, 1892, p. 236 ; Bull. R. Acad. 

 Med. di Roma, 1892, p. 67). This is said to be the most rapid method 

 of any. Phloroglucin by itself is not a solvent of lime salts ; its function 

 in the mixture gi\en below is so to protect the organic elements of 

 tissues against the action of the mineral acid that this can be used in a 

 much more concentrated form than would be otherwise advisable. 



Andeer takes a saturated solution in warm water, and adds to it 5 

 to 50 per cent, of hydrochloric acid. Wash out in running water. 



Other acids than hydrochloric may, of course, be taken. See Haug, 

 Zeit. iviss. Mik., viii, 1891, p. 8, and Ferreri, Bull. Acad. Med. Roma, 

 1892, p. 67, or (for both) fifth edition. 



DESILICIFICATION 



610. Hydrofluoric Acid (Mayer, Zool. Anz., 1881, p. 593). The 

 objects are brought in alcohol into a glass vessel coated internally 

 with paraffin. Hydrofluoric acid is then added drop by drop 

 (taking great care to avoid the fumes, which attack mucous 

 membranes with great energy). Small pieces of siliceous sponges 

 will be completely desilicified in a few hours, or at most a day. 

 The tissues do not suffer. 



For sponges we find that this dangerous method can be avoided. If 

 well imbedded, sections may be made from them Avithout previous 

 removal of the spicules, which appear to break off sharp before the knife. 



Rousseau imbeds the objects in celloidin, as described § 182, then 

 brings the block, in a covered caoutchouc dish, for a day or two into a 

 mixture of 50 c.c. alcohol and 20 to 30 drops of hydrolluoric acid, and 

 washes out the acid with alcohol containing carbonate of lithia in 

 powder. 



