324 CHAPTER XXV. 



weeks. I do not know who first recommended this admir- 

 able medium (MAYER has long used 5 per cent, acid in 90 per 

 cent, alcohol). Pure nitric acid,, even if weak, readily exer- 

 cises a gelatinising action on bone ; whilst the addition of 

 alcohol (or of alum) counteracts this action (FisH, Ref. 

 Handb. Med. Sci., Supp., p. 425). 



THOMA (Zeit. f. wiss. Mik., viii, 2, 1891, p. 191) takes five 

 vols. of 95 per cent, alcohol and 1 volume pure concentrated 

 nitric acid. Leave bones in this mixture, changing the liquid 

 every two or three days, until thoroughly decalcified, which 

 should happen, even with large bones, in two or three weeks. 

 Wash out until every trace of acid is removed (i. e. for some 

 days after no acid reaction is obtained with litmus paper) in 

 95 per cent, alcohol containing an excess of precipitated 

 chalk. This may take eight to fourteen days, after which 

 the tissues will stain well and may be treated as desired. 



562. Nitric Acid and Alum (G-AGE, quoted from FISH, Zoc, 

 cit. last ). A saturated aqueous solution of alum is diluted 

 with an equal volume of water, and to each 100 c.c. of the 

 dilute solution is added 5 c.c. of strong nitric acid. Change 

 every two or three days, until the decalcification is complete. 

 For teeth this is said to be, perhaps, a better decalcifier than 

 the alcohol mixture. 



563. Hydrochloric Acid (see above, 559). RANVIEE says that it 

 may be taken of 50 per cent, strength, and then has a very rapid action. 

 To counteract the swelling action of the acid, sodium chloride may be added 

 (VON EBNER), see HAUG'S paper quoted 559. He takes either 100 c.c. 

 cold saturated solution of sodium chloride in water, 100 c.c. water, and 

 4 c.c. hydrochloric acid. Preparations to be placed in this, and 1 to 2 c.c. 

 hydrochloric acid added daily until they are soft. Or, 2*5 parts of hydro- 

 chloric acid, 500 of alcohol, 100 of water, and 2*5 of sodium chloride. 

 HAUG prefers the proportions of TO to 5'0 of acid, 70 of alcohol, 30 of 

 water, and 0'5 of salt. 



564. Hydrochloric Acid and Chromic Acid (BAYEKL, Arch. f. mik. 

 Anat., 1885, p. 35). Equal parts of 3 per cent, chromic acid and 1 per cent, 

 hydrochloric acid. For ossifying cartilage. HAUG recommends equal parts 

 of 1 per cent, hydrochloric acid and 1 per cent, chromic acid (loc. cit.). 



565. Hydrochloric Acid and Glycerin. Glycerin, 95 ; hydrochloric 

 acid, 5 (S^uiRE's Methods and Formulae, p. 12). 



