322 CHAPTER XXV. 



purpose the commercial solution should be taken concentrated 

 and boiling (see also 576). 



If solutions diluted with 4 to 6 volumes of water be taken, 

 and chitinous structures be macerated in them for twenty- 

 four hours or more, according to size, the chitin is not dis- 

 solved, but becomes transparent, soft, and permeable to 

 staining fluids, aqueous as well as alcoholic. The most 

 delicate structures, such as nerve endings, are stated not to 

 be injured by the treatment. The method is applicable to 

 Nematodes and their ova (objects well known for the re- 

 sistance they oppose to ordinary reagents), and also to the 

 removal of the albumen from ova of Amphibia, etc. 



557. ALTMANN'S Corrosion Method (Arch.f. mik. Anat., 1879, p. 471). 

 See previous editions, or Journ. Roy. Mic. Soc., 1879, p. 610. 



On injections for corrosions see EEJSEK, Bibliogr. Anat., iv, 1897, p. 229. 



Decalcification. 



558. Decalcification. In order to obtain the best results, it 

 is important to employ only material that has been duly fixed 

 and hardened, and it is well not to put too much confidence 

 in reagents that are said to have the property of hardening 

 and decalcifying fresh material at the same time (Fisn, Kef. 

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



ROUSSEAU (Zeit. f. wiss. Mik., xiv, 1897, p. 207) imbeds 

 fixed material in celloidin, brings it into 85 per cent, alcohol, 

 decalcifies in a very acid mixture (15 to 40 percent, of nitric 

 acid in alcohol), washes out the acid in alcohol containing 

 precipitated carbonate of lime, then cuts sections. This for 

 Porifera, corals, Echinoderms, etc. Tissues are said to be 

 well preserved. 



559. Decalcification of Bone. I take the following from 

 BUSCH, Arch. f. mik. Anat., xiv, 1877, p. 481 ; see also the 

 paper of HAUG, in Zeit. f. wiss. Mik., viii, i, 1891, p. 1. 



The most widely used agent for decalcification is hydro- 

 chloric acid. Its action is rapid, even when very dilute, but 

 it has the disadvantage of causing serious swelling of the 

 tissues. To remedy this, chromic acid may be combined with 

 it, or alcohol may be added to it. Or a 3 per cent, solution 



