244 MACERATION CORROSION 



completed by teasing or pressing out, as indicated last § ; if 

 not, the soaking must be continued, fresh iodine being added as 

 often as the serum becomes pale by the absorption of the iodine 

 by the tissues. By taking this precaution the maceration may be 

 prolonged for several weeks. 



This method is intended to be applied to the preparation of 

 fresh tissues, the iodine playing the part of a fixing agent with 

 regard to protoplasm, which it slightly hardens. 



556. Iodide of Potassium (Arnold, Arch. mik. Anat., Hi, 1898, pp. 135 

 and 763). Ten c.c. of 10 per cent, aqueous sol. of potassium iodide with 5 

 to 10 drops of a similar solution, containing also 5 per cent, of iodine. 



557. Alcohol, Raxvier employs one-third alcohol (1 part of 

 90 per cent, alcohol to 2 parts of water). Epithelia will macerate 

 well in this in twenty-four hours. It macerates more rapidly 

 than iodised serum. 



Other strengths of alcohol may be used, either stronger (equal 

 parts of alcohol and water) or weaker (| alcohol, for isolation of 

 the nerve-fibres of the retina, for instance — Thin). 



558. Salt Solution. Ten per cent, solution of sodium chloride 

 is a valuable macerating medium. Weaker strengths, down to 

 0-6 per cent., are also used. 



559. MoLEscHOTT and Piso Borme's Sodium Chloride and 

 Alcohol (Moleschott's Untersuchungen zur Naturlehre, xi, 

 pp. 99 — 107 ; Ranvier, Traite, p. 242). Ten per cent, solution 

 of sodium chloride, 5 volumes ; absolute alcohol, 1 volume. 



For vibratile epithelium Ranvier finds the mixture inferior 

 to one-third alcohol. 



560. Sodium Chloride and Formaldehyde. Gage reconnnends 

 the addition of 2 parts of formalin to 1000 parts of normal salt 

 solution (quoted from Fish, Proc. Amer. Mic. Soc, xvii, 1895, 

 p. 328). 



561. Caustic Potash, Caustic Soda. These solutions should be 

 employed strong, 35 to 50 per cent. (Moleschott) ; so employed 

 they do not greatly alter the forms of cells, whilst weak solu- 

 tions destroy all the elements. (Weak solutions may, however, 

 be employed for dissociating the cells of epidermis, hairs, and 

 nails.) The strong solutions may be employed by simply treat- 

 ing the tissues with them on the slide. To make permanent 

 preparations, the alkali should be neutralised by adding acetic 

 acid, which forms with caustic potash, acetate of potash, which 

 constitutes a mounting medium (see Behrens, Kossel, and 

 Schiefferdecker, Das Mikroskop, i, 1889, p. 156). See also 

 Gage, Proc. Amer. Soc. of Microscojyists, 1889, p. 35. 



562. Baryta- water, Lime-water (Fol, Lehrb., p. 110). Baryta-water 

 will macerate nerve, muscle, and connective tissue in a few hours, lime- 

 water in a few days. 



