MACEEATION, DIGESTION, AND CORROSION. 271 



The most desirable macerating media are those which, 

 whilst dissolving intercellular substances, do not attack the 

 cells themselves. Those which contain colloids have been 

 found to give the best results in this respect. Iodised 

 serum is an example. 



521. Iodised Serum (Chap. XIX).- — The manner of employing 

 it for maceration is as follows : A piece of tissue smaller than 

 a pea must be taken, and placed in 4 or 5 c.c. of weakly 

 iodised serum in a well-closed vessel. After one day's 

 soaking the maceration is generally sufficient, and the 

 preparation may be 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. 



522. Iodide of Potassium (Arnold, Arch. mik. Anat., Va, 1898, 

 pp. 135 and 763).— 10 c.c. of 10 per cent, aqueous sol. of potassic iodide 

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

 iodine. 



523. Alcohol. — Ranvier 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). 



524. Salt Solution. — 10 per cent, solution of sodium chloride 

 is a valuable macerating medium. Weaker strengths, down 

 to 0"6 per cent., are also used. 



525. MoLESCHOTT and Pi so Boemu's Sodium Chloride and 

 Alcohol (Moleschott's Untersuchungen xur Nahirlehre, xi, pp. 

 99 — 107 ; Ranviee, Traits, p. 242). — 10 per cent, solution of 

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



