ALCOHOL. 283 



Zeit. /. wiss. Mik., vii, 4, 1891, p. 461) by melting white wax 

 and stirring into it one half to two thirds of Venice turpen- 

 tine. Care must be taken if the operation be performed over 

 a naked flame, as the turpentine vapours are inflammable. 



523. Iodised Serum. The preparation of this reagent has 

 been given ic 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 above; 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 macera- 

 tion may be prolonged for several weeks. 



It is obvious that these methods are 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. 



524. Artificial Iodised Serum (FEEY, Le Microscope, p. 131 ; 

 KANVIEE, Traite, p. 77). 



The formula has been given in Chap. XIX. Ranvier states 

 that he has been unable to obtain good results, for purposes 

 of maceration, by this method. 



525. Alcohol. Ranvier employs one-third alcohol (1 part of 

 36 alcohol to 2 parts of water) . Epithelia will macerate well 

 in this in twenty-four hours. Ranvier finds that this mixture 

 macerates more rapidly than iodised serum. 



Other strengths of alcohol may be used, either stronger 

 (equal parts of alcohol and water) or weaker (i alcohol, for 

 isolation of the nerve-fibres of the retina, for instance 

 Thin). 



All observers are agreed that one-third alcohol is a mace- 

 rating medium of the highest order; LIST (Zeit. f. wiss. MiJc., 

 1885, p. 511) states that for glandular structures it should be 

 used with precaution, on account of swellings that it produces 

 in the cells, and that M tiller's solution, or osmic acid, should 

 be preferred for such objects. 



