CHAPTER V. 59 



of alcohol of 90 per cent, (and not of absolute alcohol). See the 

 Traite Technique of Ranvier, p. 241, et passim. 



Objects may be left for twenty-four hours in this alcohol ; not 

 more, unless there be no reason for avoiding maceration, which will 

 generally occur after that time. You may conveniently stain with 

 picro-carmine. alum-carmine, or methyl green. 



This reagent is a very mild fixative. Its hardening action is so 

 slight that it is not at all indicated for the fixing of objects that are 

 intended to be sectioned. Its chief use is for extemporaneous and 

 dissociation preparations. 



105. Pyridin. Pyridin has been recommended as a hardening agent 

 (by A. DE SOUZA). It hardens, dehydrates, and clears at the same time. 

 It is said to harden quickly, and to give particularly good results with 

 brain. fSee Comptcs Eendus hebd. de la Soc. de Biologic, 8 ser., t. iv, 

 1887, p. 622. 



This substance is strongly alkaline, and, either pure or diluted with 

 \vater, dissolves many albumens and fats. It causes considerable 

 shrinkage of nuclei (not so much of cytoplasm). It is now in much use 

 in certain neuro-nbril stains, see BIELSCHOWSKY and KAMON. It is 

 soluble in water and in alcohol. Pure, it will harden and dehydrate 

 small brains in a week. 



106. Acetone is said to harden very rapidly. It precipitates 

 lipins. and may yet prove an important reagent. SCHOLZ (Zeit. 

 iriss. Mikr.. xxii. 1905, p. 415) fixes small objects in warm acetone 

 for half an hour to an hour and brings them direct, or through 

 alcohol and ether, into celloidin. 



[Similarly Fuss (Arch. path. Anal., clxxxv, 190ti, p. 5), using it- 

 cold, and LINTWAREW (ibid., ccvi, 1911, p. 36) for erythrocytes, in 

 which it preserves the haemoglobin. 



107. Lucidol. -This is a proprietary name applied to peroxide of 

 benzol (C C H 5 C0) 2 2 . It is a white powder insoluble in water, 

 but soluble in acetone and pyridin ; heated, the white powder first 

 of all melts and then explodes. The introduction of " Lucidol 5I is 

 due to EHRLICH, who suggested it to SZECSI. " Lucidol ' must 

 share with its solvents, acetone and pyridin, their defects as fixing 

 agents. Acetone, especially tends to tear cells to pieces, owing to 

 its attraction for water. So far, there have been very few references 

 to the use of : Lucidol ' in histological literature. LANGERON 

 (C. R. Soc. de Biol., Ixxvi, 1914) claims that " Lucidol " is especially 

 convenient for work on blood, faeces and cell smears, and two of 

 SZECSI'S methods are given below. It should be pointed out that 

 the Lucidol-acetone solution gives a very active penetration, and 

 unlike CARNOY'S or SCHAUDINN'S fluids, does not dissolve away lipins. 



