COLLODION AND OTHtil* IMBEDDING METHODS. Ill 



You may mount in balsam, also, without removing the 

 mass, which does no harm, and serves the useful purpose 

 of holding the parts of the sections together during the 

 manipulations. Dehydrate in alcohol of 95 or 96 per cent, 

 (not absolute, as this attacks the collodion). NIKJFOROW (Zeit. 

 ivixs. Mik., viii, 1891, p. 189) recommends a mixture of equal 

 parts of alcohol and chloroform. Clear with a substance that 

 does not dissolve collodion. The clearing agents most recom- 

 mended are origanum oil (01. Origan. Cretici, it is said, should 

 be taken, not 01. Orig. Gallici ; but see as to this reagent 

 the remarks in 125), bergamot oil (said to make* sections 

 shrink somewhat), oil of sandal-wood, lavender oil, oil of 

 cedar-wood (safe and gives excellent results, but acts rather 

 slowly), chloroform, xylol, or benzol (may make sections 

 shrink if not well dehydrated), or Dunham's mixture of 3 

 or 4 parts of white oil of thyme with 1 part of oil of 

 cloves. (As to oil of thyme, see also 125, 126.) 



FISH (Proc. Amer. Mik. Soc., 1893) advises a mixture of 

 one part of red oil of thyme with three parts of castor oil, 

 the latter being added in order to counteract the volatilit}^ 

 of the thyme oil. But later (June, 1895), writing to me, 

 Dr. Fish says he has substituted the white oil of thyme for 

 the red, and finds it an advantage in orientating. See also 

 126. 



Some specimens of clove oil dissolve collodion very slowly, and may 

 be used, but I would not be understood to recommend it. The action 

 of origanum oil varies much, according to the samples ; some sorts do 

 not clear the collodion, others dissolve it, others pucker ^it. MINOT 

 (Zeit. wiss. Mik., iii, 1886, p. 175) says that Dunham's mixture "clarifies 

 the sections very readily, and softens the celloidin just enough to prevent 

 the puckering which is so annoying with thyme alone." 



Carbolic acid has been recommended. WEIGERT (Ztit. iviss. Mik., iii, 

 1866, p. 480) finds that a mixture of 3 parts of xylol with 1 part -of 

 carbolic acid (anhydrous) clears well. But it must not be used with the 

 basic anilin stains, as it discolours them. For these anilin oil may be 

 used with xylol in the place of carbolic acid. 



Anilin oil clears well (it will clear from 70 per cent, alcohol), but 

 unless thoroughly removed the preparation becomes yellowish-brown, 

 see 134. See VAN GIBSON, Amer. Mon. Mic. Journ., 1887, p. 49, or 

 Journ. Roy. Mic. Soc., 1887, p. 519, for a review of these clearing agents. 



Beech-wood creasote has been recommended (by M. Flesch). 



EYCLESHYMER (Amer. Nat., xxvi, 1892, p. 354) advises a mixture of 

 e^ual parts of bergamot oil, cedar oil, and carbolic acid. 



