72 CHAPTER VI. 



obtain 01. Origani GretAci {" Spanisches Hopfenol "), not 01. 

 Orig. Gallici (v. Gtieson j see Zeit. wiss. Mik., iv, 1887, p. 

 482) . Specimens of origanum oil vai'y greatly in their action 

 on celloidin sections. 



Squire, in his Method.s and Formulx, etc., p. 81, says that 

 origanum oil (meaning the commercial product) is nothing 

 but oil of white thyme more or less adulterated (see next §), 

 and that the product sold as 01. Origani Cretici is probably 

 oil of marjoram. 



126. Oil of Thyme.— Pish {Proe. Amer. Mic. Soc, 1893; 

 Zeit. wiss. Mik., xi, p. 503), following Bumpus, says that for 

 most of the purposes for which origanum oil has been recom- 

 mended, oil of thyme will do just as well if not better. The 

 red oil is just as efficient as the u'hite for clearing. 



Schinimel and Co., in their Report of October, 189-5, p. 69, 

 state that in France white oil of thyme is adulterated with 

 oil of turpentine to the extent of as much as 50 per cent. 



127. Oil of Gaultheria. — Used by Unna (Monaischr. prakt. Derm., 

 Ergiinzungsh, 188-5, p. 53) for thmning balsam. The artificial oil, 

 methyl salicylate, is recommended by GuEauEN {Comp. Rend. Soc. 

 Biol., V, 1898, p. 285) both as a de-alcoiolisation aud clearing agent and 

 as a solvent of paraifin. The refractive index is 1'53. It is, unfor- 

 tnnately, very sensitive to water. 



128. Sandal-wood Oil (Neelsen and Schiefpeedeckee, loc. cit.). 

 — Very useful, but its high price is prohibitive. 



129. Oil of Cajeput. — Now much used. I have used it 

 myself and found it to clear well, but to be rather thin. 

 CAENoy and Lebeun {La Cellule, xiii, 1897, p. 71) have found 

 it useful for clearing celloidin sections. It dissolves celloidin 

 very slowly and clears without shrinkage. 



130. Oil of Turpentine.— Generally used for dissolving out the 

 parafiin from sections ; but many other reagents, such as xylol, benzol, 

 are preferable for this purpose. If used for alcohol objects, it causes 

 considerable shi'inkage, and aUcra the structure of cells more than any 

 other clearing agent known to me. Turpentine has, I believe, the 

 lowest index of refraction of all the usual clearing agents except 

 bergamot oil ; it clears objects less than balsam. 



131. Terpinol (liquid, from Schimmel and Co.) is recom- 



