248 CHAPTER XIX. 



essential oils. But they have another useful property 



their low index of refraction. I find that that of euparal is 



just right for most delicate cytological researches, giving 



just the desired increase of visibility to unstained elements. 



Thus I frequently find that unstained spindles which are 



totally invisible in balsam become strongly visible in 



the most minute details in euparal. The camsal balsam, 



n = 1'478, I have also sometimes found valuable, but its 



index is a little too low for most things, and I generally 



prefer euparal, which I find I am now using almost as much 



as balsam. I consider that all the media which have been 



recommended on the score of a slightly lower index than 



balsam, such as damar, colophonium, Venice turpentine, 



castor-oil, are now superseded by these media. 



450. Sandarac (LAVDOWSKY, from Ref. Handbook Med. Sci., Supp. p. 

 438). Gum sandarac 30 grs., absolute alcohol 50c.c. Not trustworthy, 

 the mounts scale badly. 



451 . Photographic Negative Varnish (for mounting large sections 

 without cover- glasses). See WEIGERT, Zeit. wiss. Mik., iv, 1887, p. 209. 



452. Castor Oil. See GRENACHER, Abhandl. naturf. Ges. Halle-a.-S., 

 Bd. xvi; Zeit. iviss. Mik., 1885, p. 244. I have not had good results 

 with it. 



453. Terpinol. n = 1'4S4. See 131. 



454. Parolein (a pure form of paraffinum liquiduni) is recom- 

 mended by COLES (Lancet, 1911, p. 878) as being quite neutral and 

 preserving certain coal tar stains. Ring mounts with Apathy's gum 

 syrup, 343. Its index is T471, which I find too low for most things. 



455. Cedar Oil. See 442, sub. fin. 



456. Gum Thus, dissolved in xylol, is recommended by EISEN, Zeit. 

 wiss. Mik., xiv, 1897, p. 201. 



457. Styrax and Liquidambar. See Journ. Roy. Mic. Soc., 1883, p. 

 741 ; ib., 1884, pp. 318, 475, 655, and 827 ; and the places there quoted. 

 Also Bull. Soc. Beige de Mic., 188 1, p. 178; and FOL, Lehrb., p. 141. 

 These are very highly refractive media, therefore seldom useful in 

 histology. 



