208 EXAMINATION AND PRESERVATION MEDIA. 



mersion work) as the oil soon sets hard enough to keep the 

 cover in place. 



397. Canada Balsam. Prepare with the solid balsam as 

 above described. The usual menstrua are xylol, benzol, 

 chloroform, and turpentine. Dissolve the solid balsam in one 

 of these to the required consistence. The turpentine solution 

 is to be preferred only in cases where it is desired to have a 

 medium that sets very slowly, or in view of the better pre- 

 servation of certain stains. For all other purposes the xylol 

 solution is the best. 



HEYS states that if the chloroform solution be poured into 

 long, thin, half-ounce phials, corked up, and set aside for at 

 least a month, the medium will be clearer and set much 

 quicker than if the balsam is mixed with the chloroform at 

 the time it is required for use (Trans. Mic. 8oc., Jan., 1865, 

 p. 19. BEALE, p. 51). 



SAHLI (Zeit. f. wiss. Mik., 1885, p. 5) recommends oil of 

 cedar as a menstruum. 



398. Seller's Alcohol Balsam (Proc. Amer. Soc. Mic., 1881, pp. 60-2 ; 

 Journ. Boy. Mic. Soc. (N.S.), ii, 1882, pp. 126-7)." Take a clear sample 

 of Canada balsam and evaporate it in a water or sand-bath to dryness ; i.e. 

 until it becomes brittle and resinous when cold. Dissolve this while warm 

 in warm absolute alcohol and filter through absorbent cotton." 



The advantage of this medium is stated to be that objects may be mounted 

 in it direct from absolute alcohol, without previous treatment with an essen- 

 tial oil or other clearing agent ; Seiler considers that by this means 

 "shrivelling is avoided, as well as the solution of fat in the cells." 



The process is not very easy to carry out, and I cannot recommend it for 

 general work. 



399. Damar (Gum Damar, or Dammar, or d'Ammar), The 

 menstrua are the same as for balsam, and the solution should 

 be prepared in the same way. The most beautiful of all these 

 mounting media is the solution of damar in xylol. Heat is 

 not necessary to make the solution. 



Minute directions (which I think unnecessary) for preparing 

 a working solution are given by MARTINOTTI in Zeit.f. wiss. 

 Mik., iv, 2, 1887, p. 156, and in Malpighia, ii, 1888, p. 270; 

 cf. also Journ. Roy. Mic. Soc., 1889, p. 163. 



FLEMMING, PFITZNEE, and a writer signing C. J. M., all em- 

 ploy a mixture of benzol and turpentine (see Arch. tnik. 

 Anat., xix, 1881, p. 322 ; Sci. Gossip, 1882, p. 257 ; Journ. 



