284 CHAPTER XX. 



many months. For a process of neutralising balsam with carbonate of soda 

 or potash see COLUCCI (Giorn. Ass. Med. Natural. Napoli, vii, 1897, p. 172). 



441. SEILER'S Alcohol Balsam (Proc. Amer. Soc. Mic., 1881, 

 pp. 60-2; Journ. Eoy.Mic.8oc. [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 Avarm 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 essential oil or other clearing 

 agent ; SEILBR considers that by this means " shrivelling' is 

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



The process of mounting direct from alcohol is not very 

 easy to carry out, and I cannot recommend it for general 

 work. But used in the ordinary way, after clearing by an 

 essence, or byxylol or the like, SEILER'S solution is for many 

 purposes admirable. 



As stated above, I find that it is one of the most stable 

 solutions known to me. (My stock, made up fifteen years 

 ago, is still perfectly limpid, and has not darkened in colour 

 to an injurious extent.) It works pleasantly enough (if care 

 be taken not to breathe on it during the process of mounting, 

 as this may easily cause cloudiness). The definition is very 

 fine, and the preservation of the preparations almost in- 

 variably perfect ; my oldest preparations only show a few 

 granules of little importance. Of course it has the limitation 

 that it cannot be used with the soluble coal-tar colours. 



442. 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 MARTI NOTTI in Zeit. f. iciss. 

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

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



FLKMMING, PPITZNER, and a writer signing C. J. M., all 

 employ a mixture of benzol and turpentine (see Arch. mik. 



