226 EXAMINATION AND PRESERVATION MEDIA. 



The chloroform solutions become very brown with age, and are 

 injurious to stains made with tar dyes. Benzol is good when chemi- 

 cally pure and free from water. 



SAHLI (Zeit. wiss. MiL, ii, 1885, p. 5) dissolves in cedar oil. 



APATHY (Fauna Flora Golf. Neapel, xxii, 1909, p. 18) takes 

 balsam 2 parts, cedar oil (immersion) 1, and chloroform 1. 



Samples of balsam that are acid are frequently met with, and are 

 injurious to some stains. 



443a. How to make Neutral Balsam. Take balsam crystals dry. 

 Grind up in mortar and add an equal part of sodium bicarbonate : 

 mix thoroughly. Transfer to a bottle and add enough xylol or 

 benzole to make a quite liquid solution. Allow this to stand for 

 three or four days, shaking occasionally. Filter, and place nitrate 

 on a thermostat to evaporate down to the right consistency. 

 S. G. SCOTT (Journ. Path., xvi), recommends keeping a piece of 

 marble in the balsam bottle, and either placing the latter in a tin 

 box, or painting it black outside in order to protect the balsam from 

 the light. See COLUCCI (Giorn. Ass. Med. Natural Napoli, vii, 1897, 

 p. 172). 



444. SEILEE'S Alcohol Balsam (Proc. Amer. Soc. Mic., 1881, 

 pp. 60-2 ; Journ. Roy. Mic. Soc. [N.S.], ii, 1882, pp. 126-7). 

 Dissolve solid balsam in warm absolute alcohol, and filter through 

 absorbent cotton. Objects may be mounted in it direct from absolute 

 alcohol. I find it for most purposes admirable. It is one of the 

 most stable solutions known to me. Care should be taken not to 

 breathe on it, as this may cause cloudiness. 



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

 are the same as for balsam. I find xylol the best. For directions for 

 preparing solutions, by various authors, see early editions. After ample 

 experience I am convinced that not one of these solutions can be depended 

 on for permanent preservation. Sooner or later, sometimes after a few 

 weeks or days, or it may be only after months or years, granules make 

 their appearance in the mounts. 



446. Colophonium. A solution of pale colophonium in oil of 

 turpentine keeps well and gives very good definitions. The solution 

 should not be too thick, as it thickens with age. 



This medium dries very slowly (so that ample time is afforded for 

 arranging objects in it). In the winter a slide will take about a 

 month before it will be hard enough to be safe with oil-immersion 

 lenses ; whereas an alcohol-balsam mount will be dry enough in a 

 couple of days. It injures alum-ha3matein stains ; as it sometimes 

 develops clouds of globules it is not to be depended upon. 



