TUEPENTINE. 255 



use is for attaching glass cells to slides, and for all cases in 

 which it is desired to cement glass to glass. 



Eeceipts for preparing it may be found in BEALE, p. 49, or 

 in COOLEY'S Cyclopaedia. 



441. Harting's Gntta-percha Cement (see BEALE'S How to 

 Work, &c., p. 49). Marine glue serves the same purpose, viz. 

 that of attaching cells to slides. 



442. India-rubber and Lime French Cement. See BEALE, p 



58. 



443. Knotting (Journ. Roy. Hie. Soc., 1882, p. 745). 

 " Patent knotting" from oil and colour stores, exposed to 

 the air until it has become of the proper consistency; for 

 mending cells and for preventing running-in of the finishing 

 varnish (Northern Microscopist, ii, 1882). 



444. Turpentine, Venice Turpentine (CsoKOE, Arch. mik. 

 Anat., xxi, 1882, p. 353; PAEKEE, Amer. Mon. Mic. Journ., ii,. 

 1881, pp. 229-30; Journ. Roy. Mic. Soc. [N.S.], ii, 1882, p. 

 724). Venice turpentine (Terebinthina veneta) is the liquid 

 resinous exudation of Abies larix. It is seldom met with in 

 a pure state. The following are the directions for preparing 

 and using it given by Parker : 



Dissolve true Venice turpentine in enough alcohol, so that 

 after solution it will pass readily through a filter, and, after 

 filtering, place in an evaporating dish, and by means of a 

 sand-bath evaporate down to about three quarters of the 

 quantity originally used. (The best way to tell when the 

 evaporation has gone far enough is to drop some of the 

 melted turpentine, after it is evaporated down to about three 

 quarters its original volume, into cold water; if on being 

 taken out of the water it is hard and breaks with a vitreous 

 fracture on being struck with the point of a knife, cease eva- 

 poration and allow to cool.) 



Or (CSOKOE), common resinous turpentine of commerce is 

 put in small pieces to melt over a water-bath, then poured 

 into a suitable vessel and allowed to cool. It should form a 

 brittle, dark brown mass, not yielding to the pressure of a 

 finger. It is sometimes useful, in order to attain the right 

 degree of hardness in the cold mass, to add a little resinous 



