CELLULOSE, 



[ 150 ] 



CEMENTS. 



behind, and a sessile avicularium at the 

 upper and outer angle ; orifice spinous. 



Canda. Cells with a vibraoulum in a 

 notch on the outer side ; no avicularium at 

 the upper angle. 



BIBL. That of the genera. 



CEL'LULOSE. The proximate princi- 

 ple of which the permanent cell-membranes 

 of plants are always composed; it occurs 

 also in some structures of certain animals, 

 as the mantle of the Tunicata, the skin of 

 the silkworm, the elytra of some insects, the 

 tegument of some Crustacea, &c. In plants, 

 its physical characters differ very much in 

 different cases ; sometimes it is exceedingly 

 soft, and at once acquires a blue colour 

 with iodine (amyloid?). Usually it be- 

 comes blue when soaked in tincture of 

 iodine, dried, and then wetted with water. 

 In other cases it is more dense, and does not 

 become coloured blue with iodine until after 

 treatment with sulphuric acid, when it be- 

 comes more or less bright blue (the ordinary 

 test for cellulose) . Occasionally this reaction 

 gives a purplish colour. In old, infiltrated, 

 or greatly consolidated cellulose structure, 

 this test gives only a yellow-brown colour ; 

 but boiling in nitric acid (for woody tissues) 

 or solution of potash (for epidermal tissues) 

 will generally bring the cellulose into a state 

 in which, if wetted with tincture of iodine, 

 dried, and then wetted with water, it turns 

 blue. The blue colour is produced in some 

 resisting kinds of cellulose by a solution of 

 iodine in chloride of zinc or by iodide of 

 zinc. (SCHULZE'S TEST.) Sulphuric acid 

 swells and dissolves cellulose ; solutions of 

 potash and nitric acid do not act so quickly, 

 especially the latter. But the best test for 

 ordinary cellulose is the ammoniuret of 

 copper, which quickly dissolves it. Care 

 must be taken in testing for cellulose with 

 iodine, that no extraneous matter lodges 

 on the preparation; fragments of cotton, 

 blotting-paper, &c., consisting of cellulose, 

 might give rise to error. Minute crystals 

 of iodine precipitated from the tincture will 

 give the object a bluish tint. 



In the lunicata, the intercellular sub- 

 stance consists of the cellulose, not the 

 cells (Schacht). 



BIBL. See AMYLOID and CELL-MEM- 

 BRANES. Schacht, Mull. Archiv, 1851 (Qu. 

 Mic. Jn. 1852, pp. 34 and 106) ; Huxley, 

 Qu. Mic. Jn. 1852, p. 22; Schmidt (Tay- 

 lor's Scient. Mem. v. p. 1); Kb'lliker and 

 Lowig, Ann. Sc. N. Zool. 1846, p. 193; 

 Virchow, Compt. Rend. 1853 (Ann. N. H. 



xii. p. 482) ; Schweitzer, Chem. Gaz. xvi. 

 66, 336; Gmelin, Hcmdb. d. Chem. vii. 574 ; 

 Hancock, Linn. Proc. 1867. 



CEMENTS. These are used for closing 

 the cells in which microscopic objects are 

 placed for preservation ; also for fastening 

 pieces of glass to each other, to form cells, 

 &c. Those, the method of making which 

 we have not described, can be procured at 

 any oil-shop. 



Asphalt-varnish consists of a solution of 

 asphalt (must be real) in boiling linseed-oil, 

 or oil of turpentine, or in a mixture of the 

 two ; it should be creamy. 



Black Japan consists of asphalt, gum 

 anime, amber, linseed-oil, and oil of turpen- 

 tine. 



Brunswick black consists of asphalt, dry- 

 ing linseed-oil, and oil of turpentine. 



Asphalt dissolved in benzole. 



Canada balsam : a. alone ; b. digested 

 with sufficient ether, benzole, or chloro- 

 form, to render it slightly more fluid. 



Electrical cement : a. is made by melting 

 together 5 parts of rosin, 1 part of bees'- 

 wax, and 1 of red ochre, b. The addition 

 of 2 parts of Canada balsam renders this 

 cement much more strongly adhesive to 



Gold-size may be prepared by boiling 25 

 parts of linseed-oil for three hours with 1 

 part of red lead and of a part of umber ; 

 then pour off Successive portions of a 

 finely powdered mixture of equal parts of 

 white lead and yellow ochre are then added 

 to the oil, being well rubbed and mixed with 

 it, until a tolerably thick liquid is formed ; 

 this must be once more thoroughly boiled. 

 It is also sold. 



Dammara-resm, is often used, dissolved 

 in benzole ; a third of gold-size is an advan- 

 tage. 



Gutta-percha cement is made by adding 

 15 parts of oil of turpentine to 1 part of 

 finely cut-up gutta percha, and dissolving 

 by the aid of a continued heat and stirring. 

 The solution is then strained through a cloth. 

 In the strained solution, 1 part of shell-lac is 

 then dissolved by heat and stirring. The 

 application of the heat is continued until a 

 drop of the solution let fall upon a cold sur- 

 face becomes nearly hard. It can be ren- 

 dered thinner by the addition of more oil of 

 turpentine. 



Marine glue consists of caoutchouc and 

 shell-lac dissolved in coal-naphtha by the 

 aid of heat. It is sold by microscope- 

 makers and those who mount objects. 



