CELLOIDIN 109 



in aq. dest. The sections are placed in the same solution, in 

 which they must not stay more than one hour. 



5. Sticking the sections to the slide is done by a modification 

 of Oi-t's method. Cover the slide with albumen, then with 

 gelatin, arrange the sections, press down with a cloth, and harden 

 in formol vapour. See also J. A. Murray, below. 



6. The lead-gum is then dissolved away in 5 per cent, acetic 

 acid. After washing you stain and mount in any way desired. 



Neither gum arable (acacia), plum, nor apricot give quite such 

 good results as cherry gum. Salkind recommends two fixatives 

 to precede this method of imbedding. 



A. Formol, acetic acid, sub-acetate of lead, 1 part each. Aq. 

 dest., 5 parts. 



B. Formol . . . . . .10 c.c. 



Acetone . . . . . . 30 ,, 



Water 40 ,, 



Citric acid . . . . . . 5 to 10 grm. 



Saturated with Sudan III. 



After A, it is not necessary to wash out. After B, and the 

 majority of such fixatives as bichromate especially, you must 

 wash out in running water. 



J. A. Murray (Report of Imper. Cancer Research Fund, 1919) Axes 

 cartilage in 10 per cent, formol-salt sohition for at least twenty-four 

 hours. After Salkind's lead-gum imbedding, cuts sections 10 — 1.5 /x 

 thick with sHding microtome. Transfers sections for from ten minutes 

 to one hour in 1 per cent. NaCl solution. Special slides prepared 

 beforehand by coating in 1 per cent, gelatin and allowing to dry. 

 See § 227. 



The prepared slide is immersed in the salt solution (NaCl), sections 

 arranged with a smooth-pointed glass rod, superfluous liquid drained 

 off, and a wetted cigarette paper carefully lowered over the sections. 

 Firm pressure with several layers of filter paper makes the sections 

 adhere to the slide. Withdraw the cigarette paper and expose to formol 

 vapour for a few minutes. Transfer to 10 per cent, formol five minutes, 

 then treat in the 5 per cent, acetic to remove the lead-gum. Stain. 



198. Joliet's Gum and Glycerin Method [Arch. Zool. Exper. et Gen., 

 X, 1882, p. 43). Pure gum arable dissolved in water to the consistency 

 of a thick syrup. Pour a little of the solution into a watch-glass, and 

 add from 6 to 10 drops of pure glycerin. In the winter or in rainy 

 weather less glycerin should be taken than in the summer or dry weather. 



The object is imbedded in the mass in the watch-glass and the whole 

 left to dry for from one to four days. When it has assumed a cartila- 

 ginous consistency, a block containing the object is cut out, turned over, 

 and allowed to dry again imtil wanted for use. A stove, or the sun, 

 may be employed for drying, but it is best to dry slowly at the normal 

 temperature. 



199. Strickeu's Gum Method [Jldfj. d. Geivebel., p. xxiv). A concen- 

 trated solution of gum arabic. The object is imbedded in the gum 

 in a paper case. The whole is thrown into alcohol, and after two or 

 three days may be cut. The alcohol should be of about 80 per cent. 

 (Mayer). 



