STAINING 739 



measure against the loss of sections, the routine use of albumin ad- 

 hesive is recommended. 

 . Mayer 's Albumin : 



White of egg, chopped with scalpel or scissors 



and filtered 10 c.c. 



Glycerin 10 c.c. 



Thymol a small crystal 



A drop of this fluid is rubbed evenly upon the surface of a clean 

 slide. Distilled water is added with a pipette and the paraffin sections 

 arranged upon the slide by the method detailed above. In the process 

 of drying the albumin is coagulated and the tissue becomes firmly at- 

 tached to the slide. The drying may be accomplished without special 

 heating, but requires at least twelve hours at ordinary room tempera- 

 tures. 



Celloidin Adhesive. The sections having been fastened to the slide 

 and dried, the paraffin is removed by dipping the slide into one or two 

 changes of pure xylol, the xylol removed by washing with absolute al- 

 cohol, and a few drops of very thin solution of celloidin (made by 

 diluting thin celloidin, number I (see page 734) with eight or ten vol- 

 umes of the alcohol and ether solvent) are poured over the sections. 

 The solution of celloidin should be so thin as to scarcely leave an appreci- 

 able film on the slide. The excess of celloidin is drained off and the 

 film hardened by first flooding the slide with 70 per cent, alcohol, and 

 after a few minutes transferring it to water. The sections will not now 

 be removed from the slide except by mechanical violence. In handling 

 serial sections of embryos, time may be saved, and the same end ac- 

 complished, by simply spreading by means of a soft brush a thin film 

 of the very thin celloidin solution over the dried paraffin sections. The 

 sections may then be manipulated for staining in the usual way. 



Celloidin sections do not need to be fastened to the slide before 

 being stained; they are sufficiently firm to be gently handled with a 

 needle. 



Staining 1 in Bulk. It is occasionally desirable to stain tissue in bulk 

 so that sections once cut can be immediately mounted. This is best 

 accomplished by the use of a single stain applied to small blocks of 

 tissue immediately after fixation and hardening, and is usually done in 

 aqueous media. Borax carmin is the most useful dye for the purpose, 

 and is used as described below, except that it will require two or three 



