137 



FOR STAINING IN TOTO. 



If it is desired to stain the insect specimens before cutting 

 the sections, a custom which used to be very commonly fol- 

 lowed, but is being discarded by many present-day workers, 

 a very penetrating stain must be used. Perhaps the most 

 widely used stain of this character is Grenacher's alcoholic 

 borax-carmine (see p. 134) This stain, all ready for use, can 

 be bought of any dealer in microscopical supplies. The 

 specimens, pieces of tissue or organs, or small insects with 

 weakly chitinized integument, are taken from the 70^ alco- 

 hol in which they have been kept for a day after fixing (see 

 pp. 125, 126) and are put into this stain and left there for 

 one or two days or even longer, and then put into 70^ alco- 

 hol which has been acidulated with hydrochloric acid (i 

 HCl to 1000 alcohol) for differentiation. Leave the speci- 

 mens in the acidulated alcohol until no more coloring mat- 

 ter is being extracted. Then wash in neutral 70^ alcohol 

 and harden in 85^, 95^, and absolute alcohol, clear, imbed, 

 cut, and after removing the paraffin from sections in xylol 

 (see p. 132) mount in balsam (see below). 



Mayer's acidulated carmine (see p. 134) can also be used 

 for staining in bulk as well as for staining sections. 



Clearing and mounting. — The sections after staining 

 and washing and removal to 95^ alcohol have yet to be 

 cleared and mounted. Either cedar-wood oil or xylol or 

 other similar oils may be used. We use xylol commonly. 

 The slide should go from the 95^ alcohol into a jar of abso- 

 lute alcohol for ten or fifteen minutes and then into a jar of 

 xylol for as long a time. For mounting use thin balsam and 

 no more than is necessary. The xylol is very volatile and 

 the mounting must be done rapidly to prevent a drying of 

 some of the sections. This is an accident to be carefully 



