490 PREPARATION, MOUNTING, AND COLLECTION OF OBJECTS 



Stains for Fixed and Preserved Entire Objects or Material to 

 be Stained in Bulk. These fall naturally into the two classes of 

 lUfin'ons stains and alcoholic stains. The aqueous stains are 

 generally the more precise, and are generally preferable for small 

 and permeable objects, but the alcoholic stains are absolutely 

 necessary where great penetration is required, as for instance in the 

 case of organs or organisms enclosed in thick cliitinous investments, 

 as is so generally the case amongst the Arthropoda. 



The most precise and the safest of the stains of this class are the 

 alum-carmines a general term including the divers formula? that 

 have been recommended under the names of aliim-cnrrnim'. 

 i-ii, iiiiih.i in, alum -wlii it ml. One of these will suffice. 



/'ortsch's alum-cochineal. 'Powdered cochineal is boiled for some 

 time in a 5 per cent, solution of alum, the decoction filtered, and a 

 little salicylic acid added to preserve it from mould.' 



An extremely precise nuclear stain, and one with which it is hardly 

 possible to overstain. It is permanent in balsam and, it is believed, 

 in aqueous media if not acid. Objects may be left in it for several 

 hours. They should not be very large, as the stain has no great 

 power of penetration. Objects containing calcareous elements that 

 it is desired to preserve must not be treated with this stain, nor 

 with any other stain containing alum. 



Mayers carmaltim is made with carmiiiic acid 1 grm.. alum 

 10 grm., and distilled water 200 c.c. It has the advantage of being 

 much more penetrating than the other stains of this class. 



All the alum-carmine solutions are rather weak stains. If a 

 more powerful stain be desired, take the following : 



Mayer's hcamalum. This is made with ha?matein, the essential 

 colouring principle of hsematoxylin (obtainable from G rubier and 

 Hollborn). One grm. of ha?matein is either dissolved with heat 

 in 50 c.c. of 90 per cent, alcohol, or rubbed up in a mortar with a 

 little glycerin, and added to a solution of 50 grm. of alum in a litre 

 of water. This liquid may be used for staining either concentrated 

 or diluted. Concentrated it stains almost instantaneously. For 

 ordinary purposes it may be diluted with from ten to twenty 

 volumes of distilled water, and will then stain through small objects 

 in an hour or so. Large objects will require an hour or more. The 

 solution is admirable for staining in bulk. Objects should be well 

 washed out (for as long a time as they have taken to stain) either 

 with distilled water or tap water. One per cent, alum solution is 

 also a good medium to wash out in. Overstains may be corrected 

 by washing-out with O'l to 0-5 per cent, of hydrochloric acid. In 

 this case the acid should be neutralised afterwards by treat inent with 

 <H per cent, solution of bicarbonate of soda (or other weak alkali). 



Passing now to 1 he titcoholic solut ions. (,'r<>-nftt'1trfs alcoholic bor<i.,- 

 cuniiini' may IK- recommended as affording a convenient, safe, and 

 brilliant stain. Dissolve 2 or ."> per cent, of carmine in a 4 per cent. 

 solution of borax in water; boil the solution for half an hour: 

 dilute it with an eijiial volume of 70 per cent, alcohol, allow it to 

 stand for twenty-four hours, and filter. 



Objects are pul into this solution and allowed to remain in it 



