PUEE CAEMINIC ACID. 97 



of aceto-carmine, no. Is it for staining sections ? Again, 

 no ; for, in nine cases out of ten, sections are better stained 

 by some of the anilin stains than they can be in any carmine 

 stain. Is it for staining entire objects ? for staining in the 

 mass ? Yes ; for in many, if not in most cases, that can be 

 done more satisfactorily by means of carmine than by meansi 

 of any other known agent. So that until a coal-tar colour 

 shall have been discovered that can beat alum-carmine and 

 borax-carmine on their own ground, these must still hold 

 their sway. As soon as that shall have been done and it may 

 be done any day carmine stains will become as extinct as the 

 dodo. 



In view of the far greater simplicity and precision of the 

 methods proposed by Mayer, it is probable that they, or 

 at all events methods conforming to the principles above 

 laid down, will gradually take the place of the old methods. 

 Not, indeed, that some of the old stains will not hold their 

 ground. Alum-carmine will remain a superb stain, and 

 borax-carmine remains superior to paracarmine in the power 

 and brilliancy of its stain; but the superior precision of 

 Mayer's methods will doubtless be acknowledged. And it 

 is perhaps not too much to hope that fewer formulae of the 

 old roundabout, happy-go-lucky sort, with commercial car- 

 mine or hsematoxylin as the chief ingredient, will henceforth 

 be published. 



148. Pure Carminic Acid may be obtained from E. MERCK 

 of Darmstadt, or from Dr. Gr. GEUBLER (12, Bayersche Strasse, 

 Leipzig). The price at present is from 2s. to 4s. per 10 grms. 



149. Hints. Overstains may in all cases be washed out with weak HC1 

 (e. g. O'l per cent.). HENNEGUT (Journ. de I'Anat. et de la Physiol., xxvii, 

 1891, p. 400) states that overstains may be completely removed by means of 

 permanganate of potash. Sections thus treated may then be after-stained 

 with anilin colours (see 106). All carmine stains, with the exception of 

 aceto-carmine, are permanent in balsam. Aqueous mounts should be acid 

 (except for alum-carmine), and the best plan is to let the mounting medium 

 contain 1 per cent, of formic or acetic acid. Formic acid is to be preferred. 



Kemember that none of the acid stains, except alum-carmine used as 

 directed, 155, nor any of Grenadier's fluids can be used with calcareous 

 structures that it is wished to preserve. 



Grenadier's alcoholic borax-carmine may be recommended to the beginner 

 as being the easiest of these stains to work with. 



150. Classification of the Formulae. In the treatment of the for- 



7 



