ZOOLOGY AND BOTANY, MICROSCOPY, ETO. 473 



solution from two to five minutes. A solution of equal carmine 

 strength but in absolute alcohol can be employed ; it has, however, no 

 special advantages, since with the 80 per cent, alcoholic solution the 

 sections can be washed directly in absolute alcohol, and then put into 

 oil of cloves or turpentine. Colouring in the piece before sectioning 

 never takes as long with alcoholic carminic acid as it does with ordi- 

 nary carmine solutions, and if it did take long the strong alcohol would 

 preserve the tissue from maceration. In colouring pieces of moUusca, 

 or of other equally slimy animals, the slime should be removed 

 beforehand, or the staining will be unsatisfactory, because the slime 

 congealing in the alcohol takes up the colouring matter, forming an 

 almost impervious coloured layer on the outside and leaving the 

 inside of the piece nearly uncoloured. 



Some preparations coloured in alcoholic carminic acid and then 

 put up in glycerine lost their colour in a few months, the colour 

 seeming to be entirely diffused in the glycerine, while similar prepara- 

 tions mounted in Canada balsam retained their colour perfectly. The 

 author does not know if this fading would occur with preparations 

 coloured with alcoholic ammonic carminate, or even if this diffusion 

 was not due to some impurity of the glycerine (of the purity of which 

 he was doubtful) ; time to test this matter further failed. 



An alcoholic ammonic carminate, or ammonia carmine, can be pre- 

 pared, at a moment's notice, from alcoholic carminic acid, by adding 

 ammonia drop by drop, and stirring until the entire solution changes 

 from its bright red to purple red. By this mode pure alcoholic 

 ammonic carminate can be produced with no excess of ammonia, and 

 at any time. As the carminic acid can be preserved dry without 

 decomposition, and dissolves quickly in alcohol, one can carry the 

 ingredients of a carmine solution in the vest pocket without incon- 

 venience. 



In making and using alcoholic carminic acid pure alcohol and 

 distilled water give the best results, because a portion of the carminic 

 acid is converted to carminates by the salts of impure water. In 

 making alcoholic ammonic carminate this precaution is not as neces- 

 sary, because the colour of the carminates produced by the impurities 

 of the water is so nearly like that of ammonic carminate. 



Alcoholic carminic acid may be used, as Grenacher's carmine solu- 

 tion is used, to colour sections from which the colour is to be afterwards 

 partly extracted by very dilute hydrochloric acid, leaving nuclei red. 

 Another way to use carmine solutions, which is especially applicable 

 to alcoholic carminic acid, is to precipitate the carmine in the tissues 

 by some salt, the carminate of the base of which gives a desired 

 coloration. For example, specimens hardened for a moment under 

 the cover-glass with an alcoholic solution of corrosive sublimate (mer- 

 curic chloride) and, after washing with alcohol, coloured in alcoholic 

 carminic acid, take a fine colour of mercuric carminate. So, too, 

 specimens coloured in alcoholic carminic acid can be changed by a 

 few moments' treatment with a very dilute alcoholic solution of lead 

 acetate or cobalt nitrate to a beautiful purple. Sometimes salts in the 



