150 CHAPTER XII. 



235. Alcoholic Cochineal, MAYEK'S Old Formula (J7 /////. /<><>!. 

 Stat* Nrtijwl. ii, 1881, p. 14). Cochineal in coarse powder is 

 macerated for several days in alcohol of 70 per cent. For 

 each gramme of the cochineal there is required 8 to 10 c.c. 

 of the alcohol. Stir frequently. Filter. 



The objects to be stained must previously be saturated 

 with alcohol of 70 per cent., and alcohol of the same strength 

 must be used for washing out or for diluting the staining 

 solution. The washing out must be repeated with fresh 

 alcohol until the latter takes up no more colour. Warm 

 alcohol acts more rapidly than cold. Overstating seldom 

 happens; it may be corrected by means of 70 per cent, 

 alcohol, containing ^ per cent, hydrochloric or 1 per cent, 

 acetic acid. 



Small objects and thin sections may be stained in a few 

 minutes ; larger animals require hours or days. 



A nuclear stain, slightly affecting protoplasm. The colour 

 varies with the reaction of the tissues, and the presence or 

 absence of certain salts in them. Crustacea with thick 

 chitinous integuments are generally stained red, most other 

 organisms blue. The stain is also often of different colours 

 in different tissue -elements of the same preparation. Glands 

 or their secretion often stain grey-green. 



Acids lighten the stain and make it yellowish-red. 

 Caustic alkalies turn it to a deep purple. 



All acids must be carefully washed out from the objects 

 before staining, or a diffuse stain will result. The stain is 

 permanent in oil of cloves and balsam. 



Very penetrating and especially useful for Arthropoda. 



It has over the new fluid (next ) the advantage of being 

 more highly alcoholic ; and it does not contain free acid, so 

 that it can le lifted with calcareous tstrudurcft which if- is 

 wished to preserve which the new fluid cannot. For 

 sj cciiiicns of Phileus, for instance, I find it excellent. But it 

 only gives coed results with such objects as contain the 

 necessary salts, 212. 



236. MAYER'S Alcoholic Cochineal, New Formula (Mittli. Zool. 

 St<it. Neapel, x, 1892, p. 498). Cochineal, 5 grins. ; chloride. of calcium, 

 5 grms. ; chloride of aluminium, 0'.5 grm. ; nitric acid of 1'20 sp. gr., 

 8 drops; 50 per cent, alcohol, ]00 c.c. Powder the cochineal and ruh 



