150 CHAPTER xir. 



235. Alcoholic Cochineal, Ma^ek's Old Formula {M'ULh. Zuol. 

 Stat.Nrapel. u, 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 repeattvl with fresh 

 alcohol until the latter takes up no more colour. Warm 

 alcohol acts more rapidly than cold. Overstaining seldom 

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

 alcohol, containing j-'u pPi' 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 certatn salts in them. Crustacea with thick 

 cliitinous integuments are generally stained red, most other 

 organisms blue. The stain is also often of different colours 

 in different tissue elements of the same prepai-ation. 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. 



Yery penetrating and especially useful for Arthropo.da. 



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 used uit]i calcareovs strnctvrcs which it is 

 wished to preserve- — which the new fluid cannot. For 

 specimens of T'Z^/etfs, for instance, I find it excellent. But it 

 only gives i;ood results with such objects as contain the 

 necessary salts, § 212. 



236. Mayee's Alcoholic Cochineal, Difew Forinula (MiWi. Zool. 

 Stat. Neard. x, lSt>2. p. 408).— Ccchincal. 5 grms. ; chloride of calcium, 

 5 grms. ; chloride of ahuniniiim, 5 grm. ; ijitrie acid of 120 sp. gr., 

 8 drops; 50 per cent, alcohol, 100 c.c. Powder the cochineal and rub 



