148 CARMINE AND COCHINEAL 



This may also be done with section material, if it is desired to 

 obtain a more purely nuclear stain. 



For staining bulky objects with large cavities, such as Salpa, 

 the solution should be diluted (with alcohol) ; and as this may 

 cause precipitates to form during the staining, especially if the 

 objects are not very clean, it is advisable to slightly acidify the 

 dilute solutions. 



Instead of calcium chloride, which is very hygroscopic, strontium 

 chloride may be taken, 



Paracarmine is less hurtful to delicate tissues than borax 

 carmine ; it is more highly alcoholic, therefore more penetrating ; 

 and has less tendency to form precipitates in the interior of 

 objects. But, in our hands, it does not give quite so fine a stain. 



274. Alcoholic Hydrochloric-Acid Carmine. Grenacher's receipt 

 (Arch. f. Mik. Anat., xvi, 1879, p. 468) is troublesome. That of IVIayer 

 (Mitth. Zool. Stat. Neapel, iv, 1883, p. 521 ; Intern. Monatsschr.f. Anat., 

 etc., 1897, p, 43) is better : Carmine 4 grm. ; water, 15 c.c. ; hydro- 

 chloric acid, 30 drops. Boil till the carmine is dissolved, add 95 c.c, of 

 85 per cent, alcohol, and neutralise by adding ammonia until the 

 carmine begins to precipitate. 



If it be desired to dilute the solution, it should be done with alcohol, 

 not water, and alcohol of 80 to 90 per cent, should be taken for washing 

 out, 



A very jjoiverful stain, which Lee has found useful. If it be desired to 

 have a purely nuclear stain, the alcohol must be very slightly acidulated 

 with HCl. 



For a complicated receipt of Loewenthal see Zeit. wiss. Mik., xix, 

 1902, p. 56. 



275. Alcoholic Cochineal, Mayer's Old Formula {Mitth. Zool. 

 Stat. Neapel, 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. Overstaining seldom happens ; it may be corrected 

 by means of 70 per cent, alcohol, containing xV per cent, hydro- 

 chloric or 1 per cent, acetic acid. 



Small objects and thin sections may be stained in a few minutes ; 

 larger animals require hours or days. 



This is a nuclear stain, slightly tinting the 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 



