CHAPTER XII. 143 



tendency to form precipitates in the interior of objects. But, in my 

 hands, it does not give quite so fine a stain. 



234a. Alcoholic Hydrochloric-Acid Carmine. GRENACHER'S receipt 

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

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

 etc., 1897, p. 43) is better : Carmine 4 grms. ; 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 powerful stain, which I have found useful. If it be desired to 

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

 with HC1. 



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

 1902, p. 56. 



235. 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 ^ 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. 



