CARMINE AND COCHINEAL STAINS. 149 



234. MAYER'S Paracarmine (Mitth. Zool. Stut. Neapcl, x, "3, 

 1892, p. 491). Carminic acid, 1 grrn. ; chloride of aluminium, 

 0-5 grm. ; chloride of calcium, 4 grms. ; 70 per cent, alcohol, 

 100 c.c. Dissolve cold or warm, allow to settle, and filter. 



Objects to be stained should not have an alkaline reaction, 

 nor contain any considerable amount of carbonate of lime 

 (spicules or skeletal parts of corals, etc.) which would give 

 rise to precipitates. Wash out sections or objects intended 

 to be sectioned, with pure 70 per cent, alcohol. Objects in- 

 tended to be mounted whole may be washed out with a weak 

 solution of aluminium chloride in alcohol, or if this be not 

 sufficient, with 5 per cent, common acetic acid (or 2*5 per 

 cent, glacial acetic acid) in alcohol. 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 pene- 

 trating; and has less 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 re- 

 ceipt (Aich. f. Mi/c. Anat., xvi, 1879, p. 468) is troublesome. That of 

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

 f. Anat., etc., 1897, p. 43) is better: Carmine 4 grins.; water, 15 c.c. ; 

 hydrochloric 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. 



