174 CHAPTER XII. 



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 

 sliuldhj acidify Ihe dilute solutions. 



Paracarmine gives a nuclear stain of a red colour, though 

 not so fiery red as that of borax -carmine. Its points of 

 superiority over borax-carmine are that it is less hurtful to 

 tissues ; that it is more highly alcoholic, therefore more 

 penetrating ; that it has less tendency to form granular pre- 

 cipitates in the interior of objects, and that it generally 

 keeps perfectly without precipitating (mine has precipitated 

 somewhat, though not to an injurious extent). 



229. Alcoholic Hydrochloric-Acid Carmine. Sometimes it is 

 desirable to possess a powerful staining medium more highly alcoholised 

 than the foregoing, and of acid reaction. Hydrochloric-acid carmine 

 possesses these qualities, and may, for instance, be frequently useful in 

 work on Arthropoda, especially the marine forms. 



GEENACHER'S receipt lArch. f. mik. Anat., xvi, 1879, p. 408 1 will be 

 found extremely troublesome by those who are not expert at neutralising. 

 The following method, due to PAUL MAYER (Mitth. Zool. Stat. Neapel, iv, 

 1883, p. 521; Journ. Roy. Mic. Soc. [N.S.], iv, 1884, p. 317; 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. 



If it be desired to have a purely nuclear stain, the alcohol must be very 

 slightly acidulated with HC1. 



230. Alcoholic Cochineal, MAYER'S Old Formula (Mit tJi. Zool. 

 Stat. Neap., 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, and the resulting 

 clear, deep red solution is fit for staining. (If the filter 

 paper should contain much lime,, flakes of lime carminate 

 may be thrown down.) 



The objects to be stained must previously be imbibed with 



