CARMINE AND COCHINEAL 147 



equal volume of 70 per cent, alcohol, allow it to stand some time 

 and filter. 



Preparations should remain in the stain until they arc thoroughly 

 penetrated (for days if necessary), and then be brought {ivithout 

 first washing out) into alcohol of 7Q per cent, acidulated with 4 to 6 

 drops of hydrochloric acid to each 100 c.c. of alcohol. They are 

 left in this until they have taken on a bright transparent look 

 (which may require days), and may then be washed or hardened 

 in neutral alcohol. Four drops of HCl is generally enough. 

 Three drops we find not quite sufficient. 



For delicate objects, and for very impermeable objects, it 

 may be well to increase the proportion of alcohol in the stain ; 

 it may conveniently be raised to about 50 per cent. It should 

 not exceed 60 per cent, in any case (Mayer). 



This stain used to be the most popular of any for staining in 

 bulk. It is easy to use, and gives a most splendid coloration. 

 But it is not so penetrating as is commonly supposed, and has 

 the defect of sometimes forming precipitates in the cavities of 

 bulky objects which cannot be removed by washing out. And 

 the fluid is alkaline, and therefore may not be suitable for certain 

 delicate work. 



272. Lynch's Precipitated Borax-Carmine Method. According to 

 Lynch {Zeit. zviss. Mile., xlvi, 1929, p. 465) a much more selective and 

 brilliant stain is obtained if, after staining overnight in Grenacher's 

 borax-carmine, tissue is treated in tlie following way : Add cautiously 

 to the dish containing the tissue and the dye, drop by drop, concentrated 

 hydrochloric acid until all the carmine is precipitated out as a brick-red 

 flocculent mass. Allow the dish to stand six to eight hours or over- 

 night. The tissue is now placed in a 3 per cent, solution of HCl in 

 70 per cent, alcohol and destained until the cj-toplasm is clear and the 

 nuclei are pink in colour. This usually requires two or three hours. 

 Wash out the acid with several changes of 80 per cent, alcohol, then 

 dehydrate, clear and mount in the usual way. This method is suitable 

 for objects which are to be mounted in toto, but it shoidd not be used 

 on delicate vesicular organisms as it will leave precipitates in their 

 cavities. 



273. Mayer's Paracarmine {Mitth. Zool. Stat. Neapeh x, 3, 

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

 0-5 grm. ; chloride of calcium, 4 grm. ; 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 precipi- 

 tates. Wash out sections or objects intended to be sectioned, 

 with pure 70 per cent, alcohol. Objects intended to be mounted 

 whole may be washed out with a weak solution of aluminium 

 chloride in alcohol, or if this be not sullicient. with ;} per cent, 

 common acetic acid (or 2-5 per cent, ghicial acetic acid) in alcohol. 



