ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 351 



about 1 grm. thymol, and stand in a warm place until the volume is 

 reduced to 25 c.cm. ; let the solution cool, filter, wash out the residue, 

 which should be on the filter, with 25 c.cm. water ; dilute the filtrate 

 with 50 c.cm. water. By this means a solution ready for use, which 

 will keep indefinitely, and contains carmine and picric acid in good 

 projiortions, can be prepared with certainty. 



It gives a stronger difl"erential colouring than Eauvier's picro- 

 carniine ; but over-staining must be carefully avoided. For staining 

 sections, two to five minutes are sufficient. The fluid stains con- 

 nective tissue (fibrous) deep red ; striped muscle, deep dull red ; 

 smooth muscle, blood, and horny tissue, bright yellow ; glands, 

 reddish yellow. With the kidney it gives a differentiation of the 

 different portions of the tubules ; for the central nervous system it 

 seems to be of little value. If rightly used, it gives a sharp nuclear 

 colouring. 



If the aqueous solution is evaporated to dryness, the residue may 

 be redissolved in alcohol, giving an alcoholic carmine dye, which has 

 not yet been tested sufficiently. Apparently the alcoholic solution 

 will keep only a few months. The alcoholic solubility of the dye 

 offers the advantage that sections stained in the watery solution can 

 be washed in alcohol directly. 



DifFerential Action of Safranin and Methyl-green.* — In studying 

 the sexual characteristics of the oyster Mr. J. A. Eyder found that a 

 mixture of these two dyes enabled him to distinguish both ova and 

 spermatozoa in the same follicle, the nuclei of the ova being stained 

 red by the safranin, and the heads of the spermatozoa bluish-green 

 by the methyl-green. The method of preparation is as follows : — 



1. After removing the shell the oyster is hardened in chromic 

 acid (1 to 2 per cent.) for several days. 



2. Washed in water two days, and then further hardened in 

 alcohol. 



3. Soaked for twenty-four hours in water, to remove the alcohol ; 

 then imbedded in gum arabic and cut with free hand. 



4. Sections freed from imbedding mass by washing in water ; then 

 stained in a mixture in equal parts of safranin (saturated alcohol 

 solution), methyl-green (ditto), diluted with eight times its volume 

 of water, two to three hours. 



5. Decoloured in 95 per cent, alcohol until clouds of colour no 

 longer appear (five to fifteen minutes). 



6. Clarified in- clove-oil and mounted in balsam of dammar. 



Staining Spermatogems.t — Herr Benda, in his studies on the 

 spermatogenesis of mammals, made use of a modification of Weigert's 

 hsBmatoxylin method. Sections preserved in Flemming's solution 

 were fixed to a cover-glass and placed for twenty-four hours in a 

 strong solution of oxide of copper. After careful washing in water, 

 repeated several times, they were placed in 1 per cent, watery solution 



* Bull. U.S. Firih Commission, 1S83. Cf. Whitman's 'Methods in Micro- 

 scopical Anatomy and Embryology,' 1885, p. 52. 



t Arch. f. Anat. u. Physiol. (Physiol. Abth.), 1886, p. 186. 



