STAINING. 



[ 730 ] 



STAMENS. 



removed from tlie solution and washed, and 

 then placed in a strong solution of carmine 

 and ammonia. A very few minutes will 

 suffice to stain the axis-cylinders red and 

 the medullary matter yellow (Qu. Mic. Jn. 

 1872, 160). 



A blue staining agent, useful for treating 

 specimens of the spinal cord, is formed by 

 the reaction of molybdate of ammonia, iron 

 filings, and hydrochloric acid (Qu. Mic. Jn, 

 1872,161). * 



A logwood staining solution, which con- 

 sists of an ounce of saturated solution of 

 logwood and alum mixed with two drachms 

 of 75 per cent, alcohol, is useful for the 

 nervous elements (Qu. Mic. Jn. 1873, 87, 

 & The Lens, July 1872). 



Other staining agents comprise especially 

 the chlorides of gold, potassium and palla- 

 dium, oxide of uranium, nitrate of silver, 

 and osmic acid. In these, except perhaps 

 in the last, a secondary decomposition 

 occurs before the colour is imparted to the 

 tissues ; and the greatest possible care must 

 therefore be taken to allow for the granular 

 or striated condition which such precipitates 

 may assume, and for their collecting in 

 tubes and between tissues. An excellent 

 formula for staining ganglion-cells especially 

 is as follows: Bichromate of ammonia 

 1 to 2 per cent, solution in water. Place 

 the fresh nerve-substance in it for 15 or 20 

 days. Then dip it, after having made sec- 

 tions, in water 10,000 parts, double chlo- 

 ride of gold and potassium 1 part ; wash in 

 hydrochloric acid 1 or 2 parts in 3000 water. 

 Then dip for ten minutes in the following 

 mixture: Hydrochloric acid 1 part, and 

 1000 parts of a 60 per cent, solution of 

 alcohol ; immerse in absolute alcohol, clear 

 with oil of cloves, and put up in Canada or 

 Dammar balsam. Staining with chloride 

 of gold may be conducted as follows, the 

 object being to stain nerve^fibres : Chlo- 

 ride of gold \ part, distilled water 100 parts. 

 Place pieces of fresh tissue in this for a few 

 minutes until they become tinged with 

 yellow, then in dilute acetic acid (1 to 2 per 

 cent.), or in concentrated tartaric acid solu- 

 tion for a few (10-15) minutes. Expose to 

 light until a violet colour appears. Mount 

 in glycerine. There is great uncertainty in 

 the results of this process ; but care 'and 

 experience overcome most of the difficulties 

 and produce magnificent preparations ; 

 nevertheless no results are worth recording 

 which are obtainable by this process alone, 

 and which are not the same as those visible 



wifh glycerine and carmine staining solu- 

 tions. The discrepancies of observation of 

 different and equally dogmatic observers are 

 most instructive. In fact in some tissues 

 the gold solution will stain many histolo- 

 gical elements (see Klein, Qu. Mic. Jn. 

 1872, 21 ; and Moseley, Qu. Mic. Jn. 1871, 

 58). 



Nitrate of silver for staining epithelial 

 cement in capillaries, lymphatics, &c. The 

 solution must be clear and weak, and of 

 1 part nitrate of silver to 200, 400, or 800 

 of distilled water. The fresh tissues must 

 be macerated in the solution for one to 

 three minutes, r. : :1 then in a solution of 

 dilute acetic acid (1 to 2 per cent.) for a 

 minute or two. Then place in glycerine 

 and expose to the light ; or after removal 

 from the nitrate-of-silver solution the tissue 

 should be washed in distilled water, or in 

 a weak solution of common salt before ex- 

 posure to light. 



In examining the tendinous centre of the 

 diaphragm of any of the smaller mammalia, 

 the part should be placed in the nitrate-of- 

 silver solution and brushed over with a 

 camel's hair pencil and then removed and 

 treated as above. 



Solution of osmic acid may be used as a 

 hardening agent, also as a staining medium. 

 Solution of 1 per cent., and usually of much 

 less, blackens many tissues freely, especially 

 the white substance of Schwann in nerves, 

 and fat. It is very useful in investigating 

 the minute anatomy of the Invertebrata. 



Many parts of animal tissues may be 

 stained by maceration in a weak solution of 

 acetate of lead, washing in water, and 

 digesting with weak hydrosulphuret of am- 

 monia. As usual, the nuclei are rendered 

 very black and distinct, the whole tissue 

 being rendered brown. 



Vegetable tissues may be stained in the 

 same way as the animal structures. The 

 aniline dyes answer best (Beatty, Mn. Mic. 

 Jn. xiv. 57). 



BIBL. Beale, How $c. ; Strieker's Hist., 

 Intro. ; Frey, Mikros. ; Rutherford, Hist. ; 

 Jackson, Qu. Mic. Jn. 1874, 139; Ehrlich, 

 Schultze's Archiv, 1873, xiii. 263; Gibbs, 

 Hist.-, Tafani, Jn. M. oc. 1878, i. 82; 

 Merbel, Mn. Mic. Jn. xviii. 242 ; Sternberg, 

 Jn. M. Sc. 1882, ii. 571 (staining Bacteria] ; 

 Schwartz, Sitz. Ber. Wien. Ak. 1867, Iv. 

 671. 



STAMENS. The fertilizing organs pro- 

 ducing the POLLEN, surrounding the pistil 

 in perfect Flowering plants, or occurring 



