ZOOLOGY AND BOTANY^ MICROSCOPY^ ETC. 341 



Biniodide of Mercury and Potassium as a Swelling Agent.* — 

 L. Dippel finds that a solution of iodide of mercury in iodide of 

 potassium possesses the property of causing the innermost layer of 

 the cell-wall to swell while the other layers remain unchanged. The 

 preparations after carefully washing can be preserved in glycerin or 

 calcium chloride. The degree of concentration of the solution re- 

 quires to be tested for each object. 



The inner layer can be stained without the others. The sections 

 should be placed for some hours in an aqueous solution of fuchsin, 

 and after washing the inner layer will be found at the thinnest points 

 to be stained a pale red. A dilute solution of haematoxjlin gives a 

 pale violet stain. 



Erlicki's Hardening Solution.f— This is a variation of Mailer's 

 solution. The latter is composed of bichromate of potash, 2-2^ parts ; 

 sulphate of soda, 1 part ; and water, 100 parts ; the duration of the 

 reaction being about the same as with the simple solutions of chromic 

 salts. 



In Erlicki's solution the sulphate of soda is replaced by 1/2 p. c. 

 sulphate of copper. The hardening properties are superior to those 

 of Miiller's solution. It is now very generally employed in Germany. 



Bbhm's Carmine Acetate. J — Bohm proposes the following 

 formula : — 



Three to four grms. carmine are pulverized in 200 grms. water, 

 and ammonia is added by drops until the solution becomes cherry-red 

 (the carmine should now be fully dissolved). Acetic acid is then 

 slowly added until the colour becomes brick- (or sealing-wax-) red. 

 The addition of acetic acid should be accompanied with stirring, and 

 should cease the moment the change in colour is effected. Then filter 

 until no trace of a precipitate remains. 



If the colour is not sufiiciently deep, a few drops of ammonia 

 should be added before filtering, and the solution left in an open 

 vessel until the smell of ammonia is not perceptible. 



Objects may be left for 24 hours or more in the fluid (or longer if 

 they are more than 1 mm. in thickness). The deep stain should be 

 partially removed by immersion in a mixture of water and glycerin 

 (equal parts), with 1/2 per cent, hydrochloric acid, for a few minutes. 



Staining Method for Karyokinetic Figures.!— P. Baumgarten 

 finds the following an excellent method. Place the sections for 

 24 hours in a dilute alcoholic solution of fuchsin (8-10 drops of con- 

 centrated solution in a watch-glass of water), then rinse in absolute 

 alcohol, then for 4-5 minutes in a concentrated aqueous solution of 

 methyl-blue, dehydrate for 5-10 minutes in absolute alcohol, and 

 lastly place in oil of cloves. The effect of the methyl-blue is to 

 remove the red stain almost entirely from all parts except the nuclei. 



* ZeitscLr. f. Wiss. Mikr., i. (1884) pp. 251-3. 

 t Lee's Microtomists' Vade Mecum, 1885, pp. 159 and 403. 

 I -^rch. f. Anat. u. Physiol. (Anat. Abtheil.) 1882, p. 4. Amer. Natural., xix. 

 (1885) pp. 332-3. Lee's Microtomists' Vade Mecum, p. 54. 

 § Zeitschr. f. Wiss. Mikr., i. (1884) pp. 415-7. 



