APPENDIX. 473 



872. GILSON'S Picro-alum- Carmine ( 157).- Professor Gilson writes 

 me that the formula given in 157 is erroneous as containing too much 

 picric acid, and has been good enough to send me an amended receipt, with 

 the remark, however, that all these formulae seem to have lost their raison 

 d'etre by the publication of Mayer's carminic acid stains. As that is really 

 quite the opinion I had come to myself on the matter, I suppress the new 

 formula, merely making use of this opportunity to reiterate the opinion 

 that for the present Mayer's stains are victorious ail along the line. 



873. Chloral Hydrate Jelly (kindly communicated by Prof. 

 GILSON).! vol. of gelatin, melted secundum artem, and 1 vol. 

 of Price's glycerin. Mix ; and add 1 vol. of chloral hydrate 

 (i. e. add crystals of chloral until the volume of the mixture 

 has increased by one half) ; warm till dissolved. This gives 

 a very highly refractive aqueous mounting medium, which is 

 found useful for opaque tissues that it is desired not to 

 dehydrate. 



A similar medium is published by G-EOFFROY, Journ. de 

 Botan., 1893, p. 55 (see Zeit.f. wiss. Mik., ix, 4, 1893, p. 476). 

 He dissolves, by the aid of as little heat as possible, 3 to 4 

 grins, of gelatin in 100 c.c. of 10 per cent, aqueous solution 

 of chloral hydrate. 



874. Sulphurous Acid as a Bleaching Agent. Prof. GILSON 

 writes me that alcoholic solution of sulphurous anhydride (S0 2 ) 

 is very convenient for the rapid decoloration of bichromate 

 objects. A few drops suffice. 



875. ZACHAEIAS'S Carmine Stain. Notwithstanding the remarks on 

 carmine stains in general just made ( 872), it seems worth while to call 

 attention to a process due to ZACHAEIAS (Verh. d. Vers. D. Naturf. u. 

 Aerzte, Bremen, 1891, p. 121 ; recommended by SCHUTZ, Monatschr. f. 

 praki. Dermat., xiv, 1892, p. 397 ; Zeit. /. wiss. Mik., ix, 4, 1893, p. 476), 

 as it involves a somewhat new principle. Tissues, after fixation in any of 

 the usual media, " Flernming " included, are stained for half an hour to an 

 hour in aceto-carmine ( 158), are well washed in water, and brought for 

 five hours into 1 per cent, solution of sulphate of protoxide of iron. After 

 thorough washing they are dehydrated and mounted in balsam. Karyo- 

 kinetic figures dark black, the ground of a delicate neutral .tone. 



876. Rapid Modification of Weigert's Stain. The following is 

 given by KAISER in Zeit. f. wiss. Mik., ix, 4, L-93, p. 468 : Sections 

 treated from three to five minutes with 1 per cent-solution of bichromate of 

 potash, washed in Weigert's hjematoxylin fluid ( 688), and warmed over a 

 flame in a fresh quantity of the stain until bubbles are formed, rinsed with 

 water, and differentiated by the method of Pal, 692 (sulphite of sodium 

 being, however, taken instead of the potassium salt). As will be seen on 



