942 RECORD OF CURRENT RESEARCHES RELATING TO 



logwood extract will bo retained by the filter witb the dirt, and the 

 solution consists of htcmatoxylin, alum, and sul^jhate of copper, to 

 which a crystal of thymol may be added to preserve it from mould. 

 Fresh or alcohol-hardened tissues may be stained with this after 

 sufficient dilution ; but for chromic-hardened tissues, dilute 8 drops 

 with 120 drops of water, and add one drop of j\ per cent, solution of 

 bichromate of potash just prior to use. Wash the stained solutions 

 in water as usual. A larger proportion of bichromate solution will 

 produce an ugly yellow ; and if the mixed solution be kept many 

 hours, some decomposition will go on. 



Tissues stained in logwood may be mounted in glycerine or 

 Farrant's solution or in dammar. In the two former they keep 

 unchanged for any length of time ; in the latter they are apt to fade 

 unless care be taken, in preparing them for dammar, that the sections 

 be thoroughly freed from water by absolute alcohol before being 

 brought into contact with oil of cloves. If any moisture be left, 

 fading will soon commence, and the preparation be spoiled. 



Modification of Farrant's Medium* — Professor P. Langcrhans 

 finds the following a very satisfactory modification of Farrant's 

 medium for microscopical preparations of small animals : — Gummi 

 arab., 5 ; aquse, 5 — to which after twelve hours add, glycerini, 5 ; 

 sol. aquosa acid, carbol. (5 p. c), 10. 



With living marine animals it is only necessary to use enough to 

 go under the cover-glass, and to add a little on the following day to 

 make up for evaporation, and the preparation is then ready. The 

 shrinking is very slight, and even many colours are preserved. 



Staining Fluids for Vegetable Tissues.t~Mr. A. H. Barrett 

 recommends the following as a simjjle and successful method of 

 staining one section with two fluids. 



The section is first immersed in an aqueous (1 per cent.) solution 

 of Crawshaw's aniline blue dye. It is then removed into strong acetic 

 acid, which seems to fix the colour in certain tissues, remove it from 

 others, and prepare that not stained for the reception of another 

 colouring fluid. It is then again removed into a weak solution of 

 magenta ( Judson's dye), also made strong with acetic acid ; then 

 mounted in glycerine jelly. The process efiectually shows the 

 " diflerentiation " of parts, both by the difierent colours and the 

 varying intensity of colour. 



The following are the colours with which the tissues of a section 

 of Burdock are stained : — 



Pith Very pale magenta. 



Cellular tissue Deep magenta. 



Spiral vessels of medullary sheath . . Deep blue. 



Pitted vessels Blue. 



Cambium Deep blue. 



Liber cells Dark magenta. 



Laticiferous vessels Deep b hie. 



Cuticle parenchyma Pale blue. 



Epidermis Deep blue. 



Hairs Pale magenta. 



* ' Zoo!. Anzeig.; ii. (1879) p. 575. 

 t ' Science-Gossip,' 1879, p. 255. 



