DIRECT GREEN B 



103 



DUCTS 



Direct Green B (CI, 593)— Diazine Green 

 B — a direct disazo dye of light fastness 

 3 to 4. Recommended as counterstain 

 for Crocein Scarlet 7 B of invertebrates 

 or paraffin sections, time 5 min. (Emig, 

 p. 43). 



Direct Green G (CI, 594)— Alkali Green D— 

 a direct disazo dye of light fastness 3 to 

 4. Formula for blue green algae and 

 whole mounts is given (Emig, p. 43). 



Direct Red 4B, see Benzopurpurin 4B. 



Direct Red, C, R, or Y, see Congo Red. 



Direct Sky Blue, see Niagara Blue 4B. 



Direct Steel Blue BB, see Dianil Blue 2R. 



Direct Violet B, see Azo Blue. 



Direct Violet C, see Erie Garnet B. 



Dis-Azo Dyes. Azo blue, benzopurpurin 

 4B, Biebrich scarlet, Bismark brown 

 Y and R, brilliant purpurin R, Congo 

 red, dianil blue 2R, Erie garnet B, 

 Niagara blue 4B, orseillin, trypan blue, 

 trypan red, sudan III, sudan IV, 

 vital new red, vital red, etc. 



Dissociation, see Maceration. 



Distrene 80 is a polysterene which forms a 

 water clear solution in xylol. It is 

 recommended by Kirkpatrick and Len- 

 drum (J. and A. C, J. Path, and Bact., 

 1939, 49, 592-594) as a naounting medium 

 giving good preservation of color in 

 microscopic slides. See also Kirk- 

 patrick, J. and Lendrum, A. C, J. Path. 

 & Bact., 1941, 53, 441. 



Dominici's Stain, see Eosin-Orange G and 

 Toluidin blue. 



Donaldson's lodine-Eosin Method, see lo- 

 dine-Eosin. 



Dopa, Oxidase Reaction for Melanoblasts 

 (Laidlaw, G. F., Anat. Rec, 1932, 53, 

 399-407). Dopa is short for 3.4-dihy- 

 droxyphenylalanin, a substance which 

 when applied in a certain way picks out 

 the melanoblasts by blackening them. 

 Use frozen sections of fresh material or 

 of tissues fixed 2 to 3 hours but not 

 longer in 6% formalin. Rinse 4 or 5 

 seconds in aq. dest. and immerse in 

 buffered dopa. (To make dopa stock 

 solution dissolve 0.3 gm. dopa powder- 

 manufactured by Hoffmann-La Roche, 

 Nutley, New Jersey— in 300 cc. cold 

 aq. dest. Keep in refrigerator and dis- 

 card when solution becomes dark red. 

 To make buffers dissolve 11.87 gms. di- 

 sodium hydrogen phosphate (Na2HP04 

 + 2H2O) — or what would be better 

 9.47 gm. anhydrous Na2HP04— in 1000 

 cc. aq. dest. and 9.08 gms. anhydrous 

 potassium dihydrogen phosphate 

 (KH2PO4) in an equal amount aq. dest. 

 Immediately before use buffer to pH 7.4 

 by adding 2 cc. potassium phosphate 

 solution, and 6 cc. sodium phosphate 

 solution to 25 cc. dopa solution). The 

 reaction is slow for 3-4 hours at room 

 temperature. If solution becomes 



sepia brown it is likely to overstain. 

 Observe under microscope. Wash in 

 aq. dest., dehydrate and counterstain 

 if desired with alcoholic crystal violet, 

 clear and mount in balsam. Melan- 

 oblasts should be black. 



This much used method has been 

 criticized by 11. Sliarlit et al. (Arch. 

 Dermat. and Syph., 1942, 45, 103-111) 

 chiefly on the ground that the incuba- 

 tion for 3 hrs. at room temperature may 

 itself increase the amount of melanin 

 present which happened in their ex- 

 perience at 37 °C. See also remarks 

 by Blaschko and Jacobson (Bourne, 

 p. 198) on specificity of the reaction. 

 It is given by phenoloxidases but thus 

 far they have not been found in mam- 

 malian tissues. 



Dorothy Reed Cells, see Reed-Sternberg 

 Cells. 



Double Green, see Methyl Green. 



Double Imbedding. To facilitate section 

 cutting by making a celloidin block 

 firmer, harden first in chloroform vapor, 

 then in chloroform, transfer to benzol 

 until it becomes transparent and in- 

 filtrate with 38°C. paraffin (Lee, p. 

 104). See Fleas, 



Another method of double imbedding 

 is that of Peterfi (T., Zeit. f. wiss. 

 mikr., 1921, 38, 342-345). As employed 

 in this laboratory it is as follows : Make 

 1% and 3% solutions of celloidin in 

 methyl benzoate which take about a 

 month. Foursome 1% into a dish. Add 

 absolute alcohol containing the tissue 

 which gradually sinks down into the 

 celloidin. Transfer tissue to 3% solu- 

 tion, 48-96 hrs. Drop tissue directly 

 into benzol for a few hrs. Then infiltrate 

 and imbed in 40 °C. paraffin about 

 12-24 hrs. 



Double Scarlet BSF, see Biebrich Scarlet, 

 water soluble. 



Downey's Fluid, see Megakaryocytes. 



Ducts. These structures lead (L. ducere) 

 the products of glands to the site of 

 discharge. They are of considerable 

 variety. Ordinarily they are easily 

 identified by their morphology in hema- 

 toxylin and eosin preparations. But 

 special techniques are required for their 

 visualization in whole mounts of some 

 glands. 



In the pancreas for example the 

 system of small ducts (ductules) can 

 easily be demonstrated by perfusion of 

 the pancreas with pyronin — one of the 

 many methods discovered by R. R. 

 Bensley. Proceed as described under 

 Perfusion using a solution made up by 

 adding 10 cc. of 1% aq. pyronin to 1000 

 cc. 0.85% aq. sodium chloride. When 

 the pancreas has assumed a rose red 

 color the optimum intensity of which 



