DOROTHY REED CELLS 



82 



EAR 



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 : Alake 

 1% and 3% solutions of celloidin in 

 methyl benzoate which take about a 

 month. Pour some 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 

 must be determined by trials, remove a 

 piece of it, tease out a small lobule and 

 examine under low power mounted in 

 0.85% aq. sodium chloride. The com- 

 plicated system of ducts should be 

 sharply delineated by their deep rose 

 red color in an almost colorless 

 background. If there is any question of 

 their identification examine the original 

 figures of Bensley, R. R., Am. J. Anat., 

 1911, 12, 297-388. A double staining of 

 ducts and Islets of Langerhans can be 

 obtained by perfusing in the same way 

 with pyronin solution to 1000 cc. of 

 which 6 cc. 1% aq. neutral red has been 

 added. The islets appear yellow red in 

 contrast to the rose red ductules. See, 

 in addition, ducts in whole mounts of 

 Mammary Glands and in sections of 

 Submaxillary Glands which are of par- 



ticular interest in detecting the action of 

 salivary gland viruses. 



Duodenal Fluid. Microscopic study must 

 be prompt because of the presence of 

 cytolytic engymes. Examine sediment 

 after centrifugal concentration as in the 

 case of urinary sediments. Epithelial 

 cells from the entire alimentary tract 

 leading to and including the duodenum 

 may be present, generally bile stained, 

 also a few neutrophiles. A great in- 

 crease in both or either may indicate 

 inflammatory lesions. A polarizing mi- 

 croscope is helpful, but not essential, 

 in recognizing cholesterol crystals as 

 thin, flat, colorless fragments with 

 chipped edges. The more irregular the 

 crystals the more significant they are 

 of calculi formation. Bilirubin is easily 

 detected as amorphous amber, brown or 

 black material and calcium bilirubinate 

 as bright yellow granular deposits. 

 See Gentzkow and Van Auken in Sim- 

 mons and Gentzkow, p. 63. 



Dysentery, see Endamoeba. 



Dysprosium, see Atomic Weights. 



Ear.— Written by W. P. Covell, Dept. of 

 Anatomy, Washington University, St. 

 Louis, June 5, 1946 — Microscopic exami- 

 nations of the ear are nearly always 

 made on sections. This is understand- 

 able, but it is possible that the study of 

 still living tissues, removed by careful 

 and minute dissections, is a field of con- 

 siderable promise. The close apposi- 

 tion of epithelial and nervous com- 

 ponents to bone necessitates decalcifica- 

 tion except in the case of young em- 

 bryos. The frequent use of celloidin in 

 place of paraffin for imbedding is oc- 

 casioned by the wide range of diversity 

 in resistance of the organ to the micro- 

 tome knife, fluid containing lumina 

 being surrosnded by hard dense bone. 

 The histological techniques actually in 

 use for the ear are fewer in number and 

 more limited in range than those era- 

 ployed for most other parts of the body. 

 The difficulty experienced in obtaining 

 fresh and normal adult specimens has 

 turned investigation toward human 

 fetuses and the ears of experimental 

 animals. 



The commonly used fixatives are 

 either Zenker's fluid, with or without 

 acetic acid, Zenker-formol, or 10% for- 

 malin. The best results are to be ob- 

 tained by the use of animal material for 

 which prompt fixation by perfusion 

 methods has been done. Isolated tem- 

 poral bones placed in fixative are prone 

 to show autoiytic changes in end organs 

 and ganglion cells in one-half hour fol- 

 lowing death. The literature is filled 

 with autoiytic changes described as 

 specific pathologic alterations due to 

 drugs, toxins, poisons, and so forth. 



