MCJUNKIN-HADEN BUFFER 



195 



MELANINS 



small volumes accurately at least ten 

 times the volume in each case should be 

 taken and the amount not required 

 simply be discarded. For ordinary 

 purposes employ aq. dest. in place of 

 methyl alcohol. 



McJunkin-Haden Buffer has pH 6.4 and is 

 useful in place of aq. dest. for diluting 

 Giemsa, Wright and other blood stains. 

 Monobasic potassium-phosphate, 6.63 

 gm.; anhydrous dibasic sodium phos- 

 phate, 2.56 gm.; aq. dest^ 1000 cc. 

 (Haden, R. L., J. Lab. & Clin. Med., 

 1923, 9, 64-65). 



Meat Extract Broth and other media con- 

 taining meat, see Bacteria Media. 



Mechanical Stages, see Lillie p. 287. 



Meckel's Diverticulum. Literature on 

 (Curd, H. H., Arch. Surg., 1936, 32, 

 506-523). 



Media, see Bacteria, Leishmania, Protozoa, 

 Trypanosomes. 



Megakaryocytes. These can, like blood 

 cells, be examined in fresh and stained 

 smears of bone marrow. For a deter- 

 mination of their role in platelet forma- 

 tion it is essential to clearly show the 

 granules typical of both. This can 

 best be done in sections of bone marrow 

 prepared by : 



1. Wright's method (Wright, J. H., 

 J. Morph., 1910, 21, 263-277). After 

 fixation in sat. mercuric chloride in 

 0.9% aq. NaCl, dehydrate in alcohol, 

 follow with acetone, clear first in thick 

 cedar oil and then in xylol, embed in 

 paraffin. Sections deparaffinized are 

 covered with equal parts stain (poly- 

 chrome methylene blue solution 3 parts 

 and 0.2% eosin yellowish in methyl 

 alcohol 10 parts) 10 min. A metallic 

 looking scum forms but the stain should 

 not be allowed to precipitate. Stop 

 staining when cytoplasm looks bright 

 red and reticular fibers light red. Wash 

 in water, dehydrate in acetone, clear 

 in turpentine and mount in thick 

 colophonium in pure turpentine oil. 

 See Wright's colored plates. In place 

 of the fixative suggested, Downey (Folia 

 haematol., Archiv, 1913, 15, 25) uses 

 commercial formalin 10 cc. and sat. 

 mercuric chloride in 0.9% aq. NaCI 

 90 cc. 



2. Kingsley's method (Kingsley, D. 

 M., Folia Haemat., 1937, 57, 87-98). 

 Fix in Downey's fluid (given above) 

 4 parts, saturated picric acid 1 part, 

 24 hrs. Wash in running water, 18-24 

 hrs. Dehydrate through alcohols up 

 to70%,i-lhr.each. 80% ale. + iodine, 

 overnight. 95% ale, 45 min. Repeat 

 with fresh ale. A^ butyl alcohol (techni- 

 cal), 1 hr. Repeat with fresh. Paraf- 

 fin (58°C.), ^ hr., then 3 more changes, 

 each 5 hr. Imbed. Prepare stock 



solutions A : methylene blue (U.S. P. 

 med. 88%), 0.065 gm.; methylene azure 

 A (80%), 0.01 gm.; glycerin, C.P., 

 5 cc; CH3OH (C.P.), 5 cc; aq. dest., 

 25 cc; buffer (pH, 6.9), 15 cc B: 

 methylene violet (Beruthsen 85%), 

 0.013 gm.; eosin, yel. (92%), 0.45 gm.; 

 glycerine, 5 cc; CH3OH, 10 cc ; acetone, 

 C.P., 35 cc. The buffer is 40 cc. of A 

 = 9.078 gm. KHjPOi per liter + 60 cc. 

 of B = 11.876 gm. Na2HPO«-2H20 per 

 liter of aq. dest. Immediately before 

 use mix equal parts of stock stains A 

 and B. After washing deparaffinized 

 sections in aq. dest. stain 8-10 min. 

 Wash off in current of aq. dest. Wash 

 in aq. dest. 100 cc. + 1% acetic acid, 

 0.8 cc. Wash again in aq. dest. to re- 

 move acid. Blot. Rinse in acetone, 

 100 cc + 0.001 gm. eosin -f 4 cc. 1% 

 acetic acid. Rinse in n butyl ale -\- a 

 little eosin. Neutral xylol several 

 changes. Mount in neutral xylol dam- 

 mar. See Kingsley's plate for colors. 

 Granules dark red. It is important to 

 fix the bone marrow promptly after 

 death or to obtain it by biopsy. 



Megaloblasts, see Erythrocytes, develop- 

 mental series. 



Meibomian Glands. Whole mounts of the 

 glands stained with Sudan IV in a trans- 

 parent background by a method de- 

 scribed for Sebaceous Glands. 



Meissner's Corpuscles. To investigate by 

 supravital staining with methylene 

 blue in skin of amputated fingers, see 

 Weddell, G., J. Anat., 1940-41, 75, 

 441-446. Skin from general body sur- 

 face will not do because of rarety of 

 the corpuscles. 



Meissner's Plexus, see Auerbach's. 



Melanins. Lison (p. 248) gives many dif- 

 ferential microchemical properties from 

 which the following are selected. Ex- 

 treme resistance to most chemicals, not 

 modified by concentrated acids but 

 soluble in concentrated alkalis. They 

 are depigmented by oxydants. Thus, 

 Schultze treats them with diaphanol 

 (chlordioxyacetic acid) for 24 hrs. in 

 hermetically sealed container in dark- 

 ness ; and Alfiere treats sections with 

 0.1% potassium permanganate 2-24 

 hrs. ; washes with much water, treats 

 with 0.3% oxalic acid and again washes. 

 Their power of reducing ammoniacal 

 silver nitrate, Lison regards as very 

 characteristic. Melanins occur nor- 

 mally' in epidermis, hair, choroid of eyes. 

 Greatly increased in Addison's disease. 

 Contain no iron or fat. Difficulties in 

 histological identification (Jacobsen, 

 V. C. and Klinck, G. H., Arch. Path., 

 1943, 17, 141-151). Use of Bodian 

 method (Dublin, W. B., Am. J. Clin. 

 Path., Techn. Suppl., 1943, 7, 127-128). 



