MELANOBLASTS 



196 



MESONEPHRIC TUBULES 



A method for the collection of melanin 

 for analysis by differential Centrifuga- 

 tion is described by Claude, A., Trans. 

 New York Acad. Sci., 1942, II, 4, 79-83. 

 A very complete account of the 

 melanins has been presented by Gordon, 

 H. (Organizing Chairman) : The Bi- 

 ology of Melanomas — Special Publica- 

 tions, New York Acad. Sci., 1948, 

 466 pp. 



Lillie (p. 131) cites Alfieri from 

 Romeis as advising for the bleaching of 

 melanin in sections treatment with 

 0.05% aq. potassium permanganate 

 until thoroughly brown followed by de- 

 colorization in 0.33 aq. oxalic acid and 

 repeating the process if necessary. 

 Obviously stronger solutions could be 

 employed. This removal of melanin 

 might be advantageous in some cases to 

 reveal more sharply other properties of 

 the cells like mitochondrial content. 

 Treatment with 10% hydrogen peroxide, 

 as suggested by Lillie, is perhaps a 

 better method. 



See Dopa Reaction for melanogen in 

 melanoblasts. 



Melanoblasts, see Dopa Reaction. 



Meldola's Blue, see Naphthol Blue R. 



Mercuric Chloride (corrosive sublimate) 

 in various combinations is an excellent 

 fixative. It can be used in saturated 

 aq. sol. plus 5% acetic acid or in satu- 

 rated ale. sol. with the same amount of 

 acetic acid. See (1) with formalin, 

 glacial acetic and physiological saline 

 for Centrosomes, (2) sat. in 0.9% aq. 

 sodium chloride for Megakaryocytes, 

 (3) sat. in 70% alcohol + 5% acetic 

 for Mitosis, (4) sat. aq. + equal parts 

 2.5% aq. potassium bichromate for 

 Neutral Gentian, (5) sat. aq. with equal 

 parts abs. alcohol for Thymonucleic 

 Acid, and (6) with nitric acid for Urea. 

 The mercuric chloride is removed from 

 the sections by Lugol's iodine solution. 

 See also fixatives of Zenker, Gilson, 

 Rabl and Petrunkewitsch. Zinc chlo- 

 ride is suggested as substitute for 

 mercuric chloride in Zenker's fluid 

 (Russell, W. O., J. Techn. Methods & 

 Bull. Int. Asso. Med. Museums, 1941, 

 21,47). 



Mercurochrome 220. Trade name for di- 

 brora-oxy-mercuri-fluorescein. Can be 

 used as substitute for eosin (Baldwin, 

 W. M., Anat. Rec, 1928, 39, 229) but 

 it has little to commend it. 



Mercury, microchemical tests for. 



1. Method of Almkvist-Christeller. 

 Fix tissues 2 days in sat. aq. picric acid, 

 100 cc. ; 25% nitric acid 1 cc, saturated 

 with HjS gas, filtered after 1 day. After 

 fixation wash in running water for 24 

 hrs. Imbed in paraffin. Mercury ap- 

 pears as black ppt. of sulphide. Lison 



(p. 102) explains that it is necessary to 

 make parallel tests for iron because this 

 method changes iron into the black sul- 

 phide which could be mistaken for the 

 sulphide of mercury. Simonet (M., 

 Arch. d'Anat. Micr., 1929, 25, 372-381) 

 uses instead fixation for 10 hrs. in equal 

 parts alcohol and chloroform, 100 cc, 

 + nitric acid, 2 cc. the mixture satu- 

 rated with HjS by bubbling. 



2. Method of Brandino (G., Studi 

 Sassari, 1927, 5, 85). Fix in formalin 

 or in alcohol. Treatment of sections 

 with 1% sol. of diphenylcarbazide which 

 forms with mercury a violet ppt. Gives 

 results with organs of persons killed by 

 mercury poisoning kept in formalin 

 17 years (Lison, p. 102). 



3. Method of Hand et al., J. Lab. & 

 clin. Med., 1943, 28, 1835-1841. Re- 

 agents: (A) Mercurous. 1 cc. thioglycol- 

 lic acid +9 cc. glycerol. (B) Mercuric. 

 Heat until clear 100 cc. glycerol., +5 

 gm. tartaric acid, +5 gm. stannous 

 chloride. Add few gms. metallic tin 

 and store in glass stoppered bottle. 



(C) Iodine. Dissolve 50 gm. potassium 

 iodide in 50 cc. aq. dest., add 70 gm. 

 iodine and 95% ale. to make 1,000 cc. 



(D) Chloroauric acid 1% aq. (E) Con- 

 trol. Let 5 gm. tartaric acid stand over 

 night in 100 cc. glycerol. Cut 15 m 

 frozen sections of tissue. Place on 

 slides and dry. To section on each of 4 

 slides add 1 drop of one reagent. Add 

 cover glasses. Remove with filter 

 paper excess of reagents. Seal edges of 

 cover glass with commercial gold size, 

 an adhesion intended to hold gold foil 

 on glass. Melted paraffin is less satis- 

 factory but will serve for a short time. 

 After 10 min. examine slides. Metallic 

 mercury visible as small black spherules. 

 These are soluble in C and form gold 

 amalgam losing glossy surface when 

 treated with D. Reagent A gives typi- 

 cal yellow crystals with mercurous 

 mercury in addition to globules of 

 mercury when mercuric mercury also is 

 present. Sections treated with B and E 

 are unchanged (adapted from Click 

 p. 25). 



Intravenous injections of colloidal 

 solutions of mercury in rabbits are 

 described by Duhamel, B. G., C. rend. 

 Soc. de Biol.. 1919, 82, 724-726. 



Mesentery spreads, sections and cultures. 

 Maximow, A., Arch. f. exper. Zellf., 

 1927, 4, 1-42 (nice colored plates). For 

 microinjection of small vessels of the 

 mesentery see Florey, H., Proc. Roy. 

 Soc. B, 1926 100, 269. 



Mesonephric Tubules, cultivation in vitro 

 and method for collection of fluid there- 

 from (Keosian, J., J. Cell & Comp. 

 Physiol., 1938, 12, 23). 



