NECROSIS 



222 



NEODYMIUM 



Necrosis (G. ne/crosis, a killing). The term 

 is usually appliea to indicate the local 

 death of a cell or of group of cells, not 

 that of the body as a whole. Death is 

 defined by Webster and others as the 

 "cessation of life" which merely poses 

 the question of what life is. Perhaps 

 the most fundamental vital phenomenon 

 is the oxygen consumption involved in 

 respiration. This may persist in eryth- 

 rocytes even after the loss of their 

 nuclei (Harrop, G. A., Arch. Int. Med., 

 1919, 23, 745-752). But cells frozen 

 by special techniques do not respire 

 while frozen. They endure in a state 

 of suspended animation (called vitrifica- 

 tion) indefinitely. They are not dead 

 since they retain the structural organi- 

 zation, which, when unlocked by in- 

 crease in temperature, confers renewed 

 vitality (see Luyet, B., C. rend. Soc. 

 de biol., 1938, 127, 788-789 and many 

 others). Death can therefore be better 

 defined as the disorganization of living 

 matter which makes permanently im- 

 possible all vital phenomena. Since 

 the organization of different sorts of 

 living cells is fundamentally different 

 the loss of organization in them is likely 

 also to be different. See various forms 

 of Degeneration. In general necrosis 

 of tissue is often evidenced by a break- 

 ing up of the nucleus known as caryor- 

 rhexis (G. Karyon, nucleus, -f- rhcxis, 

 rupture) or by its solution, caryolysis 

 (G. lysis, solution). Consequently any 

 good nuclear strain such as hematoxylin 

 or methylene blue is satisfactory. See 

 techniques for Dead Cells, Necrobiosis. 



Neelsen, see Carbol-Fuchsin. 



Negative Stains are used to show the back- 

 ground in which bacteria and other 

 organisms are present in smears and by 

 contrast thus to reveal them unstained, 

 that is in a negative way. The tech- 

 nique is very simple. Simply mix the 

 fluid containing the organisms with the 

 "stain", smear on a slide, dry and 

 examine. Higgins' India Ink is usually 

 employed; but congo red (Cumley, 

 R. W., Stain Techn., 1935, 10, 53-56) 

 and azo blue (Butt, E. M., Boynge, 

 C. W. and Joyce, R. L., J. Inf. Dis., 



1936, 58, 5-9) are among many other 

 materials used. See Azo Blue. 



Negri Bodies. 1. Rapid section method 

 (Schleif stein, J., Am. J. Pub. Health, 



1937, 27, 1283-1285). Fix in Zenker's 

 fluid, wash, dehydrate in dioxan, embed 

 in paraffin, cut at 4 microns, mount, 

 deparaffinize. Flood slides with 1 drop 

 1:40,000 aq. KOH in 2 cc. stock solution 

 of stain (Rosanilin of Grubler 1.8 gm., 

 methylene blue, Nat. Col., 1 gm., gly- 

 cerol 100 cc. and methyl alcohol 100 cc). 

 Steamgentlv5min. Rinse in tap water. 



Decolorize by gently moving in 90% 

 ethyl alcohol until color is faintly violet. 

 Pass quickly through 95% alcohol, 

 absolute, xylol and mount in balsam. 

 Negri bodies deep magenta with dark 

 blue inclusions. 



2. Rapid smear method (Dawson, 

 J. R., J. Lab. & Clin. Med., 1934-35, 

 20, 659-663). Remove brain to be 

 examined as quickly as possible. Cut 

 several small segments (3-4 mm. thick) 

 from Ammon's horn perpendicular to 

 its long axis and place in Petri dish. 

 Cut away adjacent tissue leaving only 

 the horn. Place a segment, cut surface 

 down, on small end of a new 1 in. cork. 

 With wooden applicator, or match, 

 gently wipe peripheral tissue outward 

 and downward. The segment is thus 

 more firmly attached to the cork and 

 the gray matter containing the pyra- 

 midal cells bulges upward. Press this 

 gently against a slide (clean and entirely 

 free from grease) held at one end be- 

 tween thumb and forefinger. Repeat 

 3 or 4 times, starting at end away from 

 fingers, quickly so tissue does not dry. 

 Immediately immerse in abs. methyl 

 alcohol 5 min. or more. Rinse in run- 

 ning water and stain in 2% aq. phloxine 

 2-5 min. Wash off excess stain in run- 

 ning water and color in Loeffler's alka- 

 line methylene blue, 10-20 sec. De- 

 colorize in 80% ethyl ale, dehydrate in 

 95% and 2 changes of absolute, clear in 

 xylol and mount in balsam. Handle 

 slides with forceps and avoid danger 

 from contact with tissue throughout 

 process. Pyramidal cells blue, Negri 

 bodies bright red to reddish brown. 

 Time including examination 25 min. 

 Stovall, W. D. and Black, C. E., 

 Am. J. Clin. Path., Tech. Suppl., 1940, 

 4, 8 recommend control of pH in staining 

 with eosin methylene blue (see Buffers) . 

 Stain with 1% eosin in 95% alcohol at 

 pH 6.0 or more alkaline. ISIegri bodies 

 pale red. The red is much more intense 

 if the pH is 3.0. Loeffler's methylene 

 blue is best as counterstain at pH 5.3. 

 At pH 6.0 it removes eosin. 



Azur B is advised for staining of Negri 

 bodies by Jordan, J. H., and Heather, 

 H. H., Stain Techn., 1929, 4, 121-126; 

 see also Carbol-Anilin Fuchsin methyl- 

 ene blue. 



Neisserian Infection. A differential stain 

 favorable for diagnosis (Scudder, S. A., 

 StainTechn., 1931, 6, 99-105). 



Neisser's Stain for Diphtheria Bacilli, 

 which see. 



Nemathelminthes is the phylum of round 

 worms. See Parasites. 



Nematodes. See Glychrogel for mounting. 

 See Parasites. 



Neodymium, see Atomic Weights. 



