SCHWEINFURT GREEN 



311 



SEPARATION OF CELL 

 COMPONENTS 



Schweinfurt Green, an exogenous pigment, 

 cupric acetoarsenite. 



Scott, see Altmann-Gersh Frozen Dehydra- 

 tion Method. 



Sebaceous Glands. Method for staining 

 intoto (Badertscher, J. A., StainTechn., 

 1940, 15, 29-30). Fix fresh skin for 24 

 hrs. in 10% formalin, or take skin from 

 dissecting room cadaver and fix in the 

 same way. Make free hand vertical 

 sections 1-2 mm. thick from region pos- 

 sessing the glands. Whole pieces of 

 skin 12 mm. square or larger (without 

 subcutaneous fat) can be used in place 

 of the sections. Pass through 50 to 

 70% alcohol. Stain for 12-24 hrs. in a 

 mixture of 70 parts absolute ethyl 

 alcohol, 20 parts 10% aq. sodium hy- 

 droxide and 10 parts of aq. dest. satu- 

 rated with Sudan IV. Wash away excess 

 stain by repeated changes of 70% alcohol 

 until glands become sharply outlined. 

 Clear in glycerin. Mount in Brandt's 

 glycerin jelly (melted gelatin, 1 part; 

 glycerin, 1^ parts -{- few drops carbolic 

 acid). Glands scarlet in transparent 

 background. This method may prove 

 useful to bring out the distribution, 

 number, size and other features of 

 sebaceous glands in different conditions 

 as well as at different ages. The same 

 method can be used for Meibomian 

 (tarsal) glands after a little preliminary 

 dissection described by the author. 



Another method of staining sebaceous 

 glands in toto employed in the Barnard 

 Free Skin and Cancer Hospital is to 

 separate epidermis from dermis by the 

 dilute acetic acid method (see Epi- 

 dermis) and stain the epidermal sheet, 

 with sebaceous glands attached, with 

 Sudan III or IV as one would a section 

 for fat. A hematoxylin counterstain is 

 useful. 



The technique of Fluorescence Mi- 

 croscopy is useful. Figge, F. H. J., 

 Bull. School of Med. Univ. Maryland, 

 1942, 26, 165-176 has described the re- 

 markable red, white or yellow fluo- 

 rescence of blackheads which is charac- 

 teristic of different individuals. 



Secretion contrasted with excretion (Cow- 

 dry's Histology, p. 259). 



Sectioning, see Celloidin, Frozen, Gelatin 

 and Paraffin Sections. Also Bone 

 grinding and Teeth cutting with power 

 lathe. 



Selectron, a synthetic resin recommended 

 by R. McClung Jones in McClung's 

 Microscopial Technique, 1950, p. 152 

 for embedding embryos. May be pur- 

 chased from Pittsburgh Plate Glass 

 Co., Grant Building, Pittsburgh, Pa. 



Selenium. Intravenous injections of col- 

 loidal solutions of selenium in rabbits 



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

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

 See Radioselenium. 



Semen Stains, examination of for sperma- 

 tozoa. Place piece of soiled cloth not 

 more than \ inch in diameter on a slide. 

 Add few drops saline solution and 

 scrape surface of cloth with blunt edge 

 of a scalpel. Carry scrapings off with 

 fluid anci spread on a slide. Dry and 

 fix with heat. Cover with 4 cc. 1% aq. 

 Wollschwartz (Grubler) -f 0.05 cc. 2% 

 aq. sulphuric acid, 5 min. Wash in 

 water. Counterstain 6-8 sec. with Loef- 

 fler's methylene blue diluted with 15 

 parts aq. dest. Wash in aq. dest., dry 

 and examine. Heads of spermatozoa 

 bright golden or yellowish color, all else 

 gray. Useful in legal medicine (Wil- 

 liams, W. W., J. Lab. & Clin. Med., 

 1936-37, 22, 1173-1175). See author's 

 figures. See Pollak, O. J., Arch. Path., 

 1943, 35, 140-196. 



Seminal Fluid. To study in sections 

 centrifuge fluid 3 to 1 hr. after ejacula- 

 tion for 20 min. at 3000 r.p.m. Fix 

 centrifugate in 4% formalin, 48 hrs. 

 2 changes. Take sediment into abs. 

 ale, then 9 parts abs. and 1 part xylol. 

 Gradually increase xylol to 9 parts to 

 1 part ale. Xylol paraffin 30 min. 

 Then 54°C. melting paraffin for 3 hrs. 

 in incubator at 58°C. After 3 hrs. in 

 60°C. melting paraffin embed and sec- 

 tion 2-3 microns thick (Joel, K., J. 

 Lab. & Clin. Med., 1939, 24, 970-972). 



Sense Organs, see Eyes, Ear, Pacinian 

 Corpuscles, Meissner's Corpuscles, 

 Krause's End Bulbs, Nerve Endings. 



Sensitol Red, see Pinacyanol. 



Separation of Cell Components by Differ- 

 ential Centrifugation— Written by A. 

 Lazarow, Department of Anatomy, 

 Western Reserve University School of 

 Medicine, Cleveland, Ohio. Novem- 

 ber 28, 1951— When R. R. Bensley and 

 N. Hoerr (Anat. Rec, 1934, 60, 449- 

 455) successfully separated mitochon- 

 dria from the cell, they initiated a new 

 era in cytochemistry. The cells are 

 disintegrated by passing the tissue 

 through bolting silk (mild homogeniza- 

 tion in a glass homogenizer may also 

 be used). This procedure ruptures the 

 cytoplasmic membranes but leaves 

 most of the cell components relatively 

 unaltered. The resulting suspension 

 of cell fragments is subsequently 

 fractionated by differential centrifuga- 

 tion. 



The sedimentation of a particle in a 

 centrifugal field is dependent upon its 

 size, its shape, and its density (relative 

 to the suspending media) and upon the 

 centrifugal force. The sedimentation 

 of non-spherical particles is slower than 



