SHADOW-CASTING 



223 



SILVER CITRATE 



plate with vacuum tight electrical con- 

 nections. Electrodes raised above the 

 level of the base plate carry a tungsten 

 filament on which metallic chromium is 

 placed for vaporizing. Cover slips 

 with affixed material (or the grid 

 screens) are arranged in a semicircle at a 

 predetermined distance from the fila- 

 ment and the metal thereon to be 

 vaporized. The height of the filament 

 and the distance from filament to speci- 

 mens determine the casting angle. 

 Both an oil-diffusion pump and a me- 

 chanical pump must be used to produce 

 the degree of vacuum required (at least 

 10"'* mm. Hg.). With a suitable vac- 

 uum provided, the filament is heated 

 electrically and a measured weight of 

 metal is vaporized. Preparations are 

 then ready for mounting or examina- 

 tion. A figure of the apparatus and the 

 formula for calculating the appropriate 

 mass of metal for the conditions of 

 shadowing are presented in the Demp- 

 ster and Williams paper. 



Sickle-Cell Trait. A critical study of 

 methods for detection by Diggs and 

 Pettit (L. W. and V. D., J. Lab. & Clin. 

 Med., 1939, 25, 1106-1111) gives first 

 place to the Moist Stasis technique of 

 Scriver and Waugh. Place a rubber 

 band about proximal part of a finger. 

 Leave 5 min. Puncture and examine 

 fresh blood for sickle cells. According 

 to Hansen-Pruss (O. C, J. Lab. & Clin. 

 Med., 1936-37, 22, 311-315) the maxi- 

 mum percentage of sickle cells is 

 produced in 4-5 hrs. by supravital 

 staining with brilliant cresyl blue or 

 janus green, while it takes 24 hrs. in 

 unstained moist preparations. 



The following rapid method of diag- 

 nosis is reported by Neuda, P. M. and 

 Rosen, M. S., J. Lab. & Clin. Med., 

 1945, 30, 456-458. Mix "cherry -size" 

 piece of feces with 5 cc. isotonic sodium 

 chloride solution. Add 0.1 cc. of fil- 

 trate to tube of nutrient broth, incubate 

 24 hrs. at 37°C. To top of suspected 

 blood on slide add drop of culture. 

 Something in broth makes susceptible 

 cells quickly assume sickle form. 



Siena Orange (K. Hollborn, Leipsig) = 

 sodium paradipicrylamine, an alleged 

 stain for potassium (Carere-Comes, O., 

 ^ Zeit. wiss. Mikr., 1938, 55, 1-6). 



Silicon. Easily recognizable in sections 

 viewed in polarized light. It often 

 occurs as sericite in combination with 

 magnesium, iron and other minerals, see 

 Jones, W. R.,J. Hyg. 1933, 33, 307-329. 

 Microtechnique is aiscussed by Poli- 

 card. A., ana Mastin, E., Bull. d'Hist. 

 Appl., 1933, 10, 22-36. Microincinera- 

 tion is useful but Scott says that an 

 exaggerated idea of amount may be 

 obtained (McClung, p. 659). 



Silver is occasionally found in the tissues 

 particularly after treatment with silver 

 nitrate or argyrol. It appears as brown 

 to black granules or masses, is definitely 

 blackened by ammonium sulphide and 

 may be removed by a mixture of sodium 

 thiosulphate and potassium ferri- 

 cyanide solutions. Recently a method 

 based on reaction between silver andp- 

 dimethylaminobenzylidenrhodanin has 

 been described and illustrated in colors 

 (Okamoto, K., Utamura, M. and Akagi, 

 T., Acta Scholae Med. Univ. Imp. in 

 Kioto, 1939, 22, 361-372). 



Silver Chloride Dichlorfluoresceinate 

 coloration of vascular endothelial cells 

 (Bensley, R. D. and S. H., Anat. Rec, 

 1935, 64, 46-49). Inject intravenously 

 0.8% aq. dichlorfiuorescein until animal 

 becomes quite yellow. Kill animal ; 

 remove tissues and immerse in 10% 

 aq. silver nitrate or in Bensley's Silver 

 Citrate solution until salmon pink color 

 develops. Fix in 10% neutral formalin. 

 Dehydrate in alcohol and Iso-Safrol, 

 clear in iso-safrol and mount in balsam. 

 Endothelial cells outlined in pink. On 

 exposure to light color changes in time 

 the silver becoming brown and black. 

 See demonstration of Chlorides in lungs 

 by this method. 



Silver Citrate injection of blood vessels 

 (Bensley, R. D., Am. J. Anat., 1929. 

 40, 146-169). This method has proved 

 of great value in the investigation of 

 efferent vessels of renal glomeruli. It 

 can be employed to advantage in other 

 situations particularly in association 

 with supravital staining of Pericapillary 

 Cells with janus green. To make up 

 the solution dissolve 4 gm. silver nitrate 

 in 100 cc. aq. dest. and remove to dark 

 room. Completely precipitate silver 

 as silver phosphate by addition of 

 sodium phosphate solution. Wash ppt. 

 repeatedly with aq. dest. decanting 

 supernatant fluid. Make up to volume 

 approximately 30 cc. Dissolve ppt. by 

 adding 28 gms. pure citric acid (or 

 tartaric acid) in crystals. Dilute with 

 aq. dest. to 1000 cc. and keep in dark. 



For use, dilute this stock solution 

 with 3 times its volume 1% aq. sodium 

 citrate. Kill the animal by bleeding. 

 For kidneys and other abdominal 

 viscera insert into aorta cannula con- 

 nected by rubber tubing with pressure 

 bottle. First perfuse with 1% aq. 

 sodium citrate with the pressure bottle 

 about 60 cm. above cannula. When 

 clear fluid, free from blood, appears in 

 inferior vena cava, clamp tube and 

 replace citrate solution with silver 

 solution. Raise bottle about 150 cm. 

 above cannula and release clamp. De- 

 termine length of time of perfusion by 

 trials. When complete, immediately 



