CELLOIDIN SECTIONS 



67 



CENTRIFUGATION 



forcing physiological saline solution into 

 vena cava thence through right heart 

 and via pulmonary arteries to lungs 

 evacuating by pulmonary veins. Allow 

 injected lung to stand in running water 

 over night thus hardening celloidin. 

 Immerse in concentrated hydrochloric 

 acid to digest away tissues leaving 

 celloidin cast. This usually takes 24 

 hrs. Wash thoroughly in gentle stream 

 of water. Mount dry or mount wet in 

 solution made up as follows : Boil for 10 

 min. 100 cc. aq. dest. + 20 cc. glycerin. 

 When cool add formalin to 2% and filter 

 until clear (Marquis, W. J., J. Tech. 

 Methods, 1929, 12, 59-64). See illus- 

 trations of Marquis and arrangement of 

 pressure bottles. A celluloid corrosion 

 technique for the kidney is described by 

 N. W. Baker, J. Tech. Methods, 1929, 

 12, 65-68. 



Celloidin Sections. Cut side of celloidin 

 block to smooth plane surface. Moisten 

 this and surface of microtome block 

 holder with alcohol-ether. Add drop 

 thick celloidin. Press together, harden 

 in chloroform and cut in 80% alcohol on 

 a sliding microtome with knife at an 

 angle. Keep surface of knife and block 

 wet with 80% alcohol from overhead 

 dropping bottle. (A method has been 

 described for treating block with cedar 

 oil and cutting dry with rotatory micro- 

 tome, Walls, G. L., Stain Techn., 1936, 

 11, 89-92). Sections are usually cut at 

 a thickness of 10-16 p. (It is possible to 

 arrange the sections serially but it is a 

 tedious business. If serial sections are 

 needed, paraffin should be selected in 

 place of celloidin.) The sections un- 

 mounted can be stained without remov- 

 ing the celloidin after which they are to 

 be dehydrated and cleared before mount- 

 ing. The object is not to remove the 

 celloidin but to soften it. The following 

 mixture is recommended by Lee (p. 108) 

 in place of xylol, toluol or benzol : creo- 

 sote, 40 cc. ; Bergamot oil, 30 cc. ; xylol, 

 20 cc. and origanum oil, 10 cc. 



Cellosolve is ethylene glycol monoethyl 

 ether. It mixes with water, acetone, 

 alcohol, ether and dissolves many oils, 

 waxes, etc. Employed by Lendrum 

 (A.C., J. Path. & Bact., 1939, 49, 590- 

 591). 



Cellulose, microchemical reaction for. Solu- 

 tion A : Dilute 20 cc. of 2% iodine in 5% 

 aq. potassium iodide with 180 cc. aq. 

 dest., add 0.5 cc. glycerin and mix by 

 shaking. Solution B : Saturate 15 cc. 

 aq. dest. with lithium chloride at 80°C., 

 cool and use supernatant solution. 

 Tease out section or fibers. Apply 2-3 

 drops "A" by glass rod and leave 10 sec. 

 Blot with filter paper and dry. Add 

 drop "B", cover and examine. Cellu- 



lose blue, green, yellow depending upon 

 its source (Post, E. E. and Laudermilk, 

 J. D., Stain Techn., 1942, 17, 21-26. 

 See Polysaccharides. 

 Cements. W. C. Tobie (in Simmons, and 

 Gentzkow, p. 356) gives two useful 

 types : 



Vacuum wax for ordinary vacuum 

 seals not subjected to high temperature 

 is made by melting together equl parts 

 of beeswax and rosin. It is pliable and 

 easily removed with hot water. 



Acid resisting cement is made by 

 mixing asbestos powder and sodium 

 silicate solution (water glass) into a 

 paste of desired consistency. Will dry 

 in 24 hrs. 



For ringing specimens mounted in 

 glycerin, etc. see Kronig's Cement and 

 Mounting Media. 

 Centigrade temperature to Fahrenheit 



1. Above 0°C. multiply by 9, divide by 5, 

 add 32. Example: 37°C. = 37 X 9 = 

 333 -^ 5 = 66.6 -f 32 = 98.6°F. 



2. Between -17.77 and 0°C. multiply by 

 9, divide by 5 subtract from 32. Ex- 

 ample: -12°C. = 12 X 9 = 108 -T- 5 = 

 21.6; 32 - 21.6 = 10.4°F. 



3. Below -17.77°C. Multiply by 9, di- 

 vide by 5, subtract 32. Example: 

 -18°C. = 18 X 9 = 162 -^ 5 = 32.4 - 

 32 = 0.4°C. 



Central Body, see Centrosome. 



Centrifugation. To even sketch in outline 

 the techniques that come under this 

 heading is difficult because the centrifu- 

 gation of so many materials and tissues 

 is helpful and the instruments vary from 

 simple hand driven machines to power- 

 ful ultracentrifuges which may weigh 

 several tons and which certainly require 

 experts to care for them. See Svedberg, 

 T. and Pedersen, K. O., The Ultra- 

 centrifuge, Oxford, Clarendon Press, 

 1940, 478 pp. 



The centrifuge has long been of help 

 in the displacement of certain com- 

 ponents of cells (especially marine eggs) 

 in order to determine their functional 

 r61es. It has also proved invaluable in 

 the investigation of cytoplasmic and 

 nuclear Viscosity, which see. 



In recent years centrifugation has 

 opened a new chapter in microchemistrj' 

 by the part which it has played in the 

 collection of cellular components in 

 sufficient volume for analysis. Pioneer 

 work was done with the liver. The 

 Bensleys (p. 6) give instructions which 

 are in part as follows. First perfuse the 

 abdominal organs of a guinea pig with 

 about 1000 cc. 0.85% aq. sodium chloride 

 (see Perfusion). This removes a good 

 deal of the blood. Excise liver and 

 grind up thoroughly in a mortar. Place 

 the resulting thick fluid in large centri- 



