PYROXYLIN 



291 



QUARTZ ROD TECHNIQUE 



Pyroxylin (collodion cotton. coUoxylin, 

 soluble gun cotton, xyloidin, cellodion 

 wood). It is chiefly cellulose tetra- 

 nitrite. Mainly used in manufacture of 

 Collodions, Celloidin, Paraloidin, Pho- 

 toxylin, etc. 

 Pyrrol Compounds, see Nitro Reaction, 



Nitrosamino Reaction. 

 "Quad" Stain. A recent modification of 

 this excellent orcein-alizarine-Orange 

 G phosphotungstic and phosphormolyb- 

 dic acid technique is given in detail 

 by Kornhauser, S. I., Stain Techn., 

 1945, 20, 33-35. 

 Quartz Fiber Balance and quartz torsion 



balances, see Balances. 

 Quartz Rod Technique for Illuminating Liv- 

 ing Organs. — Written by Dr. M. H. 

 Knisely, Department of Anatomy, Uni- 

 versity of South Carolina, Charleston, 

 S. C. June 27, 1950— The general 

 purpose of this technique is to perrnit 

 direct microscopic study of living in- 

 ternal organ in situ while maintaining 

 experimental conditions which disturb 

 the structures and processes to be ob- 

 served as little as possible. Like all 

 techniques it has advantages and limita- 

 tions; there are specific purposes for 

 which it works well, and purposes for 

 which it has not yet worked at all. The 

 method makes it possible to study at 32 

 to about 600 diameters magnification 

 those living structures whose colors 

 and/or indices or refraction differ from 

 those of adjacent structures. With 

 quartz rods we can illuminate for ex- 

 amination under nearly normal condi- 

 tions many living tissues and organs 

 which heretofore have been inacces- 

 sible. The method depends upon two 

 physical principles: 



1. Conducting light from a suitably 

 intense source directly to the structures 

 to be studied by way of a fused quartz 

 rod. Clean, smooth transparent rods 

 conduct light around bends and turns 

 by internal reflection almost like a hose 

 conducts water. With suitably shaped 

 rods brilliant illumination of relatively 

 inaccessible structures is relatively 

 easy. As evidence of intensity, with a 

 750 watt T-12 tungsten filament bulb 

 and a two foot length of 7 millimeter 

 rod, so much light can be sent into a 

 microscope objective that one can 

 scarcely look into the ocular. Lesser 

 degrees of intensity are of course easily 

 obtainable. Substitutes for quartz 

 rods have been suggested and occasion- 

 ally used. (Cole, E. C, Science, 1938, 

 87, 396-398. Williams, R. G., Anat. 

 Rec, 1941, 79, 263-270). We have 

 tested several. No substitute has yet 

 proven as effective for illuminating 

 living tissues as fused quartz itself. 



2. Maintaining the normal tempera- 

 tures of intensely illuminated living 

 structures with a slowly flowing isotonic 

 isothermal wash solution. It is im- 

 possible to illuminate a non-transparent 

 structure without heating it at the same 

 time. The color of an object, even a 

 translucent object, as seen by either 

 transmitted or reflected light is due to 

 the patterns of the wave lengths which 

 reach the eye after parts of the incident 

 light are "absorbed", and the word ab- 

 sorbed here means transformed into 

 heat by and within the substance of the 

 object seen. Light filters as commonly 

 used between light source and illumi- 

 nated object can shelter a specimen 

 from the wave lengths which the filters 

 absorb, but they do not alter the fact 

 that a part of the light energy which 

 passes the filters and falls on the speci- 

 men is always transformed into heat 

 within the specimen by the materials of 

 the specimen itself. Hence, in con- 

 tinuously illuminating a living object 

 heat is simultaneously developed in it 

 at a constant rate. If the specimen is 

 small, thin, and very nearly transparent 

 and if its illumination is dim, the small 

 amount of continuously produced heat 

 may be transferred to adjacent objects 

 so rapidly that the temperature of the 

 specimen never rises enough to interfere 

 with its normal functioning. However, 

 in illuminating relatively thick trans- 

 lucent structures such as frog kidney or 

 liver, or mammalian spleens, brightly 

 enough for microscopic study, heat is 

 developed in the illuminated structures 

 faster than it can be removed without 

 assistance. To remove this heat a, flow- 

 ing solution at constant temperature is 

 applied to the illuminated tissue, either 

 through sets of glass tubes, or more 

 recently through hollow tipped quartz 

 rods which deliver both light and flow- 

 ing solution precisely to the selected 

 portions of the specimen. The fluid 

 delivered to the tissue must of course 

 be isothermal and isotonic with the 

 fluid which normally bathes it, i.e. plain 

 water at room temperature is used to 

 carry heat from frog skin or tongue, 

 amphibian Ringer's solution at room 

 temperature to carry heat from frog 

 kidney, and mammalian Ringer's at 

 mammalian body temperature to carry 

 heat from monkey omentum. On ac- 

 count of the high specific heat of water 

 the flowing solution can take up the 

 heat as fast as it is produced with but 

 little change in its own temperature; 

 each small portion of flowing solution 

 is warmed but little as it passes through, 

 then leaves the illuminated field. By 

 these physical mechanisms the heat in- 



