QUARTS ROD TECHNIQUE 



292 



QUARTZ ROD TECHNIQUE 



escapably developed by transformation 

 of light energy is removed as fast as it 

 is produced and in consequence the 

 temperature of the illuminated tissue 

 does not rise. 



Thus far in a series of careful tests we 

 have found no visible change in any 

 structure and/or process within any 

 living tissue or organ in response either 

 to a sudden change from dim to intense 

 illumination or to hours of continuous 

 intense illumination, provided the tem- 

 perature of the illuminated specimen 

 was maintained normal by a continu- 

 ously flowing solution. In the best 

 e.xperiments the tissue being studied 

 floats on a thin film of slowly moving 

 fluid but does not itself touch the rod 

 which conducts light to it. 



For more detailed descriptions of the 

 method see Knisely, M. H., Anat. Rec, 



1936, 64, 499-524; McClung, C. E., 

 Handbook of Microscopical Techniques 

 for Workers in Animal and Plant Tis- 

 sues, New York: Paul B. Hoeber, Inc., 



1937, p. 632-642; Knisely, M. H., Anat. 

 Rec, 1938, 71, 503-508; Hoerr, N. L., 

 1944, see, Glasser, O., Medical Physics, 

 Chicago: Year Book Publishers, Inc., 



1944, 625-626. 



The limitations and range of applica- 

 bility and usefulness of this technique 

 may be roughly indicated by a few notes 

 describing some of its current and pro- 

 jected uses. As the method depends 

 upon seeing, its usefulness is continu- 

 ously limited by the mechanisms where- 

 by we see. As a brief rough statement 

 we "see" by recognizing patterns of 

 color and/or intensity of the light 

 "rays" coming to the retina. The vas- 

 cular system with its refractile (brightly 

 transparent) vessel walls, plasma and 

 white cells, and its brightly colored 

 erythrocytes is one of the most con- 

 spicuous features of living tissues and 

 has thus far in our laboratory received 

 more attention than other living struc- 

 tures. Further, the vascular system is 

 worth intensive study, because from 

 moment to moment continuously under 

 all conditions of health and disease it 

 sets the maximum rates at which oxy- 

 gen, glucose and other anabolites are 

 carried to and metabolites are removed 

 from, almost every cell, tissue, and 

 organ of the body. For an elaboration 

 of this theme see: Knisely, M. H., 

 Stratman-Thomas, W. K., Eliot, T. S. 

 and Bloch, E. H., J. Nat. Malaria Soc, 



1945, 4, 285-300. 



For microscopic study of the periph- 

 eral vascular beds of internal organs, 

 the method is limited by the necessity 

 of an anesthetic, an operation, and the 

 exposure of the surfaces of internal 



organs to the outer air, an unusual 

 gaseous environment. 



The method is most successful when 

 employed to examine structures just 

 below normal anatomical surfaces, 

 rather than just under cut surfaces of 

 tissues. Thus studies have been carried 

 out in frog skin, brain, peripheral nerves, 

 smooth muscles of the gastrointestinal 

 tract, stomach mucosa, mesentery, 

 striated muscles, lung, suprarenal, 

 kidney, and liver, and in mam- 

 malian spleen, stomach and intestinal 

 wall, intestinal villi, omentum, mesen- 

 teries, liver, and brain surfaces. All 

 these have natural anatomical surfaces 

 which can be exposed without damaging 

 the underlying microscopic structures. 

 In contrast, much as we would like to 

 study mammalian bone marrow, we 

 have not yet found a way to expose a 

 portion of it while preserving its struc- 

 tures and their functioning well enough 

 so that the specimen was worth any 

 serious attention. 



The conditions of an experiment limit 

 the phenomena which occur during that 

 experiment. An anesthetized animal 

 obviously does not run or swim about; 

 it cannot perform many obvious well- 

 known functions of normal unanes- 

 thetized animals. By extension, there 

 is no reason to assume that a particular 

 set of experimental conditions do not 

 inhibit, retard, alter, or prevent func- 

 tions as yet unknown, or one or more 

 phases of the particular functions one 

 is trying to study. When one selects 

 an anesthetic, gives an animal a specific 

 quantity of it, ties the animal down, 

 and operates upon it, he thereby puts 

 that animal's circulatory system into 

 one of its reaction states, and all tests 

 made on the animal from that time on 

 can show only various factors of that 

 reaction state or those deviations from 

 it which are possible under those par- 

 ticular experimental conditions. For 

 example, the circulatory responses to 

 exercise are not occurring in an anes- 

 thetized animal whose muscles have 

 been and are in a prolonged state of rest. 

 It cannot be too strongly emphasized 

 that within our experience each experi- 

 ment, or class of experiments, always 

 acts toward minimizing or preventing 

 known and probably unknown func- 

 tions. Each time that a new type of 

 experiment has been devised, new kinds 

 or degrees of responses of peripheral 

 vascular beds have been encountered. 

 Each time we have learned how to main- 

 tain lesser degrees of anesthesia and/or 

 to do less damaging operations the pe- 

 ripheral vascular beds have exhibited 

 increasingly complex integrated reac- 



