QUARTZ ROD TECHNIQUE 



207 



QUARTZ ROD TECHNIQUE 



care can be taken so that almost no 

 blood is lost; simultaneously care can 

 be taken to traumatize but very little 

 tissue, thus minimizing the amounts of 

 precipitated-agglutinated blood pour- 

 ing from traumatized tissues into the 

 general circulation (Knisely, M. H., 

 Eliot, T. S., and Bloch, E. H., "Sludged 

 Blood in Traumatic Shock", Archives 

 of Surgery, 1945, 51, 220-236). As (a) 

 hemorrhage and (b) precipitation- 

 agglutination of the circulating blood 

 are two separate factors which can act 

 alone or in combination in initiating 

 some of the pathologic processes which 

 are commonly included under the term 

 "shock", it cannot be too strongly em- 

 phasized that bloodless sludgeless oper- 

 ations must be performed if one wishes to 

 study the circulatory system when its 

 parts are not participating in shock 

 reactions. 



Living tissues move, and the move- 

 ments tend to limit the microscopic 

 study of living structures. When an 

 object moves under a microscope, each 

 point of its microscopic image moves as 

 many times as far as the object moves 

 as the magnifying power of the lenses 

 employed. Thus, at 100 diameters 

 magnification each point of an image 

 moves 100 times as far as the correspond- 

 ing part of the object. Further, the 

 image moves during the same time in- 

 terval that the object moves, so in each 

 small interval of time the image goes 

 100 times as far as the object : thus at all 

 times during the movement the image 

 is going 100 times as fast as the object. 

 From this example it is obvious that when 

 an object moves under a microscope each 

 point of the image moves as many times 

 as far and as many times as fast as the 

 object moves, as the magnifying power 

 of the lens sj'stem employed. These 

 factors rapidly increase the difficulty of 

 observing moving structures as higher 

 magnifications are used. However, the 

 movements of most tissues do not pre- 

 sent as formidable an obstacle as the 

 bare statement of the problem might 

 imply. For as one gains experience in 

 woridng with living tissues, many small 

 methods are developed for holding tis- 

 sues still, and for observing between 

 movements, and one learns to swing his 

 eyes with the image and observe many 

 details sharply even while the tissues 

 are in moderately rapid motion. 



The depth in the transilluminated 

 tissue to which one can observe is 

 limited by a number of factors. Most 

 important is the focal length of the 

 lenses employed, tha higher the mag- 

 nifications used the more closely are 

 observations restricted toward surface 

 struct ui'es. The natural transparency 



or translucency of the tissues also limits 

 the depth of observations. Some curi- 

 ous eifects result from this, for instance : 

 when smooth muscle is relaxed it is on 

 the transparent side of translucent, but 

 when it contracts it becomes quite 

 opaque, hence, in this tissue, the maxi- 

 mum possible depths of observations 

 are a function of the physiological state 

 of the tissue. For similar and other 

 reasons, such as the amount of blood 

 present at any moment in very vascular 

 tissues, the depth to which one can see 

 in many tissues is partly dependent on 

 the particular set of physiologic proc- 

 esses going on at the time the tissue is 

 studied. 



The maximum duration of the obser- 

 vations made in any one animal depends 

 upon the species, the care in maintain- 

 ing light anesthesia, the care exercised 

 in the initial operation, and the purpose 

 of the study itself. Individual frog 

 kidney glomeruli have often been kept 

 under continuous observation at mag- 

 nifications up to 400 (sometimes 600J, 

 up to as long as 12 hrs., without injuring 

 the tissues enough so that the blood 

 began to agglutinate or so that passing 

 white cells ever began to stick to the 

 inner surfaces of the brilliantly illumi- 

 nated glomerular endothelium. (Clark, 

 E. R. and E. L., Am. J. Anat., 1935, 57, 

 385-438). For a record of prolonged 

 observations see Knisely, M. H., Strat- 

 man-Thomas, W. K., Eliot, T. S. and 

 Bloch, E. 11., J. Nat. Malaria Soc, 

 1945, 4, 285-300. 



Thus far the limitations of the method 

 have been more considered than the 

 range of its usefulness. The limitations 

 are important and must be clearly 

 recognized and understood by all who 

 plan either to use it or to evaluate re- 

 ports of work done by means of it. 

 However, as one purpose of this book 

 is to help experimenters select methods 

 which may be useful to them, the range 

 of usefulness of the method will now 

 be roughly outlined. 



The fused quartz method, like all 

 others does not have uses which are in- 

 dependent of the purposes of those who 

 use it. Methods are always dependent 

 upon purposes. Analytical mecha- 

 nistic biologists are working on the solu- 

 tions of manj' problems including: How 

 are the bodies of the adults of each 

 species constructed? How does each 

 body develop? How does it change 

 witli time? How is it constructed while 

 it is alive? How is it constructed so 

 that it can function? What physical 

 and chemical functions does each small 

 part have? During each phase of 

 physiology how does each small part 

 behave? How do the coordinated func- 



