PATTERNS OF THE A-V PATHWAYS 



H<| 1 



Transparent Chamber 



The development of the transparent chamber 

 technique and its utilization in numerous tissues have 

 been extensively reviewed recently (3, 24, 25). For a 

 detailed description of the methods for installation 

 and observation, the reader may refer to these papers. 



Basically, the method consists of the insertion of a 

 glass and mica chamber fastened to the cartilage of 

 the rabbit ear or other applicable site. Since the first 

 chamber was designed by Sandison (104) in 1924, 

 several types have evolved, with modifications and 

 improvements introduced for specific purposes. The 

 round-table chamber, essentially the same as the 

 original Sandison model, was introduced in 1930 by 

 Clark et al. (36). The chamber is constructed to allow 

 new tissue to grow into an empty space from the 

 edges of cartilage left by a punctured hole. This 

 chamber has been used to study the growth and 

 development of blood vessels, lymphatics, and nerves. 

 The preformed tissue chamber (36) is one in which 

 the original tissues can be observed after removal of 

 the cartilage and skin of the inner side of the ear. 

 The moat chamber was developed to study the 

 response of the vessels to various chemical substances 

 (1, 2). It contains a small space or moat to permit 

 injection and withdrawal of fluids. The chamber has 

 been used to investigate absorption, diffusion, and the 

 reactions of vessels to chemical solutions. A remov- 

 able-top chamber was designed by Williams (138) 

 for the purpose of obtaining easy access to living 

 tissue of the chamber for transplantation of organs or 

 tissues. The most recent improvements have been 

 developed by Williams & Roberts (140), who de- 

 signed a versatile and highly useful chamber which 

 has the following characteristics: it has a longer life 

 than any other type of chamber, produces very little 

 irritation to the ear, is quickly and easily installed, 

 can be used for transplants of tissue, may be modified 

 to study existing or preformed vessels, and may be 

 adapted for the introduction or removal of fluids. 

 Epidermis, which invades the round-table chamber, 

 is never seen to grow into this new tantalum and mica 

 chamber. 



Clark (25) points out the many advantages of the 

 transparent chambers, among them the fact that the 

 manner of growth and extension of capillaries, the 

 growth of nerves along arterioles, and the develop- 

 ment of inflammatory reactions can be observed for 

 long periods of time in unanesthetized animals. The 

 disadvantages include injury to the nerves during 

 installation, the rigidity of the chamber which may- 



result in an abnormally high external pressure, 

 especially with inflammation, and the occurrence of 

 infection. The advantage of having an unanesthetized 

 animal is great, and equally helpful is the fact that 

 the exposed tissues need not be warmed or irrigated 

 as is the case for visceral or other exteriorized tissues. 

 A serious disadvantage of the technique is the dis- 

 ruption of normal circulatory patterns and behavior 

 by installation of the chamber in which the new 

 tissue must form. 



Fused Quartz Rod 



A lengthy discussion of this method of transillumi- 

 nation of living internal organs in situ for microscopic 

 study is given by Knisely (70). The limitations and 

 the applications of the method are fully covered. 



The method is based on conducting intense lia;ht 

 to the structure to be studied by a fused quartz rod. 

 These rods conduct light around bends and turns by 

 internal reflection. Overheating and drying of the 

 tissue is prevented by an isotonic wash solution. 

 Magnifications from 20 times to 1000 times can be 

 used. 



Transillumination with the fused quartz rod has 

 been carried out in a wide variety of tissues including 

 frog skin, tongue, brain, gastrointestinal tract, 

 stomach, bladder, striated muscle, lung, kidney, and 

 liver. In mammals, the small vessels in smooth 

 muscle, mesentery, uterus, spleen, and liver have been 

 studied. 



Knisely feels that the limitations of the method 

 include the necessity for an anesthetic, surgery, and 

 the exposure of internal organs to the air. The method 

 is best used to examine structures at their natural 

 anatomical surfaces or free edges rather than at cut 

 surfaces. In examining a thick organ, such as liver or 

 spleen, one is limited in the degree of magnification 

 of the deeper structures due to the direct relationship 

 between the focal length and magnifying power of 

 lenses. Fulton (49) points out that this procedure does 

 not reveal certain details of vascular structure or 

 permit critical discernment of individually formed 

 elements. It remains, however, the only method 

 applicable to many types of tissues, but requires 

 rational selection of the problems to be studied. 



Bulbar Conjunctiva 



Although observations of the conjunctival vessels are 

 not new, recent improvements in microscopes and 



