MICROANGIOGRAPHY VI ITH PROJECTION MICROSCOPE 



draining them form a dense palisade, whose 

 venous tributaries drain in turn into the 

 adjacent marginal vein and a coarse sub- 

 cutaneous venous network (Fig. 1). Central 

 areas of the ear (Fig. 2) show the coarse and 

 fine vascular nets, and also short circuits or 

 arterio- venous anastomoses connecting ar- 

 terioles and venules. These structures appear 

 as S-shaped side branches from the ter- 

 minal arterioles which after a short tortuous 

 course run directly into an adjacent venule. 

 Stereomicrographs of such tissue areas pro- 

 vide a three dimensional view of the blood 

 vessels and help to verify the course and 

 connections of the arterio-venous anasto- 

 moses. Also, since the size (diameter) of the 

 vascular field and its magnification can be 

 altered by varying the target specimen and 

 target-plate ratio, it is possible to select and 

 record arterio-venous anastomoses and other 

 minute vascular features for detailed study 

 and measurement (Fig. 3). 



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Fig. 1. X-ray micrograph of the margin of a 

 rabbit ear showing the coarse arterial network or 

 macromesh, fine capillary net or micromesh, and 

 small marginal veins. X5.3 



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Fig. 2. X-ray micrograph of a more central 

 area of a rabbit ear showing the vessels of the mi- 

 crocirculation. The fine vascular net or micromesh 

 is formed by the arterioles, capillary bed and ulti- 

 mate collecting venules. X6.8 



An unexpected finding, possibly of physi- 

 ological interest, was that both large and 

 small peripheral nerves could be located by 

 their vascular patterns. In the case of the 

 rabbit ear the longitudinally disposed capil- 

 lary vessels of the intrinsic vascular plexus 

 of the great auricular nerve can be easily 

 seen. The veins draining the nerve trunk are 

 more conspicuous than the arteries of supply, 

 and can be seen to pass in a regular segmental 

 manner tow^ard adjacent subcutaneous veins. 

 Minor cutaneous branches of the nerve are 

 likewise revealed by the vascular nets which 

 lie about them (Fig. 4). 



Projection x-ray microscopy can also be 

 carried out on the living animal either by 

 taking a microangiogram immediately after 

 the regional injection of contrast medium 

 (blood displacement technique) , or by taking 

 successive microangiograms following a sin- 

 gle intravenous injection of contrast medium 



631 



