CHANGES IN VASCULAR PATTERNS 



1253 



V e n e 



Vine <<^ 



■-~*lK Vent 



Vene 



Venen 



Arterie 



fig. 2. Graphic reconstructions of arteriovenous anastomoses; relatively simple (left) and complex 

 (rightj communications. The accumulations of epithelioid cells are indicated. [From Staubesand & 

 Genschovv (168).] 



been variously stated. For example, Grant & Bland 

 (62) found 593 per cm 2 in the nail bed of the toe, and 

 293 per cm 2 on the plantar side, but Popoff (134) 

 counted only 24 per cm 2 in the nail bed, and 18 on 

 the ventral aspect of the same extremity. The latter 

 considered only the more complicated glomera. Their 

 size also varies: Grosser (65) found the external di- 

 ameter to be between 55 and 85 y. in the nail bed, 

 between 90 and 150 y, in the finger pad, and the 

 internal diameter to be 18 to 22 and 10 to 30 y, re- 

 spectively. In the wings of bats the intermediate seg- 

 ment had an external diameter of from go to 280 y, 

 and an internal diameter of from 60 to 150 y. The 

 length of the junctional segment as measured in the 

 tongue of the dog by Prichard & Daniel (136) was 

 between 100 and 500 y, usually between 200 and 300 y. 

 Other locations where arteriovenous anastomoses 

 have received detailed study include: erectile tissue, 

 the ears in man (135); the nose, including skin, 

 septum, and turbinates; and the gastrointestinal tract 

 (8). Their existence in the kidney has been denied by 



Trueta (178), and by Staubesand & Hammarsen 

 (169), although Spanner (165) described them in the 

 region of the sinus renalis, and Simkin et al. (162) 

 found that spheres as large as 90 to 440 y would pass 

 from renal arteries to veins. In the lung, Weibel (186) 

 could find no precapillary connections between pul- 

 monary arteries and veins, but Prinzmetal et al. (137) 

 found that glass spherules as large as 150 y would 

 pass from the former to the latter, and Parker et al. 

 (131) observed that spheres of 75 to 80 y would 

 traverse the capillaries but those of 300 y would not. 

 Tobin & Zariquiey (176) and Rahn et al. (140) have 

 also concluded that pulmonary arteriovenous com- 

 munications must exist normally. In perfused lobes 

 Niden & Aviado (126) observed glass beads as large 

 as 420 y on the venous side in a perfusate introduced 

 intra-arterially. Bostroem & Piiper (23), however, 

 found that spheres of 28 to 36 y. would pass only 

 exceptionally, and criticized the high pressures used 

 by Tobin and his associates. Gordon et al. (60) also 

 concluded from their own work, based on an appli- 



