In the last few years there has been an increase in knowledge of the arteriovenous communications, described almost simultaneously by Sucquet and Hoyer about 1860.
The anatomists' investigations have been particularly informative, especially those of Vastarini-Cresi, Grosser, Spanner, Clara, and Bucciante. On the basis of these contributions, arteriovenous anastomotic formations are known to be present in many organs and tissues of the body. However, those in the more distal areas of the extremities are better understood. Here they present various anatomic structures, ranging from the more complex neuromuscular arterial glomus of Masson to the simpler direct anastomosis without intermediate channel. The physiology of these shunts is not well known. Generally they are considered to represent a regulating device of the capillary flow. The factors which regulate the partition of the flow between arteriovenous communications and capillary bed are still undefined, even though the object of numerous recent investigations.