Suggested function of the vascular bundles in the limbs of Perodicticus potto.

Abstract

IN the lorises, most of the principal blood vessels of the limbs become complex vascular bundles formed by a linear arrangement of many more or less parallel arteries and veins. In cross-section these vessels have a quite regular lattice-work arrangement without any arterial venous anastomoses. Major nerves may pass in the fascial sheath enclosing the whole complex, which is sometimes called a rete mirabile. Fig. 1 shows a typical cross-section of a brachial vascular bundle with its many vessels and neural tissue including a pacinian corpuscle in the sheath. Several authors1–4 have suggested that this particular type of vascular arrangement is related to the ability of these animals to maintain a strong prehensile grip with both hands and feet for prolonged periods of time. Alternatively, others5 have presented experimental evidence that similar vascular bundles in the limbs of sloths are a mechanism for conserving body heat by the principle of counter current heat exchange.