Snyder G K, Gannon B, Baudinette R V, Nelson J
Department of Anatomy and Histology, School of Medicine, Flinders University of South Australia, Bedford Park.
J Exp Zool. 1989 Sep;251(3):349-54. doi: 10.1002/jez.1402510311.
Capillaries within the central nervous system (CNS) of eutherian mammals form meshworks with numerous anastomoses, whereas capillaries in the CNS of marsupials consist entirely of hairpin-like loops, without anastomotic interconnections. Counter-current blood flow in capillary loops may have been important in the evolutionary development of a cerebral vascular supply. However, loops are not found in eutherian mammals, perhaps because of a limited benefit to the diffusive conductance of gases.
