The authors report an experimental study of the pathology and cervico-cerebral hemodynamics in the dog and discuss the normal anatomy of the carotid arteries in the dog. These results include the interpretation of 30 selective angiographies and numerous anatomical dissections. Many points distinguish the carotid arteries in the dog from those in man. Firstly, in their distribution, where the internal carotid artery appears particularly narrow the internal maxillary artery particularly large. Then and above all, their function, it seems that external carotid artery is more important than the internal carotid artery in the dog, so that the blood supply of the central nervous system seems to be obtained almost entirely through the vertebro-basilar system. Finally, there exists between each network of internal carotid arteries, the external carotid artery and the vertebral arteries numerous anastomoses. Contrary to the distrubution of arteries in man, these anastomoses usually function permanently.