Extra- and intra-cranial blood supply to brains of dog and cat.

The dog and cat are useful experimental animals, and information regarding their cerebrovascular patterns and the source of blood supplying their brains is important. Blood vessels to brains and heads of cats and dogs were injected with various contrast media. Extracranial and intracranial arteries were studied grossly and in cleared sections. The proximal part of the internal carotid artery is small in the dog and non-functional in the cat. The largest single source of arterial blood supplying the brains of these species comes from the maxillary artery over an anastomotic ramus leading to an internal rete mirabile enmeshed in the cavernous sinus. The distal segment of the internal carotid arises from this anastomosis. The brain-stem of both animals is supplied by C1 branches of the vertebral arteries, and in the dog an occipital ramus makes a large contribution to it. In addition to an internal rete mirabile, the cat possesses a large external rete mirabile surrounding the maxillary artery and giving rise to all branches in the area. It is functionally equivalent to the ramus anastomoticus in the dog. Arterial patterns over brains of Carnivora are similar. They resemble those of lower mammals more than those of primates. Extensive extracranial arterial anastomoses located in the orbit, retia mirabilia and neck musculature are significant and make it difficult to render the brains ischemic.