Arterial anastomoses in the head and neck of the sheep.

No complete description of the vascular system of the head and neck of the sheep is available, and references to isolated parts of the system are scattered. Canova (1909) has made a study of the internal maxillary artery with reference to the external ophthalmic artery, and a diagram from Canova's work is to be found in Ellenberger & Baum (1943). Daniel, Dawes & Prichard (1953) have described the carotid rete and associated arteries of various animals, including sheep. Observations have been made by Balankura (1954) on the development of the intra-cranial rete in sheep. Prichard & Daniel (1954) have made a study of the arteriovenous anastomoses in the tongue of the sheep and goat. The description of the cerebral and spinal circulations of the sheep and ox by Andersson & Jewell (1956) differs in some details from the findings of May (1965) which were based on dissections and latex injected corrosive preparations of eighty sheep. Carlysle & Grayson (1956) have investigated the contribution of the carotid artery to cerebral flow in sheep, goats and rabbits. Appleton & Waites ( (1957) have illustrated vascular structures ventral to the external ear of the sheep, and Linzell & Waites (1957) have studied the effects of occluding the carotid and vertebral arteries of sheep, and indicated one of the channels which developed subsequently. Waites (1960) has described the arteries to the brain and spinal cord of sheep. Bagedda, Maguledda, Loverci & Lepori (1963) have made arteriographs of the cerebral circulation, and Lewin (1963) has studied the blood supply of the internal ear. Baldwin & Bell (1963) have studied the dynamic distribution of blood to the cranial region of sheep and cattle by unilateral and bilateral injections of various dyes into the vertebral and common carotid arteries. May (1965) has disagreed with the origin of the ventral spinal artery, as shown in their diagram. May (1964) has described the major branches of the arterial system of the head and neck.