The Cerebral Circulation: Some New Points in its Anatomy, Physiology and Pathology.

IT is not many years since the current teaching in regard to the cerebral circulation might be summed up in the anatomical doctrine that the vessels were ' end-arteries,' without anastomoses distal to the circle of Willis; the physiological doctrine that the cerebral vessels were without vasomotor supply, and changed their calibre only passively as a result of changes in the systemic blood pressure; and the pathological doctrine that thrombosis in the brain caused softening, and rupture of a vessel caused apoplexy. During the last two decades, a large number of investigators have approached the subject afresh along many different avenues, and have established a body of data which places the whole matter in an entirely new light. To review all of the work which has been done during this period would require far more than an evening's lecture, but although it is obvious that additional facts mean additional complications, certain broad principles stand out which have won general acceptance, and it is these that I should like to present here. Not only have the structure and function of the cerebral circulation a great theoretical importance, but they possess a considerable practical importance for diagnosis and treatment as well, and promise even more for the future.