ABSTRACT
Since the days of Cohnheim, in the nineteenth century, the paucity of collateral circulation to the deep nuclei of the cerebral hemispheres had been recognized. By the middle of the twentieth century, however, there was persuasive experimental and clinical evidence that the situation in the cortical circulation was quite different and that functional anastomoses existed between the major vessels in the leptomeninges. The fluctuating nature of weakness following aneurysmal surgery and the curious phenomenon of the transient ischemic attack made it clear that some critical level of perfusion must exist in the brain. It was with these thoughts that I began the programs first in NIMR and then in Queen Square. Early work in the National Institute on the dog and cat had convinced me that the cerebral circulation of these animals, particularly the arrangements of the afferent and basal vessels, differed significantly from primates, and the subsequent work, both in NIMR and later, was carried out exclusively on large primates. The complexity of the preparations was such that I preferred to carry out all surgery myself. The basic technique was borrowed from electrophysiology, with a thermostatically warmed paraffin pool to protect the exposed cortex, and vascular occlusion carried out by the transorbital route (Fig. 1). Fortunately, my appointment to the staff of the National Hospital was combined with an appointment to the external staff of the Medical Research Council, and for many years, one day per week could be devoted to experimental surgery, each experiment occupying many hours, and data analysis then extending over most of the next week.
