The policy set out in the prefaces to the two previous editions has been adhered to. This has meant continuing throughout the text the process of clarification and correction. With the increasing availability of ultrasound scanning facilities, and with the advent of computerized axial tomography, we thought it appropriate to supplement the revised section on radiological anatomy with descriptions and illustrations referring to these newest methods of body-imaging. We also thought it necessary to introduce new material, such as surfactant, the prevention of rh disease in infants and the limbic system, all subjects not included in previous editions, but of increasing importance for the understanding of disorders and of their correction.