The safe performance of cryotonsillectomy may well depend on the normal functioning of the metabolic system of the body, with particular reference to the amino acids which have been studied by the authors using a dog’s palatine tonsil as a model for cryotonsillectomy. Following the operation, all free amino acids were estimated over a period of several days. It was noted that proline and glutamine in the blood increased greatly from the first day of surgery, but falls to preoperational levels around the seventh da