Abstract
The utilization of various substrates by peritoneal mononuclear phagocytes taken from rabbits in different thyroid states was studied. The cells of hyper-thyroid animals utilized more substrate than normal animals and responded to the injection of mineral oil with many more cells. The hypothyroid animals utilized the different substances in a degree comparable to that of the normal animals, but responded to mineral oil with far fewer cells than normal. It is suggested that these differences of metabolism and cell number might explain the conflicting observations of many investigators when studying thyroid function and resistance to infectious disease.