With our forebears, anatomy was the handmaiden of surgery; pathology its judge or jury. Modern aggressive surgery, the veritablesectio in vivo, demands of the anatomist a closer study of the viscera and ever and anon puts new problems before the physiologist. The enormous amount of anatomic, embryologic, physiologic, chemical and animal experimental work on the thyroids and the parathyroids, growing out of the recognition of definite groups of postoperative symptoms, has shed much light oh, and aroused much interest in, the functions of these important structures. I may not venture, because of the necessarily limited time alloted to this paper, to give even a cursory epitome of modern research work, but may attempt to state the conclusions which, after a fairly complete review of the work done by hosts of experimenters and observers, and my own limited part therein, appear to me to logically present the present status of