We have been interested in the clinical syndromes resulting from disturbances of rotation of the intestinal tract in the course of fetal development, in the recognition of these syndromes and in their surgical treatment. In this paper we shall discuss clinical problems which involve a single anatomic division of the alimentary tube, namely, the part derived from the midgut loop, or that portion of bowel which is supplied by the superior mesenteric artery; within this limited territory we shall ignore, save as they have occurred coincidentally or are concerned secondarily with differential diagnosis, all types of congenital malformation except those that have to do with disturbances of the process of intrauterine developmental rotation and subsequent fixation of the distal portion of the duodenum, the small intestine and the proximal portionof the colon. NORMAL DEVELOPMENT OF THE INTESTINAL TUBEIt is incumbent on the pediatrician, as well as on the surgeon, to be familiar with the embryologic development of the digestive tube, so that he may be prepared to recognize its vagaries. Descriptions of the process of intestinal rotation are given in the articles of