Yawning and associated phenomena.

In the course of some studies (1) on the vasomotor activity in human fingers I noted that definite circulatory changes occur during spontaneous yawning. An attempt to correlate these observations with existing data on yawning revealed that the few pertinent studies of this subject have not found their way into British or American publications. Although yawning and its associated phenomena appear to be of minor importance they are not without interest, and it would seem worth while to make readily available the little that is known and the rather more that has been postulated on this subject. Such is the purpose of this paper. LITERATURE. Standard sources. It is well to review the popular conceptions of yawning as set forth in the standard physiologic, psychologic and lay publications before turning to the special literature. Of the well-known text-books of physiology eight (2, 3,4, 5, 6, 7, 8, 9) contain no discussion of yawning. One of them (lo), in a section devoted to “modified respiratory movements,” defines it in the following terms: