Administrative Medicine

by suggesting a number of interesting correlations between what is observe(] physiologically and what one experiences subjectively, e.g., paradoxical cold, persisting cold sensations, and so forth. It is to be emphasized that the thermal fibers are of very small calibre. In winding up the discussion of his paper, Zotterman does the service of calling attention to the physiological significance of small fibers in general. Like the receptors, the small fibers have probably been neglected in the past because of the technical difficulties in investigating them. But being, as it were, out of sight, they have been out of mind, with the result that much more importance has been attached to the large, fast-conducting fibers whose large action potentials are much easier to record and to trace to their destination. This prevalent attitude was reflected in Zotterman's own thinking when he began to investigate depressor reflex mechanisms related to the heart and to the carotid sinus: "When we started working on them," he states, "we believed that the large afferent fibers from the right auricle were the sort of fibers subserving the real cardiac depressor effect, but," he continues, "we found out that they were not. The small delta fibers were the ones that were doing the trick. . . . It is only when the small fibers are stimulated [and this applies also to the carotid sinus] that we obtain the reflexes.... The small fibers have been overlooked before.... I found out that the small fibers are contributing much more to our sensations than the large fibers. . . . Of course, we have to look more carefully into the large fiber system and find out what they are doing centrally. The impulses reach the center much earlier than the small fiber impulses, but they are very few generally compared to the abundant mass of small fibers whose activity builds up the real emotions. The funny thing is that it is these tiny fibers which are giving us the emotions: their signalling is the basis of our emotional life." It is to be hoped that the small fibers, like the receptors, will soon lose their status as "forgotten men." It is also to be hoped, as Chairman Merritt suggested in closing, that they will be the subject of one of the conferences on the nerve impulse in the near future.