1. Hyperexcitability of the tenth cranial (head) nerve, producing bradycardia (decreased heart output), and faintness: Mildred's vagotonia resulted in over activity or irritability of her vagus nerve, which adversely affected the function of her blood vessels, stomach, and muscles.
2. A condition in which the vagus nerve dominates the general functioning of the body organs: Manfred's vagotonia was marked by vasomotor (the nerves and muscles that cause blood vessels to constrict or to dilate), instability, constipation, sweating, and involuntary motor spasms with pain.