On the Behavior of the Respiratory Muscles During Vomiting

In order to produce vomiting in the dogs decerebrated and unanesthetized, apomorphine or copper sulfate was administered. The behaviors of both the inspiratory and the expiratory muscles were studied through the course of the act of vomiting by the electromyographic technique. The results are summarized as follows: (1) The most significant signs of vomiting seems to be the recurrent vomiting volleys from the vomiting center each of which is produced abruptly and transiently. (2) The peculiarities of the vomitng volley consist in the simultaneous discharges of both the inspiratory and the expiratory muscles, resulting in the so-called retching movement. (3) The vomiting volleys, in their rhythm, seem to arise independent of the respiratory center, but the former are capable of affecting the respiratory centers at any respiratory phase. (4) The acceleration of the breathings observed prior to the retching seems to be due to the invigorated activity of the respiratory centers affected directly by the administration of the vomiting agents without an intermediate step by the vomiting centers. (5) The simultaneous contraction of the diaphragm and the abdominal muscles are merely a component of a peculiar type of the respiratory movements, namely, that of the retching. (6) The glottis muscles are, however, ruled out from the principle described in (2): the closer of the glottis muscles contracts during the retching, while the opener is completely inhibited.