Variations in the Gag, Cough, and Swallow Reflexes and Tone of the Vocal Cords as Determined by Direct Laryngoscopy in Newborn Infants *

This investigation is part of a comprehensive effort to determine the degree of vagal function in newborn infants. No particular attention has been given to this problem previously, but in the light of recent experimental work in animals there is a clear indication for such a survey in newborn infants. The presence of an effective vagal mechanism is essential to the life of newborn kittens and puppies, but the adults of these species can survive vagal deprivation indefinitely, such as results when the vagi are cut in the midcervical region.8 Vagotomy in rabbits performed in the above manner results in pulmonary edema and death within a few hours. Recently it has been shown that in addition to the pulmonary edema, hyaline membranes are formed in the alveoli and alveolar ducts of the lungs of rabbits'0 and puppies,1 the only species examined to the present time. These pulmonary hyaline membranes are similar in appearance and have the same histochemical properties as those found in the lungs of newborn infants dying in the first few hours and days after birth.2 It was this observation which led us to investigate the r6le of the vagus in newborn infants. Some evidence already exists for believing that vagal function is not fully developed in newborn infants. Wiggers has stated: "To judge from the rapid [heart] rate in infancy, its gradual decrease during childhood, and the fact that atropin does not accelerate it in children, the vagus influence has not developed in early life, but is acquired gradually."' Hoff writes: "In infancy and in old age (man), vagal 'tone' is at a minimum, while it is at a maximum during adolescence and early adulthood."8 Vagal influence on the gastrointestinal tract also appears to be minimal at this age, as indicated by the relatively reduced peristaltic activity' and the low output of hydrochloric acid by the stomach when compared to older infants.' Miller and Behrle have shown that vagal control of respiration apparently is not fully developed, particularly in premature infants.' In view of these observations it seemed important to obtain additional information concerning vagal function in the newborn period.