An analysis of the relations of the coronary constrictor and dilator nerves in the cervical vagosympathetic of the dog

Abstract

1. 1. Vagosection was performed above the ganglion nodosum. The animals were allowed to recover and the nerves to undergo a variable period of degeneration and repair after which functional tests were applied. 2. 2. Dogs with vagosection exhibit a total, or almost total, loss of coronary constriction in response to cervical vagosympathetic stimulation. Two animals have shown a mild degree of coronary constriction after cervical dilator control was reduced by injections of nicotine into the cervical sympathetic ganglia. 3. 3. These more distally placed coronary constrictor neurones have only a moderate total effect and are not always present. A satisfactory explanation of this occasional type of animal is that some few neuroblasts have migrated distally in early embryonic development. 4. 4. The loss of coronary constriction after vagotomy and degeneration indicates that the vagus is the sole pathway of the efferent coronary constrictor nerves. 5. 5. After the coronary constrictors are degenerated, stimulation of the cervical vagosympathetic produces coronary dilation of variable amount. 6. 6. Coronary dilation from stimulation of the cervical vagosympathetic trunk after vagal degeneration does not occur in all animals, and varies in amount from nothing to a medium degree of dilation among those animals in which it is present. 7. 7. There is greater reaction to stimulation of the lower cervical region just above the inferior cervical ganglion. A definite palpable middle cervical ganglion is rarely present in the dog. Histological sections, however, show that strands of nerve cells may be present among the bundles of axones of the vagosympathetic trunk at approximately the region of the middle cervical ganglion. These cells function as links in the chain of efferent coronary dilator pathways. 8. 8. Cardiac inhibitory fibers were completely absent from the degenerated vagi of the animals reported in this series.