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Histologic examination of the homografted heart at the time of "rejection" shows round cell infiltration, interstitial hemorrhage, edema, and necrosis. 1-3 With the obvious histocompatibility of cardiac autografts one would not anticipate these specific alterations in histologic appearance. However, with electron microscopy we have demonstrated certain changes in intercellular structure after excision and reimplantation of the heart. 4 Neural elements are principally involved. Therefore, we have examined the morphology of normal canine hearts and hearts subjected to sham operation, autotransplantation, and homotransplantation. Using silver impregnation and trichrome counter stain we have attempted to evaluate the effect of these operations on neural and collagenous elements in the heart. Methods Studies were carried out on four groups of mongrel dogs: (1) three normal controls; (2) two animals subjected to sham operation, including thoracotomy, extracorporeal circulation, hypothermia, and cardiac arrest; (3) five orthotopic cardiac autotransplants; (4) two dogs subjected to cardiac homotransplantation. Autotransplantation

Large nerves with myelinated fibers and ganglion cells were demonstrated in proximate relationship to the systemic heart of the California hagfish ( Eptatretus stouti ). A system of ganglion cells with fibers is distributed along the aorta, the epicardium, and the endocardium. The myocardium has a plexus of coarse and fine argyrophilic fibers and fibril branches similar to, if not as extensive as, that which occurs in the hearts of fish and amphibians. These details of anatomical structure contradict the original statement by Greene that the heart of the hagfish is aneural, a conclusion which he derived from his inability to obtain a change in the rate and force of cardiac contraction by electric stimulation of the vagus nerve. The high catecholamine content of the cardiac tissues of the California hagfish ( Eptatretus stouti ) is verified. Over 99% was determined to be epinephrine.

The administration of reserpine to dogs in doses sufficient to deplete myocardial catecholamines resulted in alterations in the affinity of the heart for silver stain. Most noticeably affected was the "perimysial plexus."

THE MAMMALIAN lung is innervated abundantly by autonomic nerves that enter the hilus for distribution in the peribronchiolar tissues into the terminal segments of the air passages.1-3Many of these hilar nerves have thick and thin myelinated axons, clusters of ganglion cells and unmyelinated fibers. These and other characteristics identify them as vagal. Hilar nerves, less frequent and more fibrillar, have thin and a few thick myelinated axons, unmyelinated fibers and by their structure are recognized as sympathetic. The mammalian lungs have many afferent receptors.4-7These terminals of myelinated axons, mainly but not exclusively vagal, are recorded as (1) fiber ramifications among the lining epithelial cells of the bronchioles, (2) encapsulated or unencapsulated sessile and pedunculated receptors in the subepithelial tissues of the bronchioles, the alveolar ducts and the alveolar sacs, (3) curved segments of thick sinuous fibers with fibrils and their branches in the walls of

AUTONOMIC nerves, the vagal associated with groups of ganglion cells, enter the hilus of the lung and are distributed peripherally along the air passages. Fascicles of fibers and their subdivisions, derived from the nerves, distribute motor and sensory axons into the lung tissues, ultimately to their respective efferent terminals and afferent receptors.1,2The efferent nonmyelinated postganglionic endings of the autonomic nerves are described3(pp 324-376)as a plexus of fibers and fibrils. The argyrophilic afferent receptors of the myelinated axons in the lungs are recorded1as (1) fiber ramifications in the lining epithelium of bronchioles; (2) encapsulated or unencapsulated, sessile endorgans in the subepithelial tissues of the bronchioles and alveolar ducts, or pedunculated in the alveolar ducts and the alveolar sacs; (3) curved segments of thick sinuous fibers and their branches in the alveolar walls; and (4) plexuses of looped fibers in the bands of smooth muscle in

Excerpt Impulses transmitted through the complex correlating pathways of the autonomic nervous system control or influence the rhythmic contractions of the mammalian heart. Physiologists interested...