Innervation of the dog's heart

The observations about the innervation of the dog's heart obtained by means of Weber's silver impregnation technique can be summarized as follows: 1. 1. The cardiac ganglia were found mainly at the base of the heart, but intramural ganglia in the depth of the right ventricle were also present. 2. 2. There were sympathetic and parasympathetic fibers in the auricles as well as in the ventricles. In the latter, the inhibitory fibers were fewer than the excitatory ones. An abundant number of efferent nerve fibers was found in the apex. 3. 3. Different forms of nerve endings were observed and discussed. Intraprotoplasmic terminations in the interior of the myocardial cells were undoubtedly present. 4. 4. Sensitory nerve fibers and their terminations were found mainly in the auricles, rarely in the ventricles. 5. 5. The auriculoventricular node of the dog's heart was not only innervated by many excitatory and inhibitory fibers, but also by a considerable number of sensitory ones. The author suggests that from the neurohistological point of view this node is a certain center of reflex. 6. 6. The common trunk, its two main branches, and their ramifications in the interventricular septum were not innervated, but some autonomic fibers in close neighborhood with the subendothelial Purkinje cells were demonstrated in the preparations.