The innervation and reactions to drugs of the viscera of teleostean fish

During recent years several workers have studied the innervation and responses to drugs of the viscera of Selachians (Lutz, 1931; Nicholls, 1933 and 1934), but much less attention has been devoted to the teleostean fish. Müller and Liljestrand (1918), in the course of their work on Selachians, investigated briefly the movements of the viscera of various freshwater Teleosts, finding that stimulation both of vagus and splanchnic nerves caused movements of the stomach. Dreyer (1928) showed that the stomach muscle of various marine fish contracts upon addition of pilocarpine, but relaxes with adrenaline. Investigation of the innervation of the viscera of these fish has probably been delayed by the awkward anatomical conditions in the majority of Teleosts. Not only are the organs closely packed in a narrow space, but usually the nerves, and particularly the sympathetic chains, lie in a deep groove below the vertebral column and are covered by dense layers of pigment. For these reasons no attempt was made during the present work to use ordinary fish, but advantage was taken of the more favourable conditions found in two angler fish,Lophius piscatorius andUranoscopus scaber . These two animals are not very closely related and they “angle” in quite different ways, yet both possess certain characteristics which make them very convenient laboratory animals. They are flattened dorso-ventrally, giving easy access to the viscera, they are almost free from internal pigmentation, and, most important of all, the branches of the vagus and sympathetic system can very easily be discovered and stimulated. The anatomy of the autonomic nervous system ofUranoscopus has already been described in some detail (Young, 1931) and that ofLophius is essentially similar.