Abstract
The heart activity in all vertebrates is regulated by the nervous system and in the phyla above the fishes the heart is under the control of augmentor and inhibitory nerves. In the Teleost fishes there is an abundance of evidence that the vagus exhibits a powerful control over the heart. McWilliam, 1 Mills, 2 Bottazzi, 3 Armstrong, 4 and Brinley 5 have shown that the hearts of various fishes can be arrested either by direct or reflex vagal stimulation. On the other hand, there is no positive evidence that the heart of the Teleost fishes is innervated by the sympathetic system. Bottazzi 3 found that stimulation of the sympathetic system produced no effect on the heart rate. Brücke 6 stated that there is no evidence that the fish heart is controlled by accelerator fibers. However, Izquierdo 7 has shown that the heart of the shark, Scyllium, is under the control of the vagus and sympathetic nerves much the same as in the other cold blooded vertebrates.
The work of Izquierdo opens the question as to whether or not there is a sympathetic innervation of the Teleost heart. In connection with a study on the effect of drugs on the fish heart, a study was made on the action of substances known to stimulate the sympathetic system of higher vertebrates, on the embryonic and adult fish heart, to determine if the cardio-regulator nerves contain accelerator fibers. It is realized that no drug is strictly specific in its action on the nerves of the cardiac apparatus but it is believed that adrenalin and nicotine in proper concentrations approach this condition to a fair degree. This paper is concerned only with the action of adrenalin on Fundulus heteroclitus embryos.
A minute droplet of adrenalin chloride, from 1 part in 1000 to 1 in 50,000 distilled water was injected into Fundulus embryos (free from chorion) anterior to the vitalline arteries.
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