STUDIES ON THE CONDITIONS OF ACTIVITY IN ENDOCRINE ORGANS

Abstract

Experiments yielding negative evidence are summarized: After complete denervation of the heart and exclusion of all known humoral cardio-accelerator agencies a momentary excitement and struggle will cause, in cats, a slow increase of the cardiac rate, reaching a maximum in about 3 min. and then slowly subsiding. Repeated struggles cause summation of effects on the heart rate. Full anesthesia (with ether, urethane or chloralose) greatly reduces and may abolish the phenomenon, i.e., stimulation of muscles and the sympathetic system under anesthesia does not produce the typical effect on the heart rate. Experiments are described which show that the phenomenon is not due to rise of arterial blood pressure, increase of temp., escape of adrenin from the denervated adrenal medulla or cortex, or from the liver, nor due to substances produced by the pancreas, gastro-intestinal mucosa, semi-lunar ganglia, pituitary body, gonads, thyroids, parathyroids, or active skeletal muscles. Transection of the thoracic spinal cord in the prepared cat leaves the fore part of the animal with the denervated heart, and the hind part with the denervated adrenal and liver, but with the lower abdominal sympathetic strands still intact. Struggle by the fore part of the animal is without effect; stimulation of the spinal cord in the lumbar region, causing muscular spasm and erection of the tail hairs, is followed by the typical slow rise and fall in the rate of the denervated heart. Obviously a substance is given off into the blood-stream by the hind part of the animal that affects the heart in the fore part. If all parts of the sympathetic system are disconnected from the spinal cord, except short ganglionated strands in the lower thorax, struggle causes the usual cardiac acceleration; but after the remnants of the system are excised, struggle no longer has that effect. This condition may last for many wks.