The Harvey Society has been founded for the purpose of forming a connecting link between the scientific research work of the laboratories and medical practice. I am greatly indebted to your president for his kind invitation to deliver a lecture before your society. It is my intention to address you to-night on the nervous diseases of the heart. It may be asked whether this is a problem sufficiently scientific to conform fully with the purpose of this society. I hope it is. As a professor of clinical medicine I hold the opinion that an observation made at the bedside is as well to be considered scientific as an observation made on an animal; nor do I think that, because it is unable to speak, the rabbit is a more scientific animal than man. I have selected this subject because it illustrates better than many others that our clinical conceptions