conditions of human existence, changes in mode of living and habits, mental disturbances, and other factors which the progressive development of so-called civilisation has brought in its train. Such disorders are not only met with independently, but not uncommonly supervene, either temporarily or permanently, in cases of organic disease, thus adding, it may be seriously, to their difficulties and dangers. While painful and other abnormal sensations in connection with the heart, even the complaint known as "angina pectoris," as well as disturbances of the cardiac action, have long been recognised in a general way, it is only within a comparatively recent period that these conditions were at all studied on methodical and scientific lines. Obviously, no rational conception or explanation of the functional disorders of the heart was possible prior to the knowledge of the muscular nature of its walls, and of its innervation and nervous relations, which were not discovered until well on in the last century, and only worked out practically during its latter half. During recent years the subject has attracted special attention on the part of numerous observers, and many important facts have been, and are still being brought to light. These are founded upon a more precise and accurate knowledge of the structure and mode of action of the heart; of the nervous apparatus associated with the organ, its functions, connections with other nerves, and relation to the
