PREFATORY ADDRESS. BEFORE entering upon the consideration of the diseases of the heart, and in order to illustrate some important pathological phenomena connected with the circulation and respiration, I propose, in the present inquiry, to draw the attention of the reader to some points in the anatomy of the circulating apparatus, and to certain functions of the heart, which I have on a former occasion endeavoured to point out, and by a knowledge of which I am confident that many disorders, not only of the heart, but also of the respiratory and nervous systems, may be satisfactorily explained and rational principles for their treatment established. Whilst prosecuting some investigations concerning the diseases of the heart, and more particularly regarding their causes and treatment, my attention was directed to certain symptoms with which various affections of that organ are accompanied; and, in seeking an explanation of them, I was led to reflect on several natural phenomena connected with the circulation of the blood in the heart, and with the function of respiration, of which no satisfactory explanation had been given, and to some of them no allusion had been made, in physiological writings. I was particularly struck with the influence of respiration on the action of the heart, and with the influence of the action of the heart on respiration, as well as with all the modifications of these functions, not only in diseases, but likewise during the acts of weeping, sobbing, crying, laughing, sneezing, and vomiting, of all which scarcely any notice, far less any satisfactory explanation, is to be found either in physiological or pathological works. I was also led to inquire how it is that the giddiness in B turning round rapidly, in swinging, and sea-sickness should be experienced in some persons and not in others. Having arrived at the conclusion that these various phenomena are intimately connected with the great function of the circulation of the blood, further observations convinced me that each of them is an instinctive act, employed for performing a specific purpose in the economy, some for increasing and others for diminishing the quantity of blood within the thoracic cavities, according as modifications in its quantity are required, or an adjustment necessary in the different organs for the due performance of their respective functions. My attention was no less arrested when contemplating the influence which the almost constant movements of the body produce both on the respiratory and circulating organs. I was led to inquire how the action of the heart and lungs is increased by violent exercise; how persons can, by a process of "training," acquire the power of using their muscles, until the muscular energy is exhausted, without causing breathlessness or a sense of suffocation; in what the art of diving consists; and, finally, how diseases of the heart are caused by inordinate muscular exertions, as well as by violent mental emotions. In pursuing these investigations, I was conducted step by step to establish three important functions-functions connected with the circulation of the blood, which had hitherto been overlooked by physiologists. of First, that the muscles, besides being the active organs locomotion, powerfully influence the circulation in the arteries as well as in the veins, and thus perform the important office of increasing the quantity of arterial as well as of venous blood within the cavities of the heart. Secondly, that the lungs, as a reservoir, regulate the supply of blood to the heart, so as to prevent congestion within the heart's cavities. Thirdly, that the subcutaneous veins likewise perform the office of a reservoir, and prevent congestion of blood within the pulmonary vessels. |