6-Secs The pneumogastric branches are as follow: 1. The superior cardiac branches, two or three in number, leave the vagus between the superior and inferior laryngeal branches. 2. The inferior cardiac branches arise partly from the superior laryngeal nerve and partly from the main vagus trunk as it enters the thorax. FIG. 6. 4 Secs. DIAGRAMMATIC REPRESENTATION OF THE CARDIAC SOUNDS The sympathetic branches are as follow: 1. The superior cardiac branch from the superior cervical ganglion. 2. The middle cardiac branches (composed of small strands) from the middle cervical ganglion. 3. The inferior cardiac branches derived from several small strands from the inferior cervical and first dorsal ganglia. Physiological experiment shows that in the dog, and presumably in man, the sympathetic fibres leave the spinal cord by the anterior roots of the second and third dorsal nerves, and then pass by the rami communicantes to the ganglia stellata (1st thoracic) and thence by the annulus of Vieussens to the inferior cervical ganglia, whence they are distributed to the heart via the cervical ganglia. 2Secs. All three branches unite in the cardiac plexus, which may be described as consisting of a superficial and a deep portion. The former lies in front of the arch of the aorta on its concave border; the latter lies behind the aorta at a higher level than the superficial portion of the cardiac plexus. From these two plexuses (i.e. superficial and deep) nerves pass directly to supply the auricular walls. The main distribution, however, is by two separate strands which accompany the right and left coronary arteries, and are called the right and left coronary plexuses respectively. The right coronary plexus supplies chiefly the posterior surface of the heart, while the left coronary plexus is distributed mainly over the left ventricle. A large number of ganglion cells are interpolated along the course of the nerves composing these plexuses, more especially in the interventricular and auriculo-ventricular grooves. From these ganglion cells a large number of fine nerve processes penetrate the substance of the heart to be distributed to the individual muscular fibres, as well as to the intermuscular, sub-endocardial, and sub-pericardial tissues. The nuclei of the pneumogastric nerves, or rather those parts of them which supply the heart, viz. the accessory portions, are situated in the medulla oblongata, in close proximity to the respiratory and vaso-motor centres. The sympathetic fibres have also a central connection with cells in the medulla and upper part of the spinal cord. The cells connected with the sympathetic fibres do not appear, however, to be aggregated into a definite centre, but seem rather to be distributed as a series of centres through the upper portion of the spinal cord, with, probably, a controlling centre in the medulla, situated near the pneumogastric nucleus. 66 The regulation of the beat of the heart, so far as this is determined by nervous influences, is effected for the most part, if not entirely, either directly or reflexly, through these centres. With regard to function the pneumogastric centres have been termed cardio-inhibitory," and the sympathetic centres "cardio-accelerator" or "cardio-augmentor," inasmuch as those impulses which diminish the force and rate of the heart's action and prolong diastole, reach the heart by way of the pneumogastric nerves; while those impulses which increase the force and rate of the heart's action and shorten diastole reach the organ by way of the sympathetic fibres. The action of the cardiac centres can be affected 1. Directly, by the condition of the blood, by drugs, by alterations in blood pressure, etc. 2. Reflexly, by— (a) Afferent impulses reaching the centres from the heart. (B) Afferent impulses from other organs, notably from the (7) Afferent impulses from the higher nervous centres originat- (8) Vaso-motor, respiratory, and other influences. It must be borne in mind that, quite apart from nervous influences, the cardiac muscle has the power of independent rhythmical contraction; a power which is, however, but feebly developed in the mammalian heart. Nevertheless the beat of the heart can be, and is, profoundly modified by influences acting directly on the cardiac muscle, and possibly on the cardiac ganglia. The function of the cardiac ganglia is not fully known, but their influence on the regulation or modification of the heart's action is probably quite subsidiary. The more important conditions which exert a direct influence on the cardiac muscle and thereby modify the beat of the heart are :— I. Mechanical stimuli.-The heart is seldom exposed to mechanical stimuli; but the pressure that is not uncommonly exerted on the organ by a distended stomach, etc., may be classed under this head. 2. Alterations in the quantity and quality of the blood, both physiological and pathological; drugs, etc. 3. The degree of distension of the cardiac chambers, as, for instance, may be affected by respiration, alterations in blood pressure, or by disease in the form of valvular incompetence or stenosis of an orifice, etc. Here the distension of one or other of the cardiac chambers increases the tension of its walls, and by this means gives rise, within certain limits, as in the case of skeletal muscle, to a more forcible contraction of the heart. CHAPTER III METHODS OF DIAGNOSIS Enumeration of Methods-Section 1. Symptomatology-Section II. Ætiology— Section III. The Physical Methods of Diagnosis-Sub-section I. Inspection; general; local-Sub-section II. Palpation; Præcordium; great vessels; other organs-Sub-section III. Percussion; Heart; Pericardium; great vessels; other organs-Sub-section IV. Auscultation; Heart Sounds and their Modifications; Adventitious Sounds; Vascular Sounds. THE diagnosis in cases of heart disease is based on 1. The symptoms. 2. The causal conditions indicated by the age, sex, occupation, and history of the patient. 3. The physical examination of the patient, which consists in the use of certain modes of procedure, distinguished under the titles of Inspection, Palpation, Percussion, and Auscultation. These physical methods of diagnosis should always be employed in the order in which they are named. Each element in the diagnosis will now be considered under the headings of Symptomatology, Ætiology, and the Physical Methods of Diagnosis. A short account of the pulse and of the clinical uses of the sphygmograph and cardiograph will complete the chapter. SECTION I SYMPTOMATOLOGY Disease of the heart may exist for a long time without giving rise to symptoms of any kind. Thus it not very uncommonly happens that the presence of a cardiac lesion remains unsuspected until some accidental circumstance, such as a medical examination for life insurance or for one of the public services, reveals its existence. The symptoms of morbus cordis are sometimes referred mainly to the heart itself, but more often they are ascribed. for the most part, to other organs, consequent on the disturbance of function that attends any mechanical derangement of their blood supply. A systemic arrangement of the symptoms will be adopted in the following brief account of the subject. Cardio-vascular system. Apart from pericarditis and angina pectoris, præcordial pain is seldom a prominent feature of heart disease. A feeling of tightness, uneasiness, or pressure in the cardiac region, accompanied possibly by palpitation, or by the FIG. 7. Diagnosis DIAGRAMMATIC REPRESENTATION OF THE DIAGNOSIS consciousness of an irregular or intermittent action of the heart, is sometimes complained of. These symptoms are, however, more commonly due to nervous causes, or to digestive disorders, than to organic disease of the heart. Pulsation may be felt in various situations, more particularly in the region of the head and neck, and is occasionally a source of much discomfort. Noises in the ears are also experienced in connection with abnormal conditions of the circulation. Hæmorrhage from the nose, lungs, stomach, uterus, etc., is by no means uncommon, and may lead to serious loss of blood. Defective supply of blood to the extremities is the cause of the C |