DEFINITION.—In the term vaso-motor and trophic neuroses it is intended to include a number of forms of disturbance of circulation and nutrition which are caused by disorders of the nervous system. Such disturbances may occur in any part of the body. They are not to be regarded as distinct diseases, but rather as symptoms of lesions in the peripheral or central nervous system. They may present themselves in various forms, as hyperæmia or anæmia or instability of vascular tone, as atrophy or hypertrophy or disintegration of normal tissue. Their consideration cannot, however, be assigned to any previous department of this volume nor relegated to various divisions of it; partly because in some cases they are to be traced to lesions of the sympathetic system, not elsewhere considered; partly because of our ignorance as to the exact location in many cases of the lesion of which they are manifestations.
It is probable that at a future time this chapter will disappear from a system of medicine, as the chapter on ascites has disappeared, and that the symptoms under consideration will be distributed among various departments as symptoms of ascertained lesions in various organs. For the present, however, they demand a separate discussion.
It is not possible to distinguish accurately in all cases between the vaso-motor and the trophic neuroses, for while in many features they are distinct, in a large proportion of cases they occur together. But it is not possible to ascribe all trophic changes to vascular disturbance, nor all vaso-motor changes to a defect or excess of trophic action. Hence a separate consideration of these allied subjects must be given. It is always to be remembered, however, that each may give rise to the other, and that in their pathology they are closely connected. Vaso-motor disturbances manifest themselves (1) by a dilatation of the vessels, producing redness, heat, and rapid metabolism in the part affected; or (2) by a contraction of the vessels, causing pallor, coldness, and malnutrition; or (3) by an alternation of these conditions and consequent temporary disturbance of function. Trophic disturbances may occur in consequence of such increase or decrease of blood-supply, or independently of any vascular change, causing (1) an abnormal production of tissue in an organ, or (2) a decrease in the size and number of its constituent cells, or (3) an actual degeneration of the elements which make it up, after which their place may be taken by another kind of tissue. Under all these circumstances the function of the part affected will be disturbed, and symptoms will be produced which will vary with the tissue or organ involved. Hence a general consideration of these symptoms must be given. Before proceeding to a detailed consideration of these neuroses it is necessary to review the physiology of the vaso-motor and trophic systems, in order to make clear the manner in which they perform their functions. And inasmuch as the pathology of these affections is best understood by comparison with experimental lesions made by physiologists in investigating their function, it will be treated together with their physiology.
Vaso-motor Neuroses.
FIG. 56.
Vaso-motor Nerves and Ganglia accompanying the Arterioles in a Frog (Gimbert): C, arterioles; N, vaso-motor nerve; G, ganglion, from which nerves issue, situated at the point of anastomosis of several capillaries; R, fibre of Remak.
PHYSIOLOGY.—Local Vascular Tone.—Since changes in the force and frequency of the heart's action, and variations in the total amount of blood in the body, affect the body as a whole, the state of circulation in any one organ or part must be dependent upon the degree of contraction or dilatation of its own vessels. This is known as the local vascular tone. It is under the control of a system of nerve-ganglia with their subservient fibres which are found in the middle coat of all arterioles (Fig. 56). The energy expended by these ganglia is manifested by a constant moderate contraction of the circular muscular coat of the artery—a contraction which is as constantly opposed by the dilating force of the blood-pressure within the vessel. An exact equipoise between these two forces never occurs, since each varies constantly, but in a state of health one never becomes permanently excessive. Considerable variations, however, in the local vascular tone are frequently observed. Thus each organ is influenced to a certain degree by every other, since an increase of blood in one part must involve a decrease in all other parts, the total amount of blood in the vessels being constant. Alteration in the heart's action is felt more quickly in some organs than in others, and thus the general blood-pressure by its variations may cause secondarily a disturbance of local vascular tone. The variations now under consideration, however, are not of this kind. They are such as are produced by influences acting directly upon the ganglia in the vessel-walls.