When the heart is not able to accomplish its work, the effect of the condition becomes apparent by the accumulation of blood within the veins and a less active circulation.  This affects the nutrition and the capacity for work of all the organs of the body, and the imperfect function of the organs may in a variety of ways make still greater demands upon an already overloaded heart.  Other conditions supervene.  The increased pressure within the veins and capillaries due to the impossibility of the blood in the usual amount passing through or from the heart increases the amount of fluid in the tissues.  There is always an interchange between the blood within the vessels and the fluid outside of them; the passage of fluid from the vessels is facilitated by the increased pressure within them, just as pressure upon a filtering fluid increases the rapidity of filtration, and the increase of pressure within veins and capillaries impedes passage of tissue fluid into them.  The fluid accumulates within the tissues leading to dropsy, or the accumulation may take place in some of the cavities of the body.  The diminished flow of blood through the lungs prevents its proper oxygenation; this may also be interfered with by the accumulation of fluid within the air spaces of the lungs.

Every additional burden thrown upon the heart increases the evil.  In women the additional burden of pregnancy may suffice to overcome a compensation which has been perfect, and the same may result from an acute attack of disease.  Age, diminishing as it does the capacity for work in all organs, diminishes the compensation capacity of the heart, and a heart which at the age of forty acts perfectly may break down at the age of fifty.  Compensation may be gained in other ways, as by reducing the demand made upon the heart by changing the mode of life, by leading an inactive rather than an active life, by avoiding excitement or any condition which entails work of the heart.  Social conditions are of great importance; it makes a great difference whether the unfortunate possessor of such a heart be a stevedore whose capital lies in the strength of his muscles, or a more fortunately placed member of society for whom the stevedore works and whose occupation or lack of occupation does not interfere with the adjustment of his external relations to the condition of his heart.

Disease of the nervous system does not differ from disease elsewhere.  The system is complex in structure and in function.  It consists in nerves which are composed of very fine fibrils distributed in all parts of the body and serve the purpose of conduction, and a central body composed of the brain and spinal cord which is largely cellular in character; it receives impressions by means of the nerves and sends out impulses which produce or affect action in all parts.  By means of the organs of special sense, the brain receives impressions from the outer world which it transforms into the concepts of consciousness.  Many of the