tion which is most natural and best suited to invite the least disturbance of the functions of the great organs. To use the analogy of the four-footed animals, and by such facts we can secure the safest guidance, the best position is on the abdomen or nearly so. Habits may, and do, vitiate our instincts here as elsewhere, and we can accustom ourselves to many departures from natural and advisable operations. This is especially forceful while in vigorous health, but we are speaking here of securing the best rest with the least tax upon our organism, hence it is well to determine those means which are normal, and employ them. The body should lie as nearly as possible on a level, head and feet as well as body, on the side inclined toward the abdomen, adjusting arms and legs in such a fashion as shall not permit undue pressure upon nerves and bloodvessels, direct or indirect.
To lie on the back is objectionable for the reason that long continued pressure on the tissues adjacent to the vertebral column, which are innervated by the posterior primary divisions of the spinal nerves, exerts a continued irritation through vasomotor connections to the viscera, disturbing the circulation in the segments. Here are the cell bodies of the vasomotor nerves, which thence pass to the organs and beyond parts, thereby governing function. Thus, dilatation is induced and maintained in the blood vessels of the viscera. Also certain results follow directly by effect of gravity. Pressure on the abdominal organs, and their varying contents, is exerted upon the great vessels, arterial, venous and lymphatic, the sympathetic plexuses, and the ebb and flow of fluid in them is deranged. Hence function and nutrition of these structures are influenced unfavorably. Man is the only animal which sleeps on the back. This attitude should only be assumed for short periods. During extreme weakness this position is often taken, but it is the duty of attendants to urge a frequent change to the side, otherwise several hurtful effects may follow, among which the least grave are nightmare and evil dreams. The poisons of katabolism circulating in the blood tend to be deposited in the outlying tissues; hence arise pneumonia and bedsores. Not only is this true for those who are suffering from one or another form of disability, but for those in robust health, especially when sleeping on the back after full meals. Many obscure forms of digestive or circulatory disorders may have been initiated in infancy through lying too long upon the back.
In animals, among whom such disorders are rare and whose spinal column is constantly horizontal, there is little or no change in the relative positions of the great organs at any time. In man, who is constantly altering the relationships of these viscera by lying, standing, stooping, the blood supply and venous return are subject to frequent interruptions, and strains are exerted upon the supporting structures
