Every nerve cell has two functions, one connected with sensation or motion, and the other with growth. If the cell be tired by excessive work along the line of sensation or motion the function as regards growth becomes later impaired, and it not only ceases to continue in strength, but becomes self-poisoned. Each of the organs (heart, liver, kidneys, &c.) has its own system of nerves (the sympathetic ganglia), which while under control by the spinal cord and brain act independently. If these nerves become tired the organ fails to perform its function, the general system becomes both poisoned and ill-fed, and nervous exhaustion results. In most cases, however, the brain and spinal cord are first exhausted. The nerves of the organs are thus allowed too free play, and exhaust themselves later. This systemic exhaustion has local expression in the testicles in the male, in the womb and ovaries in the female. Through this the body is imperfectly supplied with natural tonics (antitoxins) formed by the structures, and the general nervous exhaustion becomes still more complete. All the organs of the body are weakened in their function. Practically the neurasthenic in regard to his organs has taken on a degenerative function albeit not degenerating in structure, since the restlessness of the organs is a return to the undue expenditure of force which occurs in the lower animals in proportion as it is unchecked by a central nervous system. Through the influence of various exhausting agencies the spinal cord and the brain lose the gains of evolution and the neurasthenic is no longer adjusted to environment. Since the reproductive organs suffer particularly, children born after the acquirement of nervous exhaustion, more or less checked in development as the influence of atavism is healthy or not, repeat degenerations in the structure of their organs, which in the parent were represented by neurasthenic disorders in function. As the ovaries of the neurasthenic women generally exhibit prominently the effects of the nervous exhaustion, the offspring of these do not retain enough vigour to pass through the normal process of development. CHAPTER III HEREDITY AND ATAVISM