On this subject Mrs. Besant writes:--"The lower forms of psychism are more frequent in animals and in very unintelligent human beings than in men and women in whom the intellectual powers are well developed. They appear to be connected with the sympathetic system, not with the cerebro-spinal. The large nucleated ganglionic cells in this system contain a very large proportion of etheric matter, and are hence more easily affected by the coarser astral vibrations than are the cells in which the proportion is less. As the cerebro-spinal system develops, and the brain becomes more highly evolved, the sympathetic system subsides into a subordinate position, and the sensitiveness to psychic vibrations is dominated by the stronger and more active vibrations of the higher nervous system. It is true that at a later stage of evolution psychic sensitiveness reappears, but it is then developed in connection with the cerebro-spinal centres, and is brought under the control of the will. But the hysterical and ill-regulated psychism of which we see so many lamentable examples is due to the small development of the brain and the dominance of the sympathetic system."
Occasional flashes of clairvoyance do, however, sometimes come to the highly cultured and spiritual-minded man, even though he may never have heard of the possibility of training such a faculty. In his case such glimpses usually signify that he is approaching that stage in his evolution when these powers will naturally begin to manifest themselves, and their appearance should serve as an additional stimulus to him to strive to maintain that high standard of moral purity and mental balance without which clairvoyance is a curse and not a blessing to its possessor.
Between those who are entirely unimpressible and those who are in full possession of clairvoyant power there are many intermediate stages. One to which it will be worth while to give a passing glance is the stage in which a man, though he has no clairvoyant faculty in ordinary life, yet exhibits it more or less fully under the influence of mesmerism. This is a case in which the psychic nature is already sensitive, but the consciousness is not yet capable of functioning in it amidst the manifold distractions of physical life. It needs to be set free by the temporary suspension of the outer senses in the mesmeric trance before it can use the diviner faculties which are but just beginning to dawn within it. But of course even in the mesmeric trance there are innumerable degrees of lucidity, from the ordinary patient who is blankly unintelligent to the man whose power of sight is fully under the control of the operator, and can be directed whithersoever he wills, or to the more advanced stage in which, when the consciousness is once set free, it escapes altogether from the grasp of the magnetizer, and soars into fields of exalted vision where it is entirely beyond his reach.