Page:Popular Science Monthly Volume 25.djvu/822

804 any, in producing the effect. That it is not an essential factor is, to some extent, confirmed by the fact that a frog without the cerebral hemispheres can be easily mesmerized; it is difficult to conceive of the animal in this state being very much frightened.

It will be remembered that reflex action from all parts of the body is diminished in the mesmerized frog. After a time, then, there is a marked inhibition of activity of the whole nervous system. Now, in the brainless frog placed on its back there is no such diminution of reflex action; hence in the intact hypnotized frog the spinal cord must be inhibited by impulses coming from the brain; from which we may conclude that centers inhibited in their own proper action nevertheless send out inhibitory impulses to other centers. There appears, then, to be an irradiation of inhibitory impulses, just as we have seen that there is an irradiation of exciting impulses.

Before passing to mesmerism in man I will show you two other instances of hypnotism in the lower animals. The alligator which you see here behaves very much like the frog. It has, however, less tendency to become cataleptic. After a brief struggle, it becomes quiescent and its limbs slowly relax; its mouth may then be opened, and a cork placed between its teeth, without giving rise to any voluntary movement on its part. It may be kept for a considerable time in this limp condition by gently stroking the skin close to its eyes.

So far as I have observed, the hypnotic condition in birds and in lower mammals is not capable of any great development. It may last ten minutes, but rarely longer. In these animals, too, the emotional condition is probably the chief factor in producing the inhibition. Of impulses from peripheral sense-organs, tactile impulses seem to be most effective in the lower mammals, as in the rabbit and Guinea-pig, and visual impulses in the bird. The pigeon which I have here remains longest quiescent when, after it has been held for a minute or two, I bring my hand slowly up and down over its head.

In man the phenomena of mesmerism are of a very much more striking character than they are in the lower animals. Speaking generally, this seems to be due to a greater interdependence of the various parts of the nervous system in the lower animals. In these, when any one center is stirred up by exciting impulses, an irradiation of exciting impulses is apt to take place to all other centers, and the mesmeric state is in consequence apt to be broken. And on the other hand, when a center is inhibited, an irradiation of inhibitory impulses is apt to take place, and the whole nervous system is in consequence apt to be inhibited. Hence the activity or suppression of activity of particular parts of the central nervous system, which forms so conspicuous a feature of mesmerism in man, can be only partially produced in the lower vertebrates. Even in man there is very considerable difference, in different individuals, in the ease with which particular nerve-centers can be excited or inhibited without other centers being similarly