That does not mean that the field in which psychotherapeutics may work directly on the body is not after all a large and interesting one. Theoretically it is still little open to real understanding. The explanation has essentially to rest on the acceptance of a given physiological apparatus. A certain psychophysical excitement produces by existing nerve connections a certain effect, for instance, on the blood-vessels or on the glands of a certain region, or on a certain lower nervous center. That such apparatus exists, the physiological experiment with persons who are hypnotized to a high degree can easily demonstrate. Their nose bleeds at a command; a blister may arise on a part of the skin which is simply covered with a penny, when the suggestion is given that the penny is glowing hot. With some subjects, the pulse can become slower and quicker in accordance with the suggestion; with some even the bodily temperature can change on order. Our understanding of these indubitable facts indeed does not go further than the acknowledgment that the paths for such central connections exist. That means we simply describe the facts once more in the terms of anatomy. But after all in the same way we rely on the nervous connections, if a thought makes us blush and ultimately if our will moves our arm or if our ideas move our speech apparatus. We do not choose the muscles of our arm, we hardly know them; we know still less in speaking, of the movements of our vocal cords, and in blushing of the dilated blood-vessels. That ideas work on the lower centers of our central nervous system, centers which regulate the actions of our muscles and blood-vessels and glands, must simply be accepted as the machinery of our physiological theory. The connection of such theories with purely physical facts is given by the experience that an electrical stimulation of the nerve may have the same influence as ideas. The electric current, too, can regulate the beat of the heart, or contract and dilate the vessels, or reenforce and relax the contraction of the muscles, or strengthen and weaken the functions of the glands.