Although distention is the commonest occasion for bringing the sacral division into activity it is not the only occasion. Great emotion, such as is accompanied by nervous discharges via the sympathetic division, may also be accompanied by discharges via the sacral fibres. The involuntary voiding of the bladder and lower gut at times of violent mental stress is well known. Veterans of wars testify that just before the beginning of a battle many of the men have to retire temporarily from the firing line. And the power of sights and smells and libidinous thoughts to disturb the regions controlled by the nervi erigentes proves that this part of the autonomic system also has its peculiar affective states. The fact that one part of the sacral division, e. g., the distribution to the bladder, may be in abeyance, while another part, e. g., the distribution to the rectum, is active, illustrates again the directive discharge of impulses which has been previously described as characteristic of the cranial and sacral portions of the autonomic system. Like the cranial division, the sacral is engaged in internal service to the body, in the performance of acts leading immediately to greater comfort. The Sympathetic Division Antagonistic To Both The Cranial and the Sacral As indicated in the foregoing description many of the viscera are innervated both by the cranial or sacral part of the autonomic and by the sympathetic. _When the mid-part meets either end-part in any viscus their effects are antagonistic._ Thus the cranial supply to the eye contracts the pupil, the sympathetic dilates it; the cranial slows the heart, the sympathetic accelerates it; the sacral contracts the lower part of the large intestine, the sympathetic relaxes it; the sacral relaxes the exit from the bladder, the sympathetic contracts it. These opposed effects are indicated in Fig. 1 by + for contraction, acceleration or increased tone; and by - for inhibition, relaxation, or decreased tone.[*] *[Footnote: The vagus nerve, when artificially stimulated, has a primary, brief inhibitory effect on the stomach and small intestine; its main function, however, as already stated, is to produce increased tone and contraction in these organs. This double action of the vagus is marked thus, ∓, in Fig. 1.]