A glance at these various functions of the cranial division reveals at once that they serve for bodily conservation. By narrowing the pupil of the eye they shield the retina from excessive light. By slowing the heart rate, they give the cardiac muscle longer periods for rest and invigoration. And by providing for the flow of saliva and gastric juice and by supplying the muscular tone necessary for contraction of the alimentary canal, they prove fundamentally essential to the processes of proper digestion and absorption by which energy-yielding material is taken into the body and stored. To the cranial division of the visceral nerves, therefore, belongs the quiet service of building up reserves and fortifying the body against times of need or stress. The Sacral Division a Group of Mechanisms for Emptying Sacral autonomic fibres cause contraction of the rectum and distal colon and also contraction of the bladder. In both instances the effects result reflexly from stretching of the tonically contracted viscera by their accumulating contents. No affective states precede this normal action of the sacral division and even those which accompany or follow are only mildly positive; a feeling of relief rather than of elation usually attends the completion of the act of defecation or micturition--though there is testimony to the contrary. The sacral autonomic fibres also include, however, the nervi erigentes which bring about engorgement of erectile tissue in the external genitals. According to Langley and Anderson[25] the sacral nerves have no effect on the _internal_ generative organs. The vasa deferentia and the seminal vesicles whose rhythmic contractions mark the acme of sexual excitement in the male, and the uterus whose contractions in the female are probably analogous, are supplied only by lumbar branches--part of the sympathetic division. These branches also act in opposition to the nervi erigentes and cause constriction of the blood vessels of the external genitals. The sexual orgasm involves a high degree of emotional excitement; but it can be rightly considered as essentially a reflex mechanism; and, again in this instance, distention of tubules, vesicles, and blood vessels can be found at the beginning of the incident, and relief from this distention at the end.