The skeletal muscles receive their nerve supply direct from the central nervous system, i. e., the nerve fibres distributed to these muscles are parts of neurones whose cell bodies lie within the brain or spinal cord. The glands and smooth muscles of the viscera, on the contrary, are, so far as is now known, never innervated directly from the central nervous system.[*] The neurones reaching out from the brain or spinal cord never come into immediate relation with the gland or smooth-muscle cells; there are always interposed between the cerebrospinal neurones and the viscera extra neurones whose bodies and processes lie wholly outside the central nervous system. They are represented in dotted lines in Fig. 1. I have suggested that possibly these outlying neurones act as “transformers,” modifying the impulses received from the central source (impulses suited to call forth the quick responses of _skeletal_ muscle), and adapting these impulses to the peculiar, more slowly-acting tissues, the secreting cells and visceral muscle, to which they are distributed.[21] *[Footnote: The special case of the adrenal glands will be considered later.] The outlying neurones typically have their cell bodies grouped in ganglia (G’s, Fig. 1) which, in the trunk region, lie along either side of the spinal cord and in the head region and in the pelvic part of the abdominal cavity are disposed near the organs which the neurones supply. In some instances these neurones lie wholly within the structure which they innervate (see e. g., the heart and the stomach, Fig. 1). In other instances the fibres passing out from the ganglia--the so-called “postganglionic fibres”--may traverse long distances before reaching their destination. The innervation of blood vessels in the foot by neurones whose cell bodies are in the lower trunk region is an example of this extensive distribution of the fibres. [Illustration: Figure 1.--Diagram of the more important distributions of the autonomic nervous system. The brain and spinal cord are represented at the left. The nerves to skeletal muscles are not represented. The preganglionic fibres of the autonomic system are in solid lines, the postganglionic in dash-lines. The nerves of the cranial and sacral divisions are distinguished from those of the thoracico-lumbar or “sympathetic” division by broader lines. A + mark indicates an augmenting effect on the activity of the organ; a - mark, a depressive or inhibitory effect. For further description see text.] The Three Divisions of the Outlying Neurones