THE SUPRARENAL SYSTEM IQI 



terior extremities. The system has been variously named " vegeta- 

 tive," "sympathetic," "organic," and " ganglionary," but 

 Langley abandons these terms in favour of the more comprehen- 

 sive word "autonomous." Following Gaskell's division of the 

 system into three groups, he names them as follows : (i) the 

 cranio-cervical ; (2) the thoraci-columbal ; (3) the sacral. The 

 central portion of the thoraci-columbal system, together with the 

 thoracic and ventral chains and their plexuses and branches, forms 

 the "sympathetic" system in its more limited sense; and with 

 these must be included the plexuses which Anerbach and Meissner 

 regarded as forming a separate intestinal nervous system. 



The term "autonomous nervous system," as employed by 

 Langley and the English authors following him, includes, then, 

 all those nerves by which the involuntary organs are supplied, 

 and according to this nomenclature the " sympathetic system " is 

 a subdivision only of the great autonomous system. Other later 

 authors, and the Germans more particularly, regard the sym- 

 pathetic as distinct from the autonomous system ; they include 

 under the former heading, the prevertebral chains, and those nerve 

 fibres whose roots are centred in the cord in a series 'extending 

 from the first thoracic to the fourth lumbar nerves. Under this 

 system of classification the autonomous system comprises : (i) the 

 cranio-bulbar nerve fibres, which are derived from the meso- 

 cephalon and the medulla oblongata, and which include the 

 oculomotor (III), the facial (VII), the glossopharyngeal (IX), and 

 the vagus (X) nerves ; (2) the sacral nerve fibres, which proceed 

 from the lower lumbar and sacral portions of the spinal cord, and 

 which combine to form the pelvic nerve. 



This system of classification is based upon the fact that nearly 

 all vegetative organs possess a double innervation. 



The sympathetic system supplies the involuntary muscles all 

 over the body, including those of the organs and of the vessels, 

 and it also innervates the glands. But an exclusively sympathetic 

 innervation belongs only to the sweat glands, the hair muscles 

 of the skin, and a portion of the muscular structure of the 

 intestinal vessels. In all other parts of the body there is, in 

 addition to the sympathetic innervation, a cranial-autonomous or 

 sacral-autonomous innervation, and in certain instances, as in the 

 vasodilators of the extremities, there is also a spinal nerve supply. 

 In many cases, the autonomous nerves are actually the physio- 

 logical antagonists of the sympathetic nerves, influencing the 

 voluntary muscles, the glands, vessels and heart in a manner 

 diametrically opposed to that of the sympathetic nerves. Where 

 the sympathetic in such instances promotes activity, the auto- 

 nomous nerves inhibit it. 



It was at first believed that the stimulatory and inhibitory 

 nerves must be derived from different portions of the nervous 

 system, the one belonging to the sympathetic, the other to the 



