DIVISIONS OF THE SYMPATHETIC. 719 



Light is thrown upon the significance of the ganglia in the sympa- 

 thetic system by poisoning with nicotin. In an animal thus poisoned 

 the ganglion-cells are paralyzed, for irritation of the ganglia is without 

 effect, as is also irritation of the nerves passing to the ganglion. On the 

 other hand, irritation of the nerve-fibers that pass peripherally from the 

 ganglion is still attended with results. 



As to the functions of the sympathetic only a general summary will be 

 given here. 



I. Independent junctions of the sympathetic are those of certain 

 plexuses that persist after all the nervous connections with the cerebro- 

 spinal axis are severed. These include: 



1. The automatic ganglia of the heart. 



2. The myenteric plexus of the intestine. 



3. The plexuses of the uterus, the oviducts, the vasa deferentia, and 

 also of the blood-vessels and the lymphatics. The activity of these 

 plexuses may be in part stimulated, in part inhibited, through centrifugal 

 nerves from the cerebrospinal axis. 



II. Dependent F~ unctions. The sympathetic contains also fibers that, 

 like the peripheral nerves, functionate only in connection with the cen- 

 tral nervous system, for example the sensory fibers in the splanchnic 

 nerve. Other fibers convey to ganglia impulses received from the cen- 

 tral nervous system, the ganglia in turn conducting the stimuli further 

 on in the form of inhibition or motion to the respective organs. 



A. CEREBRAL AND CERVICAL DIVISION OF THE SYMPATHETIC. 



1. Pupil-dilating Fibers. According to Budge, these arise from the spinal 

 cord, and they pass, according to Langley, through the three or four uppermost 

 dorsal nerves in the sympathetic cord and ascend to the head (in the cat) . Division 

 of the sympathetic cord or its communicating branches causes, therefore, con- 

 traction of the pupil. The central origin of these fibers is discussed on pp. 734 

 and 749. 



2. The motor fibers for the unstriated muscles of H. Mtiller in the orbit and 

 the lids and for the external rectus pass in part through the dorsal nerves from 

 the first to the fifth (in the cat). According to Frl. Klumpke and Oppenheim the 

 communicating branch of the first dorsal nerve in man is the path for i and 2. 



3. Vasomotor fibers for the vessels of the external ear and the side of the 

 face, the tympanic cavity, the conjunctiva, the iris, the choroid, the retina (only 

 in part), the pharynx, the larynx, the thyroid gland, the brain and its mem- 

 branes, derived from the thoracic nerves from the first to the fifth. 



4. The cervical sympathetic cord contains centripetal fibers that stimulate 

 the vasomotor center in the medulla oblongata. 



5. Secretory, trophic, and vasomotor fibers for the salivary glands, appearing 

 in the thoracic nerves between the first and the fifth. 



6. The sweat-fibers are described on p. 537. 



7. Also the lacrimal glands receive sympathetic secretory fibers. 



B. THORACIC AND ABDOMINAL DIVISION OF THE SYMPATHETIC. 



1. This division includes first the sympathetic portion of the cardiac plexus, 

 which sends to the heart accelerator fibers from the inferior cervical and the 

 superior thoracic ganglion arising (in the cat) from the upper cervical nerves 

 between the first and the sixth. 



2. The vasomotors for the extremities, the skin of the trunk, the lungs (in 

 part from the vagus), passing through the sympathetic are described on p. 763, 

 the vasodilators on p. 772. 



3. The pilomotor fibers arise from the nerves between the fourth thoracic and 

 the third lumbar. They pass to the sympathetic cord, where a ganglion-cell is 



