880 THE CENTRAL NERVOUS SYSTEM 



chain, it becomes possible, by systematically painting the ganglia with 

 nicotine, to tell exactly in which of them the fiber finds its effector 

 nerve cell. 



The course and functions of the effector neurons of the three outflows 

 bulbar, thoracicolumbar, and sacral vary in many details and must be 

 considered separately. 



THE THORACICOLUMBAR OUTFLOW, OR SYMPATHETIC 

 SYSTEM PROPER 



The connector fibers are sharply confined in their outflow from the 

 cord between the first thoracic and the fourth lumbar segments, and 

 they run by the white rami communicantes to the sympathetic chain, 

 where some of them connect with effector nerve cells in its ganglia, while 

 others run beyond the chain to find their effector cells in collateral gan- 

 glia represented by the semilunar, superior and inferior mesenteric and 

 the renal in the abdomen. The fibers of the effector cells, often called 

 postganglionic, are distinguished from the connector or preganglionic 

 fibers by being nonmedullated. Those derived from cells in -the lateral 

 sympathetic ganglia proceed to their destination either by way of the 

 gray rami communicantes to the segmental nerves after the fusion of 

 the anterior and posterior spinal roots, or by the outer walls of the blood 

 vessels. (Fig. 231.) 



The effector neurons supply the following structures: 



1. The blood vessels and heart. 



2. The musculature of the sweat glands. 



3. The musculature of the hair follicles and other muscles lying under 

 the skin. 



4. The musculature of the so-called segmental duct, which is repre- 

 sented in the adult by the uterus, Fallopian tubes, ureters, etc. 



5. The sphincters of the intestine. 



Regarding the innervation of the Hood vessels, the exact situation of 

 the ganglia in which the effector neurons are situated and of the nerve 

 roots which contain the connector fibers, is shown in the accompanying 

 table (page 881). 



It is clear that the innervation of the blood vessels is practically con- 

 tinuous, the effector neurons being situated both in the lateral and in the 

 collateral chain of ganglia. Those of the former run to the vessels of 

 structures innervated by the cranial and spinal segmental nerves, while 

 those of the latter supply the vessels of the abdominal and pelvic viscera. 



The connector fibers to the sweat glands are also strictly confined to 

 the thoracicolumbar system, the cell station being found in the ganglion 



