720 PHYSIOLOGY. 



lows the lumbar vertebral chain. This prevertebral chain receives 

 elements of reinforcement by two remarkable paths. The first is 

 that of the vagus, which carries bulbar influences. The second is 

 that path formed by the nervi erigentes, which come off from the 

 second and third sacral nerves and, like the bulbar and midbrain 

 nerves, do not enter the sympathetic ganglia, but go to the hypo- 

 gastric plexus near the bladder, where the fibers have their cell-sta- 

 tion. They are vasodilator nerves to the pelvic organs, inhibit the 

 retractor penis, and are motor to the bladder, colon, and rectum. 



In the heart and lungs, the vagus is inhibitory and the sympa- 

 thetic is accelerator. For the gastric and intestinal muscles the 

 pneumogastric mainly augments, whilst the sympathetic chiefly 

 inhibits. 



Arm. These fibers come out by the fourth to tenth dorsal 

 nerves, and send fibers to the stellate ganglion and from there pass 

 into the spinal nerves, and go to the blood-vessels, sweat-glands, and 

 pilomotor muscles of the skin and limb. 



Leg. These fibers take origin from the eleventh dorsal to third 

 lumbar nerves, and come out of the last two lumbar and first two 

 sacral ganglia and go to the leg in the spinal nerves, to supply the 

 blood-vessels and pilomotor muscles and secretory nerves. 



Langley regards the nerve-cells of Auerbach and Meissner's 

 plexus of the intestinal tract (the enteric nervous system) as differ- 

 ent, both from the sympathetic and parasympathetic system. He 

 does not know if they are connected with the sympathetic or para- 

 sympathetic, but doubts it. Magnus has shown that the nerve-cells 

 of Auerbach's plexus are reflex centers for the rhythmic contractions 

 of the intestines. Langley believes that in the intestine there are 

 two sets of nerve-eel's, one motor, the other inhibitory, both acting 

 on the muscular tissue, the state of the muscle depending on the 

 balance of the two forces. 



Afferent Fibers. They have their cell-station in the ganglion of 

 the posterior root. They enter the cord largely by the white rami. 

 Normally, stimulation of their peripheral endings does not lead to 

 modifications of consciousness, and is therefore not accompanied by 

 pain. In abnormal conditions painful sensations are produced. 



Head has shown that the sensation of pain from visceral dis- 

 eases is referred to certain points on the surface of the body. Thus, 

 intestinal trouble causes pain in the skin of the back, abdomen, and 

 loins. In stomach troubles, the pain is referred to the ensiform 

 cartilage ; in disease of the heart, to the scapular region. Here the 



