526 A MANUAL OF VETERINARY PHYSIOLOGY 



the nostril and mouth, and secretory fibres to the submaxillary 

 and sublingual glands. Some fibres of the seventh are dis- 

 tributed with the fifth pair of nerves. The fibres from the tenth 

 and eleventh pairs of nerves are widely distributed through the 

 vagus. The cell stations are generally unknown, but are believed 

 to be in the tissues concerned. The autonomic fibres of these 

 pairs supply the heart with inhibitory fibres, the muscle of the 

 bronchi with motor power, viscero-motor fibres to the oesophagus, 

 stomach, and small intestines, and secretory fibres for the gastric 

 and pancreatic glands. 



Spinal Autonomic System. — This is divided into a thoracic 

 and sacral portion. There are no nerves coming off from the 

 cervical cord which joins the autonomic system. The cervical 

 sympathetic, with its ganglia, is furnished from the thorax. 

 The fibres from the thoracic and sacral portion of the cord 

 which join the sympathetic pass out of the canal by means of 

 the ventral roots of the spinal nerves. They are medullated, 

 white in colour, and are known as the white rami communicantes , 

 of which we have previously learnt something (p. 84). One 

 branch is given off at each spinal segment on both sides ; this 

 is the pre-ganglionic fibre (Fig. 156), and if the account previously 

 given of these has been followed, it is evident that this fibre has 

 now to make its way to a cell-station. For this purpose it leaves 

 the ventral root of the spinal nerve, and joins the vertebral ganglia 

 (Fig. 156). Its cell-station may be in the first ganglion of this 

 series with which it meets, and having formed a connection it 

 issues as a post-ganglionic fibre (Fig. 157), or it may pass several 

 ganglia before it comes to its own. On the other hand, its cell- 

 station may not be in the vertebral series, and, having passed 

 through, it then, by means of its fibre, seeks its station in the 

 prevertebral system (Fig. 157), failing which it passes on to the 

 terminal system and finds it there. It is evident that the cell- 

 station of the fibre is connected with its function. If, for instance, 

 the fibres of a vasomotor nerve for the hind-limbs be traced, it is 

 certain that their cell-station will not be in the intestinal wall, but 

 much nearer to the nerves with which they run to their destina- 

 tion — viz., the spinal motor nerves. As a matter of fact, the 

 cell-station for the vasomotor nerves of the hind-limbs and body- 

 wall is in the vertebral ganglia, though not necessarily in the one 

 nearest to the point of issue of the white ramus from the cord. 

 Not only is the vertebral ganglia the cell-station for the nerves 

 supplying the bloodvessels of the hind-limbs and body-wall, but 

 also for the sweat glands and pilomotor fibres of these regions. 

 Nerves for these functions are conveyed by the white ramus to the 

 vertebral ganglia, having, as we have seen, left the ventral spinal 

 root for the purpose. The cell-station having been found, it 



