200 A Manual of Veterinary Physiology. 



impulses to the vasomotor centre ; (6) excito-secretory to 

 the salivary glands; (7) excito- motor in coughing and 

 vomiting (Kirke). 



Eleventh Pair, or Spinal Accessory, arises by two roots: 

 one from low down the cervical portion of the cord, the 

 other from the medulla. It is essentially a motor nerve, 

 but through being intimately connected with the pneumo- 

 gastric it also possesses sensory fibres. The use of this 

 nerve is to supply motor power to the sterno-maxillaris, 

 trapezius, and a portion of the levator humeri muscles. It 

 is supposed also to possess an influence over the larynx. 

 Division of it produces no difficulty in breathing, as in the 

 case of the recurrent laryngeal, but it causes loss of 

 voice. 



Twelfth Pair, or Lingual, arises in the lower animals by 

 two roots, a sensory and a motor, the sensory having a 

 ganglion on it. Both roots freely communicate with the 

 pneumogastric, gustatory, and sympathetic. The branches 

 of this nerve supply the tongue with motor power, and 

 fibres to the muscles which depress the larynx. 



The Sympathetic System. 



Passing beneath the vertebra' from the cranium to the 

 coccyx is along chain of nerves, one on either side, com- 

 posed of grey nervous tissue, and possessing on them at 

 regular intervals a number of swellings or ganglia: these 

 are the two main trunks of the sympathetic system. This 

 remarkable system has free communication with all the 

 cranial nerves (excepting the first, second, and eighth), and 

 with the spinal nerves; the conned ion may be direct or 

 through ganglia. It is composed of two systems of fibres : 

 the grey fibres which possess no white substance of 

 Schwann, and the medullated or ordinary cerebro-spinal 

 fibres, the latter being remarkable tor their fineness, and 

 derived from both the superior and inferior roots of the 

 spinal nerves, 15y passing through the ganglia the medul- 

 lated become non-medullated fibres, 



The characteristic feature of the sympathetic system [a 



