516 A MANUAL OF VETERINARY PHYSIOLOGY 



furnished to the submaxillary and sublingual glands. Though 

 the facial is intimately connected with the masseter muscle, 

 as may be seen in the face of a well-bred horse, no motor fibres 

 are supplied to this, nor, in fact, to any of the principal muscles 

 of mastication, it does, however, supply fibres to the stylo- 

 maxillaris, in part to the digastricus, and to two small muscles 

 connected with the hyoid bone. The seventh pair of nerves in all 

 animals control the muscles of expression, of emotion, pain, and 

 pleasure. In the horse they are in addition respiratory nerves 

 of the first importance, as they control every movement of the 

 nostrils. 



Eleventh Pair, or Spinal Accessory. — This is a purely motor 

 nerve, with two roots of origin — viz., the bulb and the spinal 

 cord, as low down as the fifth cervical vertebra?. This latter 

 branch passes up the cord between the motor and sensory roots, 

 receiving filaments on the way, and entering the foramen magnum 

 it joins the root arising from the bulb. In company with the 

 vagus it leaves the skull, then, separating from this nerve, it 

 divides into two branches, which supply the sterno-maxillaris, 

 levator humeri, and trapezius muscles with motor power. 



This nerve furnishes motor fibres to the vagus, and is con- 

 nected with the superior cervical ganglion of the sympathetic. 

 Its course is very remarkable ; having run all the way up the neck 

 within the spinal canal, its dorsal branch passes externally down 

 the neck as far as the upper part of the scapula, and in doing so 

 its object is to innervate the trapezius. It passes by other large 

 muscles of the neck, such as the splenius, without supplying them 

 with any fibres, while all the muscles in the neighbourhood of the 

 trapezius are supplied with motor power direct from the spinal 

 cord. 



Owing to its connection with the vagus nerve, division of the 

 accessory causes loss of voice. Bernard showed that crowing 

 in birds was no longer possible after dividing the root within the 

 spinal canal. 



The Twelfth Nerve, Hypoglossal or Lingual, is the motor nerve 

 of the tongue. It is the last cranial nerve to arise from the. 

 medulla, which it does by means of several filaments. The deep- 

 seated origin is from the hypoglossal nucleus, which is situated 

 in the floor of the fourth ventricle, near the mid-line. The 

 nuclei of both sides are connected by fibres. On its passage to 

 the tongue this nerve establishes connection with the first 

 cervical and the superior cervical ganglion of the sympathetic, 

 and subsequently supplies all the muscles of the tongue, with 

 fibres to those muscles which depress the larynx. 



