5ir. THE RABBIT riiAr, 



and bulb by numerous fibres, the posterior of whicli are op- 

 posite the fifth spinal nerve, from which point it runs forwards 

 between the dorsal and ventral roots and leaves the skull 

 together with the glossopharyngeal and vagus (p. 479), sup- 

 plying certain muscles of the neck and shoulder. The 

 hypoglossal arises by a number of fibres from the ventral 

 surface of the bulb, passes out through the condylar foramen 

 and supplies the muscles of the tongue as well as certain 

 muscles of the neck. 



The origin and distribution of the first ten pairs of cereliral nerves 

 correspond in their main features with ihose seen in the frog. The facial 

 is almost entirely a motor nerve and is chiefly important in supplying 

 the facial muscles, which are ver)- highly developed in Mammals. 



The relations of the sympathetic nerves (Fig. 125,^.7) are 

 also essentially similar to those occurring in the frog (p. 162). 

 Each passes backwards along the neck close to the vagus 

 (7,'^) and alongside the carotid artery, enlarging at each end 

 of this region to form an anterior and a posterior cervical 

 ganglion. In the thorax it runs just beneath the heads 

 of the ribs, having a ganglion in each intercostal space : 

 it then passes into the abdomen, lying close to the centra 

 of the vertebrre and having ganglia at intervals. From all 

 the sympathetic ganglia branches are given off connecting 

 them with the spinal nerves, others going to the blood- 

 vessels : others again, in the thorax and abdomen, are 

 connected with plexuses from which nerves pass to the 

 heart and abdominal viscera. In the abdomen these 

 |)lexuses can be seen in the mesentery, a large celiac plexus 

 being present close to the origin of the cceliac and mesen- 

 teric arteries. 



Sensory Organs. — The sense of touch is situated in micro- 

 scopic tactile organs in the skin, and groups of cells, called 



