212 CLINICAL APPLIED ANATOMY. 



tongue, soft palate and vocal cord results. A lesion outside 

 the base of the skull may involve the same nerves after their 

 exit and produce paralysis of similar distribution. Tumours 

 and inflammatory affections at the base of the skull, disease of 

 the occipito-atloid joint and caries of the highest cervical vertebrae 

 may all implicate the hypoglossal and adjacent nerves in this 

 way. 



Unilateral paralysis of the tongue results in its deviation 

 towards the paralysed side when protruded owing to the un- 

 balanced action of the sound genio-glossus muscle. When at 

 rest in the mouth the root of the tongue appears higher on the 

 paralysed side from loss of tone in the hyoglossus of that side. 

 Unless the paralysis is bilateral there is but little interference 

 with the power of chewing, deglutition or articulation. If the 

 lesion be nuclear or infranuclear the tongue wastes, and as a 

 result the mucous membrane of the affected half appears too 

 large for it and is thrown into folds. There is also a reaction 

 of degeneration in the affected muscles. 



THE SPINAL CORD. 

 MYELITIS. 



In most cases myelitis appears to be due to an infective agent 

 carried to the spinal cord by the blood stream. The rarity with 

 which inflammation of the spinal cord follows injury is no doubt 

 due to the efficient way in which it is protected by the vertebral 

 canal, and the intervention of the membranes with their fluid 

 contents between the cord and its bony sheath. Notwithstanding 

 this, inflammation of the cord has been known to follow falls 

 from a height on to the feet, blows, twists or wrenches of the 

 spine, quite apart from fractures and dislocations. 



Inflammation may spread directly to the cord from the verte- 

 bral canal, or from the encasing membranes, and, in the latter 

 case, may show an annular peripheral distribution which is no 

 doubt brought about by the way in which the pial septa penetrate 

 the periphery of the cord carrying with them small vessels. 



