216 CLINICAL APPLIED ANATOMY. 



short distance upwards along tracts which should degenerate 

 downwards and vice versa. For instance the pyramidal tracts 

 may be found degenerated upwards for a short distance. This is 

 probably due to a direct spread of inflammation in the neuroglial 

 planes, and is quite comparable to the way in which inflammation 

 spreads by continuity in other parts of the body, and of the same 

 nature as the inflammation which is found in the nerve roots, 

 which arise from the cord at the site of the myelitis. 



Two distinct groups of symptoms occur in myelitis. The first 

 group comprises motor and sensory phenomena which are due to 

 the interference with the transmission of impulses up and down 

 the cord, the second group consists of symptoms due to the 

 destruction of local centres at the site of the myelitis. Anaesthesia 

 and loss of power below the site of the lesion belong to the first 

 group, whilst local atrophy of muscles with loss of electrical 

 reactions in them and abolition of reflexes are indications of 

 local destruction. A zone of hyperaesthesia just above the level 

 of the lesion is due to irritation of the sensory roots at the upper 

 level of the myelitis. As a rule the reflexes of the parts below 

 those actually supplied by the diseased segments of the cord are 

 exaggerated and the nutrition of the muscles fairly preserved, 

 but there is reason to believe that when the lesion is completely 

 transverse, which is equivalent to a transection of the cord, the 

 reflexes below the lesion are abolished. 



The upper limit of a myelitis is best determined by the situation 

 of the upper limit of anaesthesia, whilst the vertical extent of the 

 lesion can be gauged by the loss of reflexes and distribution of 

 muscular wasting. 



The dorsal region of the cord supplies nerves to the inter- 

 costals. the long muscles of the back and the flat muscles of the 

 abdomen. Wasting of individual intercostal muscles is not easily 

 observed, and the long muscles of the back and flat muscles of 

 the abdominal wall do not appreciably waste since they receive 

 nerves from a great number of dorsal segments. 



The cervical and lumbar enlargements supply muscles of the 

 limbs, and detection of wasting and of the reaction of degeneration 



