344 THE SPINAL CORD. 



at least, is established by intervening neurones whose cell-bodies 

 are located near the base of the posterior columna in the region 

 of the nucleus dorsalis (Clark's column). The evidence of such 

 termination of the anterior pyramidal tract is not conclusive. 



Lesions. Paralysis due to lesions of the anterior columna 

 and of the genetic nuclei of cerebral nerves is often called lower 

 segment paralysis. The cells in the anterior columna are the seat 

 of hemorrhagic inflammation and rapidly degenerate in acute 

 anterior poliomyelitis. In progressive muscular atrophy and 

 in amyotrophic lateral sclerosis they degenerate slowly. As a 

 result of the first, sudden flaccid paralysis occurs. The muscles 

 waste away in the second and third because the nerves controlling 

 the muscles and their blood supply are gradually destroyed. In 

 the last, the muscles are also spastic, because the involvement 

 of the pyramidal tracts cuts off cerebral inhibition. 



(2) Center of Crescent and Columna Lateralis (Fig. 101). 

 In the center of the crescent there are many small, closely packed 

 cell-bodies, which are probably sympathetic in function. This part 

 of the crescent appears to contain the automatic spinal centers, 

 such as, the cilio-spinal, cardia'c-accelerator, vaso-motor, secre- 

 tory, trophic, inhibito-secretory, viscero-motor, viscero-inhibitory, 

 etc. That the cell-bodies in the center of the crescent are of 

 sympathetic function is suggested by two facts ; first, the cell-bodies 

 are small, which indicates that the axones run but a short dis- 

 tance from the neurone center, as is the case with spinal sympa- 

 thetic neurones; and, second, the distribution of these central 

 neurones is limited to those regions of the spinal cord whence 

 the efferent sympathetic fibers rise. 



The intermedia-lateral column of cell-bodies (Fig. 102, B) is 

 the only one found in the center of the crescent. In the thoracic 

 segments of the cord, where the lateral columna is visible, this 

 column is contained in the lateral columna and in the white matter 

 immediately adjacent to it; so far as it is found hi the cervical 

 and lumbar enlargements it is situated in the base of the anterior 

 columna near its lateral surface. The intermedio-lateral column 

 is found hi the last cervical, all the thoracic and the first and second 

 lumbar segments, in a nearly continuous column; it is also found 



