584 THE NERVOUS SYSTEM 



dorsal and the first two lumbar segments. The cells are small and closely 

 aggregated and characteristic in appearance. These nuclei reappear in the 

 upper cervical segments and in the sacral segments that give origin to the 

 nervi erigens. They are supposed to be the motor nuclei for the vaso-motor, 

 the pilo-motor nerves, and for the nerves of the sweat glands, i.e., the auto- 

 nomic system. 4. The cells of the posterior vesicular column, or Clark's 

 column, are in the posterior portion of the gray matter of the cord. They 

 form a conspicuous column of cells, 3, 5, and 6 of figure 362, extending from 

 the last cervical to the second lumbar segments. These large cells contribute 

 their axones to the ascending cerebello-spinal (direct cerebellar) fasciculus 

 which ascends to the cerebellum and is believed to carry sensory impulses of 

 prime importance in the coordinations of muscular movements. The nerve 

 relations and the restricted location of the posterior vesicular column has also 

 led to the suggestion that its function has to do with the visceral afferent or 

 sensory nerve impulses. Sensory fibers from the posterior roots arborize 

 around the cells of the posterior vesicular column, i.e., the dorsal nucleus, see 

 figure 363. The dorsal nucleus is considerably broken up by the passage of 

 bundles of fibers through it, called the lateral reticular formation. 



Besides these groups, which have their names largely on account of their 

 location, there are distributed throughout the gray matter a very large num- 

 ber of other cells, which are known as intrinsic cells. These are of two types, 

 those restricted to connections wholly within the gray matter Golgi cells of 

 the second type and those that send out axones which pass into the adjacent 

 ground bundles of the same or of the opposite side, and pass up and down the 

 cord, to enter the gray matter again. They connect by their end-brushes with 

 cells at different levels of the cord. 



The functions of these connecting or intrinsic cells is to unite the pos- 

 terior and anterior regions of the cord, to serve as conductors between the 

 lateral halves, or to connect segments at different levels. They are also dis- 

 tributing fibers in that they bring a single or at least a small number of pos- 

 terior sensory neurones into connection with a relatively large number of 

 anterior or motor neurones. 



The Fasciculi or Tracts in the White Matter of the Spinal Cord. 

 We have already shown that the white matter of the cord is divided on each 

 side into the anterior, lateral, and posterior funiculi. But evidence of various 

 kinds discussed below has shown the following main conducting channels or 

 tracts through the cord, see figures 363 and 364 for illustration. 



Tracts of the Cord. 



Funiculus posterior. 



Fasciculus gracilis, tract of Goll (ascending). 

 Fasciculus cuneatus, tract of Burdach (ascending) 

 Comma, tract of Schultz (descending). 



