22 GRAY SUBSTANCE OF THE MEDULLA OBLONGATA. 



A moment's reflection suffices to show that by this means a relation is at once 

 established between the nerves of the posterior column of the medulla and the 

 posterior spinal roots, and that the plan in both is precisely similar, although the 

 arrangements of parts may at first sight seem to diff"er. The analogy between the 

 upper roots of the spinal accessory, vagal and glosso-pharyngeal nerves and the 

 posterior spinal roots seems to be perfect; they traverse the caput cornu, and are 

 connected with cell groups which completely correspond with each other, if not 

 in all respects identical, and this analogy is still further established by the relation 

 they form with the motor roots, as we have already had occasion to notice. 



Having noticed the relation between the nuclei of the posterior cornua of the 

 spinal cord and those of the medulla, it remains to add a few words with regard 

 to the passage into the medulla of the very interesting columns of longitudinal 

 bundles, which in the cervical region of the cord are showoi to be so intimately 

 connected with the tractus intermedio-lateralis. The situation of these bundles in 

 the spinal cord is well seen in the wood-ciits. Figs. 2, 3, 4. In Plate XIII, Fig. 

 1", Z, the same column is seen, situated close to the entrance of the spinal accessory 

 roots ; higher up these bundles are situated just behind the entrance of the roots, 

 and continually increase in size as we ascend (Figs. 3", 4", 19", 20", 21", 22"), till 

 the vagus nucleus has reached its greatest development, from which point upwards 

 they gradually diminish and finally disappear, being replaced by a similar collection 

 of longitudinal fasciculi, which are developed behind these in the substance of the 

 post-pyramidal and posterior portion of the vagus nucleus, and stand in close con- 

 nection with the outer portion of the nucleus of the auditory. 



The longitudinal columns in connection with the vagus and spinal accessory 

 nuclei have been noticed by Stilling, Schroder van der Kolk, and Clarke, and appear 

 from their connection in the medulla with the centres, as well as with the anterior 

 and posterior cornua in the spinal cord, to be intimately concerned in co-ordinating 

 and bringing into harmony the different respiratory movements. 



The connections of these fasciculi with different parts of the medulla are very 

 striking; as I have shown in various places in the present memoir, they con- 

 stantly penetrate the meshes of a network of ceUs and fibres, many of these cells 

 being of very considerable size, embracing the bundles with their processes, and in 

 many cases becoming continuous with them, while, on the other hand, some ceU 

 processes are sent transversely in all directions, many of them entering the nuclei 

 (vagal and spinal accessory). It is chiefly in this way, I think, that connection 

 is brought about between the roots and the longitudinal columns, for I have not 

 been able to find any direct communication between them, notwithstanding the 

 assertion of Schroder van der Kolk.^ On the outer side of the longitudinal column 

 in the direction of the caput, many cells are found, some of very large size, serving 

 to connect the column with the caput, through the substance of which fibres descend 

 from the trifacial. The opposite columns are brought into commissural connection 

 by means of radiating fibres, some of which join the marginal bundles passing around 



» Medulla Oblongata, 171. 



