588 MANUAL OF HISTOLOGY. 



regarded by Deiters as derived from a change in the lateral column, that 

 is to say, some of the fibres of the latter terminate provisionally in the 

 cells of this formation. The fibres passing off from these ganglionic 

 bodies centripetally we shall meet again in dealing with the formation of 

 the pyramids. The remaining portion of the lateral column advances 

 now unchanged for a certain distance towards the brain. It begins, how- 

 ever, very soon to be encroached upon by the reticulated cineritious mass 

 already alluded to ; besides which, a special nucleus, named after Deiters, 

 is developed in the lateral column as mentioned before, containing some- 

 what small ganglion cells. Like the other so-called specific nuclei of the 

 medulla oblongata, this may be regarded as a central point for arrival of 

 one and departure of another system of fibres on its way to the brain. 

 The first of these belongs to the lateral column, while the latter forms a 

 zonal system of fibres, the stratum zonale Arnoldi, which pursues its 

 course into the cerebellum. Whether other efferent fibres preserve the 

 original direction of the lateral column towards the cerebrum is still an 

 undecided question. 



Other collections of ganglionic substance in the neighbourhood of 

 the lateral columns, are the inferior olivary bodies, which also receive, in 

 all probability, some circular fibres from these. Again we meet with 

 cineritious substance in the accessory olive, and at the point of departure 

 of the cms cerebelli ad medullam ; also in the superior olivary bodies. 

 The latter appear, moreover, to be fed by fibres coming from the lateral 

 column, and to give off a zonal system of fibres which (lying in the lower 

 mammals anterior to, and in man within the pons) is known as the corpus 

 trapezoides. 



As regards the posterior columns, they were for a long time supposed, 

 and again incorrectly, to pass directly into the cerebellum as the crura cere- 

 belli ad medullam. The direction of both these sets of fibres, it is true, is 

 the same, and this explains the mistake; but the fibres of the posterior 

 columns are in their farther course replaced by quite a different species. 



From the posterior column of the spinal cord, as we have already seen, 

 its internal portion becomes distinct as the band of Goll, which then forms 

 the funiculus yracilis of the medulla, while its remaining portion is known 

 as the funiculus cuneatus in its further course. 



Both these bands become mixed internally with grey matter (ganglia 

 postpyramidalia of Clarke], and increase consequently in size to a con- 

 siderable extent. Here also the white substance of the posterior column, 

 consisting of fine nerve tubes, diminishes in a corresponding degree more 

 and more, coming to an end provisionally in the grey matter just mentioned, 

 as well as in the adjacent parts of the posterior coniu. From this it 

 again starts in the form of a system of circular fibres. Thus it may be said 

 that the posterior column disappears entirely as regards its original position. 



The fibres arising from it secondarily appear destined to augment in 

 part the pyramids (see below), but also to enter partly and gradually into 

 the formation of the crura ad medullam (seemingly a direct continuation 

 of the posterior columns). Again, some of them penetrate into the olivary 

 bodies, decussating to arrive at the opposite side, none passing straight 

 into the olive of their own half. These fibres thus constitute the chief 

 source of supply to these specific nuclei of the medulla oblongata. 



The pyramids, remarkable for the fineness of their nervous tubes, are, 

 according to Deiters, no direct continuation of the white cords ; they 

 represent rather one of those numerous secondary systems of fibres which 



