36 GRAY SUBSTANCE OF THE MEDULLA OBLONGATA 



nerve-roots and the cells of the lamina ; processes from the cells cross the root-bun- 

 dles in every direction, and I have occasionally been able to trace fibres derived from 

 these cells, running parallel to the roots and apparently accompanying them for 

 some distance towards the nucleus, but I have never been able to satisfy myself 

 that there is any direct connection between the hj'poglossal roots themselves and 

 the cells of the olivaries, not even where the roots pass directly through the lamina. 



The fibres derived from the hilus, or even from the cells of the lamina, which I 

 have been able to trace continuously for any considerable distance in a course 

 parallel with the hypoglossal roots, are very few in number, not at all corresponding 

 to the very large bundles represented by Lenhossek, which had they existed could 

 hardly have escaped the observation of StOling and Clarke. That the hypoglossal 

 nuclei are, however, connected to some extent with the olivary bodies, by fibres 

 and by the network of cells in the anterior part of the medulla, admits I think 

 of no doubt, and will be still more evident when we examine presently the 

 arrangement of these cell groups in the medulla of the sheep. 



In longitudinal sections the olivary bodies present a very beautiful appearance, 

 the convolutions being compact and numerous ; this is especially evident in Fig. 

 30, Plate VIII, representing a longitudinal section through the olivary body, in a 

 direction nearly parallel to the hilus. A series of such sections presents several 

 striking points ; in the outermost, the convoluted lamina has the appearance of a 

 closed circle or eUipse, from which various other foldings radiate, filling up the 

 whole interior, but as we approach the hilus, the lamina opens at the bottom (Fig. 

 30), into which some of the great bundles of longitudinal fibres turn, often quite 

 abruptly, radiating in every direction towards the centre of the olivary body. At 

 difi"erent heights small bundles of longitudinal fibres turn ofi" from the main bundles, 

 runnino- some upwards and some downwards towards the convolutions, which they 

 often cross, proceeding towards the interior, though not unfrequently joining cells 

 of the lamina. 



In sections cut at right angles to the raphe (Figs. 31, 32), the appearance is some- 

 what different. Near the surface of the olivary body (Fig. 31), the longitudinal 

 columns are seen ascending on each side of the raphe in a perpendicular course, 

 in the midst of which the olivary body seems to be thrust, as it were, the folds of 

 the lamina branching off from a stem of transverse and oblique fibres, like the 

 branches from a tree ; nearer the centre of the olivary body (Fig. 32) the folds of 

 the lamina are very distinctly seen, and as the plane of section has in this case gone 

 somewhat obliquely across the thickest portion of the convolutions, the lamina 

 appears nearly double the thickness of that in Fig. 30, though these two specimens 

 were from the same meduUa. 



In longitudinal sections made in this direction, the internal arciform fibres 

 pursuing a course at right angles to the raphe (Fig. 29) can often be traced for a 

 considerable distance, and may plainly be seen curving upwards and do-vvaiwards to 

 become longitudinal fibres, just as the longitudinal fibres on the other hand turn 

 off and radiate towards the interior of the lamina ; in this way it is highly probable 

 that a series of loops is formed, serving, as is so often the case in the spinal cord, 

 to connect parts lying at different heights. 



