74 PROGRESS OF MICROSCOPICAL SCIENCE. 



exclusive relations with the motor functions. All three intercross at 

 the median line with their congeners, and pass then into masses of 

 nerve cells, constituting nuclei spread out over the whole of the height 

 of the encephalic isthmus. Finally, from these nuclei start grey fibres, 

 which throw themselves into a special nervous substance, described 

 for the first time by M. Luys under the name of peripheral cerebellar 

 substance. In this way the inferior cerebellar peduncles terminate, 

 after decussation, in the grey masses of the olivary body (anterior and 

 inferior olive of M. Luys). This anatomist has found in the thickness 

 of the posterior pyramid an analogous nucleus of grey matter, which 

 enters similarly into connection with the inferior cerebellar peduncles. 

 This is the inferior and posterior olive. The median peduncular 

 fibres cross each other also in the median line, and pass into the grey 

 matter of the protuberance. Finally, the superior cerebellar pedun- 

 cles, after a similar intercrossing, terminate in a grey mass, already 

 described by Stilling as the red nucleus, and which M. Luys proposes 

 to call superior olive, seeing its striking analogy with the grey nucleus 

 of the bulbar olive. From these different nuclei start grey fibrils, the 

 ultimate termination of the peduncular fibres, which put themselves 

 in connection with the fibres of the anterior spinal system, by the 

 medium of the peripheral cerebellar substance. The latter extends 

 on the neck of tbe bulb as far as the corpus striatum in a continuous 

 layer, presenting here and there swellings, the most apparent of which 

 is the locus niger of Soemmering. Histologically, this grey substance 

 is constituted by a network of polygonal cells, provided with numerous 

 prolongations. It is probably by the medium of these branching and 

 anastomosing cells that the connections between the fibres of the 

 cerebellar apparatus and those of the spinal apparatus are established. 

 So far as concerns the latter, M. Luys is almost entirely in accoiftance 

 with accepted opinions. It should be mentioned, however, that the 

 posterior sensitive fibres of that apparatus are shown in his drawings 

 as all terminating in one ganglion. From this ganglion start two 

 orders of fibres. Those of one order connect themselves with the 

 grey centre of the spinal marrow, ganglio-spinal fibres. These are 

 properly the reflex motor fibres. The others take an ascending direc- 

 tion, cross each other at the level of the bulb, and, according to all 

 appearances, terminate in the optic thalamus (ganglio-cerebral fibres). 

 As to the anterior or motor fibres, they emerge from the large asteroid 

 cells of the grey matter of the anterior horns. Towards the bulb and 

 the protuberance, these cells are agglomerated, and unite in masses to 

 form the grey nuclei whence spring the fibres of origin of the cranial 

 motor nerves, hypoglossal, facial, external oculo-motor, masticatory, 

 &c. Finally, the cells of the anterior horns unite together, and with 

 the nuclei of the corpus striatum, by fibres of which the ensemble 

 constitutes the antero-lateral column, and, after decussation at the 

 level of the bulb, the cerebral peduncles. Combining the whole of 

 these details, the following general conception is arrived at by this 

 author. In respect to the sensitive fibres, a part of them, after having 

 traversed the spinal ganglion, take their course directly into the large 

 cells of the marrow. The impression in this case is not felt ; the 



