32 ATLAS OF NERVE CELLS 



than the one from which they start, i is such a cell, on the right side of the cord at 

 level A, with its neuraxon y in the right antero-lateral column shown as passing downward ; 

 and e is such a cell, at level C in the left anterior horn, with its neuraxon passing upward. 

 At x in the drawing, the descending fibres of the antero-lateral tract, supposed to come from 

 the cerebellum, are seen with collaterals entering and terminating in the median gray portion 

 of the cord. 



\ 



MEDULLA OBLONGATA 



The cells of the medulla do not differ essentially from those in the spinal cord, except- 

 ing in their relative position to the tracts of white matter. The numerous motor cells giving 

 an origin to the motor cranial nerves, are quite similar to the motor cells of the anterior 

 horns of the spinal cord. Throughout the medulla there lie numerous intrinsic cells which 

 are undoubtedly association cells in function, and combine the various complex acts, which are 

 automatically performed by the medulla oblongata. These resemble the intrinsic cells of the 

 cord. Small sensory cells are also found in the substantia gelatinosa of the fifth nerve 

 nucleus of the medulla, similar to those found in the posterior horns of the spinal cord. 



All these cells have numerous dendritic branches, and an axis cylinder, which passes 

 upward and downward to the brain or spinal cord, giving off in its course numerous collat- 

 erals. The arrangement of these fibres in the medulla is extremely intricate, and does not 

 concern us here. They are clearly traced by Bechterew in his " Leitungsbahnen im Gehirn 

 und Ruckenmark," and by Van Gehuchten in his "Systeme Nerveux de l'Homme." The histo- 

 logical structure which is especially peculiar to the medulla is the olivary body. This is made 

 up of a thin layer of nerve cells, which layer is highly convoluted, and which is disposed 

 upon the convex surface of the body and around a central mass of fibres, which appear to 

 issue from the olivary body, on one side only. The structure of the olivary body is identical 

 with that of the corpus dentatum of the cerebellum, shown in Plate XX. The olives are 

 connected by means of fibres with the cerebellum, and seem to be in intimate relation with 

 it, as shown in Figure 7, page 42. 



