318 S- Simpson, 



matter of tlie optic thalamus in the outer or lateral half of which 

 they appear to terminate, and there is a considerable amount of fine 

 degeneration in this region of the thalamus. The internal capsule on 

 the opposite side is quite free from degeneration as also is the grej^ 

 matter of the optic thalamus of that side. In sections taken more 

 posteriori}" through the subthalamic region the same fine degeneration 

 is seen in the gre}" matter on the left side with fibres passing into 

 it from the internal capsule. 



In the upper levels of the mesencephalon the left crusta shows 

 extensive degeneration which does not involve its lateral and mesial 

 extremities. Several detached bundles of degenerated fibres, cut trans- 

 versely, seem to be passing downwards in the substantia nigra lying 

 behind the left crusta, and there is a slight amount of fine degene- 

 ration scattered amongst the grey matter of the substantia nigra. No 

 fibres can be made out passing backwards into the tegmentum, as 

 was the case in most of the cats examined. No fine degeneration is 

 visible in the central grey matter or in that of the anterior corpora 

 quadrigemina. 



In sections through the upper, middle, and lower levels of the 

 pons the pyramidal bundles on the left side are extensively degener- 

 ated, and all around these, but more especially on the mesial and 

 antero-lateral aspects, there is very abundant fine degeneration amongst 

 the cells of the nuclei pontis. This fine degenei-ation is exceedingly well 

 marked in the dog (figs. 7 and 8. pi. XVI). In the medulla oblongata 

 above the pyramidal decussation, as in the cat, a few fibres are seen 

 to leave the posterior aspect of the degenerated pyramid; some cros- 

 snig the median raphe are soon lost amongst the internal arcuate 

 fibres of the opposite side, while a very few disappear in the for- 

 matio reticulaiis of the same side. In sections through the pyiaiiii- 

 dal decussation crossed (heterolateral) and uncrossed (homolateral) bund- 

 les come off from tlie degenei-ated pyramid and curve back\v;ii'ds and 

 outwards through the central grey matter towai'ds tlic latcijil culunins 

 of tlie oi)])Osite and of tlie same side respectively, lo take up a posi- 

 ti(m corit'S|)onding to tliat of tlic lateral column in tlif spinal cord. 

 The homolateral fibres are onh* seen in small fasciculi in sections 



