cxvi Journal of Comparative Neurology. 



processes and near the pia at the periphery. In the normal portion of the 

 ataxic specimen and in each of the controls, the nuclei of these cells are 

 surrounded by a well-marked cell body, which disappears entirely in the 

 diseased portions, leaving nothing but the bare nuclei remaining. It 

 should also be mentioned that some of these small cells send off very fine 

 processes, which are visible only in the normal. The processes of the 

 Purkinje cells show much more plainly, are longer, and have more 

 branches in the normal than in the ataxic specimen. In the diseased 

 portions, no Purkinje cell processes are to be seen. In no case have the 

 processes from one Purkinje cell been found to come in contact or unite 

 with those of another Purkinje cell ; they always remain distinct, even 

 in case of the very finest processes. In the vicinity of the Purkinje cells 

 are a few fibres that run parallel to the surface and are visible only in the 

 ataxic specimen." 



"The Purki.n'JE Cells. In the abnormal portions of the ataxic 

 specimen, some of the Purkinje cells have disappeared entirely, leaving 

 open and empty places, but for the most part the cells are only considera- 

 bly shruken. It seems that these Purkinje cells are less affected, i. f., 

 they preserve their shape, size, and general character better in the por- 

 tion of the folii near the base of the sulci than at the summits of the 

 folii. In the ataxic, the Purkinje cells in the affected portion have 

 lost their large round nuclei, which, with their nucleoli, show so 

 plainly in the normal. In the normal these Purkinje cells are very simi- 

 lar in size and shape, while in the ataxic, there is no regularity in this 

 respect. In all the specimens which served as controls, these Purkinje 

 cells were found to be much more numerous at the summits of the cere- 

 bellum, where they are packed closely together, than at the base of the 

 valleys, where they stand quite a distance apart. Small fibres extending 

 toward the granular layer can be seen at their basal end, but cannot be 

 followed save for a very short distance. One of the most marked differ- 

 ences between the tissue of the normal and ataxic specimens is that 

 which comes out in an examination of the Purkinje cells with reference 

 to their size, shape, and general appearance. In the normal portions of 

 the ataxic specimen, where these cells are more like the normal, the ra- 

 dial connective-tissue fibres are less evident. In the degeneration of the 

 Purkinje cells, tTie processes more remote from the cells are the first to 

 be affected, then the degeneration approaches the cell itself. It begins 

 to shrink and loses its nucleus with its shining nucleolus, as well as its 



