BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 139 



In the affected birds, the gray matter of the posterior horn 

 is small, both the transverse and ventrodorsal diameters being 

 reduced. Moreover, it contains few cells and few and thin 

 myelinated fibers. The fibers in the posterior horn run to the 

 reticular formation in the lateral funiculus, while those to the 

 anterior commissure are diminished in number, and are often 

 hardly distinguished in the affected specimens. The two small 

 areas of gray matter in the ventral base of the posterior funiculus, 

 the one lying medially and the other laterally, also are reduced 

 and contain fewer and smaller cells in all ataxic sections by 

 exact measurement. These areas which were called by Brandis 

 merely as 'faserfreie Stellen,' in all probability correspond to 

 the nuclei funiculi posteriores of mammals from their similar 

 localization and form. The fiber bundles dorsal to the posterior 

 horn and the two small areas noted above are reduced; the 

 fibers have a small caliber, thin myelin sheaths, and stain lighter 

 in all affected sections. No positive degenerative processes 

 are exhibited. 



The fiber area of the ventrolateral portion to the posterior 

 enlarged horn in the funiculus lateralis has not a distinct 

 boundary from the neighboring fiber bundles at this level even 

 in the normal pigeon, although it seems to be reduced in area 

 and in the caliber of the individual fibers in the affected birds. 

 In the anterior funiculus the gray matter becomes smaller as 

 one passes proximally. The nuclei hypoglossi do not exhibit 

 much difference from the normal. 



A little further proximally, laterodorsal to the central canal, 

 there appears the vagus nucleus, which shows its structure at 

 the inferior portion of the floor of the fourth ventricle where the 

 central canal opens into the ventricle. This nucleus is well 

 developed as well as its transversely running intramedullary 

 fibers in both the affected and the normal specimens. The 

 fasciculus solitarius is quite the same in both. 



In the ventral area of the medulla oblongata, along the mid- 

 line there appears a long triangular area of longitudinal fibers, 

 its base directed dorsally. This is nothing but the fasciculus 

 longitudinalis medialis and predorsalis or 'Vorderstrangrest' 



