BRAINS AND SPINAL CORDS IN ATAXIC PIGEONS 133 



If this tract runs through the anterior commissure, as Kiihn 

 and Trendelenburg contend, our findings of a decided reduc- 

 tion in the anterior commissure with a decreased number of cells 

 in the central gray substance must show the defective develop- 

 ment of this tract, at least at its origin. 



Nissl preparations. The section at various levels of the cord 

 which were stained with toluidin blue and counterstained with 

 erythrosin give almost the same results as indicated in reference 

 to the general conditions of the ganglion cells. The cells in 

 the anterior horn and in the base of the posterior horn (Clarke's 

 column) in the upper and lower enlargements reveal a marked 

 reduction, from one-half to two-thirds the normal, both in 

 reference to size and number. The Nissl bodies stain a relatively 

 light purple color in all ataxic birds, so that although the bodies 

 can be easily distinguished they usually appear more or less 

 diffuse and indistinct as the result of a less number and weaker 

 staining properties when compared with the normal numerous 

 Nissl bodies of a deep purple color. At different levels of the 

 cord, in all affected specimens, this is observed and easily recog- 

 nized in both the enlargements, where the cells are large enough 

 for minute examination of intracellular conditions. Complete 

 destruction, disappearance, and disintegration of Nissl bodies 

 or the typical grouping of this substance in one part of the 

 cell body could not be found in any of the cells. This, then, 

 indicates that the Nissl bodies are reduced throughout the 

 affected birds, but further than this there is nothing which 

 resembles new or old degenerative processes. 



Pia mater, blood-vessels and spinal roots. The pia mater is 

 not thickened, but sometimes it is slightly thinner in the 

 affected birds; the blood-vessels in the periphery of both the 

 anterior and posterior medial sulci have a smaller caliber than 

 normal (the largest diameter is 0.050 mm. in the affected and 

 0.0835 mm. in the normal on the average), but their coats show 

 no thickening or infiltration. The capillaries and small blood- 

 vessels appear in cross-section of the cord definitely in less 

 number in the sections of the affected pigeons than in the normal. 

 This may indicate an insufficient supply of blood to the spinal 

 cord of the affected pigeons. 



