STUDY OF POLYNEURITIS GALLINARUM. 441 



are not able to say whether these fibers are ascending or descend- 

 ing; that is, sensory or motor. The number of fibers of the cord 

 which show undoubted degeneration in either the axis cyHnder 

 or the medullary sheath was in no case great — much less than 

 we had expected to find. The number of the former scarcely 

 make up 0.25 per cent of the total fibers in a given cross section, 

 while the latter are approximately 1 per cent in the most ad- 

 vanced cases. These observations lead us to believe that in 

 fowls showing well-marked neuritis there is degeneration in a 

 very small percentage of the fibers of all columns of the spinal 

 cord. 



Changes in the brain. — Similar observations in Marchi prep- 

 arations were made on the fiber tracts of the medulla, pons, 

 midbrain, and internal capsule of fowl 72. Degenerated fibers 

 were found in each one of these brain divisions comparable to 

 those found in the cord, Plate V, fig. 23. 



Changes in the nerve cells. Cells of the cord. — One would 

 expect that degeneration in the fibers of all columns of the cord 

 and in the peripheral nerves would be accompanied by changes 

 in the nerve cells themselves. Our attention has been confined 

 chiefly to a study of the cells of the lumbosacral cord. From 

 what has been said above relative to degeneration in the 

 peripheral nerves and in the fiber tracts of the cord, it is evident 

 that the most marked changes in the nerve cells of the cord 

 would be found in the lumbosacral region. For a study of 

 these changes we have employed the Nissl method, Giemsa's 

 blood stain after alcohol fixation, and the mitochrondria methods. 



Plate X, fig. 19, shows a nerve cell from the anterior horn of 

 the thoracic region of a normal fowl stained by Nissl's method. 

 No nerve processes are shown. Plate X, fig. 20, is a similar 

 nerve cell stained by Giemsa's blood stain. In both cells the 

 tigroid substance is well shown. 



In the spinal cord of the fowls showing well-marked degenera- 

 tion in the sciatic, we have never been able to find a nerve cell 

 in the lumbosacral portion, in which the tigroid substance shows 

 as clear distinct areas like those in figs. 19 and 20. The stain- 

 able substance shows a marked tendency to diffusion throughout 

 the cell. Cells from these cords, however, were observed in 

 which the tigroid bodies appeared as definite though indistinct 

 globules or areas. The usual appearance of the large cells of 

 the anterior horn and of the large cells of the posterior horn was 

 a diffusion of the stainable material and a collection of it at one 

 side of the cell. The stainable material which is granular in 



