442 VEDDER AND CLARK. 



appearance shows a tendency to group itself around the base of 

 one of the processes of the cell (Plate X, figs. 21 and 22), but 

 whether this process is usually the axon as shown in fig. 22, a, 

 we are not able to say. This figure shows the typical appearance 

 of the large nerve cells of the ventrolateral horn, from which 

 the fibers of the ventral root arise, and of the large cells of the 

 posterior horn around which the terminations of the sensory 

 neuraxes from the dorsal root ganglia arborize. Its granular 

 appearance is suggestive of a disintegration rather than a 

 solution of the tigroid substance. The cells of the other parts 

 of the gray matter of the cord do not show this change to such 

 an extent. They stain poorly, the stain is easily differentiated 

 out, and the cell has a pale appearance. The stainable portions 

 are arranged in a coarse reticular network. The appearance is 

 that of a cell in which the tigroid substance is wanting. Cells 

 of somewhat similar appearance are also seen in sections of the 

 normal cord, but are not so numerous here. A comparison 

 between the large cells of the anterior and posterior horns of the 

 normal and neuritic fowl, noted above, is best made by a study 

 of figs. 19 and 20 and of figs. 21 and 22. Fig. 22 gives the 

 appearance of rather advanced retrogressive changes. The 

 stainable material is collected at one point of the cell and causes 

 a bulging here. The nucleus also suggests degenerative changes. 

 This has been noted in very few cells, and the picture is the most 

 suggestive of degeneration in the nerve cells of any we have seen. 



Since marked changes in the tigroid substance of the nerve 

 cells of the spinal cord can be brought about, as Nissl(ii) and 

 others have shown, by fatigue, direct electrical stimulation in 

 excess, toxemia, and other factors, it is impossible to say that 

 the changes noted in the nerve cells of the neuritic fowls 

 represent degenerative changes or changes due to other causes. 

 We have thus employed other methods in studying these cells. 

 By the Marchi method a few very fine, intensely black granules 

 can be seen here and there within the nerve cell. These, how- 

 ever, are so scarce that their pathologic significance is probably 

 very small. A study of the mitochondria of the nerve cells was 

 next made. 



Of recent years a great deal of work has been devoted to the 

 study of mitochondria and their significance. Mitochondria 

 occur as numerous rods and granules in all the various types of 

 cells of the embryo (Bensley,(i2) Meves,(l3) and others) and in 

 practically all types of cells of the adult, which have an active 

 metabolism or which are actively engaged in secretion, as the 



