THE STRUCTURE OF CHROMOPHILE CELLS OF THE NERVOUS SYSTEM. 33 



The mitochondria may apparently disappear more or less completely in cer- 

 tain cells, and their place be taken by a mass of amorphous material with the same 

 staining properties (figure 6). The nucleus may or may not be visible. Cajal 

 preparations of cells in the same condition (figure 9) show that the canals are unal- 

 tered. The nucleus is obscured bj' the cloud of Xissl substance. The appearance 

 of these cells, in advanced stages of chromophilia, would perhaps lead one to sup- 

 pose that they are degenerating and that their nuclei have disappeared. That this 

 is not the case may be seen if one of the mitochondrial preparations is stained with 

 hematoxylin and eosin. The hematoxylin and eosin does not color either the 

 amorphous deposit or the Xissl substance, which, in the mitochondrial and in the 

 Cajal preparations, hides the nuclei. The nuclei have in reality distinct and defi- 

 nite outlines and appear to be quite unaltered, except that they contain rather more 

 than the usual amount of chromatin. In fact, the change in the mitochondria and 

 the increase in the amount of the Nissl substance would never have been suspected 

 if hematoxylin and eosin had alone been used. 



The distribution of chromophile cells is important. They often occur singly. 

 They may be surrounded on all sides by cells which show no tendency toward an 

 assumption of the chromoi)hilic condition. They may, on the other hand, occur in 

 clumi)s. The clumps vary greatly in size. They contain cells in all stages of chro- 

 mophilia in addition to a varialjle number of unaltered cells, which are always pres- 

 ent, scattered among them. 



The neuropil in which the chromophile cells are embedded differs in no way 

 from the neuropil elsewhere. It seems, by all the mitochondrial methods, to be 

 studded with mitochondria. ]kit it must not be thought that the mitochondria 

 occur in anything like equal numbers in the neuropil of different regions, because 

 there is a remarkable variation in this respect. The mitochondria appear to be 

 intercellular, l)ut unhaj^pily a source of error is introduced by the fact that the 

 unmedullated, and to a lesser extent the meduUated, processes stain in much the 

 same way as the mitochondria, so that in some cases it is impossible to distinguish 

 between them. Undoubtedly a large number of the mitochondria in the neuropil 

 are contained in nerve-cell processes cut in section, but there is no <i priori reason 

 why they should not occiu- free from the cells as an intercellular deposit. This im- 

 portant question can, only be solved by a detailed study of staining reactions, pos- 

 sibly by the elaboration of new methods, or by taking advantage of the differential 

 solubilities of mitochondria. It has a direct bearing upon the role of intercellular 

 material in the metabolism of the central nervous system. 



Cells in the chromophilic condition are comparatively rare in the olfactory bull) 

 as compared with the cerebral cortex. In fact, they are more abundant in the cere- 

 bral cortex than in any other part of the brain. Clumps of them are more common 

 here than in other regions. The clumps vary in size, in shajie, and in position in the 

 brains of animals from the same litter, apparently treated in exactly the same way. 

 Chromophile cells are also numerous in the hippocampus. They are, on the con- 

 trary, comparatively rare in the corpus striatum and in tlu^ thalamus, in both of 

 which they are more frequently met with singly than in groups. In the midbrain 

 thev are found in about the same number. It is interesting to note that they are 



