MITOCHONDRIA VARIATIONS IN NERVE CELLS 333 



similarity is the more striking when we bear in mind that granu- 

 lar mitochondria are not at all common in the cells of the cen- 

 tral nervous system. The small cells of the Gasserian ganglion 

 contain exceedingly minute granular mitochondria (fig. 6) which 

 are usually clumped together in the vicinity of the nucleus leav- 

 ing the peripheral cytoplasm free. This last fact considered in 

 connection with Cowdry's ('14, p. 27, fig. 13) demonstration of 

 mitochondria of like nature and distributed in the small cells 

 of the spinal ganglion, which Ranson ('14, p. 123) believes to be 

 concerned in conduction of pain and temperature sensations, 

 is significant. One might expect similar functions to be the 

 property of these cells, and we should be on the lookout for 

 changes in them in cases of trifacial neuralgia. 



All nerve cells, even those with otherwise granular mitochon- 

 dria invariably contain filamentous mitochondria in their proc- 

 esses, whether they be dendrites or axones, from which it fol- 

 lows that there is greater variation in the mitochondria in cell 

 bodies than in cell processes. It may be recalled that the mito- 

 chondria are all filamentous in the cells of the neural tube of 

 the developing embryo. In other words, mitochondria retain 

 their embryonic form in the processes and become specialized in 

 the cell bodies. The mitochondria are usually filamentous in 

 the axone hillock. 



The cells of the nucleus of the corpus trapezoideum present as 

 peculiar a picture as is found in any other part of the nervous 

 system (fig. 2). Large block-like mitochondria are found in the 

 peripheral layer of the cytoplasm. The large mitochondria are 

 frequently oblong. Some of those illustrated in the figure are as 

 much as 1.74 microns long by 0.63 microns in breadth. This 

 suggests a possible relation to the unique synaptic connection of 

 these cells (Collin '05, p. 313). The peculiarity of the connec- 

 tion lies in the very large pericellular fibres which arborize 

 about the cell circumference and encompass it in a sort of cone. 

 Nowhere else in the nervous system do we find such large fibres 

 making connections of this kind. Further examination of the 

 cell shows, more centrally, a distinct diminution in the size 

 of the mitochondria which here occur as small grains or filaments, 



