THE STRUCTURE OF CHROMOPHILE CELLS OF THE NERVOUS SYSTEM. 39 



of cell granulation now known to us. They occur in almo.st all cells. Yet certain 

 cells, like the fully differentiated non-nucleated red blood-cell, unquestionabl}' con- 

 tain a large amount of phospholipin, though no formed mitochondria can be seen. 

 The mitochondrial substance is probably present in solution, just as it appears to 

 be in chromophile cells, for it would obviou.sly be absurd to state that it must always 

 occur in that state of condensation which makes it visible with the aid of certain 

 powers of the microscope. The recent investigations of Levene (1915, p. 41) on 

 cephalin are of interest. A new field of investigation is evidently opened up. It 

 may thus be possible to pursue this line of w'ork with chemical as well as with his- 

 tological and ]ihysiological methods, a combination which has been but rarely 

 effected. 



Work along these lines seems the more desirable since, as will be seen, it may 

 throw new light upon certain problems in the pathological anatomy of the nervous 

 system as well. Wells (1907, p. 460), in his discussion of mental fatigue, writes: 



".Since the lecithin forms .so important a part of the nervous system, it is tempting to imagine that 

 in fatigue exce.ssive (luantities of its toxic decomposition product, cholin, and the still more toxic 

 derivative of cholin, nenrin, are formed in considerable amounts and cause part, at least, of the 

 intoxication." 



Now we have seen that, in the opinion of certain investigators, mitochondria 

 are largely composed of lecithin. It is possible, therefore, if Wells's reasoning is 

 correct, that the symptoms of mental fatigue are the result of their decomposition. 

 Moreover, Halliburton (1907, p. 74) and others are convinced that organic diseases 

 of the nervous system may be distinguished from functional neuroses on account of 

 the formation of cholin in the one and not in the other. This opens up the possibility 

 of a differentiation between these two great groups of diseases on the basis of cell 

 structure, as to whether or not there is a change in the mitochondria. 



(3) The persistence of the canalicular apparatus in chromophile cells is of 

 interest in general cytology. In chromophile cells, in which there arc marked 

 structural changes, the canalicular apparatus remains without anj' great modifica- 

 tion. This is rather surprising, since investigators have gradually come to regard 

 the canalicular apparatus as the most labile cell organ; but it is in conformity with 

 Key's as yet unpublished observations on degenerative changes in spinal ganglion 

 cells. Key finds that the canalicular apparatus persists without much modification 

 for from 12 to 24 hours after death in spinal-ganglion cells left in the animal. 



I have shown (1912, p. 494) that a canaHcular apparatus, in the form of a 

 system of clear, uncolonnl canals, occtu's in the same cell with tyjiical mitochondria 

 and that consequently the canalicular apparatus and the mitochondria are structu- 

 rally distinct. This conclusion is strongly supported by my observation that they 

 may hkewise be seen together in chromophile cells, the difference being that while 

 the mitochondria are greatly changed, the canalicidar apparatus remains with little 

 or no modification, so that they are functionally as well as structurally different. 

 My positive impregnations of the canalicular apparatus by the uranium-nitrate 

 method of Cajal confirm this observation. 



Now, Cajal (1908, p. 123) is so certain of the identity of the clear canals 

 (described originally by Holmgren) and the "Apparato roticolare interno" of Golgi 



