THE STllUCTLKE OF CHKO.MUPHILE CELLS OF THE XEHVOUS SYSTE.\L 41 



may not be visible with the microscope or the ultra-micr()sco])e. The Nissl sub- 

 stance, argentoi^hilous material, etc., doubtless undergo changes of this sort from 

 liquid to fluid and semi-solid phases. It seems right and proper, therefore, to steer 

 an intermediate course, as I have done, between those, on the one hand, who assert 

 that the Nissl substance and the neuro-fibrils occur in living cells in approximately the 

 same form as they appear in fixed and stained prei)arations, and those, on the other 

 hand, who claim that they are artefacts pure and simple and that they can never 

 be seen in the living cell. Our problem is more one of material than it is of form. 

 In this connection the solution of mitochondria in chromophile cells is a i)he- 

 nomenon of considerable significance. In addition to variations in the chemical 

 constitution of mitochondria, there is also evidence to the effect that there may be 

 variations in the condensation or density of the mitochondrial substance (vide 

 Duesberg, 1915, p. 40). This is a factor which has been too often ignored. We are 

 inclined to look for mitochondria in all cells w^hich are functionally active and in 

 which metabolic changes are taking place. The fluidity of the mitochondrial sub- 

 stance varies and I am i)repared to believe that further investigation will bring to 

 light cells which are active functionally, but in which no trace of formed mito- 

 chondria may be seen. 



CONCLUSIONS. 



{ 1 ) Chromophile cells occur under normal conditions in the brains of white mice. 



(2) They are distributed unequally in the different parts of the nervous system. 

 They are most abundant in the cerebral cortex. They are jn-ogressively less abun- 

 dant in the cerebellum, corpus striatum, thalamus, midbrain, and medulla. They 

 are of very rare occurrence in the spinal cord, spinal ganglia, and sensory ganglia of 

 the cranial nerves. 



(3) This restriction of the chromojihile cells to the higher centers is in full accord 

 with the well-known lability of the central, more highly specialized cells as contrasted 

 with the more primitive, peripheral neurones. 



(4) Chromophile cells, as seen in fixed and stained preparations, vary greatly 

 in structure. There is usually more or less shrinkage of the cell-body. The 

 nucleus may also be shrunken. The acidophilic and basoi)hilic nucleoli are particu- 

 larly prominent and the ground-substance of the nucleus stains intensely with both 

 acid and basic dyes. There is an increase in the amount of Nissl substance. The 

 Nissl bodies become confluent and form a homogeneous mass. The cell is hyper- 

 chromatic. The canalicular apparatus is unaltered. The mitochondria either 

 increase in number and stain more intensely, or else some of them lose their discrete 

 outlines and form a diffuse deposit which stains intensely by the mitochondrial 

 methods of technique. This change in the mitochondria occurs in the cell processes 

 in the neighborhood of the cell, as well as in the cell-body. Although the nucleus 

 may be completely obscured by this cloud of mitochondrial substance, it still 

 remains and stains in the usual way with hematoxylin and eosin. 



(5) The labihty of the mitochondria and the constancy of the canaUcular 

 apparatus in chromoi)hile cells confirms my earlier contention by showing that the 

 two structures are physiologically as well as anatomically distinct. 



