THE PINEAL BODY 225 



acter. In fact, they have in the later periods of fetal and early 

 postnatal life all the appearances usually associated with glan- 

 dular cells. As compared to the cells in the glandular portion 

 of the hypophysis, the size of the pineal cells is two or three 

 times as great. This difference in size affords a striking point 

 of differentiation in those pathological conditions in which the 

 pineal cells in the course of tumor formation have migrated into 

 and through the posterior lobe of the hypophysis and invaded 

 the pituitary gland. The contrast is so marked as to present 

 no difficulty in the identification of the two varieties of cells. 

 That the epiphysis is made up of neuroglia cells in large part, 

 if not entirely, has been the contention of several observers. 

 The presence of short, branching fibers in close proximity to the 

 pineal cells has seemed to be the basis for this. On the other 

 hand, if the pineal cells in mammals are to be regarded as neu- 

 roglia, it must be granted that they are certainly unlike the 

 neuroglia cells observed in other parts of the central nervous 

 system. Dimitrova, 92 who makes out such a strong case from 

 her histological study in favor of the neuroglial character of the 

 epiphysis, seems to base her conclusions upon criteria which are 

 not wholly convincing, for the mere presence of demonstrable 

 fibers in the neighborhood of the cells does not of itself indicate 

 that these cells are neuroglial in character. Furthermore, this 

 view neglects to take into account the highly specialized char- 

 acter of the pineal cells. If, on the other hand, it be granted 

 that the cell constituency of the epiphysis is, in major part, 

 neurogliar, this admission would not wholly invalidate the idea 

 that the structure is glandular in nature, for, according to the 

 most recent researches of Nageotte 281 and Mawas, 2 " neuroglia 

 cells contain mitochondria and hence, according to these inves- 

 tigators, should be considered as glandular elements. In this 

 light, the neuroglia throughout the entire nervous system is 

 endowed with secretory function. In general, however, it 

 does not seem necessary to invoke this interpretation of the 

 neuroglia hi order to place the pineal body in the class of glan- 

 dular structures, for the character of the pineal cells is in itself 

 sufficient argument in favor of a function different from that 



MEMOIR NO. 9 



