40 Journal of Comparative Neurology and Psychology. 



inal basophile granules are now stained with acid-dyes ; (4) fol- 

 lowing the nuclear changes just described the cell body is 

 filled with the basophile granules or the Nissl substance ; (5) 

 the astral rays of the centrosome are not as clearly shown as in 

 the earlier stages. The nerve cells thus changed do not differ 

 from the adult functional cells except in size and, therefore, it 

 may be concluded that the morphological completion of the 

 nerve cell of the white rat is attained during early intrauterine 

 life. In the case of man, Makinesco ('99) and Biervliet ('00) 

 noticed such fully formed Nissl granules in the ventral horn 

 cells of the spinal cord at birth. This does not mean, however, 

 that all the Nissl granules are formed in the cells at this stage, 

 but that they are relatively as abundant as in the adult cells. 

 Therefore it is clear that when the cell body increases in volume 

 the amount of the stainable substances increases correspond- 

 ingly. The explanation of the formation of the stainable sub- 

 stance at the latter stage is not easy, since at this stage the 

 structure of the nucleus is different from that of the earlier 

 stage in which the nucleus resembles that which can be seen in 

 the cells of the active glandular tissue. Before going into a 

 further discussion of this point, it will be well to describe the 

 main features of the nucleus in the adult nerve cells. 



The nucleus in the spinal ganglion cells. — The nucleus in the 

 spinal ganglion cells in an adult white rat is slightly oval in 

 shape and is located at or near the center of the cell. The nu- 

 clear membrane is very distinct and can be distinguished easily 

 from the surrounding cytoplasm. The nucleolus appears nearly 

 in the center of the nucleus, consisting as a rule of a single cor- 

 puscle and staining an intense blue with toluidin blue and ery- 

 throsin. Several endonucleoli are often distinctly visible with- 

 in the nucleolus. These are composed of acidophile substance. 

 The nucleolus is, therefore, composed of two different substances, 

 acidophile substance within, the basophile substance without. 

 The nucleus contains a linin network and a large number of the 

 acidophile granules ; the latter hung on the threads of the for- 

 mer and most abundant along the periphery of the nuclear 

 membrane and around the nucleolus. Thus, except the baso- 



