Literary Notices. xcix 



The various parts of the axial nervous system and the sense-organs are 

 separately discussed with numerous diagrams and at the close a full 

 bibliography is added. Many of the results we have already pres- 

 ented in abstract, but the original work is invaluable to those who 

 wish to keep abreast of the recent progress in the cellular morphology 

 of the nervous system. We can give now only the author's table of 

 general conclusions. 



i. There is an essential difference between the processes of nerve 

 cells, epithelial cells and neuroglia cells. The nervous elements are 

 true cellular units, or neurons, in the sense of Waldeyer. 



2. There is no actual cellular continuity. The stimulus is carried 

 from one cell to another by contact, as a current passes between two 

 contiguous conductors. This contact is made between the terminal 

 dendrid or collateral of the axis-cylinder on the one hand, and the 

 cell body or its protoplasmic processes on the other hand. If the 

 protoplasmic processes are absent, as in the spongioblasts of the retina, 

 the unipolar cells of the spinal ganglia and the unipolar elements of 

 invertebrates, then the surface of the cell-body serves as the point of 

 application for the terminal dendrids. 



3. The apparent path of a stimulus in a cell with both kinds of 

 processes is such that the stimulus is cellulipetal in the protoplasmic 

 processes and cellulifugal in the axis-cylinder. The latter only occurs 

 in cells with only the one kind of processes (spongioblasts, etc.) The 

 receiving apparatus (the cellulipetal, or better, karyopetal sphere) is 

 the thin protoplasmic layer enveloping the nucleus. 



4. In bipolar cells (acustic, olfactory, retinal, the sensory bipolar 

 cells of worms according to Lenhossek and Retzius, the bipolar sens- 

 ory spinal ganglion cells of fishes, etc.) the peripheral process is 

 strong and corresponds to the protoplasmic process, which is adapted 

 for the reception of stimuli (cellulipetal activity.) In the unipolar 

 cells of the spinal ganglia of Batrachia, Reptilia, Aves and Mamma- 

 lia, the peripheral branch of the single process has the significance of 

 a protoplasmic process, i. e., an organ for cellulipetal activity, while the 

 central fine branch is a nerve fibre, an organ for cellulifugal activities. 

 The single stem which contains both kinds of processes does not ex- 

 ist in the embryonic period (His); it is produced later by the with- 

 drawal of the cell-body ; it thus represents a part of the cell-body, 

 not a nerve fibre. 



5. The protoplasmic processes do not constitute, as Golgi and 

 his school would have it, a nutritive apparatus, but like the axis-cylin- 

 ders they have a conducting function. The only two supports found 



