146 Journal of Comparative Neurology. 



intra-vitam staining with methylen blue is necessary to determine 

 the relations of cells, fibers and fibrillar substance completely. 



THE TYPES of NERVE CELLS. 



By the assistance of the bichromate of silver method we 

 may imagine a cell with a nerve fiber dividing at some distance 

 from the cell body into two branches that form with it a T or a Y 

 as probably the most typical of the nerve cells of the bee, or prob- 

 ably of arthropods in general. The assertion does not hold 

 ■good completely, for there are cells in the optic lobes and even 

 in the central part of the brain in which all the branches given 

 off appear as very small branches of large fibers. 



To classify for convenience of description the various mod- 

 ifications met with in the brain one may divide them into : 



1 . Afferent or setisory fibers in which the cell body is situ- 

 ated somewhere in the neighborhood of the external (to the 

 brain) organ of sense and sends its neurite into the brain and 

 its dendrite into the sense organ. Such cells may be called bipolar, 

 and in them, as in all other nerve cells, the only criterion of 

 the difference between dendrite and neurite is in the direction 

 of the passage of the neural impulse with reference to the cell 

 body, or to the trunk of the fiber leading to the cell body. 

 Such fibers do not penetrate far into the brain, where they may 

 terminate in a mass of fine branchlets as in the case of the fibers 

 from the antennas. In other fibers the terminal branching is 

 more or less loose or not massed together, as in the case of 

 whatever sensory fibers there are entering through the labral, 

 mandibular, maxillary and labial nerves or from the ventral cord. 



In the accompanying diagrams this class of fibers and all 

 others bearing sensory stimuli into the portion of the brain 

 here considered, as from the optic lobes and the ventral cord, 

 are colored blue. 



2. Connecting fibers in which the cell body is situated to 

 one side of the track of the passing stimulus — assuming that it 

 does not necessarily go to the cell body — and in which the 

 dichotomous T- or Y-shaped branching is most easily recogniz- 

 able. The peripheral of the two branches connects with the 



