224 JOHNSTON. [You. 1. 



diameter and from 32 to 240 //. in their long diameter, possess 

 from two to five thick dendrites, each of which supplies one or 

 more olfactory glomeruli, and frequently have one or more 

 slender dendrites which end freely in the glomerular zone with- 

 out forming glomeruli. The axis cylinders are moderately 

 thick fibers which take a direct course toward the fore-brain, 

 and give off collaterals which rise toward the glomerular zone. 

 The second variety of mitral cells (Fig. i,/) are smaller, meas- 

 uring 12 to 1 6 by 1 6 to 32 fi, have each a single thick den- 

 drite which immediately breaks up into a glomerulus or into 

 two or three imperfectly separated glomeruli, and have no non- 

 glomerular processes. Their axis cylinders are usually directed 

 centrally. 



(2) Stellate cells. I have found numerous cells (Fig. i, e) 

 measuring 12 to 16 by 12 to 32 /n which have from two to five 

 dendrites usually disposed parallel to the surface of the lobe, 

 so that the cells have a stellate appearance in surface view. 

 The dendrites are richly branched and long, their greatest 

 expansion sometimes exceeding i mm. The branches of the 

 dendrites end in olfactory glomeruli. The axis cylinders, which 

 I have found in only a few cases, are directed either centrally 

 or backward toward the fore-brain. 



(3) The cells with short axis cylinders (Fig. i, d) measure 

 about 16 by 20 /A. From one end of the cell arises a thick 

 dendrite whose branches end in glomeruli. A smaller process, 

 which I take to be the axis cylinder, arises from the end of the 

 cell opposite the dendrite and breaks up into numerous slender, 

 smooth fibers which are lost in the glomerular zone. These 

 cells are very few in number and very distinct in their 

 character. 



c. ZONE OF GRANULE CELLS. - - Besides the granule cells 

 which give this zone its name, I have found in it three other 

 distinct forms of cells, which I shall call stellate cells, spindle 

 cells, and cells of Cajal. 



(i) The stellate cells (Fig. i, b] measure 16 to 32 by 24 to 

 128 /A. They possess from three to five widely diverging den- 

 drites whose branches end in the glomerular zone, where they 

 enter into the formation of olfactory glomeruli. Their axis 



