330 ELIZABETH CAROLINE CROSBY 
These places of synapse are called glomeruli and, scattered 
among these glomeruli, are a number of small cells which send 
their dendrites and, probably, their axones (though there is no 
proof in the material used for this statement), into the various 
glomeruli and so serve for the correlation of impulses. These 
are the type that Cajal calls intraglomerular cells. 
Mitral cells (figs. 23 and 24). In transverse sections, the 
mitral cells have a ring-like arrangement around the granule 
cells as a center (fig. 13). Near the anterior end of the bulb 
they form a somewhat diffuse mass but soon take on their char- 
acteristic arrangements. They are replaced by other cell groups 
in the olfactory crus. 
In the ventro-medial portion of the bulb, near its anterior 
end, the mitral cells form a curious depression or ‘fossa.’ This 
‘fossa’ was first described by C. L. Herrick (’90), who said that a 
separate slip of the olfactory tract arises from it. The ‘fossa’ 
is very evident in both the toluidin blue series and those series 
prepared by the Cajal method. In the latter series, the fibers 
can be seen passing caudad from it and forming a part of the 
tractus olfactorius. There is a special thickening of the glomer- 
ular layer in that region, which pushes. the mitral cells inward 
and causes the depression. Beyond being a point of entrance 
for a particularly large number of olfactory fibers, it does not 
appear to have any special significance. 
A study of the toluidin blue preparations shows a considerable 
variation in the shape and size of the different mitral cells. 
On the whole, the nuclei tend to be rather large and are usually 
placed nearer the ventricular border of the cell. An abundance 
of Nissl substance is present in the cytoplasm. 
The variations in size among the mitral cells are brought out 
most clearly in the Golgi preparations. Some of the different 
types observed there are illustrated in figures 23 and 24. Round, 
stellate, and large pyramidal forms are seen. A mitral cell 
usually has two main dendrites and several smaller dendritic 
branches. The larger dendrites are thick and thorny and enter 
into the formation of glomeruli with the incoming olfactory 
fibers. The smaller dendrites extend as far outward as the 
