14.4 JULIA WORTHINGTON. 
next to the medulla, the largest divisions of the brain, and 
thus give a line at once as to the relative importance of the 
several sections of the brain in the physiology of that organ. 
The lobes are of equal size and symmetrical, and almost 
entirely separated from each other, being united only at their 
ventro-mesial angles. ‘Their mesial faces are flat and are 
apposed to each other, with a sufficient space between for a 
double fold of the inner layer of the dura to penetrate (fig. 
7). Dorsally, the two lobes, taken together, are somewhat 
convex, the lateral faces rounding off from the dorsal to the 
ventral surface. Ventrally they are flat across the caudal 
end, and slightly concave across the cephalic end, their 
greatest thickness, dorso-ventrally, being not near the mesial 
face, but about half-way between that and the lateral edge. 
Examined superficially each lobe is seen to have three divi- 
sions—an inner, middle, and outer or lateral one (figs. 1, 2). 
On the dorsal surface the inner and middle divisions are 
nearly equal in width, and cover the crown of the lobe, the 
outer border of the middle division being about where the 
arch begins to fall away, so that the lateral division does not 
extend as far dorsally as the other two. On the ventral sur- 
face they are more plainly marked than on the dorsal, and it 
is the inner lobe that does not extend as far ventral as the 
other two, thus making the ventral surface concave. These 
three divisions have definite relations to the ending of the 
olfactory nerves. 
The olfactory lobes, viewed in section, are highly vascular, 
and are seen to be very loose in structure, The cephalic 
half of each lobe is composed mainly of the olfactory 
glomeruli. On the ventral and lateral surfaces this glome- 
rular layer extends almost as far caudad as the end of the 
lobes; on the dorsal surface it does not spread as far. It is 
the divisions of this layer that are indicated on the surface 
of the lobes, and the absence of the layer from the inner 
ventral division that causes the concavity of the ventral 
surface. The glomeruli themselves are quite large, many of 
them measuring about 80u x 120. ‘They are packed close 
