THE AMYGDALA IN AMPHIBIA 241 
distortion by shrinkage. The relations of the posterolateral 
division of the olfactory nerve to the accessory bulb have been 
described above. 
The olfactory bulb on the whole is more simply organized than 
in the frog. The layer of granule cells is well formed throughout 
the bulb and in front it curves around the rostral end of the 
hemisphere to the medial surface. In the latter region there 
are no mitral cells or glomeruli and the granular layer reaches 
the external surface (fig. 24). The mitral cells form a compact 
layer in the rostral part of the bulb, but in the accessory bulb 
tkey are more scattered, as in the frog. Nowhere is there devel- 
oped a definite molecular layer between the granule and the 
mitral cells. 
Except as just noted, the internal structure of the accessory 
bulb seems to be essentially similar to that of the remainder of 
the bulb. Mitral cells and subglomerular cells are freely impreg- 
nated in our Golgi preparations and the relations of terminals 
of the posterolateral division of the nerve to glomeruli and mitral 
cells are similar to those of the anterior division throughout. ' 
From the whole extent of the bulb fibers pass backward into 
the lateral wall of the cerebral hemisphere as tractus olfactorius 
lateralis, whose dorsal and ventral subdivisions are not so distinct 
as in the frog. These are mostly unmyelinated, with a few 
myelinated fibers among them which run for a short distance 
only (Herrick, ’10, p. 422). Some of the myelinated and unmye- 
linated fibers from the ventral part of the bulb pass dorsocaudad 
through the deeper layers of the accessory bulb to join the dorso- 
’ lateral olfactory tract, as in the frog. 
The unmyelinated fibers of the dorsolateral olfactory tract are 
very numerous and form a wide compact superficial fibrous layer 
over the dorsolateral quadrant of the hemisphere. These second- 
ary olfactory fibers come chiefly from the rostral part of the bulb 
and are mingled with fibers of the third order (tractus olfacto- 
corticalis lateralis). The dorsolateral quadrant also receives 
numerous unmyelinated fibers from the accessory bulb which 
form a zone of open neuropil between the compact dorsolateral 
tract already mentioned and the stratum griseum. These 
fibers have been mentioned by Bindewald (14, p. 38). 
