THE AMYGDALA IN AMPHIBIA yal 7 
Il. ANURA 
The olfactory bulb 
In the frog the internal structure of the vomeronasal formation 
is, so far as observed, essentially similar to that of the remainder 
of the olfactory bulb. The fibers of the vomeronasal nerve 
enter glomeruli, where they engage dendrites of the mitral cells 
in the usual way. Beneath the mitral cells is a layer of ies 
cells bordering the ventricle (figs. 1, 19). 
The accessory bulb not only forms ie familiar eminence on the 
lateral surface of the cerebral hemisphere, but also projects into 
the lateral ventricle as a well-defined ventricular swelling (figs. 
1, 35). This is shown, somewhat imperfectly, in horizontal 
section in figures by P. Ramén y Cajal (’05, pl. 15, fig. 3, and 
pl. 17, fig. 5). Through the deeper part of this thickening there 
pass fibers of the dorsolateral olfactory tract (a few of which are 
myelinated) on their way from the ventral part of the olfactory 
formation to their definitive position in thedorsolateral quadrant 
of the hemisphere. Toward the caudal end of the accessory 
bulb these fibers form a distinct daseicke at its dorsomedial angle 
(fig. 1). 
In the olfactory formation of the bulb the layer of granule cells 
is separated from the layer of mitral cells by a distinct molecular 
layer; this latter layer, however, is absent in the vomeronasal 
formation (fig. 19), and here there is no clear boundary between 
mitral cells and granule cells. 
The ventrolateral olfactory tract 
The course of the ventrolateral olfactory tract, its termination 
in the amygdala, and the course of the dorsal olfactory projection 
tract from the latter organ to its nucleus in the chiasma ridge 
as seen in cross-sections of the brain of the frog, Rana pipiens, 
are illustrated in figures 1 to 12. These figures are drawn from 
a series of Weigert sections and for purposes of orientation all 
myelinated fiber tracts are entered on the right side of the draw- 
ings. The greater part of the courses of the ventrolateral olfac- 
tory tract and the olfactory projection tract can be followed in 
