THE AMYGDALA IN AMPHIBIA 261 
These fibers unquestionably are the precursors of the mamma- 
lian thalamic projection fibers for somesthetic, visual, and audi- 
tory sensibility. Within the hemisphere they terminate through- 
out the ventrolateral area and to some extent at least in the 
dorsolateral area, especially toward the posterior pole. The 
return paths for these somatic systems are the strio-thalamic 
and strio-tegmental fibers of the lateral forebrain bundle. These 
are myelinated and unmyelinated fibers which arise (so far as 
now known) from neurons of the ventrolateral area. 
The same part of the urodele hemisphere which receives the 
ventrolateral olfactory tract and the thalamic connections last 
described is also functionally related with the hypothalamus by 
the olfactory projection tract (tractus pallii), whose ascending 
fibers also reach the caudal part of the dorsolateral area. 
Fibers pass from the lateral wall of the hemisphere to the 
habenula from the dorsolateral area by the massive tractus 
cortico-habenularis lateralis and from the ventrolateral area 
by the smaller tractus amygdalo-habenularis. The ventrolateral 
area is connected with the opposite side of the brain through the 
anterior commissure by decussating and commissural fibers. 
And, finally, the lateral areas are ‘broadly connected with the 
medial areas of the hemisphere by extensive systems of associa- 
tional fibers, some of which form the four tracts already mentioned 
(diagonal band, stria terminalis, and dorsal and ventral olfactory 
projection tracts), while others in more diffuse formation cross 
the dorsal and ventral angles of the hemisphere. 
Briefly summarizing our analysis of the lateral wall of the 
urodele hemisphere, we notice: 
1. The olfactory bulb is lateral, with an imperfectly differenti- 
ated accessory bulb posteriorly which receives fibers from the 
supposed vomeronasal organ, as well as fibers from other parts 
of the nasal sac. 
2. The lateral wall of the hemisphere is thin and undifferenti- 
ated except for a thickened region laterally of the interventricular 
foramen, here termed the ventrolateral nucleus of the hemisphere. 
3. The entire lateral wall, except perhaps a portion of the 
ventrolateral nucleus, receives secondary olfactory fibers and 
