THE FOREBRAIN OF THE ALLIGATOR 363 
joined by fibers from the nucleus olfactorius anterior to the 
tuberculum olfactorium. Part of its fibers pass through the 
anterior commissure to the other side and end there in the nu- 
cleus olfactorius anterior and, probably, partly in the tuber- 
culum olfactortum. These connections have been described by 
nearly all the later workers on the reptilian brain. 
Johnston (15) in the turtle has considered the medial and 
intermediate tracts both under the name of the medial olfac- 
tory tract. He describes a very interesting bundle of this medial - 
tract which runs caudad with the fiber bundle of the diagonal 
band of Broca to the nucleus of the lateral olfactory tract. Quite 
probably this tract is present in the alligator but the material 
available does not permit of its identification. 
Tractus olfactorius lateralis (figs. 13 to 19, 44 to 46). Edinger 
(88), Adolf Meyer (’92), C. L. Herrick (’93), Unger (’06), Kappers 
and Theunissen (’08), DeLange (’11), and Johnston (’15) have 
described this tract in reptiles. In general it arises from the more 
laterally placed mitral cells and projection granule cells of the 
bulb but some of the fibers come from the dorso-medial portion 
and cross over to join the lateral tract. Like the medial tract, 
this lateral one at first lies internal to the mitral cell layer. While 
still in the bulb it begins to swing out to the surface and in the 
crus and lobe it lies mainly along the lateral border of the hem- 
isphere. Near the anterior end of the hemisphere it divides 
into an outer and an inner division. The inner division en- 
ters the nucleus of the lateral olfactory tract and distributes 
to it throughout its whole extent. The outer division ends in 
synaptic relations with cells of the pyriform lobe and sends 
some fibers to the more lateral portions of the tuberculum olfac- 
torium. The tractus olfactorius lateralis not only sends fibers 
to the pyriform lobe but, in the crus and the anterior end of the 
hemisphere, at least, it also receives fibers from it. This tract, 
then, carries both secondary and tertiary impulses. 
Tractus tuberculo-corticalis 
From the tuberculum olfactorium a band of fibers runs along 
the medial border of the hippocampal cortex and discharges 
