374 ELIZABETH CAROLINE CROSBY 
and the preoptic portion of the stria terminalis. Some of the 
fibers arise probably from cells of the interstitial nucleus and 
fibers from cells of the ventro-medial nucleus probably send 
collaterals into the interstitial nucleus. The fibers of this 
great olfactory projection tract as they swing medialward come 
into relation with the descending fibers of the columna fornicis 
and there turn sharply caudad and run with the latter bundle 
backward, medialward and ventralward to the mammillary body 
(figs. 20, 21). (Dr. C. J. Herrick first called the writer’s at- 
tention to the fact that fibers of this olfactory projection tract 
join the fornix fibers and accompany them ventralward). 
Ramon y Cajal (11, vol. 2, pp. 722-723, fig. 462) has de- 
scribed and figured this tract and its associated nucleus in the 
mouse. Johnston (’15) described the tract in the turtle. He 
considers it to be the characteristic connection of his medial 
large celled nucleus of the amygdaloid complex (the ventro- 
medial nucleus of this description), but does not mention the 
interstitial nucleus which accompanies it. 
Basal forebrain bundles 
Medial forebrain bundle (figs. 9, 16, to 21, M.F.B.). Thisis the 
tractus septo-mesencephalicus of Unger and DeLange. It arises 
from the parolfactory (septal) nuclei and runs, accompanied by 
fibers of the. fornix longus, medialward and ventralward until 
it meets the lateral forebrain bundle, which lies farther laterally. 
The two bundles can be distinguished from each other for a long 
distance because of a difference in the angles at which the fibers 
are running. Finally the two become closely mingled and it re- 
quires careful study to distinguish them, although such a dif- 
ferentiation is quite practicable. According to DeLange (13) 
and Unger (’11) the medial forebrain bundle runs to the midbrain. 
In the alligator in material prepared by the Cajal method a 
part of the fibers appear to end in the hypothalamus (tractus 
olfacto-hypothalamicus of the literature), while others pass 
caudad to the midbrain (tractus olfacto-peduncularis). 
There is no direct evidence in the material studied regarding 
the direction of conduction, but the probability is that impulses 
