362 ELIZABETH CAROLINE CROSBY 
' Tractus olfactorius 
Following the human terminology, the writer has considered 
this tract to consist of three divisions, a medial, an intermedi- 
ate, and a lateral, although the first two are very closely asso- 
ciated and have both been considered by many authors under 
the name of the medial olfactory tract. (For a diagram of the 
distribution of these tracts see figs. 44 to 46). The data given 
here have been obtained, partly by the study of sections 
prepared by the use of Ehrlich’s haematoxylin and by the 
Leuden van Heumen method and partly by work with a Cajal 
series in which the axis cylinders of any myelinated fibers, as 
well as the unmyelinated fibers, were brought out. The data 
in all probability are not complete. 
Tractus olfactorius medialis (figs. 18, 14, 44). This tract has 
been described in reptiles by Edinger (’88), Adolf Meyer (’92), 
C. L. Herrick (’93), Unger (06), DeLange (11), and Johnston 
(15). As its name implies, it hes medial to the ventricle of ‘the 
bulb and arises, in general, from the more medially and ventro- 
medially placed mitral and granule cells. Throughout the bulb, 
this tract is lateral to the mitral cells. In the crus many of its 
fibers end in the nucleus olfactorius anterior or send their col- 
laterals to that nucleus. The projection cells of the nucleus, 
in turn, send axones to join the tract. Thus the medial olfac- 
tory tract is made up of fibers from both primary and secondary 
olfactory centers. 
In the anterior end of the hemisphere the tractus olfactorius 
medialis has come to lie along the medial surface and it occupies 
this medial position as it passes caudad, discharging at various 
levels into the dendrites of the intrinsic cells, the double pyramids 
and the small projection cells of the hippocampus. 
Tractus olfactorius intermedius (fig. 14). This fiber tract, 
arising from mitral and granule cells and not distinguishable 
from the medial tract until the hemisphere is reached, ends in 
the nucleus olfactorius anterior and the medial part of the tuber- 
culum olfactorium. Other fibers pass farther caudad and ap- 
pear to enter the nucleus of the diagonal band of Broca. It is 
