366 ELIZABETH CAROLINE CROSBY 
certain from a series of experiments performed on the opossum 
that in this form'there are callosal fibers in the hippocampal 
commissure. He believes that callosal fibers are present in that 
commissure in reptiles also, although he does not have the ex- 
perimental proof for their presence there. 
In the alligator, some of the fibers entering into the hippo- 
campal commissure appear to come from the region of the gen- 
eral cortex and so to favor Johnston’s conclusions, but of course 
nothing definite can be settled in this regard until some further 
degeneration experiments have been carried out. Unger, Kap- 
pers, DeLange, and others have described and figured the me- 
dullated fibers of the hippocampal commissure. 
Commissura anterior (fig. 18). The following components of 
this commissure have been identified: : 
a. Stria terminalis fibers. The course of these fibers through 
the commissure is described under the account of the fiber sys- 
tems (see account of stria terminalis pars commissuralis). 
b. Fibers from the tractus olfactorius intermedius to the 
tuberculum olfactorium and the nucleus olfactorius anterior of 
the other side. These are myelinated. 
c. Also, short fibers from the nucleus olfactorius anterior and 
the tuberculum olfactorium of one side to the corresponding 
centers of the other side. 
d. So-called ‘commissura epistriata’ fibers (DeLange 711). 
These are included under the description of the stria terminalis 
fibers. This component consists of true commissural fibers of 
the stria terminalis, which connect the pyriform lobe and the 
nucleus of the lateral olfactory tract of the two sides of the brain, 
and of decussating fibers of other types. 
Tract of the diagonal band of Broca 
These fibers connect the region of the nucleus of the lateral 
olfactory tract with the parolfactory region and the nucleus 
commissurae hippocampi of the same side. These fibers pass 
ventrally of the basal forebrain bundles close to the surface of 
the brain. Caudalward many of the fibers end in the ventro- 
