510 WILLIAM H. F. ADDISON 
white substance which has not the aspect of any definite cortex- 
form. One is inclined to regard this part as being the last rem- 
nants of the olfactory lobe (fig. 11). 
So one concludes that the main part of the bulging out of the 
base of the brain is made by the caput nuclei caudati. This is 
covered anteriorly and mesially by cortex of the frontal lobe. 
Laterally it is covered by the remnants of the olfactory lobe, and 
between these two is situated what remains of the better pre- 
served, but still highly atrophied parolfactory cortex. It is also 
to be noted that the head of the striatum is separated from both 
varieties of cortical gray coverings by a thin layer of medullated 
nerve fibers. 
More caudally (fig. 9), all three sorts of cortex—frontal, 
parolfactory and olfactory—disappear, leaving only a thin layer 
of white fibers over the otherwise naked protrusion of the caput 
nuclei caudati. 
TERTIARY CENTERS AND CONNECTIONS 
The hippocampus, as shown in its general relations (fig. 7) 
and in its detailed formation (fig. 8), is an extremely small atro- 
phic structure and it is with some diffidence that one attempts to 
homologize its parts with those of even the microsmatic type of 
Fig. 7 Ventral portion of section 125, as shown in figure 6. The brain-stem 
is cut nearly transversely, showing mid-brain for the most part, but also, ven- 
trally, a small portion of the infundibular region. lLaterally and dorsally are 
portions of the temporal lobes (lob.temp.). Forming the mesial wall of the lateral 
ventricle (vent.lat.), are the fimbria (fim.) and atrophic hippocampus (hip.). A 
caudal part of the corpus callosum (corp.call:) is seen laterally, and beneath it 
the beginning of a crus fornicis (crus for.). The continuity between the fimbria 
and fornix does not show at the level of this section. 2. 
IT, optic tract; ZZ, third ventricle; ag., aqueduct of Sylvius; br.quad., brach- 
ium quadrigeminum; corp.mam.; region of corpus mamillare; lam.quad., quad- 
rigeminal plate; lob.temp., temporal lobe; pes.ped., pes pedunculi; sub.nigra, 
substantia nigra. 
Fig. 8 Detailed drawing of hippocampal region of preceding figure, showing 
small size of the constituent structures. The atrophic hippocampus shows no 
elevation within the lateral ventricle. Groups of large cells represent the gyrus 
dentatus (gy.dent.). The fissura hippocampi (f.h.) is extremely small, and below 
it, the region of the subiculum (subic.) is represented by the portion of the cortex 
containing fine medullated fibers. The nucleus amygdalae (nuc.amyg.) occupies 
a position in the floor of the lateral ventricle. > 5. 
fimb., fimbria; g.h., gyrus hippocampi; plexus, plexus in lateral ventricle. 
