RHINENCEPHALON OF DELPHINUS 499 
given to the institute by H. I. H. Prince Alexander of Oldenburg, 
and came from the Black Sea in the Caucasus. The sections were 
studied for the most part with a hand lens, or the unaided eye, 
and the use of the compound microscope was resorted to, only 
for finer details. The drawings of the sections were made with 
the aid of the Edinger projection drawing apparatus. 
MAMMALIAN RHINENCEPHALON 
The several parts of the brain which are generally considered 
to belong to the olfactory mechanism may first be mentioned. 
It is agreed that the bulbus olfactorius, the tractus olfactorius 
coming from it, and the region of the lobus olfactorius where 
this tract ends, are the most certain parts. Since the studies 
of Broca and of Zuckerkandl, the hippocampus has also been 
included as part of the olfactory centers, and guided by the work 
of Edinger, Elliot Smith, Zuckerkandl and Ramén y Cajal, we 
now consider this as a tertiary center for olfactory receptions. 
For a long time the tuberculum olfactorium (lobus parolfactor- 
ius), lying mesial to the lobus olfactorius, was also considered to 
belong to the same general olfactory apparatus, but latterly, 
especially through the work of Edinger, this has become very 
doubtful. He looks upon it as the center for a special sense, which 
he has termed the ‘oral sense,’ and which is especially large in 
those animals which have highly developed sense perceptions in 
the snout region. 
In addition to the fibers joining the lobus pyriformis to the 
hippocampus (Edinger ’11, p. 380) there arise from the olfactory 
and parolfactory lobes, several other bundles which join these 
structures to the tertiary centers. (1) The tractus olfacto-hippo- 
campanicus is strongly developed in macrosmatic animals, espe- 
cially where the corpus callosum is small or lacking, but it 
dwindles in man to the stria longitudinalis Lancisil. (2) The fas- 
ciculi parolfacto-hippocampo-septales, first described by Zucker- 
kandl (’87), pass into the septum pellucidum, and unite at the 
dorsal and caudal end of this structure with the fornix fibers. 
After this union they go back together and enter the cortex of 
the hippocampus. According to Edinger this is a very primitive 
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