196 RALPH EDWARD SHELDON 
portion of the mesal and lateral olfactory areas. The cells of the 
central part of this area are very large and conspicuous (fig. 44) 
and are quite scattered as compared with the cells of other areas of 
the basal lobes. In series stained by cytological methods, such as 
toluidin blue or thionin, it is easy to demonstrate that there is a 
gradual transition from these conspicuous cells to those typical 
of the lateral olfactory area. 
According to the Golgi method, neurones of the central portions 
of the palaeostriatum appear very large, with comparatively 
enormous perikarya, and with long, thick, very thorny dendrites 
(figs. 50, 51). In shape, the perikarya vary from short, flask- 
shaped to pyramidal (fig. 45). 
There is shown in Golgi preparations the same transition 
between the area olfactoria lateralis and the palaeostriatum, as 
in toluidin blue or thionin preparations. One may note a gradual 
change, in passing from the periphery centrally, from the small, 
flask-shaped cells with rather inconspicuous thorns, to the large 
cells, with enormous perikarya and thick, thorny processes; more- 
over, now and then, a cell of the palaeostriatal type will be found 
close to the periphery, or a small lateral area cell found in the palae- 
ostriatum. A large proportion of the cells of both the lateral 
olfactory area and the palaeostriatum send their neurites into the 
basal forebrain bundle, the different parts of which will be taken 
up later. The neurites of the cells of the nucleus teniae, however, 
enter the tractus teniae. Many of the cells of these two areas are 
apparently association cells, functioning not only to bring differ- 
ent parts of the same area, but also adjacent areas, such as lateral 
olfactory area, palaeostriatum and corpus precommissurale, into 
relation. Such is apparently the function of some of the cells of 
the type shown in figs. 50, 51. 
The word ‘palaeostriatum’ is not used in quite the same sense 
as it is used by Kappers, as will be noted from the preceding dis- 
cussion. Kappers believes that the palaeostriatum is closely con- 
nected with the olfactory apparatus, but receives no somatic sen- 
sory connections from the thalamus, which it probably does receive 
in the teleosts. The term as here used indicates that astructure is 
found in the teleosts, closely related to the secondary olfactory 
