The nucleus of BELLONCI in birds - DWC

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domestieus), viz., a transverse and a sagittal WEIGERT-PAL~paracarmine
series, a horizontal WEIGERT-PAL~alum~carmine series, and a transverse
series stained for cells by HUBER's toluidin blue method. Having found
the nucleus sought for, it was also studied in a transverse WEIGERT-PAL
series, counterstained with various sorts of carmine, of the dove (Columba
domestica) and in a transverse HUBER series of the same anima!. This
bird, due to the stronger development of the olfactory system, proved better
suited for the study of the connections.
An inspection, in the sparrow, of the foremost part of the thalamus, the
region where the nucleus of BELLONCI is found in reptiles and mammais,
immediately revealed the presence of a clearly circumscribed nucleus,
whieh by its general appearance made the impression to be the sought for
structure. As in the cases, so far known, it was a small ellipsoidal body,
whose neuropil stained strongly with paracarmine. In the dove about the
same relations were found. As was to be expected, this clearly circum~
scribed and rather conspicuous nucleus had been described before. It
appeared to be the nucleus lateralis anterior of EDINGER and WALLENBERG
(1899), a cell group about whieh, despite its distinctness, a great con fusion
has arisen, whieh I shall try to disentangle at the end of the paper.
I shall start to put forward my findings in the sparrow, and already now
shall speak of a nucleus of BELLONCI, leaving the argumentation for later.
In the sparrow the nucleus of BELLONCI is an ellipsoidal body of dense
neuropil with numerous, mostly small cells in it, lying immediately dorsal
to the margin of the foremost part of the chiasma, separated, however,
from it by the tractus isthmo~optieus (figs. I, 2, 3, 4). The major axis of
th is ellipsoidal body extends in a transverse plane from ventromedial to
dorsolateraI. and is but little longer than the longer of the minor axes,
whieh is directed sagittally. The third axis is considerably shorter than
the other two.
The nucleus of BELLONCI lies dorsolateral to the voluminous cell group,
mostly designated without specifieation as lateral genieulate, but whieh I
agree with KUHLENBECK (1937) in regarding as the ventral lateral
geniculate (figs. I, 3). This nucleus beg ins a little more caudally than the
nucleus of BELLONCI. Just in front of the latter the nucleus supraopticus
and nucleus of the diagonal band of BROCA are situated, the former
ventrally and applied to the optie tract, the latter more dorsally (fig. 4).
The nucleus of BELLONCI is immediately succeeded by the nucleus rotundus
(figs. 3, 4).
The ramus dorsalis of the tractus septo~mesencephalieus courses dorsal
to the nucleus of BELLONCI, so that it is wedged in between this tract and
the tr. isthmo~optieus (figs. I, 2, 3, 4) . Though closely applied to these
tracts, so that it may synapse with them, there is no conclusive evidence,
in our WEIGERT-PAL preparations, of such a supply, no more than by
the optie tract. As far, however, as it is possible to judge from WEIGERT­
PAL preparations, the chief supply of the nucleus of BELLONCI is provided