Proceedings of the section of sciences - DWC - KNAW

( 41 )
ficcompfinying fibl'es; ficcording 10 HUI,LES 1), this is filso the case in
the pig. A weU isolated exit is seldom to be seen owing to the fibres
not running compactly to the pel'iphery and to their being apparently
interrnpted by the masticatory nucleus. Where the tracing of the
mesene. fibres is possible (tamanclua tetraclactyla) , its exit in the
ventral part of the rad. spinalis trigeminis is clear; in this animal
a wide sepal'ation from the more ventrally running motor quintus
root is easily distinguishable.
What can be seen in all l,he other mammals is that tibl'es fl'om
the region of the rad. mesene. turn venteo-laterally and l'each the
periphery close 1,0 the. motOl' nerve. The latter passes through the
pia, ventrally frolll the sens. Ol' radix. spinal.; the lllesenc. fibres in
any case do not come to lie ventrally from the motor root.
Summing up the results of this investigation, the conclusions are
as follows:
1. In all animaIs, where the exit of the mesenc. quintus root
can be traced with certainty, th is takes place dOl'sally to the mot07'
7'00t.
2. In all these animals (scyllium canicula v. i.) it leaves the
oblongata bet1neen the fib1'es of tlw sens. trigem,inus root, in teleostei
perhaps even slightly dorsally tu them. Whethel' it runs extra-bulbar
for a part with the sens. root and its l'ollaterals, is uncel'tain, but
it is not rendered improbable bi t11e above-mentioned pathological
observation.
3. In scylliwn canicula tlle mesene. quintus root leaves in two
ways the oblongata: one part orally to the sens. root, and one part
in the way as mentioned snb.2. The first part is, however. accompanied
by a more ventral motor V stem.
4. The pl'imitive position of the mesenc. quintus nucleus is clo)'sal
in t.he tectum opticul1l, not distally fl'om it. The variations herein
in lowel' animals m'e partly due 1,0 diffel'ences in the structure in
the mid-brain. In the lowest order of lllamlllals \monotl'emata and
marsupials) this position is seen again in principle. MOl'eover in
marsupialia especially (didelphys) the nucleus consists of different
kinds of ceUs, just as in some reptiles ; while in fishes 011e
form of cell (clumsy-polyedric), and in higher lllammals and birds the
other (l'ound, oval, vesir,ulal') predominates or is exclusively present.
5. The clistal sp1'eaclin,q of the nucleus, most markec1 in insectivora,
1) HULLES: Vergl. Anatomie del' cercbr. TrigeminuSWlll'Zel. Obersteiners Arbeiten.
Hl08-
- 50 -