Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/281/
273 
FIFTH PAIR OF NERVES. 
the same part as the greater packet, and poste¬ 
rior to it. (See Jig. 140). This view of the con¬ 
nection of the lesser packet, if confirmed, must 
lead to interesting results with regard to the rela¬ 
tions of the two portions of the fifth nerve at least ; 
it will at all events decide the question as yet in 
dispute, whether they are to be regarded as 
distinct nerves, or parts of the same ; upon 
this point further light will be thrown by the 
disposition of the same part in fish, in which 
the source of the uncertainty prevailing with 
regard to the nerve in the higher classes does 
not exist to the same amount ; inasmuch as the 
ganglionic and non-ganglionic divisions of the 
nerve seem for the greater part associated in 
their distribution. 
Fig. 141. 
Back view of pons, bulb, and course of the Fifth 
Nerve in man. 
18 Tubercula quadrigemina. 
19 Continuation upward of the tract from which 
the Fifth Nerve arises. 
The other references indicate the same parts as 
in the preceding figure. 
When the adjoining matter has been care¬ 
fully cleared away from the part to which the 
packets of the nerve are attached, that part ap¬ 
pears to be a longitudinal tract of a yellowish- 
white colour, composed of fibres running in the 
same direction, and capable of being followed 
both upward and downward : upward this tract 
seems continued beneath the superior peduncle 
of the cerebellum ;* downward it descends from 
* Of the nature of the structure continued up¬ 
ward from the attachment of the nerve the author 
is not satisfied : it presents, when cleared, the ap¬ 
pearance given to it in fig. 141,19, but it is very cine- 
ritious in character, and he is not prepared to say 
whether it be a continuation of the tract from which 
the nerve appears to arise, or a part of the floor of 
the fourth ventricle at its upper extremity, con¬ 
nected to the attachment of the nerve : the mode 
in which the nerve arisès in the bird and the turtle 
appears to the author opposed to the opinion that 
the tract to which the nerve is attached is, in them 
at least, any thing more than a continuation or 
VOL. 1L. 
behind the pons into the spinal bulb, and after 
a short course divides into two cords, one for 
each column of the spinal marrow (see Jigs. 
140, 141). At the entrance of the tract into 
the bulb it is situate deep, before the floor of 
the fourth ventricle and behind the superficial 
attachment of the two portions of the seventh 
pair, which must be separated from each other 
and displaced in order that it may be ex-* 
posed : externally the tract corresponds to the 
peduncles of the cerebellum, and is united in¬ 
ternally to the cineritious matter of the floor 
of the ventricle. At the point of attachment 
the tract presents a somewhat prominent en¬ 
largement, (figs. 140, 141, 12,) which the au¬ 
thor will venture to call an eminence, though 
with hesitation, lest it be considered an ex¬ 
aggeration, from which the nerve may be held 
to arise. 
It is said that the nerve may be held to arise 
from this tract, because, though it be certainly 
not its ultimate connection with the brain, and 
though cords can be traced from it to more 
remote parts, yet the union of the cords at the 
point, and the attachment of both portions of 
the nerve to it, seem to mark it as the origin 
of the nerve ; the change of character too which 
will be described as occurring at the attach¬ 
ment of the nerve, countenances the opinion 
that the tract is not simply a continuation of 
the nerve. 
It may be doubted whether the eminence 
really exist, or whether it be not merely the 
result of dissection : the author will not insist 
upon it, but several considerations induce him 
to consider it real : in the first place, he almost 
uniformly finds it,* and secondly, it seems to 
be a common point to the two portions of the 
nerve and to the other cords, which form part 
of its encephalic connections ; and lastly, this 
view is corroborated by the disposition of the 
same part in other animals ; for a similar ap¬ 
pearance will be found, at the attachment of 
the nerve behind the pons, in other mammalia 
as well as in man after the separation of the 
adjoining matter, e. g. in the horse ; and it is 
even asserted by Desmoulins that an eminence 
may be observed naturally upon the floor of 
the fourth ventricle, in some animals, at the 
attachment of the nerve. His statement is : 
“ on observe même dans les rongeurs, les 
taupes, et les hérissons, un petit mamelon ou 
tubercle sur l’extremité antérieure du bord du 
ventricule ; mamelon, dans lequel se continuent 
les fibres postérieures de la cinquième paire, et 
de l’acoustique.’7 When the tract has reached 
the point at which the inferior peduncle of the 
cerebellum first inclines outward toward the 
hemisphere, it separates, as has been stated, into 
two parts or cords, (seefigs. 140, 141,) destined, 
one, as is already known, to the posterior, the 
other, according to the author’s belief, to the an¬ 
terior column of the spinal cord. The course and 
disposition of these cords are remarkable and 
root of the nerve, but admitting this, he cannot* 
satisfy himself that it is to be regarded in the same 
light in the Mammalia. 
* The attachment of both the packets must be 
made out, el^e the enlargement -will not appear. 
T
        

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