904 
the posterior auricular, the digastric, and the 
stylo-hyoid. 5 
The posterior auricular nerve passes off from 
the anterior part of the portio dura ; it passes 
upwards and forwards round the anterior sur- 
face of the mastoid process, and is joined by 
the great auricular nerve of the cervical plexus; 
it then becomes superficial, accompanies the 
artery of the same name, and is distributed to 
the ear and side of the head. ' 
The digastric nerve passes backwards and is 
distributed by several filaments to the posterior 
belly of the digastric muscle. It sends an anasto- 
motic filament to the glosso-pharyngeal nerve. 
The stylo-hyoid nerve arises often from a 
common trunk with the preceding ; it enters the 
stylo-hyoid muscle after passing along its supe- 
rior border. ; 
After the portio dura has given off the above- 
mentioned branches it passes forwards through 
the substance of the parotid gland below the 
meatus auditorius externus; it then crosses over 
the posterior auricular artery and the styloid 
process, the external jugular vein and the ex- 
ternal carotid artery, and before reaching the 
ramus of the jaw it divides into two branches, 
the tempero-facial and the cervico-facial, which 
diverge from each other. 
The tempero-facial division passes upwards 
and forwards in the substance of the parotid, 
forming with the trunk of the facial nerve an 
arch, the concavity of which is above; it then 
crosses the neck of the lower jaw and receives 
at this point one and sometimes two branches 
from the auriculo-temporal branch of the in- 
ferior maxillary nerve. The tempero-facial 
nerve then breaks up into a number of branches 
which anastomose and form arches, from the 
convexities of which proceed a number of di- 
verging filaments, some of which pass upwards 
and others forwards, emerging from beneath 
the parotid, to be distributed to the muscles of 
the bee, ean 
The cervico-facial division is smaller than 
the preceding ; it takes the same direction as 
the trunk of the nerve, passing downwards 
and forwards in the substance of the parotid ; 
at the angle of the jaw it divides into three or 
four branches ; these subdivide into secondary 
branches, some of which pass forwards to sup- 
ply the muscles of the lower part of the face, 
while others are distributed to the upper part 
of the cervical region. 
Lymphatic glands.—Several lymphatic glands 
are found imbedded in the superficial surface, 
and in the substance of the parotid. These 
may readily be distinguished from -the tissue 
of the parotid by their red colour. They 
are not uncommonly the seat of disease, and 
if their removal becomes necessary the opera- 
tion may be done without much difficulty and 
without great risk of wounding any important 
textures. But a slight consideration of the 
deep connexions of the parotid and of its close 
relations to the many important parts which 
s through it, and by which it is surrounded, 
will be sufficient to convince the surgeon that 
the removal of this gland cannot be effected 
without extreme difficulty and danger, and 
PARTURITION. 
that it must necessarily be attended by injury 
to some of the important in this region. 
The division of the facial nerve, and conse- 
quent palsy of the face, may be looked 
as one of the most serious and certain conse- 
quences of an attempt to excise the parotid. 
( George Johnson. ) 
PARTURITION, MECHANISM OF, 
Parturition is the act in which the matured frait 
of healthy conception and gestation is transmit- 
ted along the passages of the mother. “ Rien 
de plus curieux que le méchanisme par lequelle - 
foetus est expulsé ; tout s’y passe avec une pré- 
Cision admirable,” is the quotation which 
celebrated Naegelé has used for a heading to his — 
essay on this important process in the human 
subject, the first in which it has been completely 
and accurately described. Perhaps in no de- 
partment of physiology do we gain so much 
instruction from comparative anatomy as here; 
when we examine the ovipara, especially the 
higher orders of them, we are struck with the 
simplicity of the parturient process, and with 
the equally simple laws by which it is governed. 
The oval form of the egg shows that its long dia- 
meter must run parallel with the canal through - 
which it has to , and in these classes of 
animals this single law constitutes nearly the 
whole mechanism of parturition in them. 
In the vivipara the process becomes some- 
what more complicated ; the foetus enveloped 
in its soft and fluctuating bag of membrane 
and the more perfect pelvis bring many other 
relations into play which do not exist in the 
lower classes ; hence in the viviparous animals 
we see that the manner in which the feetus 
vances through the passages of the mother 
varies considerably, still however not so much 
as to render it incompatible with the law above 
mentioned. 4 
In considering the process of parturition ii 
the lower classes of animals it will be scarcel: 
necessary to go beyond the Vertebrata, for im 
the lowest classes, especially the zoophyte 
admits of but little comparison with them, 
analogy rather inclining in the contrary dire 
tion, viz. towards the vegetable kingdom. | 
some of the other classes, viz. Vermes, 
little certain is known as to this process beyo 
that the generative organs are of the sim 
tubular character; we must except, ho 
the Insecta, in many of which the ova and | 
mode of their expulsion strongly resemble 
much higher class, viz. the Aves. iy 
The Fishes, which are the lowest class of 
Vertebrata, have no bony canal or pelvis; 
whole apparatus for parturition is a tube 
lower part of which at least is fibrous; im 
larger fishes it is muscular and capable of ¢ 
siderable dilatation. In the Ray and § 
tribe we first see this canal divided int 
parts, viz. the ovary and oviduct; still the’ 
cess is of the simplest character, the ova t 
propelled precisely like the contents of am 
testinal tube. In the viviparous sharks, the Ble 
nius viviparus, and still more remarkably 
the Cetacea, where as belonging to the ¥ 
malia we first see the oviduct divided in 
