Francis Lieber.

Library of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) online

. (page 128 of 203)
Online LibraryFrancis LieberLibrary of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) → online text (page 128 of 203)
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skittles are made of hard wood, ar.d they are placed upon ihe floor cf the shed in a
square with one corner toward the player.' The player throws a wooden ball, and tries
to knock down the whole of the skittles in a given number of throws. The rules of the
game vary in different places. It is sometimes called "ninepins," from the number of
skittles used.

SKOPIN . a t, of Russia, government of Riazan, and 160 m. s.e. of Moscow, is situated
on the Vcrda, a tributary of the Oka, Avhicli is itself a tributary of the Volga. It has
manufactures of Russian" leather, and a trade in corn and cattle. Pop. '67, 9,511.

SKU A, or SKUA GULL, fast r is. a genus of birds of the family larj^ce. also known by
the name JAOKR (Ger. hunter), and differing from the gulls in having the upper man-
dible more hooked at the tip. and the nostrils larger and further forward in the bill, the
base of which is covered with a cere. The skuas are bold and powerful birds, and gen-
erally obtain their food by pursuing gulls or terns, and causing them todl.-gorge the fish
which they have captured, which they dart upon and seize in the air. They also eat
eggs and small birds. The COMMON SKUA (//. cataracte*) is fully 2 ft. in length, of a
brown color, with lighter streaks on the head and neck. It inhabits the northern seas,
and breeds in some of the Shetland isles.

SKULL The skull is divided into two parts, the cranium and the face. In human
anatomy, it is customary to describe the former as consisting of 8 and the latter of 14
bones; the 8 cranial bones, which constitute- the brain-case, being tbe ocsipital. tiro parie-
tal, fmnrnl, tiro temporal, sphenoid, and cflnnmd; while the 14 facial bones are the tiro
nasal, two superior maxillary, tiro lachrymal, tiro malar, tiro palate, tiro inferior tuihinated,
vomcr, and inferior mari'hiry. The bones of the ear. the teeth, and the Wormian bones are
not included in this enumeration. The morphologist, however, who wishes to trace



Skull.



554



out the fundamental similarity of type in the structure of the various modifications
of the vertebrate skull, will not be content with this arrangement, in which, as, for
example, in the occipital, temporal, and sphenoid bones, the human anatomist consid-
ers as a single bone an osseous mass consisting primarily iu man, and persistently in.
some of the lower vertebrates, of several distinct pieces or elements. Postponing to the
close of this article any remarks on the structure of the vertebrate skull generally, we
shall proceed to notice the ordinary anatomical relations of the human skull. The de-
velopment of the skull is a subject of great interest, not only in itself, but as throwing
light on many points which the study of the adult skull would fail to explain. At a very
earl} r period of fetal existence, the cerebrum is inclosed in a membranous capsule exter-
nal to the dura mater, and in close contact with it. This is the first rudiment of the
skull, the cerebral portion of which is consequently formed before there is any indica-
tion of a facial part. Soon, however, four or five processes jut from it on either side of the
m'-sial line, which grow downward, incline toward each other, and unite to form a series of
inverted arches, from which the face is ultimately developed. Imperfect development
or ossification of these rudimentary parts of the face gives rise to the peculiarities known,
as "hare-lip" and "cleft-palate," or in very extreme cases to the form of monstrosity
termed " Cyclopean," iu which, from absence of the frontal processes, the l\vo orbits
form a single cavity, and the eyes are more or less blended in the mesial line.

The following is a brief summary of the succession of events that occur in the ordi-
nary or norm .1 development of the skull. Cartilage is Sor-med at the base of the mem-





Fig. 1. Side view of Human iSlcull

1, Frontal bone: 2, Parietal bone; 3, Occipital bone; 4.
Temporal bone (sjuanrms portion); 4*, I>o. (mastoia
porton); 5, Sphenoid bone; 6, Malar bone; 7. Nasal
bone: 8. Superior maxillary or jaw bona; 9, Inferior
maxillary or jaw bone.



TIG. 2.



I. Anterior fontanelle: 2. Posterior fon-
tanelle: 3, Sagittal suture: 4. 4. Coron-
al suture; 5 Lambdoidal suture; 6. 6,
Parietal bones; 7.7, Two halves of
the frontal bone,still ununited; 8, Oc-
cipital bone.



branous capsule, which has been already described as thrown round the brnin, and
capable of enlarging with it. This is speedily followed by the deposition of ossifie mat-
ter at various points of the capsule, which soon becomes converted into flakes of bone,
which afford protection for the brain, while the intervening portions, which remain
membranous, permit the skull to expand as its contents enlarge. The formation of
the-je bony flakes on the convexity of the cranium is soon followed by the appearance
of caseous nuclei in the cartilage at the base, corresponding to the future occipital and
sphenoid hones. Lastly, the various bones, some originating in membrane, and some
in cartilage (as described in the article OSSIFICATION), approach one another by gradual
enlargement, a;id become united in variuous ways, so as to form a continous. and ulti-
mately an unyielding bony case, which, in the words of Dr. Humpjirey, "is admirably
adapted for th defense of the brain, for the accommodation of the organs of special
K>nse, and for the attachment of the ligaments and muscles by which the skull is sup-
ported and moved ori the spine." J%e Human Skeleton, p. 185. At the period of birth
most of the principal bones have grown into apposition with their neighbors, forming
the nature* (<i.v.). but one large vacuity remains at the meeting-point of the parietal and
frontal bones, which is termed the anterior fontanelle,* which does not clofc till the sec-
ond year after birth, and sometimes remains open much longer. The deficiency of the
osseous brain-case at this position not only facilitates the act of delivery, but also nets,
according to Humphry, to some extent like a safety-valve during the first months of
infantile life, at which time the brain bears an unusually large proportion to the rest of

* S i called from the pulsations of the hrnin, which may be here seen, resembling the rising of water
at a spring or fountain. There are two fotitanelles iri the mesial line, as shown in Fig~, ami two lateral
f outauelles on either side, as shown in Fig. 3.



555



Skull.



the body, and is liable to sudden variations of size from temporary congestion, sudden
wasting of its substance, and other causes. The sutures remain distinct long afler llie
closure of the fontanelles, and probably serve a purpose both in permitting an increase
of the size of the cranium by the growth of the bonesat their edges (although the enlarge-
ment of the cranial cavity does not entirely depend upon this growl li at the edges), and
in diminishing and dispersing vibrations from blows, and thus contributing to the secu-
rity of the bruin.

The number of centers of ossification in the skull is tolerably constant ; each bone
having ;x certain number. (Thus the occipital has 7 centers, the temporal 5, the sphenoid
12, etc. ; the total number being about 59). In addition to these, centers frequently occur
in the course of the sutures, giving rise to independent pieces, which are called the .w*
triqiwtra, or the \Yoniuau bone*. They are regarded by Humphry as stop-gaps, developed
in the membranous covering of the brain, when the extension of the regular osseous
nuclei is likely, for some reason, to be insufficient to cover in the cranial cavity; and
this view is supported by the observation that, in cases of rickets and hydrecephalus, the
"\Vormian bones are especially abundant.

After the sutures have been formed, and the skull has acquired a certain thick-
ness, a process of resorption commences in the interior of the bones, and reduces tne
originally dense structure to a more or less cellular or cancellated state. The interior
thus altered is called the diploe, and by this change the weight of the skull is much
diminished, while its strength is scarcely affected.

The diploe usually begins to be apparent about the tenth year, and is most developed
in those skulls which are thickest. Dr. Humphry has observed it to be especially
thick in idiots, and where the brain is small. " Hence," he observes, "the propriety of
the term tfrick-headed, as a synonym for stupid, derives some confirmation from anatomy."
A continuation of the same process of resorption, which causes the diploe, gives rise to
the formation of the cavities known as the frontal and sphenoid sinuses. The formation
of the diploe divides the walls of the cranium into three layers, viz., an outer tough layer;
an inner dense, brittle, and somewhat glass-like layer, known as the vitreous table or
layer; and the intervening cancellous diploe. The vitreous table being more brittle than
the outer layer, is apt to be fissured to a greater extent in fracture of the skull; and is
even sometimes broken while the outer layer, which received the blow, has remained
entire; although the diploe must have great power in lessening the concussions trans-
mitted from the outer to the inner layer of the skull. The growl h of the skull after the
seventh year proceeds slowly,~but a slight increase goes on to about the age of twenty.
The skull-bones are freely supplied with blood from arteries which pass from the dura
mater internally and the pericranium externally, through the numerous foramina
observed on both surfaces; the blood being returned by veins which take various di-
rections

The fact that concussion of the brain scarcely ever proves fatal, unless there is also
fract-.ire of the skull, affords the most distinct evidence that the skull is constructed in
such a manner that so long as it maintains its integrity, it is able to protect its con-
tents from serious lesion. This marvelous protective power is due to its rounded shape
whereby its strength is increased, and in consequence of which blows tend to glide off
it, without doing material damage. Moreover, the curved lines or ridges which may be
traced round the skull tend to strengthen it. The weakest part of the skull is ut the
base. Hence, notwithstanding its removal from exposure to direct injury and the pro-
tection afforded by the soft parts, fracture takes place more frequently at the base than
ot any other part of the skull, fracture often hiking place here even when the skull
was not broken at the part struck. There are two points in the architecture of the
bones of the face which deserve especial notice, viz., (1) the great strength of the nasal
arch, and (2) the immobility of the upper jaw, which is fixed by three buttresses, the na-
sal, the zygomatic, and the pterygoid.

The base of the skull, whether seen from within or from below, presents many objects
of physiological interest in relation to the nervous system. As seen from within, the base
presents on each side three fossa?, corresponding to the anterior and middle lobes of the
cerebrum and to the cerebellum. These fossae are marked, as is the whole skull-cap. Lv
the cerebral convolutions, and they contain numerous " foramina" and "fissures" which
give passage to various sets of nerves and blood-vessels. The external or outer surface
of the base of the skull, if we consider it from before backward is formed by the
palate processes of the superior maxillary and palate bones; the vomer; the pterygoid
and spinous processes of the sphenoid and part of its body; the under surface of the
temporal bones, and by the occipital bone. The most important of the parts which it
presents are named in the description of Fig. 3.

The anterior region of the skull, which forms the face, is of an irregularly ovnl form,
and the bones are so arranged as to inclose the cavities for the eyes, the nose, and llie
mouth, and to give strength to the apparatus for masticating the food. The size of the
face and the capacity of the cranial cavity stand in an inverse ratio to one another, as
may be readily seen by comparing vertical sections (throusrh the mesial line) of human
and other mammalian skulls; and if, in place of mammalian skulls, we take sk .11s of
lower vertebrates (the crocodile, for example), this ratio is far more striking. In man
the face is at its minimum as compared with the cranial cavity, chiefly in consequence



Skullcap.



556



of the facial bones being arranged in a nearly vertical manner beneath the crap'um,
instead of projecting in front of it. The human face is also remarkable for its relatively
great breadth, which allows the orbits for fie reception of the eyes to be placed in front
instead of on the sides of the head, and renders their inner walls nearly parallel. "This
parallelism," says Dr. Humphry, " in man is associated with the parallelism of the optic
axes, and contributes to that clear, accurate, and steady vision which results from the
ready convergence of the eyes upon every object." Each orbit is of a pyramidal form,
with the apex behind, and is composed of seven bones viz , the frontal, ethmoid, lach-
rymal, sphenoid, superior maxillary, malar, and palate, which last contributes very
slightly to the human orbit, but is an important constituent in the orbit of many ani-
mals. The nasal cavities have been sufficiently described in the article NOSE.

The different varieties of mankind present certain well-marked and characteristic
peculiarities in the form of the skull. There are three typical fo-rms of the skull which
seem to be well established from the examination and comparison of a large number of
crania viz., the prognathous, the pyramidal, and the oval or elliptical cranium. When
the upper jaw slopes forward, the insertion of the teeth, instead of being perpendicular,
is oblique. A skull with this peculiarity is pi-oynathous or prog nat hie (Gr. pro, forward,
and gnathos, a jaw); the opposite condition being termed orthognathou* or orthorjnalhic
(Gr. orthox, upright). The negro of the Guinea coast and the negrito of Australia present
the prognathous character in its most marked form. The pyramidal form is character-
ized by the breadth and flatness of the face, which, with the narrowness of the forehead,
gives this sh.-.pe to the hea.d. The Mongolian and Esquimaux skulls belong to this type.
The oval or elliptical type is that which is presented by the natives of western or so'uih-
ern Europe, and which is not distinguished by any particular feature so much as by the
absence of the longitudinal projection of the first type, or the lateral projection of the
second, and by a general symmetry of the whole configuration. The length of the
kull, which to a great degree corresponds to the degree of development of the posterior
cerebral lobes, has been taken by the late prof. Eetzius as a basis of c!as!-illci>!ion. He
arranges all the varieties of mankind into two great classes the dolicoctphalcc, or long-
Jieads, whose celebral lobes completely cover the cerebellum; and the brachyccphalct, or
thort-Jicadg, in whom the cerebral lobes do not extend so far. Each of these classes con-
tains ortJuH/nathous and prognathous varieties. See ETHNOLOGY.

It has been already stated in the article SKEI.KTON that the skull is only the r.ntrrior
prolongation of the backbone, and that it consists of four vertebrae or segments, corres-
ponding to the four consecutive enlarg<iuents of the nervous system which ultimately
form the brain viz., the rhinencephawu, \\ieprosencephalon, the menencejUialvn, and the
cpencephalov embryonic segments giving rise to the nerves of smell, sight, taste, ai.d
bearing. These four vertebrae, taken from behind forward, are tcnmd the occipital,
the parietal, the frontal, and the nasal vertebrae. For the anatomical evidence by which
these cranial vertebrae are resolved into the essential elements of a vertebra, as described
in the article SKELETON, we must refer to prof. Owen's various works on the skeleton,
or to the admirable summaries of them contained in Humphry On the Human Skeleton
(for which we are indebted to many of the details introduced into this article), ni.el to
Holden's Human Osteology. There has been much discussion as to who originated
" The Theory of the. Vertebrate Skull." The claim undoubtedly rests between Goethe,
the great poet, and Oken, one of the most original and distinguished comparative anat-
omists of the early part of the present century. We believe the truth to be tl.at the idea
of the true nature of the skull flashed across the poet's mind in 1790, but that nothing
definite was published on the subject till 1807, when Oken independently arrived at and
promulgated similar views. Our limited space has prevented us from noticing the tkull
of birds, reptiles, or fishes. On these subjects the reader is referred to Huxley's Lectures
on Comparative Anatomy, 1864, in which the structure and development of the human
skull, as well as the skulls of all the lower vertebrate animals, are most copiously and
philosophically discussed.

Fracture of the skull is an accident of such importance as to demand a special para-
graph. As already remarked, fracture may take place either in the vault or :;t the base
of the skull. We shall first consider fi-actu res of the ranlt. Here the fracture is usually
direct, the bone giving way at the point at which it was struck, and the result being
either a simple fissure or a breaking of the bone into several fragments (a comminuted
fracture). Although fractures may be limited to the outer or to the inner surface of
the skull, they most commonly extend through the whole ,thickne8s, and the broken
bone is generally driven inward; and the most ordinary form of fracture with depres-
sion is that in which several fragments of a somewhat triangular form have their points
driven down and wedged into each other, while their bases remain on a level with the
surrounding bone. There are no signs by which we a n in all cases recognize the exist-
ence of fracture of the vault. " Fissures," says Mr. Prescott Hewett, "involving the
whole thickness of the vault of the skull, constantly exist without ever having been
suspected during life, and even an extensive and comminuted fracture, with great
depression of the fragments, may, and often does, ercape notice when the broken bone
lies hidden under the temporal muscle or under a large extravasation of blood." ITolmes's
System of fiurtjcrii, vol. ii p. 116. When, however, the fracture is accompanied by a
wound leading down to the bone it may, in general, be easily detected. With regard



557



Skullcap.



to treatment, it is now an established rule that simple fractures of the skull with depres-
sion, and without symptoms, are to be let alone. The depression may be so marked aa
to be easily detected; and yet so long as there are no symptoms all operative interfer-
ence, of whatsoever form, is carefully lo be avoided." Prescott llewett, op. cit. If,
however, there be a wound leading down to the bone in a depressed fracture without
symptoms, immediate operative interference is called for. When a depressed fracture
is accompanied by primary brain-symptoms, an operation for the purpose of raising or
removing the depressed fragments is usually necessary. If, however, the fracture is a
simple one. and the symptoms are not urgent, milder remedial agents, as bleeding, purg-
i:;g. and low diet may be first tried. Cases occasionally occur in which very urgent
symptoms of cerebral pressure persist for a long time, and are relieved at once on the
pressure being removed. A remarkable case is recorded by Cline (Medicn-Chir. Rev.,
vol. i. p. 471), in which a sailor remained in a state of unconsciousness for 13 months iu
consequence of a wound causing fracture and depression of one of the parietal bones.
Ciine trcp-mned the part and elevated the bone, and on the evening of the same day, the
sailor sat up in bed, and though at first stupid and incoherent, soon became rational and
well, upward of a year having elapsed in which his life was a complete blank.

Fracture* <if ' ihe baxe may be direct or indirect, but in most cases are indirect, that is
' to say, the bones give way at a point remote from the seat of the blow, as has been
already shown. At certain parts, however, the bones of the base are so thin that if
direct pressure be brought to bear upon them they readily give way. Thus scissors,
slate-pencils, tobacco-pipes, etc., have often been thrust into the skull through the orbits
or the nostrils, and these wounds are very serious, from the readiness with which the
brain may be thus injured. The only symptoms that can be depended upon as indicat-
ing a fracture of the base of the skull are connected either with an escape of the sub-
stance of the brain, or blood, or watery fluid, or with an injury done to the nerves as
they emerge at the base. Out of 33 cases of fractured base observed by Hewett, bleed-
ing from the mouth or nose occurred in 14 and bleeding from the ear in 15 cases. A
copious watery discharge from the ear was, until very recently, regarded as a diagnostic
sign of fracture of the base; and there can be no doubt that when such a discharge of
cerebro-spinal fluid occurs either from the ear or nostrils, that it most probably is con-
nected with fracture. Operative interference is very seldom required in these frac-
tures, our treatment being directed not against the broken bones, but against the
accompanying cerebral lesions.

SKULLCAP, a genus (scutettaria) of herbs of the mint family (?abiafce). The generic
characters are: calyx bell-shaped wht-n in flower, two-lipped, the upper lip with a helmet-
like appendage; calyx splitting at the b:ise at maturity, the upper lip usually falling
away; corolla having an elongated curved ascending tube, dilated at the throat, two-
lippe 1; stamens tour; anthers approximate in pairs and bearded. The followingspecies
grow in the United States: 8. versicolor, from 1 to 3 ft. high, stem erect, leaves heart-
shaped; river banks from Pennsylvania to Wisconsin and southward: S. saxt'dis;
stem weak, from 6 to 18 in., sometimes having runners; leaves heart shaped, crenate,
from 1 lo 2 in. long; growing on m >ist shady banks in southern Ohio, Virginii,
and Kentucky, and on mountains farther south: 8. canexcens; 2 to 4 ft. high,
stem-branched above, with panicled, many-flowered racemes; lance-ovate, crenate
leaves, whitish, with fine soft down; upper lip of corolla shorter than lower; rich soil
from Pennsylvani i to Illinois and southward: X. terrain; stem from 1 to 3 ft. high,
simple, with single, loosely flowere-l racemes; leaves ovate, serrate, and acuminate '"at
both ends; corolla one inch long, lips equal; growing in woods from Pennsylvania
to Illinois and southward: 8. pifai; stem simple, 1 to 3 ft. high; leaves oblong-
ovate, crenate; racemes short; corolla rather narrow; growing on dry ground in southern
New York to Michigan and southward: S. hi ten flora if, a species which has been used
as a quack medicine in hydrophobia, and hears the common name of mad-dog skullcap.
It has a smooth, upright stem, much branched; 1 to 2 ft. high; leaves lanceolate-
ovate, coarsely serrate; growing in wet, shady placas in many parts of the United
States. Other species are 5. integrifolia, S. nerrosa, S. partultt-, and S. galericulata.

SKUNK, Mephiti*, a genus of quadrupeds of the weasel family (nvixtflirfti'), but
departing very considerably from the typical characters of that family, and approaching
to the badgers and gluttons in general appearance, in habits, in the lengthened claws of
the fore-feet, in the plantigrade hind-feet, arid in some of the teeth. There are six
incisors and two canine teeth in each jaw, eight molars in the upper, and ten in the
lower; the teeth generally resemble those of the polecat. Skunks depend very much
for defense against enemies on an excessively fetid fluid, which is secreted by glands
near the anus; and when assailed, they turn the rump toward the assailant, elevate the
tail, and discharge this fluid with considerable force. The odor proceeding from it,
even when a dead skunk has been flung into an inclosure, has been known to cause
nausea to the inmates of an apartment with closed windows at the distance of 100
yards. So confident does the skunk seem of the efficacy of its peculiar mode of defense,
that it permits itself to be approached till it is just on the point of being seized, which,
however, is only attempted by the inexperienced, when the battery is discharged. It is
almost impossible to remove the odor from clothes. Dogs flee at once, and rub their



Online LibraryFrancis LieberLibrary of universal knowledge. A reprint of the last (1880) Edinburgh and London edition of Chambers' encyclopaedia, with copious additions by American editors (Volume 13) → online text (page 128 of 203)