It is exceedingly diflficult to give
an absolute definition of this group of Mammals. But all the Insectivora
possess more than two incisors in the mandible;
and their molar teeth, which are always coated with enamel
have tuberculated crowns, and form roots.
The fore-limbs have the structure usual among unguiculate
Mammals; and, in both limbs, the digits are provided
with claws. The hallux is not opposable, and, like the other
digits, it is provided with a claw.
In addition to these distinctive characters there are others
which are met with in all members of the group.
are, almost all, either plantigrade or semiplantigrade.
The clavicles are completely developed in all,
. The stomach is simple. The testes of
the male are either inguinal or abdominal, and do not descend
into a scrotum. The female has a two-horned uterus.
The cerebral hemispheres leave the cerebellum uncovered,
in the upper view of the brain; and are almost, or wholly,
devoid of sulci and gyri. The corpus callosum is sometimes
No Insectivore attains a large size, and some, such as the
Shrew Mice, are the smallest of the Mammalia.
present a great diversity of organization,
the common Hedgehog being an almost central form. The
Shrews tend toward the Rodentia
, the Tupayae
toward the Lemurs
; while the Moles, on the one hand, and the Galeopitheci
on the other, are aberrant modifications. Relations of
a more general character connect them with the Carnivora
and the Ungulata.
The Hedgehog (Erinaceus Europaeus
) is pentadactyle and
plantigrade. It has a long flexible snout. The eyes are
small; the pinnae of the ears are rounded, and the integument
lining the concha is produced into a transverse, shelf-like fold.
The under surface of the body bears hairs of the ordinary
kind; but, on the dorsal aspect of the head and trunk, the
hairs are converted into strong fluted spines. There are
twenty-one dorso-lumbar vertebrae (of which fifteen are dorsal,
and six lumbar), three or four sacral, and twelve to fourteen
caudal. Accessory processes, or metapophyses, are developed
on several of the dorso-lumbar vertebrae. The sternebrae
are laterally compressed, except the manubrium, which is
broad; and eight of the fifteen pair of ribs are connected with
The occipital foramen is placed completely at the hinder
extremity of the skull, in the lower part of the perpendicular
occipital face of the cranium, and looks backward. There are
large paramastoid processes. The glenoidal surface for the
mandible is flattened. The zygoma is stout, and the jugal
bone is, as it were, applied upon the outer side of it. The
orbit has no posterior osseous boundary. The lachrymal foramen
lies upon the face. There are unossified spaces in the
bony palate, and the posterior margins of the palate are thickened,
as in the Lemurs. The large and bullate tympanic bone
does not anohylose with the squamosal, or the periotic, and is
readily lost from the dry skull. The alisphenoid contributes
largely to the formation of the front wall of the tympanum;
and a large portion of the inner wall of the tympanic cavity is
formed by a broad process of the basisphenoid, the outer and
lower edge of which joins, by a sort of harmonia, with the
inner and lower edge of the tympanic.
The ascending portion of the ramus of the mandible is
short, and the angle is slightly inflected. The two rami are
not anchylosed at the symphysis. The supra-scapular fossa is
wider than the infra-scapular. The spine is strong, and the
acromion bifurcates, sending a prolongation backward. The
clavicles are long and convex forward. The humerus has an
intercondyloid foramen; but there is no foramen above the
inner condyle, and this circumstance is unusual among the Insectivora
. The bones of the antibrachium are fixed in the
prone position. There is an os centrale
in the carpus, so that
it has nine bones. The scaphoid and lunare are anchylosed,
as in the Carnivora
, and the pisiform bone is much elongated.
The pollex and the fifth digit are the shortest.
The pelvis is remarkably spacious. The symphysial union
of the pubes is always small, and, sometimes, the bones remain
separate. The subpubic arch is much rounded. The ilium is
narrow, and a mere ridge separates the iliac fossa from the
gluteal surface. The femur has a round ligament, and a
prominent ridge represents a third trochanter. The distal
ends of the tibia and fibula are anchylosed together.
One of the most notable peculiarities of the Hedgehog is
its power of rolling itself up into a ball, from all sides of
which the spines protrude. This is effected, for the most part,
by the contraction of the greatly-developed cutaneous muscle,
the chief fibres of which are disposed as follows: A very
broad band, the orbicularis panniculi
, encircles the body laterally.
In front, it partly arises from the nasal and frontal
bones, and partly is the continuation of a thick mass of fibres
which pass over the occiput. Posteriorly, each lateral division
of the muscle spreads out into a very broad band, which is
thick ventrally and thin dorsally, and adheres closely to the
skin, from the line at which the hairy and spinigerous surfaces
join, to near the median line of the back. Posteriorly, the
two lateral halves of the orbicular muscle pass into one another
upon the distal half of the short tail.
The action of this muscle will depend upon the attitude
of the animal when it contracts. If the head and tail are fully
extended, the orbicularis
can only diminish the dimensions of
the spinigerous region of the skin and erect the spines. But
if the head and tail be more or less flexed, as they always are
in the ordinary attitude of the Hedgehog, the orbicularis
play the part of a powerful sphincter, approximating the
edges of the spinigerous area toward the centre of the ventral
side of the body, and forcibly enfolding the trunk and limbs
within the bag thus formed. It is, in fact, the chief agent in
coiling the body up, and keeping it so coiled.
Numerous muscular bundles take a radiating direction on
the dorsal aspect of the body, and antagonize the orbiculari
1. A pair of slender occipito-frontales
arise from the occipital
crest, and are inserted into the integument over the frontal
and nasal bones. 2. A pair of occipito-orbiculares
the same crest, and pass into the anterior part of the orbicularis.
3. A pair of broader cervico-orbiculares
Ihe fascia of the neck, and pass to the dorsal part of the anterior
fourth of the orbicularis.
4. Slender dorso-orbiculures
arise close to the hinder ends of the trapezii
and spread out
above the foregoing. 5. Two stout muscles, coccygeo-orbiculare
arise from the middle caudal vertebrae, and, after receiving
fibres from the ventral region, end in the dorsal margins
of the orbicularis.
6. Two muscles attached to the
pinnae of the ears (auriculo-orbiculares
) pass backward to the
orbicularis on each side.
On the ventral aspect are certain muscles which assist the orbicularis:
1. Two broad muscles (sterno-faciales
) arise in
the middle line, over the anterior part of the sternum, and
pass outward and forward to the sides of the lower jaw and
the integument of the face and ears. Muscular slips from
these are sent up over each shoulder to the orbicularis
. 2. A humero-abdominalis
arises from each humerus beneath the insertion
of the pectoralis major,
and, passing backward over
the sides of the abdomen, these become connected with the
ventral edges of the orbicularis
. The external fibres of these
muscles are continued round the ischial regions to the coccygeo-orbicularis;
the internal fibres pass to the prepuce, and
over the middle line of the abdomen, in front of it. 3. A humero-dorsalis
arises from the humerus close to the foregoing,
and, passing upward and backward through the axilla, spreads
out in the mid-dorsal integument and the orbicularis.
The contraction of all these muscles must tend to bring
together the edges of the integumentary bag, and to tuck the
head, tail, and limbs into it.
In the myology of the limbs the following points are noteworthy:
The supinator longus, pronator teres,
are absent. The palmaris brevis
is present. A single
muscle takes the place of the extensor secundi internodii pollicis
and extensor indicis
, and sends a third tendon to the middle
digit. The extensor minimi digiti
supplies the other two
digits. The flexor perforans
and flexor pollicis longus
by five distinct muscular heads, each with a tendon
of its own; but all the tendons unite in the middle of the forearm,
and the common tendon again subdivides into only four
slips, the pollex receiving no tendon. There are no lumbricales
The pollex has only a rudimentary flexor brevis
and an abductor
. The other digits have each two interossei
, or flexores
, inserted into the metacarpo-phalangeal sesamoids.
In the leg, the soleus
has only a fibular head, and the flexor
arises wholly from the calcaneum. The flexor
and flexor perforans
have a common tendon, which,
in the sole, divides into five tendons, one for each digit.
There are no lumbricales,
nor flexor accessorius.
seems to be represented by twc small muscular beles
one of which arises from the prominent end of the tibia,
and the other from that of the fibula. The tendons of both
pass behind the inner malleolus, and that of the former muscle
goes to the tibial and plantar surface of the hallucal metatarsal,
while the latter is inserted into the ento-cuneiform
bone. The interossei pedis
are represented by a pair of flexores
for each digit except the hallux.
The adult Hedgehog has thirty-six teeth, of which twenty
are in the upper, and sixteen in the lower jaw. The dental formula is i.
The grinding surface of the crowns of the first and second
upper molars exhibits a pattern fundamentally similar to that
of the corresponding teeth in Man, the Anthropomorpha,
the majority of the Lemurs; that is to say, there are four
cusps, and the antero-internal is connected with the posteroexternal
cusp by an oblique ridge. The cusps are remarkably
sharp and pointed, and the outer surface of the postero-external
one alone is somewhat inflected.
In the lower jaw, the corresponding molars are each marked,
as in most Lemurs, by two transverse ridges. In front of tbe
anterior ridge is a basal prolongation of the tooth, on to which
a curved ridge is continued inward and forward from the anterior
principal ridge, giving rise to an imperfect crescent with
its convexity outward.
According to Rousseau there are twenty-four milk-teeth, i.
4.4/1.1, which fall out seven weeks after birth.
The brain of the Hedgehog is remarkable for its low organization.
The olfactory lobes are singularly large, and are
wholly uncovered by the cerebral hemispheres; which, on the
other hand, do not extend back sufficiently far to hide any
part of the cerebellum. Indeed, they hardly cover the corpora
quadrigemina. Only a single shallow longitudinal sulcus
marks the upper and outer surface of each hemisphere. On
the under surface, a rounded elevation corresponds with the
base of each corpus striatum. Behind this, another elevation
represents the end of the uncinate gyrus and the termination
of the hippocampus major; and therefore answers, in a manner,
to the temporal lobe. The inner face of the hemisphere
presents neither convolution nor sulcus, except behind and
below, where a very broad depression follows the contour of
the fissure of Biohat and the fornix, and represents the dentate
sulcus. Above, this sulcus ends behind the posterior margin
of the corpus callosum. The latter is remarkably short, and
directed obliquely backward and upward. It has no genu, and
the pre-commissural fibres of the ventricular wall spread out,
beneath its anterior end, upon the face of the hemisphere.
The part of the corpus callosum which answers to the lyra
very thick in proportion, and is inclined at an acute angle to
In a transverse section, the corpus callosum is seen to be
verv thin, and to curve upward and outward into the roof of
the ventricular cavity. The inner walls of the lateral ventricles,
which answer to the septum lucidum, are thick, while
the fornix is comparatively thin and slender. The anterior commissure
is very stout. In this circumstance, as in the small
corpus callosum, the brain of the Hedgehog closely approaches
that of the Didelphia
. There is no trace
of a posterior cornu, or calcarine fissure, and the lateral ventricle
extends forward into the olfactory lobe. The optic nerves
are very slender; the corpora geniculata externa
are large and
prominent; the nates are smaller than the testes, and transversely
elongated. The cerebellum has a large vermis and
small lateral lobes; the flocculi
are prominent and are lodged
in fossae of the periotic bones. The pons Varolii
small; the corpora trapezoidea
The spinal cord is remarkable for its thickness, and, at the
same time, for its brevity, as it ends in the middle of the dorsal
region. As a consequence of this arrangement, the cauda
is particularly large and long.
The stomach is simple, but the mucous membrane of the
considerable cardiac dilatation is thrown into numerous, and
very strong, longitudinal rugae. The intestine is about six
times as long as the body, and presents no distinction into
small and large; nor is there any caecum. The liver is
divided by deep fissures into six lobes; a cential one which
bears the gall-bladder, a bifid spigelian lobe, and, on each side
of these, two other lobes. The pancreas is a large and
irregularly-ramified gland; and the spleen is elongated and
The pericardium is extremely thin. The arteries arise
from the arch of the aorta, as in Man, by an anonyma
, a left
carotid and left subclavian. The course of the internal
sarotid is remarkable. When it reaches the base of the skull
it enters the tympanum and there divides into two branches,
of which one traverses the stapes, and, passing forward in a
groove of the roof of the tympanum, enters the skull and gives
rise to the middle meningeal and ophthalmic arteries. The
other branch passes over the cochlea, enters the skull by a
narrow canal near the sella turcica,
and unites with the circle
The external jugular vein is very much more capacious
than the internal, the latter being very small and hardly
traceable to the internal jugular foramen. It is by the external
jugular vein, in fact, that the great mass of the blood within
the skull is carried away, a foramen in the squamosal bone
allowing of a free communication between the external
jugular vein and the lateral sinus. There is a left superior
vena cava, which winds round the base of the left auricle,
receives the coronary vein, and opens into the right auricle.
The vascular system thus retains many embryonic characters.
The right lung is four-lobed; the left may possess from one
to three lobes.
Two ossifications, one on each side of the opening for the
aorta, occur in the diaphragm.
The testes of the male do not leave the cavity of the
abdomen, but they descend as far as the inner side of the inguinal
ring, to which they are connected by a short gubernaculum
and cremaster. The vasa deferentia
descend to the
base of the bladder and then enter a hollow muscular sheath
on their way to a "chamber," which is lodged in the distal
end of that sheath. This "chamber" passes into the penial
urethra; the cystic urethra opens into it by a narrow slit in
its front wall; and it receives the ducts of three pair of
appendages. The proximal pair consist of a multitude of
ramified tubuli, which have been found to contain spermatozoa,
and are usually regarded as vesiculae seminales. The
middle pair (the so-called "prostatic glands") have a similar
structure and have also been observed to contain spermatozoa.
The lowermost pair are Cowper's glands. The "chamber"
appears to represent the urogenital sinus of the embryo, which
has not become differentiated into prostatic and bulbous
The ovaries are enclosed in wide-mouthed peritoneal sacs,
and a ligamentous band, the diaphragmatic ligament, extends
from the ovary to the posterior surface of the diaphragm.
The cornua uteri are large and long. There are five pair of
teats; the anterior pair being axillary and the posterior
inguinaL The other three pair are equidistant, and lie along
the ventral surface, internal to the edge of the orbicularis panniculi.
Like the Rodentia
, the Insectivora
have a great diversity
of habit; some Galeopitheci
flitting through the air after the
fashion of the flying Squirrels; some arboreal, as the Tupayae
some terrestrial and cursorial, like the majority of the order.
A few are swimmers; and some, like the Mole, are the most
completely fossorial of Mammals.
The most aberrant form of the Insectivora
is the genus Galeopithecus,
essentially an Insectivore of arboreal and
frugivorous habit, with very long and slender limbs. These
are connected with one another, with the sides of the neck and
body, and with the tail, by a great fold of the integument,
which is called patagium
; and, unlike the web of the Bat's
wing, is hairy on both sides, and extends between the digits
of the pes. By the help of this great parachute-like expansion,
is enabled to make floating leaps,
from tree to tree, through great distances. When at rest,
suspend themselves by their fore-and hindfeet,
the body and the head hanging downward; a position
which is sometimes assumed by the Marmosets among the Primates.
The fore-limbs are slightly larger than the hind-limbs.
There are four axillary teats. The male has a pendent penis
and inguinal scrotal pouches. The pollex and the hallux are
short, and capable of considerable movement in adduction and
abduction, but they are not opposable; and their claws are
like those of the other digits.
The occipital foramen is in the posterior face of the skull.
The orbit is nearly, but not quite, encircled by bone. The
lachrymal foramen is in the orbit. The bony roof of the palate
is wide and its posterior margin is thickened. There is a
strong curved post-glenoidal process of the squamosal, which
unites with the mastoid, beneath the auditory meatus, and
restricts the movement of the mandible to the vertical plane.
A longitudinal section of the skull shows a large olfactory
chamber projecting beyond that for the cerebral lobes, and two
longitudinal ridges, upon the inner face of the latter, prove that
these lobes must have possessed corresponding sulci. The
tentorial plane is nearly vertical and the floccular fossae are
The ulna is very slender inferiorly, where it becomes anchylosed
to the distal end of the radius, which bears the carpus.
When the ilia are horizontal, the acetabula look a little upward
and backward as well as outward. The fibula is complete.
As in the Sloths and most Primates
, the navicular and
cuboid readily rotate upon the astragalus and calcaneum, so
that the planta pedis
is habitually turned inward.
The dental formula is i.
The outer incisor, in the upper jaw, has two roots, a
peculiarity which is not known to occur elsewhere. The
canines of both jaws also have two roots, as in some other Insectivora.
The lower incisors are single-fanged; and their
crowns are broad, flat, and divided by numerous deep longitudinal
fissures, or "pectinated."
The length of the whole alimentary canal from mouth to
anus is not more than six times that of the body. The sacculated
caecum is as long as the stomach, and its capacity
must be greater than that of the latter organ.
has, at one time, been placed among the
Lemurs, and at another, among the Bats. But the resemblances
with the former are general and superficial, and the
differences in the form of the brain, the dentition, the structure
of the limbs and of the skull, exclude it from the order of the Primates
agrees with the Bats in the disposition of
the tail, and in the existence of a patagium
special muscles. Further, in a slight obliquity of the acetabula,
such as is seen in its extreme development in the Bats;
in the imperfect condition of the ulnae; and in the pectoral
position of the teats and the pendent penis. Both of these
last, however, it must be recollected, are also Primatic characters.
Finally, the somewhat similarly pectinated lower incisor
teeth are found in the Cheiropteran genera, Diphylla
differs from the Bats completely in the
structure of the fore-limbs; in the position of the hind-limbs
and the absence of a calcar;
in the two-fanged outer incisors
and canines; and in the presence of a caecum.
On the other hand, the peculiarities of the skull and brain
are mainly insectivorous, as is the two-fanged canine; and I
see no reason for dissenting from Prof. Peters's view that Galeopithecus
belongs neither to the Primates, nor to the Cheiroptera,
but that it is an aberrant Insectivore.
With respect to other Insectivora,
it is worthy of note,
has the radius and the ulna ancbylosed.
possess a large caecum. Chrysochloris
mammary glands; Centetes
and the Moles have the penis
are soft-furred, long-tailed, tree-loving animals,
with complete bony orbits and a large cacum, and are
which most nearly approach the Lemurs.
The Shrews (Sorices
) most nearly resemble Rodents outwardly,
being very like small mice. The zygoma is imperfect,
the tibia and fibula are anchylosed, and the pubic bones do not
meet in the symphysis. There are sixteen to twenty teeth in
the upper jaw and twelve in the mandible. Canines are
absent, and there are six incisors above and four below. The
inner lower incisors are greatly elongated and proclivous, and
some of the teeth not unfrequently become anchylosed with
the jaws. There is no caecum, and peculiar musk-glands are
sometimes developed at the sides of the body.
The Moles (Talpinae
) have no external ears, and the eyes
are rudimentary. The fore-limbs are much larger than the
hind, and are inclosed within the integument up to ihe carpus.
The palmar surface of the broad manus is turned outward and
|Fig. 199. - The skeleton of a Flying-Fox. (Pteropus).
The manubrium of the sternum is very broad, and its ventral
surface gives rise to a strong median crest. The scapula
is as long as the humerus and the radius together. It is triquetral
and possesses an acromial process, but no distinct corracoid. The
clavicle, which is verv strong, is perforated by a
great foramen, and at the middle of its posterior margin sends
off a truncated reentering process. Proximally, it furnishes
an articular surface for the humerus. In the carpus there is a
, and a large accessory C-shaped bone lies on
its radial side. The pubes are separate at the symphysis, and
an accessory styloid bone is connected with the naviculare of
The distribution of the Insectivora
is singular in this
respect, that, although they are met with, under very various
climatal conditions, throughout the Old World and North
America, there are none in South America or Australia.
In the fossil condition they are not certainly known to
occur in strata older than the tertiary.