c, apertures of intestinal tubes, opening irregularly
in these intervals.
from a point corresponding to the centre
of the fossa. And both they, and those
more equidistant to the several follicles, are
very different from the villi seen elsewhere :
being fewer (b,fig. 269; a, fig. 270.), shorter,
of more irregular form, and often confluent
at their bases.
To demonstrate the structure and arrange-
ment of the several constituent follicles of the
agminate clusters, requires great care, and
very delicate manipulation. At the free
surface of the mucous membrane, they are
extremely difficult to isolate ; both from
their great tenuity, and their intimate union
to the neighbouring tubes. Hence the best
way of gaining access to them is from the
outside of the intestine, where they may
often be seen through the peritoneal and mus-
cular coats.f The removal of these tunics
brings them directly into view. To this
method of examination must be added care-
ful section in the vertical and horizontal
planes.
A proper combination of all these methods
of investigation reveals the following facts.
Each follicle is a shut sac : having a round^h
form, but a somewhat conical apex, which is
directed towards the surface of the mucous
membrane. Their diameter varies from 1 to
2 or 3-50ths of an inch. The base of each
is in contact with the muscular coat (which is
somewhat thinned in this situation) ; and is
united to it by an areolar tissue that resembles
the ordinary loose sub-mucous texture, in
which the follicle is imbedded by the greater
part of its bulk. The short apex of the
follicle extends upwards between the lower
extremities of the intestinal tubes : and,
below their middle, it terminates in the
immediate neighbourhood of the general
mucous surface, which has already been
* This appearance is somewhat incompatible with
that seen in a vertical section. Hence it is perhaps
partially due to pressure or over-distention of the
follicle.
t Especially after having been rendered opaque
by soaking in dilute acids, which coagulate their
contents.
A A 3
358
described as depressed into a fossa in this
situation. The thin stratum of tissue which
270.
STOMACH AND INTESTINE.
Plan of an agminate follicle, as seen by a vertical
section. Magnified 40 diameters.
a, short and conical villi surrounding the follicle ;
b, intestinal tubes in the same situation ; c, muscu
lar stratum of the mucous membrane ; d, submu-
cous areolar tissue, in which the follicle is chiefly
situated ; e, circular layer of the muscular coat ;
/, longitudinal layer of the same ; g, peritoneal coat ;
h, follicle enclosing nuclear contents ; z, apex of the
follicle projecting into the cavity of the bowel.
intervenes between the follicle and the interior
of the bowel (at i,fig. 270.) is so delicate,
that its exact anatomy is not easily verified by
vertical sections. It appears, however, to con-
sist of a very small quantity of indistinctly
fibrous tissue ; which encloses some capillaries,
and is covered by the ordinary layer of co-
lumnar epithelium.
The frequent rupture of the follicle in this
situation has led many to regard it as either
possessing a permanent orifice here, or ac-
quiring one by a kind of natural dehiscence.
But later researches seem to show that this open
state is quite exceptional and accidental ; being
due to disease, putrefaction, or mechanical
violence. The author can at least express
his own conviction that as Boehm long ago
stated, the agminate follicles are closed sacs.
This conclusion is much confirmed by the
fact, that the follicles of some animals are
altogether beneath the mucous membrane and
the tubes, and quite distinct from both of
them ; so as to lie wholly in the sub-mucous
areolar tissue.* While the vascular arrange-
ments which we are about to describe seem
equally incompatible with any theory of their
normal dehiscence.
Each of these follicles essentially consists
of a capsule, enclosing a number of delicate
capillaries, the interstices of which are occu-
pied by a cell-growth consisting of various
forms.
The capsule is a structure which, though
analogous to a basement membrane, differs
from such a delicate homogeneous lamina, both
in being much thicker, and in offering an in-
distinctly fibrous texture. Its smooth outer
surface contains elastic fibres, and is attached
by loose areolar tissue to the surrounding
sub-mucous structures.
The vessels of the follicle offer a very
peculiar arrangement. The small arteries in
the sub-mucous areolar tissue give off branches
that ramify amongst the several follicles of
each "patch;" and thus form a network of
Fig. 271.
Vessels of the three agminate follicles of the Rabbit ; as seen by a horizontal section, at about the middle of
their height, (^fter Koelliker ; from an injection by Fret.')
a, , minute vessels surrounding the capsule of the agminate follicles ; b, b, b, delicate capillary loops
, penetrating their interior, and bending back from c, c, c, the centres of the follicles.
capillary arteries, chiefly occupying the hori- contact with the capsule of the follicle, break
zontal plane. These vessels, which are in * Compare Koelliker, Op. tit. pp. 153. 188.
STOMACH AND INTESTINE.
359
up into numerous capillaries of about
of an inch in diameter. The latter surround
the membranous wall of the follicle with an
irregular plexus. But where they reach the
middle of that part of it which projects into
the interior of the intestine, they are curved
back upon themselves ; so as to form long
loops, that radiate from a central space quite
uncovered by vessels. And this appeal ance,
which was depicted long ago by Boehm, does
but represent, at the surface of the follicle,
what the more recent researches of Frei prove
to be the vascular arrangement that per-
vades the whole of its interior. The injections
of this anatomist show, that the capsule is not
only surrounded by the network just men-
tioned, but is also penetrated by a number of
minute capillaries. These, which are of a
still smaller diameter than the former ves-
sels, leave them at right angles, and reach
nearly to the centre of the follicle, before
looping back again to its exterior. And
finally, some of the uppermost of them have
been traced by Koelliker uniting to form the
radicle of one or two veins of about T ^oo tn
of an inch in diameter; which descend verti-
cally through the follicle, without receiving
any further branches from the neighbouring
capillaries.
The remaining contents of the follicle form
a soft pulpy mass. This is remarkably con-
trasted with the contents of the neighbouring
lacteals, in the fact that it is always of a pale,
semi-transparent, greyish colour ; while the
latter are, during digestion, of a brilliant
white. The application of reagents under the
microscope shows this greyish pulp to be
composed of a proteinous substance closely
akin to albumen. The addition of water
causes it to swell up, and effects its partial
solution. And as regards its structure, the
mass consists of a moderate quantity of
fluid, mingled with a variety of cells. These,
however different in their characters, may
probably be all reduced to various forms
of cell-growth, on the one hand; and various
stages of the retrograde solution of blood-cor-
puscles, on the other. The latter process,
though by no means uncommon, appears
always due to an extravasation of a more or
less accidental character. It is the cell-
growth which constitutes the specific histo-
logical character of these albuminous contents
of the follicle.
The cell-growth ranges from distinctly nu-
cleated cells, of^J^oth of an inch in diameter,
to cells of about one-half, and through these
to nuclei of barely one-third, the above size.
The latter, however, are of nearly the same
bulk as those contained in the largest cells.
Hence it would seem that the process of
growth which these differences indicate,
consists chiefly in the isolation and removal
of the cell-watt, from its previously close
apposition around the nucleus. In the Sheep,
however, Koelliker has sometimes observed
an endogenous multiplication of large cells, by
a subdivision of their nuclei. And in other
specimens from the same animal, he has
noticed what is very possibly the opposite
extreme of the cell-life : the cavity of a
large cell filled with large angular corpuscles.
These corpuscles are sometimes nucleated;
they have albuminous reactions; and they
appear to be produced from the ordinary
cells of the pulp. They ultimately disappear.
The function of the agminate follicles it is
impossible to specify. Few organs in the
body have been the subject of more numerous
speculations: speculations, the absurdity of
most of which renders them unworthy of
any serious mention. And hence, although
what we know respecting the structure of
these organs justifies (or rather requires)
some attempt to indicate their physiological
import, the mistakes of others may well teach
us how much caution is requisite in making
such conjectures. They are, at most, mere
guesses at truth.
The contents of the follicle have just been
stated to be composed of a cell-growth that
lies in contact with a large vascular surface.
Hence it is in the reaction of these innu-
merable minute agents on a copious and rich
nutritional fluid exsuded from the blood,
that we must look for the chief office of the
follicle. The fact of various stages of cell-life
being present simultaneously, appears to in-
dicate, that the cells do not merely select
certain materials, but more or less produce
them ; by a process which, directly or indi-
rectly by absolutely consuming their tissue,
or otherwise involves their own decay and
death. So far, then, the agminate follicle, which
closely resembles the vascular gland in its
structure, might be conjectured akin to it in
its function ; that function being a choice
from the nutritional fluid of certain of its con-
stituents, which, after undergoing a metamor-
phosis, are subsequently returned into the
general current of the blood.
But such a view omits to recognize some of
the circumstances it ought to explain. And it
especially neglects one which must be sup-
posed of great importance : namely, the situa-
tion of the follicle ; or, in other words, its
peculiar relation to the cavity of the intestine.
It is obvious that the position of the agmi-
nate follicle with respect to the intestinal canal
will admit of a double interpretation. On the
one hand, the materials on which its enclosed
cells have to act, will probably be derived
from the contents of the alimentary canal, as
well as from the blood. And on the other
hand, they may be ultimately excreted from
the body through the intestine, as well as re-
turned into that system of closed canals which
the blood vessels compose.
The degree in which the intestine forms the
channel of such an ingress and egress, must of
course depend upon the directness and effi-
ciency of the communication between its ca-
vity and that of the follicle. Hence, where
the two are in such close contiguity to each
other as in the case of the agminate glands
of the human subject, we may presume
that an efficient transudation of this two-
fold nature really does obtain. But where,
A A 4
360
STOMACH AND INTESTINE.
as in some of the follicles of the Calf,
the cavity of the intestine is separated from
that of these minute sacs by the inter-
vention of a thick compound mucous mem-
brane, it is difficult to avoid the conclusion ;
that a transit of their fluid contents, in
either, direction can only obtain to a compa-
ratively small amount.
In addition to these important relations
between the agminate follicle on the one
hand, and the vascular and intestinal cavi-
ties on the other, recent observations have
shown that there is a third, which is perhaps
quite as intimately connected with its func-
tion : namely, the connection of the follicle
with the commencement of the lacteal system.
For the general analogy of the intestinal
follicle to the vascular gland is far surpassed
by that close structural resemblance which
Koelliker has shown that it possesses to the
follicles of the lymphatic glands. The
latter, indeed, exhibit a remarkable similarity
to the structure of the agminate follicles. Like
them, they enclose vessels as well as cells,
within the cavity formed by their limitary wall.
Hitherto it has certainly been found impossible
to verify the presence of lacteals within the
agminate follicles; or to establish the existence
of any direct communication between their
cavities and that of the lacteal vessels them-
selves. But in spite of this, it seems
certain, both that the lacteals occupy the
patches in numbers quite disproportionate
to the small and few villi here present ;
and that they possess the closest proximity
with the contents of the follicles. Such a *
conclusion must, I think, be drawn from
Bruecke's researches ; in which the cavity of
the follicle soon became slightly coloured with
reddened turpentine, which had been injected
into the lacteals by compressing the distended
intestine.
It remains, however, for future researches
to determine how far this view is correct, and
whether the agminate follicles do really par-
take of the nature and office of lymphatic
glands. In any case, their very variable
number, and their occasional absence, would
seem to indicate, that (like the similar struc-
tures always present in the tonsils, and some-
times found in large numbers within the mucous
membrane of the stomach) their function is
either not very important; or what is far
more likely can be more or less replaced by
that of other kindred organs. And from the
number and size of these follicles, we may
perhaps conjecture, that their merely quanti-
tative effect on the chemistry of the organism
is not very great.
The little that is known of their changes
in health and disease confirms what has just
been stated respecting their relations to the
* That direct communication between the agmi-
nate follicles and the lacteals, -which Bruecke de-
duced from his observations, is, however, contradicted
by the time at which the colour above mentioned
appeared, and by its diminished intensity of hue :
as well as by the fact, that the agminate follicle never
contains white chyle.
vascular and lymphatic systems. Thus, dur-
ing digestion, they become so swollen, as
to project from the inner surface of the intes-
tine : a condition that may, perhaps, be due
to increased absorption from the intestine, but
is better ascribed to that energetic determina-
tion of blood to the whole of the intestinal
structures which then takes place. During
the violent drain of cholera the same tumid
condition obtains : probably from a similar
cause. And finally, the remarkable parallel
between the disease of these follicles and
that of the neighbouring mesenteric glands,
which is seen both in phthisis and typhoid
fever, is a strong additional argument for the
reality of that analogy which physiology indi-
cates to exist between the two structures.
Solitary follicles. The solitary follicles are
so completely what their name implies
isolated structures of the same kind as those
which are aggregated to form the "patch"
that any further description of their mi-
nute anatomy would be quite superfluous.
Indeed, those smaller patches which are
formed by two or three follicles, may be
almost regarded as a transition between the
"solitary" and" agminate" arrangement. But
these scattered solitary follicles are seldom
or never surrounded by a definite circle of the
apertures of intestinal tubes. And they often
sustain villi of the usual size and shape.
Their number is extremely variable. Some-
times they seem to be altogether absent. But
a very careful examination will now and then
show, that such a deficiency is one in appear-
ance only ; and is due to the very slight degree
of distention which obtains in the follicles
really present. Whether this explanation
would always hold good is more doubtful:
though the remarkable constancy with which
these structures are found in most animals
and in the human foetus is, to say the least,
a strong confirmation of its general truth.
In other instances they are strewn thickly
over the whole intestinal canal, from the
oesophagus to the anus. Such an excessive
development is perhaps strictly a morbid
phenomenon. But it is also capable of ex-
planation as a mere collective hypertrophy ;
an overgrowth which results in an increased
number of these minute organs, instead of
an increased size of each individual follicle.
Which of these two views is the more correct,
will only be decided when we know more
respecting their office.
They usually occupy the whole of the small
and large intestine in considerable numbers.
They are, however, more numerous in the
latter of these two segments of the diges-
tive tube. And here they also present a
larger size, as well as what is generally a
deeper situation in the sub-mucous areolar
tissue. Hence the depression that indi-
cates the follicle in the small intestine is
exaggerated, in the large intestine, into a deep
fossa ; which, commencing by an aperture over
each follicle, widens as it passes downwards
between the opposed sides of a few contigu-
ous intestinal tubes, to terminate, near their
STOMACH AND INTESTINE.
361
extremities, on the bulging surface of the fol-
licle.
Racemose, or Brumfs glands. The re-
maining constituent of the compound intes-
tinal membrane is one which, unlike all the
preceding minute organs, is limited to a very
small segment of the canal. It consists of a
number of highly ramified tubes, which are
usually termed the glands of Bnmn, but
might preferably be named the racemose or
duodenal glands. These glands occupy that
upper part of the small intestine already
distinguished as the duodenum ; of which
segment they are thus, as it were, the natural
index, or the characteristic structure.
The racemose glands are small " conglo-
bate " masses ; which in their size, structure,
and position, closely resemble those accessory
salivary organs that stud various parts of the
mucous membrane lining the cavity of the
mouth. Like these " labial" and "buccal"
glands, they occupy the sub-mucous areolar
tissue : and are therefore best examined by
pinning out a piece of the duodenum on some
flat surface, with its mucous side downwards,
and then carefully removing the serous and
muscular coats. Such a dissection easily ex-
poses them, as small roundish white granules
of about the size of a millet seed.
They vary considerably in size and arrange-
ment. Immediately beyond the pylorus, they
are of one-tenth to one-eighth of an inch
in diameter ; and are present in such num-
bers, as to form what is almost a glandular
layer around this part of the intestine. But
lower down in the duodenum, their size
dwindles to one-half or one-third of the
above : and their scattered grains gradually
become more sparing in number; until, shortly
before the termination of its inferior transverse
portion, they cease altogether.
On tracing out the structure of an isolated
duodenal gland under the microscope, it is
seen to consist of numerous lobules; which
are aggregated into a single mass (c c,fig. 272.),
by an enveloping layer of fibrous tissue. And
on applying a still higher magnifying power,
each of these lobules may be again resolved
into smaller ones, which resemble a bunch of
grapes, and constitute the true or ultimate acini
of the gland. As seen in situ, these vesicles
have a globular or slightly polyhedral form;
and a diameter which is about -s^th to ^^th
(on an average, m^th) of an inch. But when
separated from each other, they often exhibit
more irregular shapes (d,fig. 273.). They are
the terminal dilatations of tubes, which are
themselves about two-thirds of this size. On
tracing these minute tubes towards the general
mucous surface, they will be found uniting with
other similar ones, to form larger ducts. The
successive union of these with other ducts
formed in the same way, and of these larger
ducts with their neighbours, gradually causes
all their cavities to converge into a single canal
of outlet, which is the proper efferent duct of
the gland. This duct now passes between the
intestinal tubes before described, to open on
the free surface of the intestine, in the depres-
sions which intervene between the rudimen-
tary villi present here. The valvulae conni-
Fi%. 272.
Racemose or duodenal gland, as seen in a vertical
section of the duodenum. Magnified 40 diameters.
a, intestinal tubes ; b, muscular stratum of the
mucous membrane ; c, c, acini of the duodenal gland,
which occupies the submucous areolar tissue ; d,
transverse layer of the muscular coat ; e, longitudi-
nal layer of the muscular coat ; /, peritoneal tunic
of the bowel.
ventes are not permeated by any such ducts.
But in all other parts of its surface, the
general mucous membrane is pretty evenly
Fig. 273.
Diagram of the arangement of the lobules of a duode-
nal gland.
a, duct of the lobule ; b, collateral branch of this
duct ; c, the acini around such a duct in situ ; d, the
same separated, and the duct unfolded.
studded by their apertures, two or more some-
times 'passing through it in company with each
other.
Hence each of these glands may be briefly
described as a tube, which branches'repeatedly,
and ends in very minute canals, with some-
what vesicular extremities.
The whole of this involution of mucous
membrane is composed of the usual elements j
namely, limitary membrane and epithelium.
The former constituent offers no peculiarity
worthy of note. The latter consists of a single
tesselated layer of cells. These have a poly-
gonal and slightly flattened shape, which some-
362
STOMACH AND INTESTINE.
what resembles that of the cells lining the
smaller branches of the straight urinary tubules.
Where the smaller tubes converge to form the
efferent duct that perforates the mucous
membrane, these cells are exchanged for
short cylinders, the structure of which rapidly
merges into that of the ordinary columnar
epithelium of the general intestinal surface.
As regards the secretion of these racemose
glands, we can only state that their ducts
contain a structureless mucus, which has an
alkaline reaction.
With such an imperfect knowledge of its na-
ture, we can scarcely wonder that the office of
this fluid remains unknown to us. Like many
other animal matters, it converts starch into
sugar. But until the precise rapidity and energy
of this change have been established, it is im-
possible to determine how far this action is
really comparable to that of the saliva. From
the close resemblance between the sub-mu-
cous glands of the mouth and these of the duo-
denum, many have assumed them to prepare
a salivary fluid. But, besides that we are
not warranted in regarding the secretion of
the buccal glands as identical with the saliva
(of which it forms but a very small ingredient),
a very moderate knowledge of histology
might suffice to indicate the danger of inferring
the nature of any secretion from the mere
arrangement of the structures by which it is
furnished. Hence it must remain for the
present undecided, whether this mucus is a
salivary or pancreatic fluid ; or merely a more
concentrated form of intestinal juice, secreted
by glands which here reach a higher degree of
development than that attained by the short
cylindrical tubes of the rest of the bowel.
Large intestine. The remaining portion of
the alimentary canal forms the large intestine
Fig. 274.
Large intestine, as seen in situ, in a state of moderate
inflation. The anterior wall of the belly, and the
small intestine, are supposed to have been removed.
c, caecum ; a, ascending portion of the colon ; t,
transverse portion ; d, descending portion ; s, sig-
moid flexure ; r, rectum.
(c a t d s r^fig. 276.) (intestinum crassum, Lat. ;
gros intestm, Fr.; dickes Gedarm, Germ.): a
name which alludes to the size that is one of its
chief characteristics. Beginning at the termi-
nation of the ileum, in the right iliac fossa, it
passes upwards to the under surface of the
liver. Here it turns at a right angle, and runs
horizontally below the stomach, to the left
extremity of this organ. By a second bend,
it here resumes the vertical direction, and
then passes downwards towards the left iliac
fossa. In this region it undergoes a remark-