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sion for the right kidney on the posterior surface of the liver ; the situation of the two kidneys is well
shown by the corresponding impressions in the cast ; asc. col., desc. col., ascending and descending
colon ; pt, back of the peritoneum ; m, line of attachment of the mesentery ; VIII, IX, X, XI, the
corresponding ribs ; il, ilium.

anterior and right aspect, and the pylorus often touches it when the stomach is
distended.

The lody and tail together (fig. 162, B) are four or five inches long. After
crossing from the right side in front of the aorta the body curves backwards in its
course to the left, and close to the spleen the tail turns sharply upwards and backwards.
The body is prismatic in form and has three surfaces, anterior, posterior, and inferior.
The inferior surface is narrow but better marked on the left than on the right side.
The surfaces, like those of the liver, are moulded to the adjacent organs.

The anterior surface is concave, looks upwards as well as forwards, and is covered
by the stomach, the lesser sac of the peritoneum intervening. At its right extremity
it often forms a well-marked prominence called the omental tuberosity (His).



THE PANCREAS.



141



The posterior surface lies in front of the aorta, the origin of the superior
mesenteric artery, the pillars of the diaphragm, the splenic vein, the left kidney and
its vessels, and the left suprarenal capsule.

The inferior surface is narrow and rests upon the duodeno-jejunal flexure, and
frequently also upon some convolutions of the jejunum and upon the transverse
colon near its left end.

The superior border lies in relation with the cceliac axis, the hepatic branch of
this trunk passing to the right just above it, while on the left side the splenic artery
in its tortuous course to the spleen grooves it.

At the anterior border the two layers of the transverse meso-colon separate, the
anterior layer ascending in relation with the anterior surface of the pancreas, whilst
the posterior layer passes backwards in contact with the inferior surface. The
posterior surface is thus devoid of peritoneum.




Fig. 164. THE PANCREAS AND ADJOINING VISCERA FROM BEFOUK. 3

The liver, the stomach, the greater part of the small intestine, and the transverse colon have been
removed. P, pancreas; d, duodenum; d.j., duodeno-jejunal flexure; above the duodenum, and
between it and the head of the pancreas are seen the bile-duct, portal vein, and hepatic artery ; asc.
col., desc. col., ascending and descending colon ; spl., spleen ; r.k., l.k., right and left kidneys ; s.r..
s.r', right and left suprarenal capsules ; pt, peritoneum at the back of the abdominal cavity ; m, line
of reflection of the mesentery ; the line of reflection of the transverse mesocolon is seen along the lower
edge of the pancreas and crossing the duodenum.

The tail of the pancreas is in contact with the lower part of the inner surface of
the spleen.

The principal excretory duct, called the pancreatic duct or canal of Wirsung,
runs through the entire length of the gland from left to right, buried entirely in its
substance. Commencing by the union of the small ducts derived from the groups
of lobules composing the tail of the pancreas, and receiving in succession at various
angles and from all sides the ducts from the body of the gland, the canal of Wirsung
pursues a nearly straight course in the axis of the gland until it reaches the neck.
Here it turns obliquely downwards, backwards, and to the right through the neck
and head, gradually approaching the posterior surface of the latter. Near its
termination it comes in contact with the left side of the common bile duct, which it
accompanies to the second part of the duodenum. As it traverses the head of the
pancreas it is joined by numerous branches, one of which coming from the lower
part of the head is larger than the others. The bile and pancreatic ducts placed
side by side, pass very obliquely through the muscular and arcolar coats of the



142 ORGANS OF DIGESTION.

intestine, and terminate, as already described, on its internal surface, by a common
orifice, situated near the junction of the second and third portions of the duodenum,
between three and four inches below the pylorus. The pancreatic duct, with its
branches, is readily distinguished within the glandular substance, by the very white
appearance of its thin fibrous walls. Its widest part, near the duodenum, is from
T Vth to |th of an inch in diameter, or nearly the size of an ordinary quill. It is
lined by a remarkably thin and smooth membrane, which near the termination of
the duct may present a few scattered recesses.

Varieties of pancreas and its ducts. Symington (Journal of Anatomy and Physiology,
1885) described a case in which the upper part of the second portion of the duodenum was
encircled by a ring: of pancreatic tissue. A somewhat similar case has been recorded by
G-enersich (Verhandl. x. Internat. Med. Congress, 1890). The tail of the pancreas is sometimes
bifid ; and the part of the head lying behind the mesenteric vessels may be separate from the
remainder of the gland, and form what is called the lesser pancreas.

Various examples of an accessory pancreas have been described. They occur most fre-
quently in the wall of the upper part of the jejunum, more rarely in the wall of the stomach
(see Zenker, Nebenpanorea* in dcr Darmirand, Arch. f. path. Anat., Bd. xxl).

Accessory duct, or duct of Santorini. Occasionally the main duct gives off at the neck
an accessory duct, which passes to the right and opens into the duodenum about an inch
above the common opening of the bile and main pancreatic ducts. This accessory duct is
occasionally found of large size, and evidently serving as the principal channel for the
passage of the pancreatic secretion into the duodenum, the lower part of the duct of Wirsung
being small. On the other hand the accessory duct may not open into the duodenum, but
terminate in the upper and right part of the head in small branches. In such cases its
contents must pass from right to left, and be discharged into the duct of Wirsung.

Schirmer (Seitrag ziir Geschichte imd Anat. deg Pancreas, Basel. 18113), has investigated
the arrangement of the ducts of the pancreas in 105 specimens. In fifty-six of these the
duct of Santorini arose from the main duct, and opened into the duodenum upon a papilla
situated above the common orifice of the bile and pancreatic ducts. In nineteen the duct of
Santorini, although well developed, did not open into the duodenum. In four there was
only one pancreatic duct, and that the upper, the common bile-duct opening by itself lower
down. In none of his specimens did he meet with an example of an arrangement described
by Claude Bernard, in which there were two ducts running throughout the whole length of
the gland.

The variations of the pancreatic ducts are of interest in connection with the mode of
development of the pancreas. From the observations of Zimmermann and Hamburger it
appears that in the human subject the pancreas is formed from two distinct outgrowths from
the wall of the duodenum. One of these, the smaller, is in close relation with the duodenal
end of the common bile-duct ; the other, which is situated nearer the pylorus, is much larger,
and forms the greater part of the pancreas. About the sixth week of embryonic life the two
processes join, and their contained ducts subsequently communicate with one another. The
portion of the upper duct on the duodenal side of the point of union grows less rapidly than
the lower duct. It becomes the duct of Santorini. while the lower duct, with the peripheral
portion of the upper one, forms the main channel for the pancreatic secretion, and is
generally known in the adult as the main pancreatic duct, or canal of Wirsung.

Structure. The pancreas belongs to the class of acino-tubular glands. In its
general characters it closely resembles the salivary glands, but it is somewhat looser
and softer in its texture than those organs, the lobes and lobules being less compactly
arranged.

The ducts are lined with a simple layer of long columnar epithelium, the cells
becoming shorter and more cubical in the smaller ducts. They do not exhibit any
well-marked longitudinal striation like that met with in the duct-cells of some of the
salivary glands. The ultimate branches of the ducts which are connected with the
alveoli (intercalary ducts'), are much narrowed, and are lined with flattened cells,
looking spindle-shaped in optical section. The alveoli of the gland are distinctly
tubular, and somewhat convoluted. In the inactive condition of the gland, and
during the earlier stages of activity, the alveoli are almost completely occupied by
the secreting cells, scarcely any lumen being visible. Moreover the middle of the



THE PAXCKEAS.



1415



alveolus is in the dog and some other animals occupied by spindle-shaped cells
(centro-acinar cells, fig. 165) which according to Langerhans are continuous with
the epithelium-cells of the intercalary ducts.

The secreting cells of the pancreas have a very characteristic appearance. They



Group of cells :

probably an

interalveolar

islet.




Larger duct, \



_ Centro-acinar
cell.



Centro-acinar
'cell.



Commencement
gjr f duct.

- Iiiivr zone of

alveolar cells.



Fig. 165. SKCTION OF HUMAN PANCKKAS. (Bohm and Davidoff. ) ^2

frequently, if not constantly, contain, besides the ordinary nucleus, a paranucleus
(Nebenkern), a spherical mass, staining more readily than the rest of the proto-
plasm, and said to be formed by extrusion of material from the nucleus (Gaule,
Xicolaides). In shape they are columnar, in some parts approaching the polygonal
form, and they show very distinctly, even in the loaded condition of the gland, two





A. B.

Fig. 166. AN ALVEOLUS OF THE RABBIT'S PANCREAS.

A., during rest, the cells loaded with granules, and the inner zone, a, large, and the outer zone, b,
narrow.

B., after activity, the inner zone small, and the outer zone large and distinctly striated. The cell
outlines are also now visible, c, lumen of alveolus ; d, basement membrane. (Kiihne and Lea.)

parts or zones ; an inner granular zone next the lumen, and an outer clear and finely-
striated zone next the basement membrane (figs. 16f> and 1(50).

When the gland is stimulated to activity the cells at first enlarge arid bulge the
basement membrane ; subsequently the granules of the inner zone become fewer in
number and aggregated near the lumen, and the outer clear zone extends over the
greater part of the cell (Heidenhain, Kiihne and Lea (fig. 166)). It is stated by



144



ORGANS OF DIGESTION



Ogata that these zymogen granules are forme .1 from the p irmucleus, but the state-
ment requires confirmation.




Fig. 167. OlUGIN OF THE DUCTS OF THK PANCREAS, AS SHOWN BY THE CHROMATE OF SILVER

METHOD. (E. Miiller. )

A, duct cut longitudinally, lined by columnar epithelium giving off laterally the intercalary or
lobular ductules, m, to the alveoli, I. The manner in which these commence within the alveoli is
shown under a higher power in B.

Various observers, after forcing injections into the alveoli of the paucrens
backwards from the duct, have seen fine intercellular canaliculi, comparable to those

Fig. 168. SECTION OF PANCIIKAS OF

ARMADILLO, SHOWING SEVERAL
ALVEOLI AND ONE OF THE INTER-
ALVEOLAR CELL-ISLETS. (V. D.

Harris. )

The alveolar cells are much more
elongated here than ia man and in
most animals.

of the liver, passing from
the lumen of an alveolus
between the secreting cells.
These can also be shown by the
use of Golgi silver chromate
method (fig. 167, A), and with a high magnifying power, the canaliculi can be seen
penetrating not only between the cells of the alveoli, but even into the interior of the
individual cells (fig. 167, B).




LITERATURE OF PA AC RE AS. 145

Connective tissue ; interalveolar cell-islets. The connective tissue of the
gland, afterforming a sort of external investment, penetrates between its lobes or lobules
conveying the blood-vessels to all parts. They are not, however, everywhere equally
numerous, for some acini are not surrounded by the capillary network. On the
other hand, in certain parts of the interalveolar tissue collections of small cells
(interalveolar cell-islets, figs. 105, 168) are met with, which are permeated with a very
close network of large convoluted capillaries. The cells in question are like the cells
met with in the carotid and coccygeal glands, but their meaning is entirely
unknown. They are very characteristic of the pancreas, being apparently always
present in it.

Blood-vessels, lymphatics, and nerves. The arteries of the pancreas
are derived from the splenic and hepatic divisions of the codiac axis, and from the
inferior pancreatico-duodenal branch of the superior mesenteric. Its veins are
tributaries of the splenic and superior mesenteric, and therefore belong to the portal
system. The lymphatics pass to some of the neighbouring cceliac glands. Their
arrangement within the pancreas is similar to that found in the salivary glands.

The nerves are derived from the solar plexus, and accompauy the arteries to the
organ. They are almost exclusively non-medullated and have minute ganglia on
them as they traverse the gland. Besides these ganglia, small cells, apparently of
nervous nature, are found upon the nerves, near their distribution to the epithelium-
cells of the alveoli, over and between which they ultimately ramify.



RECENT LITERATURE OF THE PANCREAS.

Assmann, E., Zur Kenntnlss der Pankreas, Virchow's Archiv f. path. Anat. , Bd. cxi., 1888.

Cajal, S. Ramon y, and Sala Claudio, Terminaddn de los nervios y tubas glanduhires del
paticrtfis de los vertebrados, Barcelona, 1891.

Dogiel, S. , Zur Fraye iiber die Ausfilhrunysyanyc des Pankreas des Menscken, Arch. f. Anat. u.
Entwickelungsgesch., 1893.

Eberth, C. J., and Miiller, K. , Untersuchunyen iiber das Pancreas, Zeitschr. f. wissensch.
Zoologie, Bel. liii.

G-enersich, Anton, Seltene Anomalie des Pancreas, 10th International Aledical Congress, 1890,
Bd. xi.

Hamburger, Ove, Zur Entwickelung der Bauchspeicheldriise des Mcnschen, Anat. Anzeiger,
Bd. vii., 1892.

Herzen, A., Le jeune, le pancreas ct la rate, Arch, de physiol. norm, etpathol., 5se"r. t. vi., 1894.

Laguesse, E., Sur la formation des Hots de Lanyerhans dans le pancreas, C. R. soc. biol., t. v. ,
1893.

Nicolaides, R., Ucber die mikroskopischen Erscheinunyen der Pancreaszetten lei der Sckretion,
Centralbl. f. Physiol., No. xxv., 1889.

Nicolaides, R. , und Melissinos, C., Untersuchungen iiber einiye intra- u. extra-nuclear e
(rtblf.de im Pankreas der Sdugetiere auf Hire Beziehung zu, der Sckretion, Archiv f. Anat. u. Physiol.,
Physiol. Abt., Jahrg. 1890.

Schirmer, A. M. , Beitrag zur Geschichte und Anatomic des Pancreas, Basel, 1893.

Stoss, Zur Enticickelunys(jeschichte des Pancreas, Anat. Anzeiger, Dec., 1891.

Symington, J., Notes on a rare abnormality of the pancreas, Journal Anat. and Pays., vol. xix.,
1885.

Trolard, P., Note sur la direction de la rate et du pancreas chez le foetus et chez I 'enfant,
Comptes rendus hebdom. de la soc. de biol., serie ix., t. iv., 1892.

Ver Eecke, A., Modifications de la cellule pancreatique pendant Vactivite secretaire, Arch, de biol.,
t. xiii., 1893.

Zimmermann, ReJtonstruktionen eines menschlichen Embryos, Yerhandlungen der Anat. Gesell-
schaft, Berlin, 1889.



VOL. in., PT. 4.



ORGANS OF RESPIRATION AND VOICE

BT E. A. SCHAFER AND J. SYMINGTON.



THE organs of respiration and voice comprise the larynx, trachea, and bronchi,
and the lungs, with their serous investments, named the pleura.

The respiratory organs are developed as a median outgrowth from the ventral
wall of the fore-gut, and this primitive connection between the alimentary canal and
the respiratory apparatus is maintained in the adult, the upper end of the air-passage
opening on the anterior wall of the pharynx. Below, this median air-tube divides
into two lateral branches, one for each lung, while its upper part is modified to
form the organ of voice. In the majority of mammals the windpipe opens above
into the nasal part of the pharynx, the anterior boundary of the orifice (the
epiglottis) projecting upwards behind the soft palate. This is not the case, how-
ever, in the human subject, either during intra-uterine or extra-uterine life.

THE LARYNX, OR ORGAN OF VOICE.

The larynx is placed at the upper and fore part of the neck, where it forms a
considerable prominence in the middle line. It lies between the large vessels of the
neck, and below the tongue and hyoid bone. It is covered in front by the skin and
cervical fascia along the middle line, and on each side also by the sterno-hyoid,
sterno-thyroid, and thyro-hyoid muscles, by the upper end of the lateral lobe of the
thvroid body, and by a small part of the inferior constrictor of the pharynx.
Behind, it is separated from the 4th, 5th and 6th cervical vertebrae by the laryngeal
part of the pharynx and the prevertebral muscles. Above, it opens into the cavity of
the pharynx, and below, into that of the trachea.

Its dimensions, according to Sappey, are, on an average of eight males and eight
females, as follows :

Vertical diameter, measured from the upper border of the thyroid cartilage to the
lower border of the cricoid, 44 mm. in the male and 36 in the female ;

Transverse diameter, represented by the distance between the posterior borders of
the thyroid cartilage, 43 mm. in the male and 41 in the female ;

Antero-posterior diameter, measured from the most prominent part of the anterior
border of the thyroid cartilage to a line uniting its posterior borders, 36 mm. in the
male and 26 in the female.

The larynx consists of a framework of cartilages, articulated together, and
connected by elastic membranes or ligaments, two of which, projecting into the
interior of the cavity, are named the true vocal cords, being more immediately
concerned in the production of the voice. It possesses special muscles, which move
the cartilages one upon another, and modify its form and the tension of its ligaments,
and it is lined by a mucous membrane, continuous above with the mucous
membrane of the pharynx and below with that of the trachea.

CARTILAGES OF THE LARYNX.

The cartilages of the larynx (figs. 169A, and 169B) consist of three single and
symmetrical pieces, named respectively the thyroid cartilage, the cricoid cartilage,
and the cartilage of the epiglottis, and of three pairs, namely, the two arytenoid



CARTILAGES OF THE LARYNX.



147



cartilages, the cornicula larynyis, and the cuneiform cartilages. In all there are nine
distinct pieces, but the cornicula and cuneiform cartilages are very small. Only
the thyroid and cricoid cartilages are visible on the front and sides of the larynx ;
the back of the cricoid cartilage, surmounted by the arytenoid cartilages, and these
again by the cornicula, are seen behind ; whilst the epiglottis is situated in front of,
and the cuneiform cartilages on each side of, the upper opening.

The thyroid cartilage, the largest, consists of two flat lateral plates, which are
united in front at the isthmus, and form an angle of about 90 with one another like
the letter V, most prominent at the upper part. This angular projection is
subcutaneous, and is much more marked in the male lhan in the female,
being named in the former thepomum Adami. The two symmetrical halves, named
the aim, are somewhat quadrilateral in form. Of each half the anterior border
is the shortest, the pomum Adami being surmounted by a deep thyroid notch (see
fig. 1G9A). The free posterior border is thickened and vertical, and is prolonged





Fig. 169A. FRONT VIEW OF THE LARYNGEAL CARTILAGES AND LIGAMENTS. (Sappey.)

1, hyoid bone ; 2, its large cornua ; 3, its small cornua : 4, thyroid cartilage ; 5, thyro-hyoid
membrane ; 6, lateral thyro-hyoid ligament, containing the cartilaf/o triticea, 7 ; 8, cricoid cartilage ;
9, crico -thyroid membrane ; 10, lateral crico-thyroid ligaments ; 11, uppermost ring of trachea.

Fig. 169B. BACK VIEW OF THE LARYNGEAL CARTILAGES AND LIGAMENTS. (Sappey.)
1, thyroid cartilage; 2, cricoid cartilage; 3, arytenoid cartilages; 4, their muscular processes;
5, a ligament better marked than usual, connecting the lower cornu of the thyroid with the back of
the cricoid cartilage ; 6, upper ring of the trachea ; 7, epiglottis ; 8, ligament connecting it to the
angle of the thyroid cartilage. The cornicula are seen surmounting the arytenoid cartilages.

upwards and downwards into two processes or cornua ; it gives attachment to the
stylo-pharyngeus and palato-pharyngeus muscles. The upper and lower borders
have each a well-marked concavity close to the cornu ; otherwise the upper is
convex, and the lower nearly straight. The flattened external surface of each ala
is marked by an indistinct oblique line or ridge (fig. 169A), which, commencing
above at the posterior part of the superior border in a slight prominence called
the superior tubercle, passes downwards and slightly forward, and ends at the lower
border in an inferior tubercle, so as to mark off the anterior three-fourths of the sur-
face from the remainder. This line gives attachment below to the sterno-thyroid, and

L 2



148 ORGANS OF RESPIRATION AND VOICE.

above to the thyro-hyoid muscle, whilst the small smooth surface behind it gives
origin to part of the inferior constrictor of the pharynx, and affords attachment, by
means of areolar tissue, to the thyroid body. On their internal surfaces the alae
are smooth and slightly concave. Of the lour cornua, all of which bend inwards,
the two superior or great cornua (fig. 169), pass upwards with sometimes ?i slight
backward curve, and terminate each by a blunt extremity, which is connected, by
means of the lateral thyro-hyoid ligament, to the tip of the corresponding great
cornu of the hyoid bone (fig. 1G9A, 2). The inferior or smaller cornua, which are
somewhat thicker but shorter, are directed slightly forwards, and, on the inner
aspect of the tip, show a smooth surface, for articulation with a prominence on
the side of the cricoid cartilage.

Occasionally there is a forameu in the ala of the thyroid cartilage situated near the upper
part of its posterior border ; an abnormal branch of the superior laryngeal artery passes
through it. In the infant the isthmus of the thyroid cartilage differs from the two alse
in being less opaque and more flexible.

The cricoid cartilage (fig. 169A, 8), which is shaped like a signet ring, is thicker
and stronger than the thyroid. It is deep behind (fig. 109B, 2), where it is expanded
into a squarish plate or lamina, measuring in the male about an inch from above
downwards ; but in front it forms a narrow ring or arch, with a vertical measure-
ment of only one-fourth or one-fifth of an inch. Corresponding with this, the
superior border, which is markedly elevated behind, descends with a deep concavity
in front below the thyroid cartilage ; while the inferior border is horizontal, and
connected by membrane to the first ring of the trachea. The posterior elevated part
of the upper border is slightly depressed in the middle line, and on the sides of this
depression are the elongated oval facets for articulation with the arytenoid
cartilages. These facets are slightly convex, and they look outwards as well as
upwards. The external surface of the cartilage is convex and smooth in front and
at the sides, where it affords attachment to the crico-thyroid muscles, and behind
these to the inferior constrictors of the pharynx ; in the middle line posteriorly is a
slight vertical ridge to which some of the longitudinal fibres of the oesophagus are
attached. On each side of this ridge is a broad depression occupied by the posterior
crico-arytenoid muscle, outside which is a small flat, oval, and slightly raised surface
for articulation with the inferior coruu of the thyroid cartilage. The internal
surface is covered throughout by the mucous membrane of the larynx. At its lower
border the cricoid is circular, but higher up the cartilage is somewhat compressed
laterally, so that the passage through it is here elliptical.

The arytenoid cartilages (fig. 1G9B, 3) are two in number, and symmetrical in
form and position. They may be compared in shape to irregular three-sided
pyramids, and they rest by their bases on the posterior and highest part of the
cricoid cartilage, while their somewhat curved apices approach one another. Each is
about half an inch high and one quarter of an inch wide. Of the three faces the



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