Chapter IV: Part 4

The circumstances of the time and the country turned Coehoorn's attention to the art of fortification, and the events of the late war showed him that existing methods could no longer be relied upon. His first published work, _Versterckinge de Vijfhoeks met alle syne Buytenwerken_ (Leeuwarden, 1682), at once aroused attention, and involved the author in a lively controversy with a rival engineer, Louys Paan (Leeuwarden, 1682, 1683; copies are in the library of the Dutch ministry of war). The military authorities were much interested in this, and entrusted Coehoorn with the reconstruction of several fortresses in the Netherlands. This task he continued throughout his career; and his experience in the work made him the worthy rival of his great contemporary Vauban. He formulated his ideas a little later in his chief work, _Nieuwe Vestingbouw op en natte of lage horizont_, &c. (Leeuwarden, 1685), in which he laid down three "systems," the characteristic feature of which was the multiplicity and great saliency of the works, which were calculated and in principle are still eminently suited for flat and almost marshy sites such as those of the Low Countries. He borrowed many of the details from the works of his Dutch predecessor Freytag, of Albrecht Durer, and of the German engineer Speckle, and in general he aimed rather at the adaptation of his principles to the requirements of individual sites than at producing a geometrically and theoretically perfect fortress; and throughout his career he never hesitated to depart from his own rules in dealing with exceptional cases, such as that of Groningen. Subsequent editions of _Nieuwe Vestingbouw_ appeared in Dutch (1702, and frequently afterwards), English (London, 1705), French (Wesel, 1705), and German (Dusseldorf, 1709).

From 1688 to the treaty of Ryswick Coehoorn served as a brigadier. At the battle of Fleurus he greatly distinguished himself, and in 1692 he defended Namur, a fortress of his own creation. Namur was taken by Vauban; but the Dutch engineer had his revenge three years later, when the place, on which in the meantime Vauban had lavished his skill, fell to his attack. Coehoorn became lieutenant-general and inspector-general of the Netherlands fortresses, and the high-German peoples as well as his own countrymen honoured him. He commanded a corps in the army of the duke of Marlborough from 1701 to 1703, and in the constant siege warfare of these campaigns in the Low Countries his technical skill was of the highest value. The swift reduction of the fortress of Bonn and the siege of Huy in 1703 were his crowning successes. At the opening of his following campaign he was on his way to confer with Marlborough when he died of apoplexy at Wijkel on the 17th of March 1704.

His "first system" was applied to numerous places in Holland, notably Nijmwegen, Breda and Bergen-op-Zoom. Mannheim in Germany was also fortified in this way, while the "secondsystem" was applied to Belgrade and Temesvar in eastern Europe.

His son, Gosewijn Theodor van Coehoorn, wrote his life (re-edited
Syperstein, Leeuwarden, 1860). See also v. Zastrow, _Geschichte der
bestandigen Befestigung_ (Leipzig, 1828); von Brese-Winiari, _Uber
Entstehen und Wesen der neueren Befestigungsmethode_ (1844); Cosseran
de Villenoisy, _Essai historique sur la fortification_ (1869); Mandar,
_Architecture des forteresses_ (1801); Krayenhoff, _Verhandeling over
de erste versterkingsmanier van Coehoorn_ (Hague, 1823); Bosscha,
_Nederlandsche heldend te Land_ (Amsterdam, 1838); Dewez, _Histoire de
Belgique_ (Brussels, 1823); Ypey, _Narratio de rebus gestis Mennonis
Cohorni_ (1771); Hennert, _Dissertation sur la fortification
permanente_ (1795); Bohms, _Grundliche Anleitung zur Kriegsbaukunst_
(1776); _Axiomatas of allgemeene bekentnisse over de Vestinghbouw door
Menno Baron van Coehoorn, Uytgewerkt door E. W. Berg_ (MS. in Dutch
Ministry of War); Bousmard, _Essai general de fortification_ (1797);
also the article FORTIFICATION AND SIEGECRAFT.

COELENTERA, a group or grade of the animal kingdom, the zoological importance of which has risen considerably since the time (1887) of the publication of the first article under that heading in the _Ency. Brit._ (9th edit.), even though their numbers have been reduced by the elevation of the Sponges or Porifera to the rank of an independent Phylum under the title Parazoa (W. J. Sollas, 1884). For the Coelentera thus restricted, the term Enterocoela, in contrast to Coelomocoela (the old Coelomata), was suggested by E. R. Lankester (1900).

From the more complex colonial Protozoa the Coelentera are readily separated by their possession of two distinct sets of cells, with diverse functions, arranged in two definite layers,--a condition found in no Protozoan. The old criterion by which they and other Metazoa were once distinguished from Protozoa, namely, the differentiation of large and small sexual cells from each other and from the remaining cells of the body, has been broken down by the discovery of numerous cases of such differentiation among Protozoa. The Coelentera, as contrasted with other Metazoa (but not Parazoa), consist of two layers of cells only, an outer layer or ectoderm, an inner layer or endoderm. They have hence been described as Diploblastica. In the remaining Metazoa certain cells are budded off at an early stage of development from one or both of the two original layers, to form later a third layer, the mesoderm, which lies between the ectoderm and endoderm; such forms have therefore received the name Triploblastica. At the same time it is necessary to observe that it is by no means certain that the mesoderm found in various groups of Metazoa is a similar or homologous formation in all cases. A second essential difference between Coelentera and other Metazoa (except Parazoa) is that in the former all spaces in the interior of the body are referable to a single cavity of endodermal origin, the "gastro-vascular cavity," often termed the coelenteron: the spaces are always originally continuous with one another, and are in almost every case permanently so. This single cavity and its lining serve apparently for all those functions (digestion, excretion, circulation and often reproduction) which in more complex organisms are distributed among various cavities of independent and often very diverse origin.

In the Coelentera the ectoderm and endoderm are set apart from one another at a very early period in the life-history; generally either by delamination or invagination, processes described in the article EMBRYOLOGY. Between these two cell-layers a mesogloea (G. C. Bourne, 1887) is always intercalated as a secretion by one or both of them; this is a gelatinoid, primitively structureless lamella, which in the first instance serves merely as a basal support for the cells. In many cases, as, for example, in the Medusae or jelly-fish, the mesogloea may be so thick as to constitute the chief part of the body in bulk and weight. The ectoderm rarely consists of more than one layer of cells: these are divisible by structure and function into nervous, muscular and secretory cells, supported by interstitial cells. The endoderm is generally also an epithelium one cell in thickness, the cells being digestive, secretory and sometimes muscular. Reproductive sexual cells may be found in either of these two layers, according to the class and sub-class in question. The mesogloea is in itself an inert non-cellular secretion, but the immigration of muscular and other cells into its substance, from both ectoderm and endoderm, gives it in many cases a strong resemblance to the mesoderm of Triploblastica,--a resemblance which, while probably superficial, may yet serve to indicate the path of evolution of the mesoderm.

The Coelentera may thus be briefly defined as Metazoa which exhibit two embryonic cell-layers only,--the ectoderm and endoderm,--their body-cavities being referable to a single cavity or coelenteron in the endoderm. Their position in the animal kingdom and their main subdivisions may be expressed in the following table:--

I. PROTOZOA.
II. PARAZOA or PORIFERA.
III. METAZOA.
|
+----------+--------------+
| |
Coelentera Triploblastica
= Diploblastica. (including Coelomata).
|
+------+-----------+-----------------+
| | |
Hydromedusae. Scyphozoa. Ctenophora.
|
+--------+----------+
| |
Scyphomedusae. Anthozoa.

In the above-given classification, the Scyphomedusae, formerly included with the Hydromedusae as Hydrozoa, are placed nearer the Anthozoa. The reasons for this may be stated briefly.

The HYDROMEDUSAE are distinguished from the Scyphozoa chiefly by negative characters; they have no stomodaeum, that is, no ingrowth of ectoderm at the mouth to form an oesophagus; they have no mesenteries (radiating partitions) which incompletely subdivide the coelenteron; and they have no concentration of digestive cells into special organs. Their ectodermal muscles are mainly longitudinal, their endodermal muscles are circularly arranged on the body-wall. Their sexual cells are (probably in all cases) produced from the ectoderm, and lie in those radii which are first accentuated in development. They typically present two structural forms, the non-sexual hydroid and the sexual medusoid; in such a case there is an alternation of generations (metagenesis), the hydroid giving rise to the medusoid by a sexual gemmation, the medusoid bearing sexual cells which develop into a hydroid. In some other cases medusoid develops directly from medusoid (hypogenesis), whether by sexual cells or by gemmation. The medusoids have a muscular velum of ectoderm and mesogloea only.

The SCYPHOZOA have the following features in common:--They typically exhibit an ectodermal stomodaeum; partitions or mesenteries project into their coelenteron from the body-wall, and on these are generally concentrated digestive cells (to form mesenterial filaments, phacellae or gastric filaments, &c.); the external musculature of the body-wall is circular (except in _Cerianthus_); the internal, longitudinal; and the sexual cells probably always arise in the endoderm.

The SCYPHOMEDUSAE, like the Hydromedusae, typically present a metagenesis, the non-sexual scyphistomoid (corresponding to the hydroid) alternating with the sexual medusoid. In other cases the medusoid is hypogenetic, medusoid producing medusoid. The sexual cells of the medusoid lie in the endoderm on interradii, that is, on the second set of radii accentuated in the course of development. The medusoids have no true velum; in some cases a structure more or less resembling this organ, termed a velarium, is present, permeated by endodermal canals.

The ANTHOZOA differ from the Scyphomedusae in having no medusoid form; they all more or less resemble a sea-anemone, and may be termed actinioid. They are (with rare exceptions, probably secondarily acquired) hypogenetic, the offspring resembling the parent, and both being sexual. The sexual cells are borne on the mesenteries in positions irrespective of obvious developmental radii.

The CTENOPHORA are so aberrant in structure that it has been proposed to separate them from the Coelentera altogether: they are, however, theoretically deducible from an ancestor common to other Coelentera, but their extreme specialization precludes the idea of any close relationship with the rest.

As regards the other three groups, however, it is easy to conceive of them as derived from an ancestor, represented to-day to some extent by the planula-larva, which was Coelenterate in so far as it was composed of an ectoderm and endoderm, and had an internal digestive cavity (I. of the table).

At the point of divergence between Scyphozoa and Hydromedusae (II. of the table of hypothetical descent), we may conceive of its descendant as tentaculate, capable of either floating (swimming) or fixation at will like Lucernaria to-day; and exhibiting incipient differentiation of myoepithelial cells (formerly termed neuro-muscular cells). At the parting of the ways which led, on the one hand, to modern Scyphomedusae, on the other to Anthozoa (III.), it is probable that the common ancestor was marked by incipient mesenteries and by the limitation of the sexual cells to endoderm. The lines of descent--II. to Hydromedusae, and III. to Scyphomedusae--represent periods during which the hypothetical ancestors II. and III., capable of either locomotion or fixation at will, were either differentiated into alternating generations of fixed sterile nutritive hydroids (scyphistomoids) and locomotor sexual medusoids, or abandoned the power of fixation in hypogenetic cases. During the period represented by the line of descent--III. to Anthozoa--this group abandoned its power of adult locomotion by swimming. During these periods were also attained those less important structural characters which these three groups present to-day. (G. H. Fo.)

Hydromedusae. Scyphomedusae. Anthozoa.
\ | /
\ | /
\ | /
\ | /
\ | /
\ | /
\ | /
\ | /
\ | /
\ |/
\ III.
\ /
Ctenophora? \ /
\ II.
\ |
\ |
\ |
\ |
\ |
\ |
\ |
\ |
\ |
\|
I.

COELLO, ALONSO SANCHEZ (1515-1590), Spanish painter, according to some authorities a native of Portugal, was born, according to others, at Benifacio, near the city of Valencia. He studied many years in Italy; and returning to Spain in 1541 he settled at Madrid, and worked on religious themes for most of the palaces and larger churches. He was a follower of Titian, and, like him, excelled in portraits and single figures, elaborating the textures of his armours, draperies, and such accessories in a manner so masterly as strongly to influence Velazquez in his treatment of like objects. Many of his pictures were destroyed in the fires that consumed the Madrid and Prado palaces, but many good examples are yet extant, among which may be noted the portraits of the infantes Carlos and Isabella, now in the Madrid gallery, and the St Sebastian painted in the church of San Geronimo, also in Madrid. Coello left a daughter, Isabella Sanchez, who studied under him, and painted excellent portraits.

COELLO, ANTONIO (1610?-1652), Spanish dramatist and poet, was born at Madrid about the beginning of the 17th century. He entered the household of the duke de Albuquerque, and after some years of service in the army received the order of Santiago in 1648. He was a favourite of Philip IV., who is reported to have collaborated with him; this rumour is not confirmed, but there is ample proof of Coello's collaboration with Calderon, Rojas Zorrilla, Solis and Velez de Guevara, the most distinguished dramatists of the age. The best of his original plays, _Los Empenos de seis horas_, has been wrongly ascribed to Calderon; it was adapted by Samuel Tuke, under the title of _The Adventures of five Hours_, and was described by Pepys as superior to _Othello_. It is an excellent example of stagecraft and animated dialogue. Coello died on the 20th of October 1652, shortly after his nomination to a post in the household of Philip IV.

COELOM AND SEROUS MEMBRANES. In human anatomy the body-cavity or coelom (Gr. [Greek: koilos], hollow) is divided into the _pericardium_, the two _pleurae_, the _peritoneum_ and the two _tunicae vaginales_.

The _pericardium_ is a closed sac which occupies the central part of the thorax and contains the heart. Like all the serous membranes it has a visceral and a parietal layer, the former of which is closely applied to the heart and consists of endothelial cells with a slight fibrous backing: to it is due the glossy appearance of a freshly removed heart. The parietal layer is double; externally there is a strong fibrous protective coat which is continuous with the other fibrous structures in the neighbourhood, especially with the sheaths of the great vessels at the root of the heart, with prolongations of the fascia of the neck, and with the central tendon of the diaphragm, while internally is the serous layer which is reflected from the surface of the heart, where the great vessels enter, so that everywhere the two layers of the serous membrane are in contact, and the only thing within the cavity is a drop or two of the fluid secreted by the serous walls. When the parietal layer is laid open and the heart removed by cutting through the great vessels, it will be seen that there are two lines of reflection of the serous layer, one common to the aorta and pulmonary artery, the other to all the pulmonary veins and the two venae cavae.

The _pleurae_ very closely resemble the pericardium except that the fibrous outer coat of the parietal layer is not nearly as strong; it is closely attached to the inner surface of the chest walls and mesially to the outer layer of the pericardium; above it is thickened by a fibrous contribution from the scalene muscles, and this forms the _dome of the pleura_ which fits into the concavity of the first rib and contains the apex of the lung. The reflection of the serous layer of the pleura, from the parietal to the visceral part, takes place at the root of the lung, where the great vessels enter, and continues for some distance below this as the _ligamentum latum pulmonis_. The upper limit of the pleural cavity reaches about half an inch above the inner third of the clavicle, while, below, it may be marked out by a line drawn from the twelfth thoracic spine to the tenth rib in the mid axillary line, the eighth rib in the nipple line, and the sixth rib at its junction with the sternum. There is probably very little difference in the lower level of the pleurae on the two sides.

A, Aorta. D, Duodenum.
P, Pancreas. B, Bladder.
I, Intestine. St, Stomach.
R, Rectum. C, Colon.
L, Liver. V, Vagina.

(The fine dots represent the great sac of the peritoneum, the coarse dots the lesser sac.)]

The _peritoneum_ is a more extensive and complicated membrane than either the pericardium or pleura; it surrounds the abdominal and pelvic viscera, and, like the other sacs, has a parietal and visceral layer. The line of reflection of these, though a continuous one, is very tortuous. The peritoneum consists of a _greater_ and _lesser sac_ which communicate through an opening known as the _foramen of Winslow_, and the most satisfactory way of understanding these is to follow the reflections first in a vertical median (sagittal) section and then in a horizontal one, the body being supposed to be in the upright position. If a median sagittal section be studied first, and a start be made at the umbilicus (see fig. 1), the parietal peritoneum is seen to run upward, lining the anterior abdominal wall, and then to pass along the under surface of the diaphragm till its posterior third is reached; here there is a reflection on to the liver (L), forming the anterior layer of the _coronary ligament_ of that viscus, while the membrane now becomes visceral and envelops the front of the liver as far back as the transverse fissure on its lower surface; here it is reflected on to the stomach (St) forming the anterior layer of the _gastro-hepatic_ or _lesser omentum_. It now covers the front of the stomach, and at the lower border runs down as the anterior layer of an apron-like fold, the _great omentum_, which in some cases reaches as low as the pubes; then it turns up again as the posterior or fourth layer of the great omentum until the transverse colon (C) is reached, the posterior surface of which it covers and is reflected, as the posterior layer of the _transverse meso-colon_, to the lower part of the pancreas (P); after this it turns down and covers the anterior surface of the third part of the duodenum (D) till the posterior wall of the abdomen is reached, from which it is reflected on to the small intestine (I) as the anterior layer of the _mesentery_, a fold varying from 5 to 8 in. between its attachments. After surrounding the small intestine it becomes the posterior layer of the mesentery and so again reaches the posterior abdominal wall, down which it runs until the rectum (R) is reached. The anterior surface of this tube is covered by peritoneum to a point about 3 in. from the anus, where it is reflected on to the uterus and vagina (V) in the female and then on to the bladder (B); in the male, on the other hand, the reflection is directly from the rectum to the bladder. At the apex of the bladder, after covering the upper surface of that organ, it is lifted off by the urachus and runs up the anterior abdominal wall to the umbilicus, from which the start was made. All this is the greater sac. The tracing of the lesser sac may be conveniently started at the transverse fissure of the liver, whence the membrane runs down to the stomach (St) as the posterior layer of the lesser omentum, lines the posterior surface of the stomach, passes down as the second layer of the great omentum and up again as the third layer, covers the anterior surface of the transverse colon (C) and then reaches the pancreas (P) as the anterior layer of the transverse mesocolon. After this it covers the front of the pancreas and in the middle line of the body runs up below the diaphragm to within an inch of the anterior layer of the coronary ligament of the liver; here it is reflected on to the top of the Spigelian lobe of the liver to form the posterior layer of the coronary ligament, covers the whole Spigelian lobe, and so reaches the transverse fissure, the starting-point.

A, Aorta. H.A, Hepatic Artery.
Sp, Spleen. K, Kidney.
B.D, Bile duct. L, Liver.
V.C, Vena Cava. St, Stomach.
P, Pancreas. P.V, Portal Vein.

The dotting of the peritoneum is as in fig. 1.]

This section, therefore, shows two completely closed sacs without any visible communication. In the female, however, the great sac is not absolutely closed, for the Fallopian tubes open into it by their minute _ostia abdominalia_, while at the other ends they communicate with the cavity of the uterus and so with the vagina and exterior.

A horizontal section through the upper part of the first lumbar vertebra will, if a fortunate one (see fig. 2), pass through the foramen of Winslow and show the communication of the two sacs. A starting-point may be made from the mid-ventral line and the parietal peritoneum traced round the left side of the body wall until the outer edge of the left kidney (K) is reached; here it passes in front of the kidney and is soon reflected off on to the spleen, which it nearly surrounds; just before it reaches the hilum of that organ, where the vessels enter, it is reflected on to the front of the stomach (St), forming the anterior layer of the _gastro-splenic omentum_; it soon reaches the lesser curvature of the stomach and then becomes the anterior layer of the lesser omentum, which continues until the bile duct (B.D) and portal vein (P.V) are reached at its right free extremity; here it turns completely round these structures and runs to the left again, as the posterior layer of the lesser omentum, behind the stomach (St) and then to the spleen (Sp) as the posterior layer of the gastro-splenic omentum. From the spleen it runs to the right once more, in front of the pancreas (P), until the inferior vena cava (V.C) is reached, and this point is just behind the portal vein and is the place where the lesser and greater sacs communicate, known as the foramen of Winslow. From this opening the lesser sac runs to the left, while all the rest of the peritoneal cavity in the section is greater sac. From the front of the vena cava the parietal peritoneum passes in front of the right kidney (K) and round the right abdominal wall to the mid-ventral line. The right part of this section is filled by the liver (L), which is completely surrounded by a visceral layer of peritoneum, and no reflection is usually seen at this level between it and the parietal layer. Some of the viscera, such as the kidneys and pancreas, are retro-peritoneal; others, such as the small intestines and transverse colon, are surrounded, except at one point where they are attached to the dorsal wall by a _mesentery_ or _mesocolon_ as the reflections are called; others again are completely surrounded, and of these the caecum is an example; while some, like the liver and bladder, have large uncovered areas, and the reflections of the membrane form ligaments which allow considerable freedom of movement.

The _tunica vaginalis_ is the remains of a process of the peritoneum (_processus vaginalis_) which descends into the scrotum during foetal life some little time before the testis itself descends. After the descent of the testis the upper part usually becomes obliterated, while the lower part forms a serous sac which nearly surrounds the testis, but does not quite do so. Posteriorly the epididymis is in close contact with the testis, and here the visceral layer is not in contact; there is, however, a pocket called the _digital fossa_ which squeezes in from the outer side between the testis and epididymis. The parietal layer lines the inner wall of its own side of the scrotum.

For a full description of the topography of the serous membranes see
any of the standard text-books of anatomy, by Gray, Quain, Cunningham
or Macalister. Special details will be found in Sir F. Treves'
_Anatomy of the Intestinal Canal and Peritoneum_ (London, 1885); C. B.
Lockwood, _Hunterian Lectures on Hernia_ (London, 1889); C. Addison,
"Topographical Anatomy of the Abdominal Viscera in Man," _Jour.
Anat._, vols. 34, 35; F. Dixon and A. Birmingham, "Peritoneum of the
Pelvic Cavity," _Jour. Anat._ vol. 34, p. 127; W. Waldeyer, "Das
Becken" (1899), and "Topographical Sketch of the Lateral Wall of the
Pelvic Cavity," _Jour. Anat._ vol. 32; B. Moynihan, _Retroperitoneal
Hernia_ (London, 1899). A complete bibliography of the subject up to
1895 will be found in _Quain's Anatomy_, vol. 3, part 4, p. 69.

FIG. 3.--Diagram of Longitudinal Section, showing the different areas of the Blastodermic Vesicle.

_a_, Pericardium. _e_, Placental area.
_b_, Bucco-pharyngeal area. _d_, Entoderm.
_c_, Ectoderm.]

_Embryology._--As the mesoderm is gradually spreading over the embryo it splits into two layers, the outer of which is known as the _somatopleure_ and lines the parietal or ectodermal wall, while the inner lines the entoderm and is called the _splanchnopleure_; between the two is the coelom. The pericardial area is early differentiated from the rest of the coelom and at first lies in front of the neural and bucco-pharyngeal area; here the mesoderm stretches right across the mid-line, which it does not in front and behind. As the head fold of the embryo is formed the pericardium is gradually turned right over, so that the dorsal side becomes the ventral and the anterior limit the posterior; this will be evident on referring to the two accompanying diagrams.

FIG. 4.--Diagram of a Developing Ovum, seen in Longitudinal Section.

_f_, Spinal cord. _i_, Brain.
_g_, Notochord. _k_, Extra embryonic coelom.
_h_, Dorsal wall of alimentary canal. Other numbers as in fig. 3.]

The two primitive aortae lie at first in the ventral wall of the pericardium, but with the folding over they come to lie in the dorsal wall and gradually bulge into the cavity as they coalesce to form the heart, so that the heart drops into the dorsal side of the pericardium and draws down a fold of the membrane called the _dorsal mesocardium_. In mammals A. Robinson (_Jour. Anat. and Phys._, xxxvii. 1) has shown that no ventral mesocardium exists, though in more lowly vertebrates it is present. Laterally the pericardial cavity communicates with the general cavity of the coelom, but with the growth of the Cuvierian ducts (see development of veins) these communications disappear. Originally the mesocardium runs the whole length of the pericardium from before backward, but later on the middle part becomes obliterated, and so the two separate reflections from the parietal to the visceral layer, already noticed, are accounted for.

Just behind the pericardium and in front of the umbilicus, which at first are close together, the mesoderm forms a mass which is called the _septum transversum_, and into this the developing lungs push bag-like protrusions of the coelom, consisting of visceral and parietal layers, and these eventually lose their connexion with the rest of the coelom, as the diaphragm develops, and become the pleural cavities. After the pericardium and pleurae have been separated off the remainder of the coelom becomes the peritoneum. At first the stomach and intestine form a straight tube, which is connected to the dorsum of the embryo by a _dorsal mesentery_ and to the mid-ventral wall in front of the umbilicus by a _ventral mesentery_. Into the ventral mesentery the liver grows as diverticula from the duodenum, so that some of the mesentery remains as the _falciform ligament_ of the liver and some as the lesser omentum. Into the dorsal mesentery the pancreas grows, also as diverticula, from the duodenum, while the spleen is developed from the mesoderm contained in the same fold. As the stomach turns over so that its left side becomes ventral, the dorsal mesentery attached to it becomes pulled out, in such a way that part of it forms the great omentum and part the gastro-splenic omentum. After the caecum is formed as a diverticulum from the intestine it is situated close to the liver and gradually travels down into the right iliac fossa. This passage to the right is accompanied by a throwing over of the duodenal loop to the right, so that the right side of its mesentery becomes pressed against the dorsal wall of the abdomen and obliterated. This accounts for the fact that the pancreas and duodenum are only covered by peritoneum on their anterior surfaces in man. The formation of the lesser sac is due to the turning over of the stomach to the right, with the result that a cave, known sometimes as the _bursa omentalis_, is formed behind it. Originally, of course, the whole colon had a _dorsal mesocolon_ continuous with the mesentery, but in the region of the ascending and descending colon this usually disappears and these parts of the gut are uncovered by peritoneum posteriorly. The transverse mesocolon persists and at first is quite free from the great omentum, but later, in man, the two structures fuse[1] and the fourth layer of the great omentum becomes continuous with the posterior layer of the transverse mesocolon.

For further details see Quain's _Anatomy_ (London, 1908).

_Comparative Anatomy._--In the Amphioxus the coelom is developed in the embryo as a series of bilateral pouches, called _enterocoeles_, from the sides of the alimentary canal; these are therefore entodermal in their origin, as in Sagitta and the Echinodermata among the invertebrates. In the adult the development of the atrium causes a considerable reduction of the coelom, represented by two dorsal coelomic canals communicating with a ventral canal by means of branchial canals which run down the outer side of the primary gill bars. Into the dorsal canals the nephridia open. In the intestinal region the coelom is only present on the left side.

In the higher vertebrates (_Craniata_) the coelom is developed by a splitting of the mesoderm into two layers, and a pericardium is constricted off from the general cavity. In all cases the ova burst into the coelom before making their way to the exterior, and in some cases, _e.g._ amphioxus, lamprey (Cyclostomata), eels and mud-fish (Dipnoi), the sperm cells do so too. The Cyclostomata have a pair of _genital pores_ which lead from the coelom into the urino-genital sinus, and so to the exterior.

In the Elasmobranch fish there is a _pericardio-peritoneal canal_ forming a communication between these two parts of the coelom; also a large common opening for the two oviducts in the region of the liver, and two openings, called _abdominal pores_, on to the surface close to the cloacal aperture. In the Teleostomi (Teleostean and Ganoid fish) abdominal pores are rare, but in most Teleostei (bony fish) the ova pass directly down oviducts, as they do in Arthropods, without entering the peritoneal cavity; there is little doubt, however, that these oviducts are originally coelomic in origin. In the Dipnoi (mud-fish) abdominal pores are found, and probably serve as a passage for the sperm cells, since there are no vasa deferentia. In fishes a complete dorsal mesentery is seldom found in the adult; in many cases it only remains as a tube surrounding the vessels passing to the alimentary canal.

In the Amphibia, Reptilia and Aves, one cavity acts as pleura and peritoneum, though in the latter the lungs are not completely surrounded by a serous membrane. In many lizards the comparatively straight intestine, with its continuous dorsal mesentery and ventral mesentery in the anterior part of the abdomen, is very like a stage in the development of the human and other mammalian embryos. In the mammalia the diaphragm is complete (see DIAPHRAGM) and divides the pleuro-peritoneal cavity into its two constituent parts. In the lower mammals the derivatives of the original dorsal mesentery do not undergo as much fusion and obliteration as they do in adult man; the ascending and descending mesocolon is retained, and the transverse mesocolon contracts no adhesion to the great omentum. It is a common thing, however, to find a fenestrated arrangement of the great omentum which shows that its layers have been completely obliterated in many places.

In those animals, such as the rabbit, in which the tests are sometimes in the scrotum and sometimes in the abdomen, the communication between the peritoneum and the tunica vaginalis remains throughout life.

For further details and literature up to 1902, see R. Wiedersheim's
_Vergleichende Anatomie der Wirbeltiere_ (Jena, 1902). (F. G. P.)

FOOTNOTE:

[1] Some authorities hold that this alteration is not brought about
by fusion, but by a dragging away of the posterior layer of the great
omentum from the dorsal wall of the abdomen.

COEN, JAN PIETERSZOON (1587-1630), fourth governor-general of the Dutch East Indies, was born at Hoorn, and spent his youth at Rome in the house of the famous merchants the Piscatori. In 1607 he sailed from Amsterdam to the Indies as second commercial agent, and remained away four years. He had proved so capable that in 1612 he was sent out a second time at the head of a trading expedition. In the following year he was made a councillor and director-general of the East Indian trade. Afterwards he became president at Bantam, and on the 31st of October 1617 he was promoted in succession to Laurens Reaal to the post of governor-general. To his vigour and intrepidity the Dutch in no small measure owed the preservation and establishment of their empire in the East. He took and destroyed Jacatra, and founded on its ruins the capital of the Dutch East Indies, to which he gave the name of Batavia. In 1622 Coen obtained leave to resign his post and return to Holland, but in his absence great difficulties had arisen with the English at Amboina (the so-called massacre of Amboina), and in 1627 under pressure from the directors of the East India Company he again returned as governor-general to Batavia. In 1629 he was able to beat off a formidable attack of the sultan of Mataram, sometimes styled emperor of Java, upon Batavia. He died the following year.

COENACULUM, the term applied to the eating-room of a Roman house in which the supper (_coena_) or latest meal was taken. It was sometimes placed in an upper storey and reached by an external staircase. The Last Supper in the New Testament was taken in the Coenaculum, the "large upper room" cited in St Mark (xiv. 15) and St Luke (xxii. 12).

COENWULF (d. 821), king of Mercia, succeeded to the throne in 796, on the death of Ecgfrith, son of Offa. His succession is somewhat remarkable, as his direct ancestors do not seem to have held the throne for six generations. In 798 he invaded Kent, deposed and imprisoned Eadberht Praen, and made his own brother Cuthred king. Cuthred reigned in Kent from 798 to 807, when he died, and Coenwulf seems to have taken Kent into his own hands. It was during this reign that the archbishopric of Lichfield was abolished, probably before 803, as the Hygeberht who signed as an abbot at the council of Cloveshoe in that year was presumably the former archbishop. Coenwulf appears from the charters to have quarrelled with Wulfred of Canterbury, who was consecrated in 806, and the dispute continued for several years. It was probably only settled at Cloveshoe in 825, when the lawsuit of Cwoenthryth, daughter and heiress of Coenwulf, with Wulfred was terminated. Coenwulf may have instigated the raid of Aethelmund, earl of the Hwicce, upon the accession of Ecgberht. He died in 821, and was succeeded by his brother Ceolwulf I.

See Earle and Plummer's edition of the _Anglo-Saxon Chronicle_, 796,
819 (Oxford, 1892); W. de G. Birch, _Cartularium Saxonicum_, 378
(London, 1885-1893). (F. G. M. B.)

COERCION (from Lat. _coercere_, to restrain), an application of moral or physical compulsion by which a person is forced to do or refrain from doing some act or set of acts apart from his own voluntary motion. Where the coercion is direct or positive, _i.e._ where the person is compelled by physical force to do an act contrary to his will,--for example, when a man is compelled to join a rebel army, and to serve as a soldier under threats of death,--his act is not legally a crime. Where the coercion is implied, as when a person is legally under subjection to another, the person coerced, having no will on the subject, is not responsible. But this principle is applied only within narrow limits, and does not extend to the command of a superior to an inferior; of a parent to a child; of a master to his servant or a principal to his agent. Where, however, a married woman commits a crime in the presence of her husband, she is generally presumed to have acted by his coercion, and to be entitled to acquittal, but this presumption does not extend to grave crimes, nor to those in which the principal part may be supposed to be taken by the woman, such as keeping a brothel. In civil matters, such as the making of a contract, where the law requires the free assent of the person who undertakes the obligation, coercion is a ground for invalidating the instrument.

The term "coercion" is inevitably somewhat ambiguous, and depends on the circumstances of the case. In a political sense, the application of the Crimes Act of 1887 to Ireland was called "coercion" by those opposed to the English Unionist party and government, as being special legislation differing from the ordinary law applicable in the United Kingdom.

COEUR, JACQUES (_c._ 1395-1456), founder of the trade between France and the Levant, was born at Bourges, in which city his father, Pierre Coeur, was a rich merchant. Jacques is first heard of about 1418, when he married Macee de Leodepart, daughter of Lambert de Leodepart, an influential citizen, provost of Bourges, and a former valet of John, duke of Berry. About 1429 he formed a commercial partnership with two brothers named Godard; and in 1432 he was at Damascus, buying and bartering, and transporting the wares of the Levant--gall-nuts, wools and silks, goats' hair, brocades and carpets--to the interior of France by way of Narbonne. In the same year he established himself at Montpellier, and there began those gigantic operations which have made him illustrious among financiers. Details are wanting; but it is certain that in a few years he placed his country in a position to contend not unsuccessfully with the great trading republics of Italy, and acquired such reputation as to be able, mere trader as he was, to render material assistance to the knights of Rhodes and to Venice herself.

In 1436 Coeur was summoned to Paris by Charles VII., and made master of the mint that had been established in that city. The post was of vast importance, and the duties onerous. The country was deluged with the base moneys of three reigns, charged with superscriptions both French and English, and Charles had determined on a sweeping reform. In this design he was ably seconded by the merchant, who, in fact, inspired or prepared all the ordinances concerning the coinage of France issued between 1435 and 1451. In 1438 he was made steward of the royal expenditure; in 1441 he and his family were ennobled by letters patent. In 1444 he was sent as one of the royal commissioners to preside over the new parlement of Languedoc, a dignity he bore till the day of his disgrace. In 1445 his agents in the East negotiated a treaty between the sultan of Egypt and the knights of Rhodes; and in 1447, at his instance, Jean de Village, his nephew by marriage, was charged with a mission to Egypt. The results were most important; concessions were obtained which greatly improved the position of the French consuls in the Levant, and that influence in the East was thereby founded which, though often interrupted, was for several centuries a chief commercial glory of France. In the same year Coeur assisted in an embassy to Amadeus VIII., former duke of Savoy, who had been chosen pope as Felix V. by the council of Basel; and in 1448 he represented the French king at the court of Pope Nicholas V., and was able to arrange an agreement between Nicholas and Amadeus, and so to end the papal schism. Nicholas treated him with the utmost distinction, lodged him in the papal palace, and gave him a special licence to traffic with the infidels. From about this time he made large advances to Charles for carrying on his wars; and in 1449, after fighting at the king's side through the campaign, he entered Rouen in his train.

At this moment the great trader's glory was at its height. He had represented France in three embassies, and had supplied the sinews of that war which had ousted the English from Normandy. He was invested with various offices of dignity, and possessed the most colossal fortune that had ever been amassed by a private Frenchman. The sea was covered with his ships; he had 300 factors in his employ, and houses of business in all the chief cities of France. He had built houses and chapels, and had founded colleges in Paris, at Montpellier and at Bourges. The house at Bourges (see HOUSE, Plate II. figs. 7 and 8) was of exceptional magnificence, and remains to-day one of the finest monuments of the middle ages in France. He also built there the sacristy of the cathedral and a sepulchral chapel for his family. His brother Nicholas was made bishop of Lucon, his sister married Jean Bochetel, the king's secretary, his daughter married the son of the viscount of Bourges, and his son Jean became archbishop of Bourges. But Coeur's gigantic monopoly caused his ruin. Dealing in everything, money and arms, peltry and jewels, brocades and woollens--a broker, a banker, a farmer--he had absorbed the trade of the country, and merchants complained they could make no gains on account of "that Jacquet." He had lent money to needy courtiers, to members of the royal family, and to the king himself, and his debtors, jealous of his wealth, were eager for a chance to cause his overthrow.

In February 1450 Agnes Sorel, the king's mistress, suddenly died. Eighteen months later it was rumoured that she had been poisoned, and a lady of the court who owed money to Jacques Coeur, Jeanne de Vendome, wife of Francois de Montberon, and an Italian, Jacques Colonna, formally accused him of having poisoned her. There was not even a pretext for such a charge, but for this and other alleged crimes the king, on the 31st of July 1451, gave orders for his arrest and for the seizure of his goods, reserving to himself a large sum of money for the war in Guienne. Commissioners extraordinary, the merchant's declared enemies, were chosen to conduct the trial, and an inquiry began, the judges in which were either the prisoner's debtors or the holders of his forfeited estates. He was accused of having paid French gold and ingots to the infidels, of coining light money, of kidnapping oarsmen for his galleys, of sending back a Christian slave who had taken sanctuary on board one of his ships, and of committing frauds and exactions in Languedoc to the king's prejudice. He defended himself with all the energy of his nature. His innocence was manifest; but a conviction was necessary, and in spite of strenuous efforts on the part of his friends, after twenty-two months of confinement in five prisons, he was condemned to do public penance for his fault, to pay the king a sum equal to about L1,000,000 of modern money, and to remain a prisoner till full satisfaction had been obtained; his sentence also embraced confiscation of all his property, and exile during royal pleasure. On the 5th of June 1453 the sentence took effect; at Poitiers the shameful form of making honourable amends was gone through; and for nearly three years nothing is known of him. It is probable that he remained in prison; it is certain that his vast possessions were distributed among the intimates of Charles.

In 1455 Jacques Coeur, wherever confined, contrived to escape into Provence. He was pursued; but a party, headed by Jean de Village and two of his old factors, carried him off to Tarascon, whence, by way of Marseilles, Nice and Pisa, he managed to reach Rome. He was honourably and joyfully received by Nicholas V., who was fitting out an expedition against the Turks. On the death of Nicholas, Calixtus III. continued his work, and named his guest captain of a fleet of sixteen galleys sent to the relief of Rhodes. Coeur set out on this expedition, but was taken ill at Chios, and died there on the 25th of November 1456. After his death Charles VII. showed himself well disposed to the family, and allowed Jacques Coeur's sons to come into possession of whatever was left of their father's wealth.

See the admirable monograph of Pierre Clement, _Jacques Coeur et
Charles VII_ (1858, 2nd ed. 1874); A. Valet de Viriville, _Charles
Sept et son epoque_ (3 vols., 1862-1865); and Louisa Costello,
_Jacques Coeur, the French Argonaut_ (London, 1847).

COEUR D'ALENE ("awl-heart," the French translation of the native name _skitswish_), a tribe of North American Indians of Salishan stock. The name is said to have been originally that of a chief noted for his cruelty. The tribe has given its name to a lake, river and range of mountains in Idaho, where on a reservation the survivors, some 400, are settled.

COFFEE (Fr: _cafe_, Ger. _Kaffee_). This important and valuable article of food is the produce chiefly of _Coffea arabica_, a Rubiaceous plant indigenous to Abyssinia, which, however, as cultivated originally, spread outwards from the southern parts of Arabia. The name is probably derived from the Arabic K'h[=a]wah, although by some it has been traced to Kaffa, a province in Abyssinia, in which the tree grows wild.

The genus _Coffea_, to which the common coffee tree belongs, contains about 25 species in the tropics of the Old World, mainly African. Besides being found wild in Abyssinia, the common coffee plant appears to be widely disseminated in Africa, occurring wild in the Mozambique district, on the shores of the Victoria Nyanza, and in Angola on the west coast. The coffee leaf disease in Ceylon brought into prominence Liberian coffee (_C. liberica_), a native of the west coast of Africa, now extensively grown in several parts of the world. Other species of economic importance are Sierra Leone coffee (_C. stenophylla_) and Congo coffee (_C. robusta_), both of which have been introduced into and are cultivated on a small scale in various parts of the tropics. _C. excelsa_ is another species of considerable promise.

The common Arabian coffee shrub is an evergreen plant, which under natural conditions grows to a height of from 18 to 20 ft., with oblong-ovate, acuminate, smooth and shining leaves, measuring about 6 in. in length by 2-1/2 wide. Its flowers, which are produced in dense clusters in the axils of the leaves, have a five-toothed calyx, a tubular five-parted corolla, five stamens and a single bifid style. The flowers are pure white in colour, with a rich fragrant odour, and the plants in blossom have a lovely and attractive appearance, but the bloom is very evanescent. The fruit is a fleshy berry, having the appearance and size of a small cherry, and as it ripens it assumes a dark red colour. Each fruit contains two seeds embedded in a yellowish pulp, and the seeds are enclosed in a thin membranous endocarp (the "parchment"). Between each seed and the parchment is a delicate covering called the "silver skin." The seeds which constitute the raw coffee "beans" of commerce are plano-convex in form, the flat surfaces which are laid against each other within the berry having a longitudinal furrow or groove. When only one seed is developed in a fruit it is not flattened on one side, but circular in cross section. Such seeds form "pea-berry" coffee.

The seeds are of a soft, semi-translucent, bluish or greenish colour, hard and tough in texture. The regions best adapted for the cultivation of coffee are well-watered mountain slopes at an elevation ranging from 1000 to 4000 ft. above sea-level, within the tropics, and possessing a mean annual temperature of about 65 deg. to 70 deg. F.

The Liberian coffee plant (_C. liberica_) has larger leaves, flowers and fruits, and is of a more robust and hardy constitution, than Arabian coffee. The seeds yield a highly aromatic and well-flavoured coffee (but by no means equal to Arabian), and the plant is very prolific and yields heavy crops. Liberian coffee grows, moreover, at low altitudes, and flourishes in many situations unsuitable to the Arabian coffee. It grows wild in great abundance along the whole of the Guinea coast.

_History._--The early history of coffee as an economic product is involved in considerable obscurity, the absence of fact being compensated for by a profusion of conjectural statements and mythical stories. The use of coffee (_C. arabica_) in Abyssinia was recorded in the 15th century, and was then stated to have been practised from time immemorial. Neighbouring countries, however, appear to have been quite ignorant of its value. Various legendary accounts are given of the discovery of the beneficial properties of the plant, one ascribing it to a flock of sheep accidentally browsing on the wild shrubs, with the result that they became elated and sleepless at night! Its physiological action in dissipating drowsiness and preventing sleep was taken advantage of in connexion with the prolonged religious service of the Mahommedans, and its use as a devotional antisoporific stirred up fierce opposition on the part of the strictly orthodox and conservative section of the priests. Coffee by them was held to be an intoxicating beverage, and therefore prohibited by the Koran, and severe penalties were threatened to those addicted to its use. Notwithstanding threats of divine retribution and other devices, the coffee-drinking habit spread rapidly among the Arabian Mahommedans, and the growth of coffee and its use as a national beverage became as inseparably connected with Arabia as tea is with China.

Towards the close of the 16th century the use of coffee was recorded by a European resident in Egypt, and about this epoch it came into general use in the near East. The appreciation of coffee as a beverage in Europe dates from the 17th century. "Coffee-houses" were soon instituted, the first being opened in Constantinople and Venice. In London coffee-houses date from 1652, when one was opened in St Michael's Alley, Cornhill. They soon became popular, and the role played by them in the social life of the 17th and 18th centuries is well known. Germany, France, Sweden and other countries adopted them at about the same time as Great Britain. In Europe, as in Arabia, coffee at first made its way into favour in the face of various adverse and even prohibitive restrictions. Thus at one time in Germany it was necessary to obtain a licence to roast coffee. In England Charles II. endeavoured to suppress coffee-houses on the ground that they were centres of political agitation, his royal proclamation stating that they were the resort of disaffected persons "who devised and spread abroad divers false, malicious and scandalous reports, to the defamation of His Majesty's government, and to the disturbance of the peace and quiet of the nation."

Up to the close of the 17th century the world's entire, although limited, supply of coffee was obtained from the province of Yemen in south Arabia, where the true celebrated Mocha or Mokka coffee is still produced. At this time, however, plants were successfully introduced from Arabia to Java, where the cultivation was immediately taken up. The government of Java distributed plants to various places, including the botanic garden of Amsterdam. The Portuguese introduced coffee into Ceylon. From Amsterdam the Dutch sent the plant to Surinam in 1718, and in the same year Jamaica received it through the governor Sir Nicholas Lawes. Within a few years coffee reached the other West Indian islands, and spread generally through the tropics of the New World, which now produce by far the greater portion of the world's supply.