Elias Owen - "Welsh Folk Lore"

Anne Douglas Sedgwick - "A Fountain Sealed"

Maurice Maeterlinck - "The Blue Bird: A Fairy Play in Six Acts"

United States Tariff Commission - "Men's Sewed Straw Hats"

Annual Bibliography of Commonwealth Literature 2007
This paper argues that discourses of love in Ghanaian market literature for youth offer a view into complex negotiations of agency and empowerment. Drawing on Deborah Durham's notion of youth as "social `shifters'" and Francis Nyamnjoh's conception of the "interconnectedness" of agency, I take Ghanaian market literature as one specific case of how African literature for youth foregrounds questions of continuity and change as African societies enter into increasingly complex global relations. In this literature for youth, received notions of love, often constructed out of impressions from American pop and hip hop music, carry new notions of agency that compete with existing "domesticated" forms. Authors like Ike Tandoh and Evelyn Tay employ discourses of love to offer youth alternative avenues for empowerment in a context of socio-economic disenfranchizement. In a creative process of "straddling", this writing both reveals and reproduces the contradictions that obtain in youth configurations of agency.

Form and Function

E >> E. S. (Edward Stuart) Russell >> Form and Function




[Illustration: FIG. 9.--Meckel's Cartilage and Ear-ossicles in Embryo
of Pig. (After Reichert.)]

In this paper Reichert made a distinct advance on the previous workers
in the same field--Rathke, Huschke, von Baer, Martin St Ange, Duges.
Huschke was indeed the first to suggest that both upper and lower jaws
were formed in the first gill-arch. But both von Baer and Rathke[207] held
that the upper jaw developed as a special process independent of the
lower jaw rudiment, and the actual proof that the upper jaw is a
derivative of the first visceral arch seems to have been first supplied
by Reichert. His brilliant work on the development of the ear-ossicles
founded what we may justly call the classical theory of their
homologies. His views were attacked and in some points rectified, but
the main homologies he established are even now accepted by many,
perhaps the majority of morphologists.

In a paper of 1838 on the comparative embryology of the skull in
Amphibia,[208] Reichert added to his results for mammals and birds an
account of the fate of the first and second visceral arches in Anura and
Urodela.

The first visceral arch, he found, gave in Amphibia practically the same
structures as in the higher Vertebrates. Its skeleton segmented, as in
mammals and birds, into three parts; the upper part gave rise to the
palatine and pterygoid in Anura, but seemed to disappear in Urodeles,
where the so-called palatine and pterygoid developed in the mucous
membrane of the mouth; the middle part gave, as in birds, the quadrate,
which formed a suspensorium for both arches; the lower part, as Meckel's
cartilage, formed a foundation for the bones of the lower jaw. Of arch
II., the lower part became the horn of the hyoid, the upper part had a
varying fate. In some Anura it formed the ossicle of the ear (homologue
of the columella of birds and the stapes of mammals), in others it
disappeared. In reptiles the upper segment of the second arch formed, as
in birds, the columella.

The account of the metamorphoses of the visceral arches in Amphibia
forms only a small part of Reichert's memoir of 1838, the chief object
of which was to discover the general "typus" of the vertebrate skull,
and to follow out its modifications in the different classes. Von Baer
had shown that the generalised type appeared most clearly in the early
embryo; Reichert therefore sought the archetype of the skull in the
developing embryo. He brought to his task the preconceived notion that
the skull could be reduced to an assemblage of vertebrae, but he saw that
comparative anatomy alone could not effect this reduction; he had
recourse, therefore, to embryology, hoping to find in the simplified
structure of the embryo clear indications of three primitive cranial
vertebrae (p. 121, 1837).

In the head he distinguished two tubes, the upper formed by the dorsal
plates, the lower by the ventral or visceral plates. Both of these tubes
were derived from the serous or animal layer (_cf._ von Baer, _supra_,
p. 118). The walls of the lower tube were formed by the visceral
processes, within which later the skeleton of the visceral arches
developed. The walls of the upper tube formed the bones and muscles of
the cranium proper. The facial part of the head was formed by elements
from both upper and lower tubes. The dorsal tube showed signs of a
division into three cranial vertebrae (_Urwirbeln_, primitive vertebrae).
In mammals and birds, as Reichert had shown in his 1837 paper, the three
cranial vertebrae were indicated by transverse furrows on the ventral
surface of the still membranous skull (see Fig. 10, p. 148).

Even in mammals and birds, however, the positions of the eye, the
ear-labyrinth, and the three visceral arches were the safest guides to
the delimitation of the cranial vertebrae (pp. 134-138, 1837). In
Amphibia generally there were no definite lines of separation on the
skull itself. "At this stage," he writes of the cartilaginous cranium of
the frog, "we find no trace of a veritable division into vertebrae in the
cartilaginous trough formed by the _basis cranii_ and the side parts. On
the contrary, it is quite continuous, as it is also in the higher
Vertebrates during the process of chondrification" (p. 44, 1838). The
vertebrae in the membranous or cartilaginous skull could be delimited in
Amphibia by the help of the eye and the ear-labyrinth, which lie more or
less between the first and second, and the second and third vertebrae,
but, above all, by the vesicles of the brain.

As in the higher Vertebrates, the visceral arches are associated with
the cranial vertebrae as their ventral extensions, being equivalent to
the visceral plates which form the ventral portion of the "primitive
vertebrae" or primitive segments of the trunk.

[Illustration: FIG. 10.--Cranial Vertebrae and Visceral Arches in Embryo
of Pig. Ventral Aspect. (After Reichert.)]

If the three cranial vertebrae are not very distinct in the early stages
of development when the skull is still membranous or cartilaginous, they
become clearly delimited when ossification sets in. Three rings of bone
forming three more or less complete vertebrae are the final result of
ossification. The composition of these rings is as follows:--

+-------------------------------------------------------------------+
| | Base. | Sides. | Top. |
|----------------+---------------+-----------------+----------------|
|First vertebra |Presphenoid |Orbitosphenoids |Frontals |
| | | | |
|Second vertebra |Basisphenoid |Alisphenoids |Parietals |
| | | | |
|Third vertebra |Basioccipital |Exoccipitals |Supraoccipital |
+-------------------------------------------------------------------+

The other bones of the skull are not included in the vertebrae, and this
is in large part due to the fact that the sense capsules are formed
separately from the cranium (p. 29, 1838). The ear-labyrinth, it is
true, fuses indissolubly with the cranium at a later period, but the
bones which develop in its capsule are not for all that integral parts
of the primitive cranial vertebrae. This point, it is interesting to
note, had already been made by Oken in his _Programm_ (1807). But many
of the bones developed in relation to the sense organs can find their
place in the generalised embryonic schema or archetype of the vertebrate
skull, for they are of very constant occurrence during early
development.

Having arrived at a generalised embryonic type for the vertebrate skull,
of which the fundamental elements are the three cranial vertebrae and
their arches, Reichert goes on to discuss the particular forms under
which the skull appears in adult Vertebrates. He accepts in general von
Baer's law that the characters of the large groups appear earlier in
embryogeny than the characters of the lesser classificatory divisions.
"When we observe new and not originally present rudiments in very early
embryonic stages, as, for instance, that for the lacrymals, the
probability is that they belong to the distinctive development of one of
the _larger_ vertebrate groups. From these are to be carefully
distinguished such rudiments as arise later during ossification, mostly
as _ossa intercalaria_, in order to give greater strength to the skull
in view of the greater development of the brain, etc.; the latter give
their individual character to the _smaller_ vertebrate groups, and
comprise such bones as the _vomer_, the _Wormian bones_, the lowermost
turbinal, etc." (p. 63, 1838).

He did not accept the Meckel-Serres law of parallelism. He recognised
the great similarity between the unsegmented cartilaginous cranium of
Elasmobranchs, and the primordial cranium of the embryos of the higher
Vertebrates, but he did not think that the cranium of Elasmobranchs was
simply an undeveloped or embryonic stage of the skulls of the higher
forms. Rather "do the _Holocephala_, _Plagiostomata_, and _Cyclostomata_
appear to us to be lower developmental stages individually
differentiated, so that the other fully differentiated Vertebrates
cannot easily be referred directly to their type" (p. 152, 1838). The
skull of these lower fishes is itself a specialised one; it is an
individualised modification of a simple type of skull. And this holds
good in general of the skulls of the lower Vertebrates--they are
individualised exemplars of a simple general type, not merely unmodified
embryonic stages of the greatly differentiated skulls of the higher
Vertebrates (p. 250, 1838). Differentiation within the vertebrate phylum
is therefore not uniserial, but takes place in several directions.
Reichert describes two sorts of modifications of the typical
skull--class modifications and functional modifications. The causes of
the modifications which characterise classificatory groups are unknown;
the second class of modifications occur in response to adaptational
requirements.

Reichert's two papers are of considerable importance, and Mueller's
remark in his review[209] of them is on the whole justified. "These
praiseworthy investigations supply from the realm of embryology new and
welcome foundations for comparative anatomy" (p. clxxxvii.).

The development of the skull was, however, more thoroughly worked out by
Rathke, and with less theoretical bias, in his classical paper on the
adder.[210] This memoir of Rathke's is an exhaustive one and deals with
the development of all the principal organ-systems, but particularly of
the skeletal and vascular. He confirmed in its essentials Reichert's
account of the metamorphoses of the first two visceral arches,
describing how the rudiment of the skeleton of the first arch appears as
a forked process of the cranial basis, the upper prong developing into
the palatine and pterygoid, the lower forming Meckel's cartilage, while
the quadrate develops from the angle of the fork. The actual bone of the
upper jaw (maxillary) develops outside and separate from the
palato-pterygoid bar. The cartilaginous rod supporting the second
visceral arch divides into three pieces on each side, of which the lower
two form the hyoid, the uppermost the columella. Like Reichert he held
the visceral arches to be parts of the visceral plates, containing,
however, elements from all three germ-layers--the serous, mucous, and
vessel layers.

The first gill-slit, or, as Rathke here prefers to call it, pharyngeal
slit, closes completely in snakes and in Urodeles. It forms the
Eustachian tube in all other Tetrapoda. As regards the vertebrae, Rathke
describes them as being formed in the sheath of the chorda from paired
rudiments, each of which sends two branches upwards, and two branches
downwards. The two inner pairs of processes coalesce round the chorda,
and later form the centrum; the upper outer pair meet above the spinal
column; the lower outer pair form ribs. The odontoid process of the axis
vertebra is the centrum of the atlas (p. 120). The formation of
vertebral rudiments begins close behind the ear-labyrinth, but in front
of this the chorda-sheath gives origin to a flat membranous plate which
afterwards becomes cartilaginous. This plate reaches forward below the
third cerebral vesicle as far as the infundibulum. The notochord ends in
this plate, which is the _basis cranii_, just at the level of the
ear-labyrinth. In no Vertebrate does the notochord extend farther
forward (p. 122). The _basis cranii_ gives off three trabeculae. The
middle one is small and sticks up behind the infundibulum; it is absent
in fish and Amphibia, and soon disappears during the development of the
higher forms. The lateral trabeculae are long bars which curve round the
infundibulum and reach nearly to the front end of the head. Together
they are lyre-shaped. The cranial basis and the trabeculae are formed,
like the vertebrae, in the sheath of the notochord, and the only
differences between the two in the early stage of their development are
that the formative mass for the cranial basis is much greater in amount
than that for the vertebrae, and that the cranial basis by means of its
processes, the trabeculae, reaches well in front of the terminal portion
of the notochord (p. 36). The capsule for the ear-labyrinth develops
quite independently of the cranial basis and the notochord. It resembles
on its first appearance, in form, position, composition, and
connections, the ear-capsule of Cyclostomes, and so do the ear-capsules
of all embryonic Vertebrates (p. 39). It manifests clearly the embryonic
archetype, ... "there exists one single and original plan of formation,
as we may suppose, upon which is built the labyrinth of Vertebrates in
general" (p. 40). When ossification sets in, the ear-capsule forms three
bones, of which two fuse with the supraoccipital and exoccipitals.

[Illustration: FIG. 11.--Embryonic Cranium of the Adder. Ventral Aspect.
(After Rathke.)]

During the formation of the ear-capsule the cranial basis develops from
a plate to a trench, for in its hinder section the side parts grow up to
form the side walls of the brain, in exactly the same way as the
processes of the vertebral rudiments grow up to enclose the spinal
column (pp. 122, 192). The foundations of the skull are now complete,
and ossification gradually sets in. The basioccipital is formed
in the posterior part of the _basis cranii_, and the exoccipitals in the
side walls of the trench in continuity with the fundament of the
basioccipital (see Fig. 11). The supraoccipital is formed in cartilage
above the exoccipitals. The basisphenoid develops, like the
basioccipital, in the flat _basis cranii_, but towards its anterior
edge, between the large foramen (_h_) and the pituitary space (_i_). It
is formed from two centres, each of which is originally a ring round the
carotid foramen. The presphenoid develops in isolation between the
lateral trabeculae, just behind the point where they fuse. The side parts
of the basisphenoid and presphenoid (forming the alisphenoids and the
orbitosphenoids respectively) develop in cartilage separately from the
cranial basis, not like the exoccipitals in continuity with it. The
hinder parts of the trabeculae become enclosed by two processes of the
basisphenoid; their front parts remain in a vestigial and cartilaginous
state alongside the presphenoid. The frontals and parietals show a
peculiar mode of origin in the adder, differing from their origin in
other Vertebrates. The frontals develop in continuity with the
orbitosphenoids, the parietals in continuity with the alisphenoids, and
so have much resemblance with the vertebral neural arches which surround
the spinal column (p. 195).

Through Rathke's work the real embryonic archetype of the vertebrate
skull was for the first time disclosed. Rathke discussed this archetype
and its relation to the vertebral theory of the skull in another paper
of the same year (1839), but before going on to this paper, we shall
quote from the paper on the adder the following passage, remarkable for
the clear way in which the idea of the embryological archetype is
expressed. "Whatever differences may appear in the development of
Vertebrates, there yet exists for the different classes and orders a
universally valid idea (plan, schema, or type) ruling the first
formation of their separate parts. This idea must first be worked out,
though possibly with modifications, before more special ideas can find
play. The result of the latter process, however, is that what was formed
by the first idea is not so much hidden as partially or wholly
destroyed" (p. 135).

Rathke's general paper on the development of the skull in Vertebrates[211]
treats the matter on a broader comparative basis than his paper on the
adder, and takes into account all the vertebrate classes, in so far as
their development was then known. He here makes the interesting
suggestion, later entirely confirmed, that the _basis cranii_ or basilar
plate is first laid down as two strips, one on each side of the
chorda--the structures now known as parachordals (pp. 6, 27). For this
supposition, he thinks, speaks the structure of the skull in
_Ammocoetes_, which in this respect is the simplest of all Vertebrates
(pp. 6, 22). In _Ammocoetes_, as Johannes Mueller had shown, the
foundation of the skull is formed by two long cartilaginous bars,
between the hinder portions of which the notochord ends. In these Rathke
was inclined to see the homologues of his trabeculae, and of the
parachordals which he was ready to assume from his embryological
observations.

Mueller was, of course, very ready to accept Rathke's opinions on this
subject, for he considered that they supported his own theory of the
vertebral nature of the skull. After describing in his _Handbuch der
Physiologie_ the cartilaginous bands in _Ammocoetes_ and their highly
differentiated homologues in the Myxinoids, he writes in the later
editions, "Hence we see that in the cranium, as in the spinal column,
there are at first developed at the sides of the chorda dorsalis two
symmetrical elements, which subsequently coalesce, and may wholly
enclose the chorda. Rathke has recently observed, in the embryos of
serpents and other animals, before the formation of the proper cranial
vertebrae, two symmetrical bands of cartilage, similar to those which I
discovered as a persistent structure in _Ammocoetes_.... At a later
period the _basis cranii_ of vertebrate animals contains three parts
analogous to the bodies of vertebrae, the most anterior of which, in the
majority of animals, is generally small, and its development frequently
abortive, whilst in man and mammiferous animals the three are very
distinct. These parts are developed by the formation of three distinct
points of ossification, one behind the other, in the basilar
cartilage."[212]

Rathke was very cautious about accepting the vertebral theory of the
skull; he saw that the facts of development were not altogether
favourable to the theory, and he gave his adherence with many
reservations and saving clauses. His general attitude may be summed up
as follows.[213]

The chorda sheath is the common matrix of the vertebrae and of a large
part of the skull. The basilar plate and the trabeculae, which are
developed from the chorda sheath, give origin to three bones, which
might possibly be considered equivalent to vertebral centra--the
basioccipital, the basisphenoid, and the _Riechbein_ (ethmoid). The
_Riechbein_ develops from the fused ends of the trabeculae. The
presphenoid might also be considered as a vertebral body, but it
develops independently of the basilar plate and trabeculae.

Now of these bones, the basioccipital is in every way equivalent to a
vertebral centrum, for it develops in the basilar plate round the
notochord. With the exoccipitals, which arise just like neural arches,
it forms a true vertebra. The supraoccipital is an accessory bone
developed in relation to bigger brains. The basisphenoid appears in the
basilar plate, but in front of the notochord, nor does it arise in
exactly the same way as the centrum of a vertebra. The basisphenoid with
the alisphenoids, which develop independently in the side walls of the
brain, may, however, still be considered as forming a vertebra, though
the resemblance is not so great as in the case of the occipital ring.
The presphenoid, being long and pointed, is very unlike a vertebral
body. The orbitosphenoids develop separately from it. The ethmoid also
differs from a vertebra, for it surrounds not the whole nervous axis as
the two hinder "vertebrae" do, but only two prolongations of it, the
olfactory lobes. In its development and final form it shows no
particular resemblance to a vertebra. Its body, the _pars
perpendicularis_ (mesethmoid) shows no similarity with a vertebral
centrum. Completing the three hinder cranial "vertebrae" and roofing in
the brain are the supraoccipital, the parietals and the frontals. The
premaxillaries, vomer, and nasals do not belong to the cranial scheme;
they are covering bones connected with the ethmoid. So, too, the
ear-capsule is not part of the cranial vertebrae, but is rather to be
compared to the intercalary bones in the vertebral column of certain
fish. Summing up as regards the cranial vertebrae Rathke writes, "We find
that the four different groups of bones, consisting of the basioccipital
with its intercalary (the supraoccipital), the basisphenoid with its
intercalaries (parietals), the presphenoid with its intercalaries
(frontals), and the ethmoid with its outgrowths (turbinals and
cribriform plate), taking them in order from behind forwards, show an
increasing divergence from the plan according to which vertebrae as
commonly understood develop, so that the basioccipital shows the
greatest resemblance to a vertebra, the ethmoid the least" (p. 30).

In a posthumous volume published in 1861 the same opinion is put
forward. "In the head, too," he writes, "some vertebrae can be
recognised, although in a more or less modified form. Yet at most only
four cranial vertebrae can be assumed, and these differ from ordinary
well-developed vertebrae in their manner of formation the more the
farther forward they lie."[214]

Rathke was an able and careful critic of the vertebral theory of the
skull, but he accepted it in the main. Actual attack on the theory upon
embryological grounds was begun by C. Vogt, in his work on the
development of _Coregonus_,[215] and in his paper on the development of
_Alytes_.[216] He described for _Coregonus_ an origin of the skull in the
main similar to that established by Rathke for the adder. There was a
"nuchal plate" in which the front end of the notochord was imbedded; the
notochord ended at the level of the labyrinth; there were two lateral
bands, comparable to Rathke's lateral trabeculae; a "facial plate" was
also formed, which seems on the whole equivalent to the plate formed by
the fused anterior ends of the trabeculae. A little later the cranium
formed a complete cartilaginous box surrounding the brain, very similar
to the adult cranium of a shark.

In his criticism of the vertebral theory of the skull, Vogt started by
defining the vertebra as a ring formed round the chorda. Now since only
the occipital segment of the skull is formed actually round the
notochord, the parts of the skull lying in front of this cannot
themselves be vertebrae, though they may be considered as prolongations
of the occipital or nuchal vertebra. "We must regard the nuchal plate as
a true vertebra, modified, it is true, in its formation and development
by its particular functions. Now, since the notochord ends with the
nuchal plate we can no longer regard as vertebrae the parts of the skull
that lie beyond, such as the lateral processes of the cranium and the
facial plate, for they have no relation with the notochord" (p. 123).

To support this view he adduced the fact that the vertebral divisions
(primitive vertebrae) visible in the trunk do not extend into the head.
He used precisely the same arguments in his paper on _Alytes_ to destroy
the vertebral theory of the skull. We quote the following passage
translated by Huxley (1864, p. 295) from this paper. "It has therefore
become my distinct persuasion that the occipital vertebra is indeed a
true vertebra, but that everything which lies before it is not fashioned
upon the vertebrate type at all, and that efforts to interpret it in
such a way are vain; that, therefore, if we except that vertebra
(occipital) which ends the spinal column anteriorly, there are no
cranial vertebrae at all."

L. Agassiz, himself a pupil of Doellinger, in the general part (1844) of
his _Recherches sur les Poissons fossiles_ (Neuchatel, 1833-43), repeats
in the main his pupil Vogt's criticism of the vertebral theory (vol. i.,
pp. 125-9).

These arguments of Vogt and Agassiz were not considered by Mueller to
dispose of the theory,[217] which maintained a firm hold even upon
embryologists. It was still upheld by Reichert, and Koelliker in 1849
showed himself convinced of its general validity.

A useful step in the analysis of the concept "vertebra" was taken by
Remak,[218] who showed what a complex affair the formation of vertebrae
really is, involving as it does a complete resegmentation
(_Neugliederung_) of the vertebral column, whereby the original
vertebral bodies were replaced by the secondary definitive bodies (p.
143). Remak showed, as he thought, that the protovertebral segmentation
of the dorsal muscle-plates did not extend into the head, and he denied
Reichert's assertion (1837) that the cranial basis in mammals showed
transverse grooves delimiting three cranial vertebrae (p. 36). The
gill-slits, he considered, could not possibly be regarded as marking the
limits of head vertebrae.

In 1858 appeared Huxley's well-known Croonian Lecture, _On the Theory of
the Vertebrate Skull_,[219] in which he stated with great clearness and
force the case for the embryological method of determining homologies,
and criticised with vigour the vertebral theory of the skull. By this
time the two rival methods in morphology had become clearly
differentiated, and Huxley was able to contrast them, or at least to
show how necessary the new embryological method was as a corrective and
a supplement to the older anatomical, or, as he calls it, "gradation"
method. Applied to the "Theory of the Skull," the gradation method
consists in comparing the parts of the skull and vertebral column in
adult animals with respect to their form and connections. "Using the
other method, the investigator traces back skull and vertebral column to
their earliest embryonic states and determines the identity of parts by
their developmental relations" (p. 541). This second method is the final
and ultimate. "The study of the gradations of structure presented by a
series of living beings may have the utmost value in suggesting
homologies, but the study of development alone can finally demonstrate
them" (p. 541). As an example of the utility and, indeed, the necessity
of applying the embryological method Huxley takes the case of the
quadrate bone in birds. This bone had been generally regarded by
anatomists as the equivalent of the tympanic of mammals, on account of
its connection with the tympanum; but Reichert showed (1837) that the
same segment of the first visceral arch developed into the incus in
mammals, and into the quadrate in birds, and that therefore the quadrate
was homologous with the incus. Similarly, on developmental grounds, the
malleus or hammer of mammals is the homologue of the articular of birds,
since both are developed from a portion of Meckel's cartilage identical
in form and connections in the two groups. The homologies of the bones
connected with the jaws in bony fishes had long been a subject of
contention among comparative anatomists; Huxley shows from his personal
observations how the development of the visceral arches throws light
upon these difficulties. The mandibular arch in the developing fish is
abruptly angled, as in the embryo of Tetrapoda; the upper prong of it
ossifies into the palatine and pterygoid; at the angle is formed the
quadrate (jugal, Cuvier), and to the quadrate is articulated the lower
jaw, which ossifies round the lower prong or Meckel's cartilage. The
scheme of development of the jaws is accordingly similar in fish to what
it is in other Vertebrates, and this similarity of development enables
Huxley to recognise what are the true homologues of the quadrate, the
palatine and the pterygoid in adult bony fish, and to prove that the
symplectic and the metapterygoid (tympanal, Cuvier) are bones peculiar
to fish. In developing Amphibia Huxley found a suspensorium of hyoid and
mandibular arches similar to the hyomandibular of fish.

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