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51
den udvendige Flade af deres bagerste Forlængelse, ved
stærke tendinøse Baand. Disse Rør med deres . mangfoldige
Blærer vise i histologisk Henseende den samme Bygning,
som Tarmen; udvendig have de et flimrende
Peritoneal-overtræk med sit Epithel, saa et tyndt, tibrillært
Bindevævslag. hvortil Muskelhuden er bunden. Denne, der
bestaar af langs- og tvergaaende Fibre, danner et rigt
Maskenet, der var udfyldt af koaguleret^Blodplasma; om dette
indesluttes i en Karforgrening, der udfylder Maskenettet,
eller det strømmer frit om i Lagene af Muskelhuden, kunne
vi ikke afgjøre.
Indenfor Muskellaget sees atter en Bindevævshud. i
hvis indre Lag. som er det bredeste, og som bestaar af en
hyalin, saagodtsom fiberfri Masse, tindes saavel forgrenede
Bindevævsceller, som de tidligere omtalte isolerede, aflange,
klare Celler med kornet Indhold. Disse ere her tilstede i
temmelig stor Mængde. Men foruden de her nævnte Celler
have vi iagttaget en Mangfoldighed af brunlige Legemer,
som have en mere eller mindre Kolbeforra. og som skyder
Epithelet foran sig, saa de beklædt af dette rage frem i
Rørets Lumen. Tab. IX, Fig. 38. Det er fornemmelig
heide findes i stor Mængde, og de gruppere sig stundom
saaledes. at de faa Udseende af Drueklaser. I Blærerne ere
de sjeldnere og . rage aldrig frem i dem, saaledes som i
Rørets Hulhed. Man kan med Loupen iagttage dem som
brunlige Punkter, der dels ligesom en Krands omgive
Blærernes Udspring, dels staa spredte rundtom baade paa Røret
og Blærerne. Disse brune Legemer dannes af et
Agglomerat af bronlige Molekiiler, uden at være omgivne af nogen
Membran; de have forskjellig Størrelse og synes at have
noget tilfælles med de Blodplasmaklumper, som vi have
truffet paa baade i Tarmkanalens og Hudens Væv. De
ere, saavidt vi have kunnet forfølge dem. ikke organiserede,
og kunne visselig ikke betragtes som særegne functionelle
Redskaber.
Det indre Bindevævslag støder umiddelbart til det
indre Epithel. Dette danner i selve Røret flere Lag
Cylinderceller, som bidrage til at danne de stærkt fremstaaende
paalangs gaaende Folder, der iagttages paa Rørenes indre
Flade; i Blærerne er der neppe mere end et Lag Celler.
De nu nylig beskrevne Lunger afvige i flere Punkter
fra,, hvad der hidtil er bekjendt om disse Organer hos
Mol-padiderne og Aspidochiroterne. Hos disse er den ene
Lungestamme uden Karforgrening og fri. imedens den anden
følger Tarmen, er bunden til denne, og erholder en
Karforgrening fra dens Rygkar; men begge tage de Udspring
fra Kloaken.
Hos Trochostonia er det helt anderledes. De
udspringe fra Tarmen (Kloak mangler, men en Rectum trøder
i dennes Sted); den venstre Stamme ligger tæt til Tarmens
and is webbed to the two dorsal radial segments of the
calcareous ring. viz. on the outer surface of their posterior
prolation. by strong tendinous bands. These tubes with
their numerous vesicles exhibit the same histological
structure as the intestine; externally, they are invested with a
vibratile peritoneal tunic and its epithelium, overlying
which is a thin fibrillous layer of connective tissue,
webbed to the muscular integument. The latter, which is
composed of longitudinal and transverse fibres, constitutes
an intricate network, having its meshes tilled with
coagulated sanguineous plasma; but whether this plasma be enclosed
in a’ vascular ramification filling the meshes of the network,
or whether it circulate freely through the layers of the
muscular integument, is a question we are unable to decide.
Beneath the muscular layer, too. extends a tunic of
connective tissue, the inner and broadest layer of which,
consisting of a hyaline, almost fibreless substance, contains alike
ramose cells of connective tissue and the bright, elliptic-shaped,
isolated cells previously described, which are comparatively
numerous here. But. exclusive of the above-mentioned
cells, we have observed great numbers of brownish, more or
less claviform corpuscles, that, invested with the
epithelium. which they push, as it were, before them, project
upwards into the lumen of the tube, Pl. IX. fig. ’38. It is
more particularly here that they occur in great
numbers, and so grouped as sometimes to assume the
appearance of clusters of grapes. In the vesicles, they are
less numerous, and never project into them as they do into
the hollow interior of the tube. Viewed under a lens, they
appear like brownish points, some of which surround
chaplet-like the origin of the vesicles ; others lie scattered round
the tube and the .vesicles. These brown corpuscles are
composed of an agglomeration of brownish molecules,
without however being enveloped in a membranous covering;
they vary in size, and have apparently something in
common with the lumps of sanguineous- plasma observed in the
tissue of the intestinal canal and of the integument.
So far as our observations extend, they are not distinguished
by an organic structure, and cannot therefore be regarded
as having a special functional character.
The inner layer of connective tissue is connate with
the inner epithelial layer. The latter forms in the tube
itself several layers of cylindric cells, which contribute to
the formation of the strong, projecting, longitudinal folds
observed on the inner surface of the tubes; in the vesicles
there can hardly be more than one layer of cells.
The respiratory organs described above differ in several
respects from what is yet known concerning them in the
Molpadidæ and the Äspidochirotæ. In these animals,
one of the respiratory stems is free, and without a
vascular ramification; the other accompanies the intestine, to
which it is attached, being furnished with a vascular
ramification from its dorsal vessel; both however originate
in the cloacum.
In Trocliostoma. quite another arrangement is observed.
The tubes have their origin in the intestine (there is no
cloacum. its place being supplied by a rectum); the left
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