Eustachian tube and guttural sacs.1—The eustachian tube opens into the sac ■
of the posterior nares on a line with the posterior margin of the soft palate, a very
short way above the inner border of the thick constriction of the nasal orifice. I had
an opportunity of examining these parts only in the foetus, in which the eustachian
orifice is 0-2 inch above the part indicated. I t is an oval slit from before forwards
0'02 inch in length, and it is situated in the centre of one of the thickened bands
which surround the arched crypts. I t leads into a short passage which runs up the
wall of the sac for a little distance ; then it bends upon itself, running outwards
and slightly backwards as a passage 0T0 inch broad, which gives off small lateral
passages protected by valvular folds, and which burrow in the textures surrounding
the mucous wall of the posterior nares, in the same way as the similar passages in
Elatanista, but not to the same extent. I t thus crosses the pharynx, but I have
not had the opportunity to trace it to the internal ear. As it reaches the outer wall
of the pharynx it gives off three sacs much smaller than in Elatanista, and which
lie between the stylohyal and the anterior corner of the thyroid cartilage. The_se
sacs lie one above the other, and the most superior is closely related to the thyroid
cartilage ; all are directed downwards and backwards ; the most inferior burrowing
downwards in eke direction of the body of the thyroid cartilage. Each sac has the
same structure as in Elatanista, but I cannot detect any tendinous bands connected
with folds like those that occur in that genus. I t must be borne in mind also that
the sacs are mere rudiments in this foetus compared with, those of Elatamsta.
I t will be observed that the cartilages of the larynx of the species are surrounded
with little cavities, possessing much the same characters as the finer
passages of the guttural sacs. I t has occurred to me that if materials existed to
trace out the ramifications of these structures, they would probably be found to have
some communication with the curious sinuous passages which surround the larynx.
If any connection should be proved to exist between them, it would seem as if
these finer ramifications of the guttural sacs being filled with air must exercise
some influence in depurating the blood in the vessels surrounding the larynx, and
thus contribute to the functional activity of the complex mechanism of the orifice
of the respiratory tube.
Larynx (Plate XXVIII, fig. 2).—The tube of the larynx of Orcella presents
certain differences in its foetal and adult condition. I t may be premised, however,
that it has the general characters distinctive of the Cetacea, but differs from that
of Elatamsta- in its much greater length, although its opening is shorter, and in
the? narrow character of its aryteno-epiglottidean folds. In an adult, of about the
same size as the Elatamsta from which the laryngeal measurements of that species
were taken, the opening was only 0-80 inch long. In the foetus- the tube was
projected 0‘82 inch up the posterior nares. The epiglottis projected beyond the
‘.For remarks on the guttural pouch of Cetacea, see particularly Hunter's Memoir in Phil. Trans, and his essays
and observations ; also Eschricht on the Gangetic Dolphin, Danish Transactions, 5th ser. vol. ii. 1851, and translated ;
Annals and Mag. Nat. Hist. 1852, vol. iz. p. 174; and Mûrie, op. cit.; Huxley’s Anat. of Verteb. An,. 1871,
pp. 410, Ac.
tips oi the arytenoids which lay in two depressions on its upper surface 0-15
inoh behind its free margin; whereas in the adult they completely overlay the
epiglottis with their tips nearly on a line with its free margin. In the foetus they
were also much more bent down upon the epiglottis than in the adult. The epiglottis
too, instead of having its thick margin reverted and strongly projecting as is
the case in the adult; in the foetus was flush with the rest of the tube. The
epiglottis differs from that of Flatamista gemgetioa in being relatively broader and
in its external angles being much thicker and prolonged further into the free
margin of the aryteno-epiglottidean membrane.
On opening into the larynx (fig. 2) a remarkable and beautiful structure was
displayed, lining the lower part of the cartilage of the epiglottis and the aryteno-
epiglottidean membrane and the whole floor of the cavity, and part of the sides
of the cricoid cartilage. A strong fold arising by three origins from the lower
third of the cartilage of the epiglottis is attached along that cartilage to its
base, where it gives off a series of short folds, three of which occur on the left
and one on the right side. The most anterior of the former' is attached to the
base of the aryteno-epiglottidean membrane, and the two others to the main border
of the base of the body of the arytenoid. The fold of the opposite side is attached
to the same portion of the last mentioned cartilage of the right side, but it gives
off four fine septal folds from its outside, which are prolonged up the sides of
the cartilage of the epiglottis. These folds are connected together by transverse
tendinous folds, which constitute little recesses by the generally arched lower border
being free. ' Indeed this part of the structure has a close resemblance to the
structure of the guttural eustachial pouch of Flqtmista. On the left side, only
the most anterior fold gives off a tendinous fold, which runs up the side of the
cartilage of the epiglottis, and has the same structure as already described on
the right. The central fold is continued backwards between the base of the
arytenoids as a thin sharp ridge-like fold, but behind that point it gradually
expands, and about an inch behind the arytenoids divides into a number of tendin-
ous-looking bands. Radiating from the posterior border and base of the arytenoids,
and passing backwards along the sides and floor of the cavity, are numerous strong
bands which die away posteriorly at the first ring of the trachea. These folds are
connected together on the floor of the cavity by arched transverse folds and these
again by secondary folds, so that a deeply honeyoombed structure is produced,
the space defined by the last mentioned folds constituting a series of deep pockets,
pits or crypts. The folds when viewed with a hand lens are seen to be thrown into
more or less-exceedingly fine transverse rugse. On making a verticalsection through
the larynx, it is demonstrated that none of the deep pits communicate with any air
sac, nor is there any trace of such a structure. The floor of the larynx above the
cricoid, from the base of the arytenoids backwards for some distance, presents
a glandular structure, divided off into lobules presenting open, orifices. Immediately
below the base of the arytenoids, several orifices, appear separated from
each other by fine septa, and it is apparent that they form a complex series of
A 3