membrane is not very thick. The third stomach is shut off from the duodenum by
a broad flattened portion of the wall constituting a septum, in the centre of which,
is the pyloric opening, about 0T2 of an inch in diameter.
The duodenal sac1 (fig. 5, iv.) is a capacious cavity which is rapidly contracted
into a very narrow tube one inch before the opening of the common bile duct. The
mucous membrane is smooth, but around the pyloric area, especially on the anterior
wall of the sac, there are rough areas of the same character as those of the third
stomach. A few pillar-like folds radiate from the pyloric septum which has a much
greater expansion on this than on its other side, and a few deep funnel-shaped pits
occur between the folds. A few solitary glands are scattered here and there, but
there are no Peyer’s patches. The gut-like portion of the duodenum (fig 5, d.)
available for observation, extends only to three inches. I t is thrown into numerous
longitudinal and transverse convoluted folds, approaching in character to valvulæ
conniventes, and at its commencement it is covered by numerous deep pits.
Minute structure o f the walls o f the stomach.—As has been above stated, the
superficial aspect of the mucous membrane of the gastric cavities differs even to the
naked eye, so likewise when examined microscopically there are certain differences.
I t may be as well, however, before mentioning these, to state that both*in the case
of Or celia and of J?lat<mista, a large series of microscopical preparations were made
by myself and partly by Mr. A. Stirling of the University Anatomical Museum,
Edinburgh, whose skill in microscopy and accuracy in manipulation are well known.
The specimens were prepared from materials which had been preserved in alcohol ;
staining by re-agents in some cases being adopted where clear definition of
textural character was desirable. Various preservative media were used, but most
of the specimens were of sufficient consistence to be mounted in Canada balsam.
Erom their oily nature Cetacean tissues are well known to anatomists to retain their'
original characteristics intact and uninjured for a long period, and to be little
affected or altered by their alcoholic preservation. Hence those sketches delineated
in Plates XXXVI, XXXVII, and XXXVIII of dermal, visceral, placental, and other
parts of the round-headed and Gangetic Dolphins (Orcella and JPlatanista), and
most carefully drawn from the objects themselves under different microscopic powers
will be. found to convey clear impressions of their minute structural peculiarities.
These will be described in detail, and will be considered, I trust, to have contributed
somewhat towards the elucidation of the minute anatomy, physiology, and organic
economy of at least two highly interesting genera of Cetacea. Those especially
which relate to certain glandular structures or organs, and to placentation are, I
conceive, highly important, in some cases corroborating and in others offering points
of divergence from facts and opinions expressed by such authorities as Eschricht,
Stannius, Ercolani, Elower, Turner, Alf. M.-Edwards, Murie, &c.
To return to the stomach of Orcella : when sections are made, for example that
shown in Plate XXXVI, fig. 14, viz., a vertical section of the wall of the first cavity,
it is seen that this chamber, structurally, is but a passive recipient in the digestive
*. Cuvier, Leçons d’Anat. Comp. Ire Edit. t. v. p. 345, p'. xxxviii, fig. 2 ; Flowers’ Lectures, I. c.~, p. 427;.
process. In this respect, therefore, it is comparable to the paunch of ruminants, or it
may be, to the gizzard of birds. Superficially, at e, there is relatively a considerable
thickness of a somewhat coriaceous or homy epithelial layer, and which follows the
sinuosities of the ridges and furrows. The epithelium. is chiefly squamous and in
horizontal ¡compressed layers on the free surface, but, here and there, and deeply,
groups of cylindrical epithelial cells are less -or more aggregated together. These
somewhat wavy horizontal layers, without any very marked line of demarcation, abut
against and seem to constitute aperies of vertical papillae, similar to those of the skin,
but their general appearance simulates the true gastric follicules of th e , succeeding
stomach cavities. The series of columnar tubes (e.g.) descend in nearly parallel
straight lines , to the subjacent areolar tissue; their inferior differing from their upper
extremities by terminating in clear and distinct, obtusely tapering or occasionally
bulbous ends. These cylindroid columns are evidently of a solid consistence, and
composed of epithelial cells varying in figure according as they are more loosely
or more densely packed. The papillary interspaces are less than half the thickness
of the columns and much more transparent; they have a somewhat fibroid character
from the upright closely pressed position of elongate cells. Inferiorly this lineo-
cellular character passes into .the more distinct fibro-cellular. tissue beneath. Here
and there, muscular bands or cut ends of muscular fibres form an imperfect layer in
the areolar tissue; the latter is wider-meshed and more fibrous below, and many
minute blood-vessels («.) traverse it in diverse directions.
A similar vertical section.of the wall of the second stomach as seen somewhat
more highly magnified (fig. 15) reveals the presence of a comparatively very thin
and scarcely appreciable layer of free epithelium. The smoothish surface.is everywhere
perforated by orifices, the mouths of capacious gastric glands. These latter,
are long and tubular, mostly single, and: straightish throughout or with wrinkled
walls, although some either obscurely or more definitely point to saccular, branching
in their lower segments. The tubules are filled with the so-called peptic cells
of the ordinary character. The sub-mucous, fibro-cellular and areolar tissue, with
occasionally muscular fibrilhe, agrees to a certain extent with that of the first
cavity -of the stomach, but it differs in being more copiously supplied with bloodvessels,
which are of great calibre and exceedingly thick-walled, and more shall be
said of them presently. Indeed, as fig. 5, v,_ shows, their interior is reduced to a
small hollow centre surrounded by a circular fibrous wall far exceeding the apparent
necessities of the narrowed channel.
The third cavity of the stomach, and wherein possibly digestion is most actively
carried on, has abundance of gastric glands, as in the preceding chamber, and, like.it,
many blood-vessels ramify within its musculo-serous coats.
Vascular channels of the stomach.—Under this head it, is desirable to call
attention to their general distribution along with certain other glandular structures
in connection with them. In Professor Turner’s account of the great Einner Whale
stranded at Longniddry,1 he has given some interesting observations on a remarkable
1 Trans. Roy. Soc. Edinb. 1870, voL xxvi. pp. 231, See.
z 2