Those that I examined microscopically led me to regard them as identical
with the vasculo-lymphatic pulmonary glands already referred to in detail in
Orcella. . j '
JUinute structure o f Lung Gland.—If fig. 4, PI. XXXVII, being a microscopic
section of one of these glands from the lnng of JPlatanista, be compared with
figs. 8 and 5 in the same plate, respectively the stomach and pulmonary glands of
Orcella, the identity of all three becomes manifest. In each there is a copious
blood supply, the walls of the larger vessels, specially noticeable in fig. 4, being
obliquely perforated with orifices for subsidiary capillary tubes. These ramify
everywhere amidst the gland tissue. The basis of this latter is a fine retiform
connective tissue, the minute fibrillse in the mesh work of which radiate from points
which, under a high power, appear to be nucleate corpuscular centres. In the
meshes of the trabeculae are masses of much larger cells, in all respects agreeing
with lymph corpuscles (fig. 4, c).
Lastly, there are irregularly shaped and differently sized spaces, which to all
intents have the nature of lymph sinuses. The gland tissue proper or pulp is very
unequally distributed, not only as respects quantity, near or further distant from the
larger blood canals, but inter se a thickened patch appears surrounded by a space,
this latter again joined by sparse retiform tissue being encompassed by a dense
area of large corpuscular gland tissue. The aggregation of gland substance then
is most variable, as are the open spaces or sinuses.'
Heart.—When fully injected with plaster of Paris the heart of JPlatanista
(PI. XXIX, fig. 1) is a great broad relatively short organ. I t then measures some
6-50 inches across from border to border at the base of the ventricles. The ventricles
themselves are no more than 4-50 inches in length, but from the apex of the heart to
the upper tip of the distended auricle is 6'50 inches. Roughly speaking, then, the
heart is as broad as it is long. The ventricular apex exhibits a tendency to cleavage,
or indistinctly shows a bifid extremity, the incision being very shallow, and the more
lengthened left ventricle tending to the appearance of a double apex. The cavities
and valves offer few points of interest. One which simulates a pathological character,
though I believe it to be in this case normal, is the nature of the chordae tendinege.
-These generally have a peculiar knotted aspect due to the swellings of a number of
ring-like cartilages, which produce an appearance that may be likened to the nodular
character of the underground stem of the bamboo.
Arch o f Aorta and great vessels.—Three distinct vessels spring from the
transverse portion of the arch of the aorta, as in Man and many other mammals,_
namely, a right brachiocephalic, a left carotid, and a left subclavian; and from the
descending thoracic aorta arises the left posterior thoracic artery, as is sometimes the
case in the porpoise.1 The brachiocephalic artery is of considerable length and,
above 2 inches from its origin, it gives off a small twig to the thyroid gland.
A little in excess of this distance it divides into two large branches, the first the
right carotid which passes forwards, and the second the right subclavian passing out-
1 Turner: Joum. Anat. and Phys., vol. ii, 1868, p. 68.
wards.; the former after its origin gives off a considerable branch from its right
side to the thyroid gland, but after this it runs forwards unbranched for about four
inches. A mass of vessels then arise, first a bundle from its left and then another
from its right side, the two being in close relationship to each other. In these
combined tufts I have counted as many as fifteen branchlets, each of which, immediately
after its origin, broke up into numerous smaller vessels producing an intricate
rete mirabile. About one inch beyond this, the carotid passes below the posterior
angle of the root of the zygoma, and at this point again gives off another tuft of
vessels likewise forming a rete mirabile. I t then dips below the glenoid process
of the squamous, and at the anterior extremity of the tympanic is again resolved
into yet another and a similar bundle of vessels. Tip to this "point, in the
whole course of the carotid, no prominent branch has sprang, and the calibre
of the artery has been but little diminished, nor is there much reduction here
where it terminates in this rete mirabile, among which, however, there are some
twigs larger and longer than the others; but these I have not succeeded in
tracing to any distance. I t is evident that no large branch enters the interior
of the skull, in which probably all the vessels assume the character of a rete
mirabile.
The right subclavian divides at once into two branches, the internal mammary,
and the continuation of the subclavian itself, the latter very much smaller than
the former. Erom the anterior surface of the subclavian division a small artery
passes inwards below the common carotid coursing forwards along the side of the
trachea. The subclavian is continued outwards for a short distance and gives off
a branch', the transversalis colli, and then breaks up into a plexus of small vessels
constituting a rete mirabile, a continuation of which invests the brachial nerve, no
distinct axillary artery existing, and the brachial being only represented by the foregoing
plexus. The internal mammary is very large, but one inch from its origin
it gives off the posterior thoracic artery which rapidly describes a sigmoid flexure
and then passes forwards, itself also ultimately breaking up into a rete mirabile.
The internal mammary does not divide into a plexus but it becomes small and can
be traced a long way backwards. A twig springs from it and runs along the margin
of the sternum internally.
The left common carotid has its origin from the arch of the aorta, about a half
inch to the left of the brachiocephalic, and courses forwards for about five inches
unbranched; after this point, it occasionally gives off branches to the thyroid, preserving
in the rest of its distribution the same characters and divisions as in the right
common carotid. The left subclavian arises close to the side of the left common
carotid, separated from it by about 0-30 inch, and passes on undivided for almost
an inch, when it breaks up into two, a small artery from the point of division proceeding
to the thyroid. Of the two branches the posterior is the internal mammary,
but where it leads backwards, a few twigs arise to form a plexus. Where the
external Tna.mma.ry originates, a small artery runs backwards to the pericardium.
The subclavian branch, after a course of an inch and quarter, sends forwards an