sections of vascular channels(«.); There are, however, others, chiefly round openings,
of much smaller calibre and with remarkably thick walls as compared with their
narrowed central channels. Besides these (best shown in fig. 4i) are what may
correspond partly to oblique or in some cases to the longitudinal sectional view of
capacious blood-vessels, which apparently have a great number of tributaries piercing
their fibrous walls (fig. 4, lv.).
JEEearf and blood-vessels.1—/The heart of Orcella is of considerable size, but not
so large proportionally to the animal as is the heart of Platanista, neither is it so
markedly bifurcated at the apex, nor are the auricles so loculated as in the latter
dolphin. The ventricular septum passes downwards slightly to the right side and
the base of the organ is flattened, but its right half is lower and its right ventricle
and auricle smaller than those of the left side ; the former cavity is larger, but
much narrower than its fellow. The left auricle, when the heart is distended, is
closely applied over its base, and the right margin of this auricle touches the pulmonary
artery ; but the right auricle under similar circumstances projects upwards
from the base of its ventricle, anteriorly exposing a considerable portion of it. The
heart measures in the adult 5 inches across the base of the ventricles, and 3"'50
from the origin of the pulmonary artery to the apex of the left ventricle ; antero-
posteriorly it is 3 inches through the thickest portion of the right ventricle, and
across the auricles about 5*75 inches. (See Plate XXIX, fig. 2.)
At the point where the pulmonary artery has the pericardium reflected on to it,
and occupying about the position of the ductus arteriosus, two pits occur, separated'
from each other by an interval of 0‘25 inch. These are about 0'25 inch in
diameter and the same in breadth, and the one to the left is a blind sac, defined on
each side by tendinous or pillar-like folds of the pericardium prolonged on to the
pulmonary artery. The other is protected at its upper border by a cord-like band
that stretches across it transversely. To the left side it gives off a thinner and
fibrous cord directed obliquely forwards. At the bottom of the pit there is a deep
recess that admits a large probe, and passes dorsally obliquely outwards. Unfortunately
the parts at the side of the left bronchus where the probe appears have
been cut across, but the probe is seen to lie in a well-defined tube. There seems
little doubt but that these invaginations of the pericardium mark the remains
of the ductus arteriosus.
In the cavities and valves- of the heart nothing specially worthy of npte
occurs.
I had the opportunity of examining the distribution of the vascular trunks and
branches which spring from the aorta both in an adult and in a foetal specimen.
A sketch of the former is given in Plate XXIX, fig. 2, in whieh figure, the
numerous cervical and upper pectoral glands in relation with the vessels are also
given.
1 Besides Hunter, Carte and Macalister, Murie, &c., Turner in his “ Account of the Great Firmer Whale,”
I. c., p. 227, gives a good description of the circulatory organs.
In the adult animal, the aortic arch and gréât arteries somewhat correspond tb
the condition described and figured by Prof. Turner in the Pilot Whalè.1 Prom
near the summit Of the arch of the aorta two main vessels of considerable
capacity are given off. These evidently are right and left innorbinates, sub-
clavians of Turner. Half an inch from its origin the so-called left innominate or
brachio-cephalic throws forwards and sinistrally a large vessel equivalent to a left-
subclavian. Erom this at its upper bend there springs from right to left a small
branch equivalent to a vertebral (y.), and which bifurcates a quarter of an inch
from its origin. To the left of this vertebral is a slightly larger branch which may
correspond to a thyroid axis (it is Turner’s transversàlis colli), and at about an equal
distance to the left is a yet larger branch, the axillary or brachiai, while the
continuation of the main .stem into the chest coustittites the internal mammary
artery (m.). The left innominate, about a quarter of an inch above its subclavian
division, splits into two unequally sized trunks, the inner of which is thé
larger and may represent the carotid, the outer a trifle less in calibre^
The right or true innominate artery has a capacity little if at all greater than
the left division. There. springs half an inch from the aorta and behind it a
moderately thick artery which passes upwards and to the right, and supplies the
deep cervical and upper thoracic region of that side (de.). This evidently corresponds
to the “ thoracica posterior dextra” of Turner in G-lobiCephalus. Derived
from the right innominate close above the last, but more to the dextral than the
posterior side, and passing beneath or deeper than what shall presently be referred
to as the right subclavian, is a fairly-sized vessel, apparently the right axillary artery
(ax.*) ; and still higher than it, though almost overlapping it, is a thicker Vessel
which, judging from its position, may be termed the right subclavian (s.*), although
possibly objection may be’ found to this term, as the axillary branch is not continued
from it. Erom this main right subclavian trunk, at half an inch distance from its
origin, is what I take to be the right thyroid axis (¿A*)—an artery springing from
its upper borderj and which almost immediately thereafter splits into two branches
from which subsidiary branchlets are given off. To the right of this thyroidal axis,
another smaller artery (tc.), which may be equivalent to a transversalis cOlli, comes
off from the right subclavian stem, and it likewise splits into several branches.
The continuation of the subclavian trunk meantime courses backwards into the
chest forming the large internal mammary artery (mJ*) of the right side. This same
vessel, as likewise that of the opposite side of the chest, besides supplying blood to
the sternal parts, pleuræ, etc., proceeds to the peculiar pulmonary glands already
described, and each vessel, moreover, seems to join an anastomotic branch derived
directly from the abdominal aorta behind the apex of the heart (see fig. 2, m.*).
In the foetal specimen of O. brevirostris the arterial distribution in the
main corresponds to what has been above described in the adult. There are in this
1 Camb. Journ. Anat. and Physiol, vol. ii. p. 67; Knox, Cat. p. 18; Esclmckt, Die Nordisohen Wallthiere,
p. 104; Malm, Anat. Salcenoptera Carolina; G2fvers Vet.-Ala Forhandl. 1868, and- Barkow, Die Blutegefasse, etc.,
Breslau.