the vascular, the muscular, and the osseous systems of the human
body, are analyzed by comparison through the animal series. Numerous
cases are on record of the subclavian artery being found complicated
with supernumerary ribs jutting from the 5th, 6th, or 7th cervical
vertebrae. [Footnote] To these I shall add another, in respect of the
carotid arteries--viz., that I have found them complicated with an
osseous shaft of bone, taking place of the stylo-hyoid ligament, a
condition which obtains permanently in the ruminant and other classes of
mammals.

[Footnote: I have given an explanation of these facts in my work on
Comparative Osteology and the Archetype Skeleton, to which, and also to
Professor Owen's work, entitled Homologies of the Vertebrate Skeleton, I
refer the reader.]

DESCRIPTION OF PLATES 7 & 8.

PLATE 7.

A. Common carotid at its place of division.

B. External carotid.

C. Internal carotid, with the descending branch of the ninth nerve lying
on it.

D. Facial vein entering the internal jugular vein.

E. Sterno-mastoid muscle, covered by

F. Part of the platysma muscle.

G. External jugular vein.

H. Parotid gland, sheathed over by the cervical fascia.

I. Facial vein and artery seen beneath the facial fibres of the platysma.

K. Submaxillary salivary gland.

L. Upper part of the platysma muscle cut.

M. Cervical fascia cut.

N. Sterno-hyoid muscle.

O. Omo-hyoid muscle.

P. Sterno-thyroid muscle.

Q. Fascia proper of the vessels.

R. Layer of the cervical fascia beneath the sterno-mastoid muscle.

S. Portion of the same fascia.

T. External jugular vein injected beneath the skin.

U. Clavicle at the mid-point, where the subclavian artery passes
beneath it.

V. Locality of the subclavian artery in the third part of its course.

W. Prominence of the trapezius muscle.

X. Prominence of the clavicular portion of the sterno-cleido-mastoid
muscle.

Y. Place indicating the interval between the clavicular and sternal
insertions of sterno-cleido-mastoid muscle.

Z. Projection of the sternal portion of the sterno-cleido-mastoid
muscle.

[Illustration: Right side of the head and neck, showing blood vessels,
muscles and other internal organs.]
Plate 7

PLATE 8.

A. Clavicular attachment of the sterno-mastoid muscle lying over the
internal jugular vein, &c.

B. Subclavian artery in the third part of its course.

C. Vein formed by the union of ext