annot exist
compatible with life after birth. Those which involve a more or less
imperfect discharge of the blood-aerating functions of the lungs, are in
those degrees more or less fatal, and thus nature aborting as to the
fitness of her creation, cancels it.

[Footnote 1: This physiological truth has, I find, been applied by Dr.
R. Quain to the explanation of a numerous class of malformations
connected with the origins of the great vessels from the heart, and of
their primary branches. See The Lancet, vol. I. 1842.]

[Footnote 2: For an analysis of the occasional peculiarities of these
primary veins in the human subject, see an able and original monograph
in the Philosophical Transactions, Part 1., 1850, entitled, "On the
Development of the Great Anterior Veins in Man and Mammalia." By John
Marshall, F.R.C.S., &c. ]

IX.--The portal system of veins passing to the liver, and the hepatic
veins passing from this organ to join the inferior vena cava, exhibit in
respect to the median line of the body an example of a-symmetry, since
appearing on the right side, they have no counterparts on the left. As
the law of symmetry seems to prevail universally in the development of
organized beings, forasmuch as every lateral organ or part has its
counterpart, while every central organ is double or complete, in having
two similar sides, then the portal system, as being an exception to this
law, is as a natural note of interrogation questioning the signification
of that fact, and in the following observations, it appears to me, the
answer may be found. Every artery in the body has its companion vein or
veins. The inferior vena cava passes sidelong with the aorta in the
abdomen. Every branch of the aorta which ramifies upon the abdominal
parietes has its accompanying vein returning either to the vena cava or
the vena azygos, and entering either of these vessels at a point on the
same level as that at which itself arises. The renal vessels also have
this arrangement. But all the other veins of the abdominal viscera,
instead of entering the vena cava opposite their corresponding arteries,
unite into a single trunk (vena portae), which enters the liver. The
special purpose of this destination of the portal system is obvious, but
the function of a part gives no explanation of its form or relative
position, whether singular or otherwise. On viewing the vessels in
presence of the general law of symmetrical development, it occurs to me
th