a
laminated clot. Near the blood-current the clot is soft, red, and
friable (Fig. 72). The laminated clot not only strengthens the sac,
enabling it to resist the blood-pressure and so prevent rupture, but, if
it increases sufficiently to fill the cavity, may bring about cure. The
principle upon which all methods of treatment are based is to imitate
nature in producing such a clot.

Sacculated aneurysm, as compared with the fusiform variety, tends to
rupture and also to cure by the formation of laminated clot; natural
cure is sometimes all but complete when extension and rupture occur and
cause death.

An aneurysm is said to be _diffused_ when the sac ruptures and the blood
escapes into the cellular tissue.

#Clinical Features of Aneurysm.#--Surgically, the sacculated is by far
the most important variety. The outstanding feature is the existence in
the line of an artery of a globular swelling, which pulsates. The
pulsation is of an expansile character, which is detected by observing
that when both hands are placed over the swelling they are separated
with each beat of the heart. If the main artery be compressed on the
cardiac side of the swelling, the pulsation is arrested and the tumour
becomes smaller and less tense, and it may be still further reduced in
size by gentle pressure being made over it so as to empty it of fluid
blood. On allowing the blood again to flow through the artery, the
pulsation returns at once, but several beats are required before the sac
regains its former size. In most cases a distinct thrill is felt on
placing the hand over the swelling, and a blowing, systolic murmur may
be heard with the stethoscope. It is to be borne in mind that
occasionally, when the interchange of blood between an aneurysm and the
artery from which it arises is small, pulsation and bruit may be slight
or even absent. This is also the case when the sac contains a
considerable quantity of clot. When it becomes filled with
clot--_consolidated aneurysm_--these signs disappear, and the clinical
features are those of a solid tumour lying in contact with an artery,
and transmitting its pulsation.

A comparison of the pulse in the artery beyond the seat of the aneurysm
with that in the corresponding artery on the healthy side, shows that on
the affected side the wave is smaller in volume, and delayed in time. A
pulse tracing shows that the normal impulse and dicrotic waves are lost,
and that the force and rapidity of the ti