An Essay on the Circulation. [Volume: 2, Issue: 12, July, 1861, pp. 651-658]

656 THE DENTAL COSMOS.
mentary tissues. Microscopic observation proves them to be merely fine
tubes, no vessels arising from them, and there being no open mouths;
serous vessels may exist, but as yet have not been demonstrated. These
minute vessels appear to have coats, and they are considered to aid or
augment the power of circulation.
The veins arise from the capillaries; they have the same coats as the
arteries, but are less strongly developed. The capacity of the veins is
said to be two or three times that of the arteries. The veins are filled
with valves, to prevent the reflux of the blood. This circulation is due
to the vis a tergo, aided by the vis a fronte, or suction of the heart,
also inspiration; finally, muscular movements are among the most important.
In the pulmonary circulation, the venous blood is in the arteries, and
the arterial blood in the veins. The portal circulation is entirely independent of the pulsations of the heart, but under the influence of the
pressure of the abdominal walls.
The passage of the blood from the heart to the teeth is as follows:
from heart to aorta, thence to the innominata, or left carotid, right
carotid, external carotid, and internal maxillary. From this the inferior
dental, the superior dental, alveolar or maxillary, and the infra-orbital are
given off. The first enters the posterior mental foramen, supplying the
nerves of the teeth of the lower jaw, through their roots' apices, by fine
branches. The second enters the superior maxilla by a number of foramina at the tuberosity of the upper jaw, giving branches to the nerves of
superior molar teeth, antrum, and gums. The third sends branches to the
nerves of the anterior superior teeth.
The venous blood being emptied into the facial vein, into the internal
and external jugular; thence to the subclavian, vena innominata, and descending vena cava, to the heart.
Having pursued the subject thus far, it may be best to give a short
glance at the different tissues of these structures in the human subject, so
as the more ably to handle the important point of the circulation here.
According to most, if not all, the authority of the present day, the
teeth are divided into three structures, of different density and composition, namely: enamel, dentine, and cementum; the first covering the
crown, the latter being the main body of the tooth, that portion of this
which is in the bone of the jaw being covered by the cementum. Outside
of the cementum is the periodental membrane, or periosteum, a vascular
structure, while in the centre of the dentine is a highly organized, vascular organ, the pulp or nerve. These two tissues are plentifully supplied
with blood-vessels, and from their position are beautifully adapted to the
nourishment of the tooth.
The dentine is composed of two distinct parts-dental tubuli and intertubular tissue; the former having distinct parietes, about the same thick