(seq. 53)

23 Lect. 2^d

the nervous Coat of the Artery, so called by the Antients.
This is not properly a Coat; but a Connecting Medium, between
the Artery & Muscles, every Fibre being surrounded in the same
Manner, this was their fourth Coat, a fifth Coat is added by
some in particular parts, as the Pericardium, & Peritoneum,
tho' very improperly. The Coats of an Artery have Blood Vessels
like other Parts, called Vasa Vasorum, but the Blood in these is
^{said to be} not red. These may be seen in a Preparation first injected minute-
ly with red, then the red Injection forced out, & green thrown in
its Room, which being of a darker Colour permits the red
Vasa Vasorum to be seen - Blood enters into the Combination
of every Part, but of some in no great Quantity, or not so as to
carry red Globules; hence these Vessels appear white. Nervous
Filaments are also bestowed on them, tho' not to be easily demon-
strated, & are supposed to serve some important Use. The whole Bo-
dy of the Artery is elastic; & has different Strata or Layers for
different Purposes, & from their being in all Directions, they bring
the Artery to its former State, & strengthen the Artery both later-
ally & longitudinally, which is more expanded than lengthened
by the Blood - The internal Coat answers two purposes; it both
gives a smooth Surface, & does not hinder the Circulation, & is
dense in Texture, that the finer Parts of the Blood may not tran-
sude. After Death the red Globules will transude, but not