CHAP. 89.—THE ARTERIES; THE VEINS: ANIMALS WITHOUT
ARTERIES OR VEINS. THE BLOOD AND THE SWEAT.
The arteries are destitute of sensation, for they are devoid of
blood. They do not, all of them, however, contain the vital
spirit, and when one of them has been cut, it is only that part
of the body that is reduced to a torpid state. Birds have
neither veins nor arteries, which is the case also with serpents,
tortoises, and lizards; and they have but a very small proportion of blood. The veins, which are dispersed beneath the
whole skin in filaments of extreme thinness, terminate with
such remarkable fineness, that the blood is able to penetrate no
further, or, indeed, anything else, except an extremely subtle
humour which oozes forth from the skin in innumerable small
drops, and is known to us as "sweat." The knot, and place
of union of the veins, is the navel.