1. A representation of a lymphatic
vessel highly magnified. 2. Lymphatic
valves. 3. A lymphatic gland and its vessels.]

In all animals which possess a lacteal system there is also a lymphatic
system, the one being the complement of the other. The fact that lymph
and chyle are both conveyed into the general current of circulation,
leads to the inference that the lymph, as well as the chyle, aids in the
process of nutrition. The body is continually undergoing change, and
vital action implies waste of tissues, as well as their growth. Those
organs which are the instruments of motion, as the muscles, cannot be
employed without wear and waste of their component parts. Renovated
tissues must replace those which are worn out, and it is a part of the
function of the absorbents to convey nutritive material into the general
circulation. Researches in microscopical anatomy have shown that the
skin contains multitudes of lymphatic vessels and that it is a powerful
absorbent.

Absorption is one of the earliest and most essential functions of animal
and vegetables tissues. The simpler plants consist of only a few cells,
all of which are employed in absorption; but in the flowering plants
this function is performed by the roots. It is accomplished on the same
general principles in animals, yet it presents more modifications and a
greater number of organs than in vegetables. While animals receive their
food into a sac, or bag called the _stomach_, and are provided with
absorbent vessels such as nowhere exist in vegetables, plants plunge
their absorbent organs into the earth, whence they derive nourishing
substances. In the lower order of animals, as in sponges, this function
is performed by contiguous cells, in a manner almost as elementary as in
plants. In none of the invertebrate animals is there any _special_