MRS. B.
No; that is not supposed to be the case: for the human species, who are of the mammiferous tribe, live on more substantial food than birds, and yet the latter exceed them in muscular strength. We shall hereafter attempt to account for this difference; but let us now proceed in the examination of the animal functions.
The next class of organs is that of the vessels of the body, the office of which is to convey the various fluids throughout the frame. These vessels are innumerable. The most considerable of them are those through which the blood circulates, which are of two kinds: the arteries, which convey it from the heart to the extremities of the body, and the veins, which bring it back into the heart.
Besides these, there are a numerous set of small transparent vessels, destined to absorb and convey different fluids into the blood; they are generally called the absorbent or lymphatic vessels: but it is to a portion of them only that the function of conveying into the blood the fluid called lymph is assigned.
EMILY.
Pray what is the nature of that fluid?
MRS. B.
The nature and use of the lymph have, I believe, never been perfectly ascertained; but it is supposed to consist of matter that has been previously animalised, and which, after answering the purpose for which it was intended, must, in regular rotation, make way for the fresh supplies produced by nourishment. The lymphatic vessels pump up this fluid from every part of the system, and convey it into the veins to be mixed with the blood which runs through them, and which is commonly called venous blood.
CAROLINE.
But does it not again enter into the animal system through that channel?