Amongst a multitude of examples, which teach us how little we can infer the importance of anything in nature from its size, or other impressions which it may convey to mere sense, we might adduce the wonderful little tubes, certain relations of which were the objects of this paper. Those constant mutations in animal bodies which are every moment in progress, are, in great part, due to a very curious order of vessels, of such extreme minuteness and tenuity, that, being in the dead animal usually empty and transparent, they are very commonly invisible, and thus long eluded discovery. There is one situation, however, in which circumstances combine to expose them to observation. Transparent though they be, they are here usually rendered visible; first, by being loaded with a milk-like fluid; and secondly, by being placed between the folds of a membrane, itself beautifully transparent (the mesentery). This fluid they have just taken up from the digestive surfaces on which their mouths open, and they are now carrying it off to pour it into the blood-vessels, that it may be added to the general stock of the circulation. In the situation above mentioned they were at length discovered, about the commencement of the 17th century. Every thing destined to support the body with new material, as well as the old, which is to be taken away, must first be sucked up by the myriads of inconceivably minute mouths of these vessels, which, from their office, are called the _absorbents_. These absorbents may therefore be regarded as the sentinels of the body. They are very sensitive and excitable; but, besides this, there are placed in the course of their journey, from the surfaces whence they bring their contents, and the blood-vessels to which they are carrying them, a number of _douaniers_, or custom-house officers (the glands, or kernels, as they are popularly called), whereby, as we have every reason to believe, the fluids they are importing are subjected to rigid examination; and, if found to be injurious, to some modification, tending to render them more fit for admission into the system. If the contents are very irritating, these vigilant guards—these kernels—become very painfully affected, and sometimes inflammation is set up, sufficient even to destroy the part; as if, faithful to their trust, they perished themselves, rather than give entrance to anything injurious to the body. We should never advance, however, in our story, if we were to tell all the interesting peculiarities of these curious vessels.