.

will require a farther difference in the strength of their coats; for those of the arteries must be equal to the greatest natural preffure; and if the arterial blood propels the venal, that is a farther reafon for the different strength of their coats.

ALL these things being confidered, it appears to be a difficult thing to determine nearly, what proportion the fluids of an animal body bear to the folids, or what proportion the fum of all the minutest arteries bear to the aorta, without which I think we can neither determine the comparative velocity of the blood moving in the different veffels, nor the quantity of blood in any animal body, nor the time in which the whole mass of blood, or a quantity equal to the whole mafs, is flowing thro' the heart. But if each ventricle of the heart holds five ounces of blood, and they are filled and emptied every fyftole and diaftole, which I think is true, and if eighty pulfes in a minute be allowed to be a common number, there then flows twenty five pounds of blood through each ventricle of the heart in a minute. Dr. KEIL has fhewn that the fum of all the fluids in a man exceed the fum of all the folids, and yet the quantity of blood which all the visible arteries of a man will contain, is lefs than four pounds; and if we may suppose all the visible veins, including the vena portæ, hold four times as much, the whole then that the vifible veffels can contain is not twenty pounds; but the whole that they do contain is but very little more than the

veins can contain, feeing the arteries are always found almost empty in dead bodies; but how much the invifible arteries and veins contain, I mean those which contain fuch a compound fluid as is found in the larger veffels, I know no way to judge, unlefs we knew what proportion these veffels bear to those that carry the nutritious juices and serum (if there are fuch) without the globuli of the blood. Cæteris paribus, is not the velocity of the blood in all animals proportionable to their quantity of a ction; and their neceffity of food alfo in proportion to their quantity of action? If so, it appears how those animals which use no exercise, and whose blood moves extremely flow in the winter, can fubfist without any fresh supply of food, while others that use a little more exercise, require a little more food; and those who use equal exercise winter and fummer, require equal quantities of food at all times, the end of eating and drinking being to repair what exercise and the motion of the blood has deftroyed or made ufelefs; and is not the lefs velocity of the blood in fome animals than in others, the reason why wounds and bruifes in those animals do not fo foon destroy life, as they do in animals whofe blood moves fwifter?

I HAD a patient, whofe mufcles on the infide of the thigh were torn to pieces with the cramp, from whence was a vaft effufion of blood among the muscles. The tumor being opened, it was judged neceffary to take off the limb. The patient, having

a great

a great discharge from the wound, was eafy for about ten days; but the cramp then returned into the stump with fuch exceffive torment that he died foon after. I have never heard but of one other cafe of this kind, which ended in the fame man

ner.

WHEN any of the veffels are lacerated by bruifes, ftrains, or otherwife. without any external wound, purging (which is of more use than one can well account for) and cooling applications are always proper to prevent as much as may be extravasations of blood or ferum; but the lacerations once healed, which may be in eight or ten days, and the pain quite gone, then warm medicines may be applied, with opium, or fp. cornu cervi (which powerfully separate coagulated fluids) to help to attenuate and thereby diffipate the extravafated juices.

WHEN the blood-veffels become unable to preferve the circulation in the extreme parts, whether from particular weakness in the veffels, or any other decay, I have always observed it to be hurtful to fcarify. It lets out the juices that should affift nature to make a feparation of the mortified part; nor can it be known in what place we may fafely amputate till fuch a feparation, which teaches us where it can be fupported, and in any place short of that an operation will be both ufelefs and mifchievous. I have known many fucceed well who have been thus left to feparate, but very few that were otherwise treated; nay, have known fome

extra

extraordinary instances of fuccefs where the patient had the happiness to have no one about them to interrupt the kind affiftance of nature.

CHAPTER X.

Of the lymphæducts.

YMPHÆDUCTs are small pellucid cylindri¬ cal tubes which arife invisible from the extremities of the arteries throughout the whole body, but more plentifully in glands than other parts, and in greatest number from fuch glands as feparate the vifcideft fluids, as may be observed in the liver and teftes. They cannot be difcerned in a natural state to have more than one coat, and that exceeding thin, having valves at small and uncertain distances, to prevent the regress of their fluid. They have frequent communications like the veins, but do not unite so often; the larger trunks are in many places attended with small glands, thro' which they run, and at the fame time fend communicant branches over them, that they might be secured against obstructions from difeafes in those glands. They all terminate in the vafa lactea, or in the large veins. All that rife in the abdomen empty into the venæ lacteæ fecundi generis and receptaculum chyli; those in the cavity of the thorax into the ductus thoracicus and the fubclavian veins. Their ufes are

to carry lymph to dilute the chyle, to make it incorporate more readily with the blood (but not to make it flow the better in the lacteals, as appears fufficiently from their not entering into the minuteft lacteals) and to carry off so much lymph as is neceffary to leave the blood in fit temper to flow through the veins; for it is always observed that in fuch perfons as have their blood too thin, the globuli cohere and form moleculæ, or polypufes, which I imagine may arise from the globuli of the blood not rubbing often enough, and with fufficient force one against another to difunite them as fast as they cohere. These polypufes are frequently found in all the large veins, and in the right auricle and ventricle of the heart, especially in fuch bodies as die hydropic or of any chronic diseases.

AUTHORS have defcribed and painted thefe veffels as they appear when injected with mercury; in which cafe the coat of these veffels being exceeding thin, it is not able any where between the valves to refift the mercury's attracting itself into globules: And the fame appearance alfo happens when they are vaftly diftended; because the valves hindering a diftention where they are feated, the spaces between them approach to a spherical figure from the equal preffure of the fluid, according to the degree of their diftention: but in a natural state when they are filled with lymph, or when they are moderately injected with air or water, they appear as cylindrical as the veins. Any of these vessels being

burst,