the fat, which is gradually taken up by the villi along the small intestine.

The Lacteals, the vessels the villi contain, were discovered, in 1622, by Asselli, in the mesentery of a dog which he had fed on fatty food. He thought they ended in the vena porta. They begin by a branching tube in the villi, which may be com

pared to the spongioles of the root of a plant. The finely divided or emulsified fat is taken up by the epithelial cells, and transferred to the lacteal within the villus, as Weber believes ; whereas Goodsir thought the epithelium was shed before absorption, and it was once believed that the lacteals began by open mouths. That fat is chosen was said to indicate a selective power, but it is merely because fat has passed through before, and is thus more readily absorbed than other fluids. We have before mentioned that Peyer's glands seem connected with nutritive absorption. A patch A Peyerian patch. of them is here represented, and they are described at page 89. The chyle flows through the lacteals at very inconstant rates, but Cruikshank stated its velocity as 4 inches per second. It passes next through the mesenteric glands, where more fibrin and cells are developed, and is poured by 5 or 6 trunks into the thoracic duct. Pecquet, by vivisection-for he condemned dissection as a "mute and frigid science"-first demonstrated this duct. It courses through the posterior mediastinum and opens into the left subclavian vein, re

ceiving all the lymphatics, save those of the right side of the head, and the neck, and the upper extremity, which open by the right lymphatic duct of Steno into the right subclavian vein. What is termed the anterior thoracic duct is but a lymphatic from the liver passing behind the sternum. Through the lacteal system, while fasting, ordinary lymph is passing, from which chyle differs by the amount of fat; but the fibrin and other materials are not increased by the digestion of food.

Many other matters are absorbed rather by veins than lacteals, such as salts, poisonous substances, &c.-a view so fully argued by Hunter and Monro. Panizza proved it by placing hydrocyanic acid in a fold of gut in a living horse, after having separated the vein leading from it. As long as he kept the vein compressed, no effect occurred; but when the pressure was removed, the animal was poisoned, and some of the blood extracted from the vein contained the poison. Similar experiments were performed on the leg, all but the vein being divided, and lest it might be the absorbents in the coats of the vein which carried up the acid, a tube was placed between two divided portions of it. Waller found the poison was much more rapidly absorbed if the sciatic nerve were divided. The chyle is moved upwards, in opposition to gravitation, by the vis a tergo which succeeding portions acquire from the muscularity of the villi, the lacteals, and the thoracic duct, and the pressure of the aorta against the latter, but mainly by the rapid flow of blood in the large vessels into which it is poured. Venturi proved that the flow through a capillary tube is much promoted if it opens into a transverse tube in which fluid is passing, a principle applied to drainage.

The Chyle poured into the blood gradually disappears from that fluid by replacing materials which have been exhausted; but if dogs are bled after a full, fatty meal, their serum is found turbid from fatty chyle. In cases of apoplexy occurring after a meal, chylous blood has

often been found. Chyle, under a microscope, is seen to contain fat cells, and cells similar to the white ones of blood and lymph, and a "molecular base," as Gulliver termed it, whose particles are but doo That the colour of chyle depends on the fat of food, is shown by its being quite transparent if animals are fed on jelly. Bidder and Schmidt calculate that 61b is daily poured into circulation. The most reliable analysis is that of Dr. G. O. Rees, who obtained chyle from the thoracic duct of a criminal who had taken two ounces of bread and four ounces of meat the night previous, and two cups of tea and some toast an hour before execution. It contained

Alkaline phosphates, chlorides, carbonates, and chlorides and oxide of iron.....

0.44

Fat..

0.92

100.00

Traces of sugar can also be discovered in chyle and in very minute amount in lymph. The chyle of lower animals is often combined with blood, and even in man that from the upper part of the thoracic duct is very often pink, and becomes red on exposure to air. The fat gradually decreases; the fibrin, white cells, and molecular base increase as it passes upwards.

The Discovery of lymphatics has been claimed for Joliffe and also for Bartholin, who described them in 1652. They spread through every tissue in a manner like the drainage of a country. None have been demonstrated in nervous matter or the organs of sense. Those of the limbs are in 2 sets, superficial and deep, running along with the veins and passing through axillary and

inguinal glands to terminate in the thoracic duct. Their course can be displayed by injection, especially in a thin or dropsical subject. The coats of lymphatics are transparent, and consist of 3 layers: 1, an areolar; 2, intermixed elastic and muscular fibres; 3, an epithelium, composed of spindle-shaped cells. Semilunar valves with their concavity towards the heart occur in pairs, and the vessel being much distended above them, and narrow below, has a beaded appearance. A valve is always found where they enter a vein. These coats are elastic, and contractile in about the same degree as veins. Ruysch long since asserted he could inject lymphatics

from blood vessels, and the converse has been maintained, so that the only communication is not that at subclavian vein. Kölliker, whose representation is here copied, describes the lymphatics as beginning in the tissues by fine pointed vessels, arranged in a stellate form, and although apparently, closed, blood cells enter, perhaps by rupture.During impeded respira

The commencement of the Lymphatics, tion they often regurgiwith two Stellate cells in the act of uniting. tate into lymphatics from the veins. The lymph is moved by a vis a tergo, by the contraction of the vessels, and, as discovered by Müller, by lymph-hearts in reptiles and some birds.

The absorbent glands are oval, firm bodies of a pink colour, save when stained by the absorbed matters, being thus black from carbon about the lungs, yellow from bile about the liver, and white from chyle in the mesen

tery. The lymphatics entering the gland (vasa inferentia) are smaller than those leaving (vasa efferentia), which are always less numerous, and there may be but a single vessel. The outer coat of the vessels supplies a capsule which dips into the interior of the gland. Mercury, when injected, shows that the vessels appear to twist up; and it is believed that the coats of the vessels do not remain perfect but break into spaces, freely communicating with each other, and supplied by numerous blood-vessels on the outer surface. This cellular appearance was long since noticed by Nuck and Abernethy. The epithelium of the lymphatic spaces in the gland is constantly generating abundant oval nucleated cells, which Goodsir believes are shed into the current of the lymph. The

absorbent power of lymphatics is best shown by the imbibition of the syphilitic virus and of animal poisons, as that from dissecting wounds, which produce tracks of their course in the angioleucitis, and inflammation, hardening, or suppuration of the glands through which they pass. Cinnabar has been found in the axillary glands of a man who had tattooed a figure with it on his arm years before. The skin owes its great absorbent power to the lymphatics, which it contains most abun