cells containing the other or more liquid part; and, if the solid portion be separated, the latter coagulates.

Mr. Brande collected the lymph from the thoracic duct of an animal, which had been kept without food for twenty-four hours. He found its chief constituent to be water; besides which, it contained muriate of soda and albumen ;—the latter being in such minute quantity, that it coagulated only by the action of galvanism. The lymph of a dog yielded to Chevreul, water, 926.4; fibrine, 4.2; albumen, 61.0; muriate of soda, 6.1; carbonate of soda, 1.8; phosphate of lime, phosphate of magnesia, and carbonate of lime,

0.5.

It is impossible to estimate the quantity of lymph contained in the body. It would seem, however, that notwithstanding the great capacity of the lymphatic vessels, there is, under ordinary circumstances, but little fluid circulating in them. Frequently, when examined, they have appeared empty, or pervaded by a mere thread of lymph. Magendie endeavoured to obtain the whole of the lymph from a dog of large stature. He could collect but an ounce and a half; and it appeared to him, that the quantity increased, whenever the animal was kept fasting; but on this point he does not seem to express himself positively.

Physiology of Lymphosis.

The term lymphosis has been proposed by Chaussier for the action of elaboration, by which lymph is formed; as chylosis has been, for the formation of chyle; and hæmatosis, for that of the blood. In describing the organs, concerned in this function, the striking similarity, we might almost say, identity, in structure and arrangement between them and the chyliferous organs, will have been apparent. A part, indeed, of the vascular apparatus is common to both; and they manifestly constitute one and the same system. This would be sufficient to induce us to assign them similar functions; and it would require powerful and positive testimony to establish an opposite view. At one period, the lymph was considered to be simply the watery portion of the blood; and the lymphatic vessels were regarded as the mere continuation of the ultimate arterial ramifications. It was affirmed, that the blood on reaching the final arterial branches, separated into two parts; the red and thicker portion returning to the heart by the veins; and the white, serous portion passing by the lymphatics. The reasons for this belief were, the great resemblance between the lymph and serum of the blood; and the facility with which an injection passes, in the dead body, from the arterial, into the lymphatic, capillary vessels. Magendie has revived the ancient doctrine; and, of consequence, no longer considers the lymphatics to form part of the absorbent system; but to belong to the circulatory apparatus, and to serve, as we shall see, the office of waste pipes, in cases of emer

gency.

Without canvassing this subject, now, we may assume it for granted, that the lymph, which circulates in the lymphatic vessels, is identical in its nature, or as little subject to alteration as the chyle; and that, consequently, whatever may be the materials, that constitute it, an action of elaboration and selection must be exerted in its formation.

That it strongly resembles the blood is no evidence of its being formed from that fluid; the chyle, which it resembles even more than it does the blood, is procured from materials differing largely from its own nature; more, indeed, than any of the substances, whence the lymph is formed, differ from that fluid.

Assuming, for the present, that the lymph is obtained from materials already deposited in the body; the next inquiry is;--into the mode in which the separation and simultaneous absorption are effected. On this topic, we have no additional arguments to employ to those adduced, regarding the function of the chyliferous radicles. In every respect they are identically situated; and to their history we refer for an exposition of how little we know of this part of lymphosis.

Fig. 100.

The causes of the progression of the lymph in the vessels are the same, also, as those that influence the chyle. In addition, however, to those mentioned under chyliferous absorption, there is one, which applies equally to chyliferous and lymphatic vessels; and arises from the mode, in which the thoracic duct enters the subclavian vein. It has been already observed, that this occurs at the point of junction between the jugular and subclavian, as at D, Fig. 100, where J represents the jugular; and VS, the subclavian, in which the blood flows from V towards S, the cardiac extremity. Now it is a physical fact, that when a small tube is inserted perpendicularly into the lower side of a horizontal coni

M

cal pipe, in which the water is flowing from the narrower to the wider portion; and if the small vertical tube he made to dip into a vessel of water, not only will the water of the larger pipe not

descend into the vessel; but it will actually draw up the water through the small tube, so as to empty the vessel. Instead of supposing the canals in Fig. 100, to be veins and the thoracic duct; let us presume, that they are rigid mechanical tubes; and that the extremity of the tube D, which represents the thoracic duct, dips into the vessel B. As the fluids, proceeding from J to S and from V to S are passing from the narrower portions of conical tubes to wider, it follows, that the fluid will be drawn out of the vessel B, simply by traction, or, by what Venturi terms, the lateral communication of fluids. This would happen in whatever part of the vessel the tube B D terminated. But its insertion at D has another advantage. By the mode in which the current, from J towards S, unites with that from V towards S, a certain degree of diminished pressure must exist at D; so that the atmospheric pressure, on the surface of the water, in the vessel B, will likewise be exerted in propelling it forwards. In the progress of the chyle and lymph, then, along the thoracic duct, not only may the attraction of the more forcible stream along the veins draw the fluid in the thoracic duct along with it, but, owing to the diminished pressure at the mouth of the duct, atmospheric pressure may have some, although probably but little influence, in forcing the chyle and lymph from the chyliferous and lymphatic radicles onwards. The lymphatic glands have been looked upon as small hearts for the propulsion of the lymph; and Malpighi accounts for the greater number in the groin in this way;—the lymph having to ascend to the thoracic duct against its own gravity: this appears, also, to have been somewhat the opinion of Bichat.There seems, however, to be nothing in their structure, which should lead to this belief; and, if not muscular or contractile, it is manifest, that their number must have the effect of retarding rather than of accelerating the flow of the lymph. The most prevalent sentiment is, that they are somehow concerned in the admixture of the lymph; and by many it is conceived, that some kind of elaboration is effected by them; but, on this topic, we have only conjectures for our guidance. Of their true functions we know nothing definite.

On the subject of the moving powers of the lymph, Adelon has judiciously remarked, that if we admit the lymph to be the serous portion of the blood, and that the lymphatics are vessels of return, as the veins are, the heart might be considered to have the same influence over lymphatic, that it has been presumed to have over venous, circulation; and it is somewhat singular, that its action has not been invoked by those who embrace that opinion.

Hereafter, however, we shall see, that even in the circulation in the veins the agency of the heart can have little or no influence. Still less can it be expected to exert an influence over a system, so obscurely connected with the arteries as the lymphatic, especially when regard is paid to the numerous ganglions, which must have the effect of destroying such force, if exerted.

The course of the lymph is by no means rapid. If, a lymphatic vessel be divided, in a living individual, the lymph oozes out slowly, and never with a jet. Cruikshank estimated its velocity along the vessels to be four inches per second or twenty feet per minute; but the data, for any such evaluation, are altogether inadequate.

In man and in living animals, the lymphatics of the limbs, head, and neck rarely contain lymph; their inner surface appearing to be merely lubricated by a very thin fluid. Occasionally, however, the lymph stops in different parts of the vessels; distends them; and gives them an appearance very like that of varicose veins, except as to colour. Soemmering states that he has seen several in this condition on the top of the foot of a female; and Magendie one around the corona glandis of the male. In dogs, cats and other living animals, lymphatics, filled with lymph, are frequently seen at the surface of the liver, gall-bladder, vena cava, vena portæ, and at the sides of the spine. Magendie remarks, that he has never met with the thoracic duct empty, even when the lymphatics of the rest of the body were entirely so. It must be recollected, however, that the thoracic duct must always contain the product of the digestion either of food or of the secretions from the alimentary tube. This kind of stagnation of lymph in particular vessels has given occasion to the belief, that the lymph flows with different degrees of velocity in the different parts of the system; and this notion has entered into the pathological views of different writers, who have presumed, that something like determinations of lymph can occur, so as to produce lymphatic swellings. Bordeu, indeed, speaks of currents of lymph. The whole phenomena of the course of the lymph negative such presumption; and induce us to believe, that its progress is pretty uniform and always slow; and when an accumulation or engorgement or stagnation occurs in any particular vessel, it is more probably owing to increased secretion by the lymphatic radicles, which communicate with the vessel in question, and the consequently augmented quantity of lymph.

The lymph, which proceeds by the thoracic duct, is emptied, along with the chyle, into the subclavian vein. At the confluence, a valve is placed, which does not, however, appear to be essential, as the duct opens so favourably between the two currents from the jugular and subclavian, that there is no tendency for the blood to reflow into it. It has been suggested, that its use may be, to moderate the instillation of the fluid of the thoracic duct into the venous blood. With regard to the question, whether the lymph is the same at the radicles of the lymphatics as in the thoracic duct, or whether it does not gradually become more and more animalized in its course towards the venous system, and especially in its progress through the lymphatic glands, the reVOL. II.

5

marks, made upon the subject, as respects the chyle, apply with equal force to the lymph; and our ignorance is no less profound.

The glands of the mesentery and of the lymphatics in general seem to be concerned in some of the most serious diseases. Swelling of the lymphatic glands of the groin indicates the existence of a venereal sore on the penis. A wound on the foot will produce tumefaction of the inguinal glands; one on the hand will inflame the glands in the axilla. Whenever, indeed, a lymphatic gland is symptomatically enlarged, the source of irritation will be found at a greater distance from the vein into which the great lymphatic trunks pour their fluid, than the gland is. In plague, one of the essential symptoms is the appearance of swelling of the lymphatic glands of the groin and axilla; hence, it has been termed by some adeno-adynamic fever (from αδην, a gland.). In scrofula, the lymphatic system is generally deranged; and, in the doctrine of Broussais, a very active sympathy is affirmed to exist between the glands of the mesentery and the mucous surface of the stomach and intestines. This discovery, we are told, belongs to the "physiological doctrine," which has shown, that all gastro-enterites are accompanied by tumefaction of the mesenteric glands: although chyle may be loaded with acrid, irritating or even poisonous matters, it traverses the glands with impunity, provided it does not inflame the gastro-intestinal mucous surface. "Our attention," Broussais adds, "has been for a long time directed to this question, and we have not observed any instance of mesenteric glanglionitis, which had not been preceded by wellevidenced gastro-enteritis." The discovery will not immortalize the "doctrine." We should as naturally look for tumefaction of the mesenteric glands or ganglia, in cases of irritation of the intestine, as for enlargement of the glands of the groin when the foot is irritated.

Lastly; the lymph, from whatever source obtained—united with the chyle—is discharged into the venous system. Both of these, therefore, go to the composition of the body. They are entirely analogous in properties; but differ materially in quantity;—the nutritious fluid, formed from materials obtained from without, being by far the most copious. A due supply of it is required for continued existence; yet the body can exist for a time, even when the supply of nutriment is entirely cut off. Under such circumstances the necessary proportion of nutritive fluid must be obtained from the decomposition of the tissues; but from the perpetual drain, that takes place through the various excretions, this soon becomes insufficient, and death is the result.

We have seen, that both chyle and lymph are poured into the venous blood;—itself a compound of the remains of arterial blood, and of various heterogeneous absorptions. As an additional preliminary to the investigation of the agents of internal absorption,