We shall pass over the anomalies which the great lymphatic vessel, the thoracic duct, presents at its origin, in its course, and at its mouth, and proceed at once to:

1. Anomalies Of Texture. A. Inflammation

Our anatomical knowledge of inflammation of the lymphatic vessels (lymphangioitis) is very deficient in several points, which is in part owing to the delicacy and inaccessibility of the lymphatic vessels, and in part to our imperfect knowledge in relation to their function, and to the extent to which they can absorb heterogeneous substances. In reference to the fine ramifications of the lymphatics, they are so far positively affected in every inflammation of the tissue, that at their numerous points of contact with the products of the inflammatory process, they absorb morbid matters by imbibition into their cavities, and, according to circumstances, sometimes lose their permeability by the swelling of their coats or the coagulation of their contents, and sometimes present torn walls. It is on the absorption of these morbid matters that the consensual inflammatory swellings of the lymphatic glands pertaining to the inflamed organ are based. In inflammations with copious exudation into the tissue, the lymphatics undoubtedly sometimes undergo a transitory occlusion, and sometimes a persistent atrophy where the inflammation terminates in induration; when there is purulent, ichorous fusion of the tissue, they suffer a destruction corresponding to the extent of the process.

It is more easy to observe the manner in which the larger lymphatic vessels are affected by inflammation, but even here there are difficulties to which we will refer after we have considered inflammation of the lymphatic vessels in a purely anatomical point of view.

Lymphangioitis presents the following persistent signs: a. Injection and Reddening of the cellular coat of the vessel; we very often find small ecchymoses on it, and on the inner coat. In other respects the vascularization is very frequently insignificant, and, sometimes none can be detected.

b. Infiltration of the cellular sheath with serous, sero-fibrinous, purulent moisture, and swelling.

The simultaneous vascularization and infiltration of the surrounding cellular tissue are often very strongly marked; abscesses often occur at various points along the vessel.

c. The inner coat is lustreless, dull, villous, easily wrinkled, and at some parts presents a red or bluish-red speckled appearance from the ecchymoses seen through it.

d. The wall of the vessel is consequently thickened, while its coats become loosened in texture, easily lacerable, and removable in layers.

e. The vessel is dilated and varicose.

f. Exudation occurs in the form of more or less opacity, of distinct coaguluted flocculi, or even of larger occluding coagula, or of pure pus, in the canal of the lymphatic vessel.

Whether the occluding coagula, like those in inflamed bloodvessels, notwithstanding the slighter coagulability of the fibrin in the lymphatics, and the lesser exudative tendency of the lymph, may not sometimes be coagula derived from the lymph and not solidified exudations, cannot at present be decided.

Inflammation of the lymphatic vessels may terminate in Obliteration or Suppuration, as well as in Resolution.

1. The lymphatic vessel may close around a coagulum adhering to the inner coat of the vessel and metamorphosed into a fibroid string. We have observed the thoracic duct in a phthisical patient, who was worn to a mere skeleton, present an obliteration of this nature and a conversion into a solid cord.

2. The lymphatic vessel may suppurate, and this ensues not so much from the interior and from the purulent exudation deposited in its canal and in its coats, as from a neighboring abscess denuding and destroying the vessel. The lymphatic vessel then lies as it were in the walls of the abscess, whose contents will receive an admixture of lymph, till, in consequence of inflammation around the abscess, the vessel ceases to be permeable.

When the above-described changes present themselves in a lymphatic vessel, no doubt can be entertained regarding its inflammation; but we very often meet with lymphatics in a condition presenting many essential similarities with inflammation, and yet, according to our views, not actually inflamed. Thus we often find the lymphatics proceeding from inflamed parenchymatous organs, or from abscesses filled with pus, varicose, dull, and pilous on their inner surface; while, further, we observe that the surrounding cellular tissue presents a vascular and infiltrated appearance, as is very commonly seen in the lymphatic vessels of the hypogastric and lumbar plexuses after delivery. There are, however, absent, on the one hand, the infiltration and swelling, giving rise to the loosening of the coats of the vessel, while, on the other, the injection and infiltration of the retroperitoneal cellular substance investing the lymphatic plexus appear in puerperal cases as an integral part of the peritonitic process. We believe that in these cases the pus is not, or at all events is not always, produced in the lymphatic vessel itself, but is conveyed there from the inflammatory centre or abscess, whether it reach the lymphatic vessels by absorption of the purulent fluid, or has exuded into their cavity; or, finally, whether it has been taken up by lymphatics opening into the abscess; - that the dilatation of the lymphatic vessels arises from the accumulation of pus within them, since its further transmission is impeded by the swelling of the lymphatic glands; - and, finally, that the loss of lustre presented by the inner coat is induced by the loosening and fusing action of the pus.

On the other hand, it is unquestionable that a lymphatic vessel containing pus not unfrequently becomes inflamed, probably in consequence of its coats imbibing pus. The period which such an inflammation occupies is frequently a long one; this is analogous to the singularly long period of incubation, which occurs in the case of poisoned wounds, from the time of the injury to the formation of a decided inflammation of the lymphatic vessels, and to the impunity with which the lymphatic vessels can convey all varieties of ulcerous products and contagious matters, while the glands are highly affected. This indicates that the lymphatic vessels possess a very subordinate sensitiveness to the irritation produced by the contact of heterogeneous matters, especially as compard with the lymphatic glands.

The appearances presented by inflammation of the larger lymphatic vessels, are in accordance with the observations which have been already made; as in phlebitis, inflammation of the coats of a lymphatic vessel may be the primary phenomenon, which occasions an anomaly of its contents by exudation into the canal of the vessel, or inflammation may be excited by the presence of a heterogeneous substance within the lymphatic vessel.

An infection of the blood by the matter produced in the lymphatic vessel, or absorbed into it from without, and the secondary (metastatic) phenomena consequent on such an infection, are in general rare; the rarity being in proportion to the distance of the process from the central anastomosis of the lymphatics and bloodvessels, and to the number of glands through which the heterogeneous substances contained in the lymphatic vessel have to pass.

Inflammation of the lymphatic vessels is often observed along the course of an inflamed vein; this may sometimes arise through the inflammation of the common cellular bed of the vein and the lymphatic vessel, and may sometimes be dependent on the same cause as the phlebitis, namely, the absorption of heterogeneous matter.

B. Adventitous Products

These are limited to Tubercle and Cancer. Each occurs in a special form, as an adventitious mass closing the tube of the vessel, and invariably as a secondary phenomenon. In order that they may occur, there must be an absorption of softened tubercle, or of cancerous blastemata, into the lymphatic vessel. The lymphatic glands act as centres of absorption of the morbid matter, occasioning tuberculosis and cancer of those organs. Tuberculous pus and the cancerous blastema coagulate with the other contents of the lymphatic vessel; the former into a yellow cheesy, the latter in a whitish, more or less brainlike (encephaloid) molecular mass, which finally closes the nodulary dilated lymphatic vessel. Lymphatic vessels plugged with tuberculous matter sometimes present thickened coats and a lardaceous infiltration, doubtless in consequence of having undergone inflammation.

We may often observe both these forms, particularly tuberculosis of the lymphatic vessels, which especially occurs in the lymphatics between the intestinal and mesenteric glands, between the different mesenteric glands, and between the latter and the glands of the lumbar plexus, in tuberculous ulceration of the intestines in tuberculous disease of the mesenteric glands (cavities in the glands), etc.; cancer of the lymphatics especially occurs in cases of medullary cancer.

2. Anomalies Of Calibre

A moderate dilatation of one or more lymphatics, which may either be uniform or nodular (varicose), is by no means rare; it may be dependent on pressure or on the impermeability of some of the coils in lymphatic glands. The coats of the vessel are in these cases sometimes relaxed and attenuated, and sometimes thickened. That certain cysts and hydatids (such, for instance, as the structures occurring in the choroid plexus of the lateral ventricles, and formerly regarded as hydatids), consist of varicose lymphatic vessels, as is taught even in the present day, is, in our opinion, by no means proved: but this does not exclude the possibility that lymphatics may sometimes assume a bladder-like dilatation at certain spots, as, for instance, between two pairs of valves, where they may present a constricted appearance. An extraordinary and very rare example of general dilatation of the lymphatics has been recorded by Breschet (Le Syst. Lymph., Paris, 1836), for which he was indebted to Amussat.

Contraction of the lymphatics occurs independently in general or partial atrophy, and arises from the compression exerted by every variety of tumor. It is also manifested in the form of occlusion - obliteration.