The Division Of Phlebitis into an adhesive and a suppurative form is well known, and has been generally followed. The two forms we have established may participate in either of the above characters. We would, however, expressly notice the error into which French observers have fallen, in regarding the purulent mass, which is in the centre of the coagulum, as the product of the inflamed coats of the veins. Cruveilhier attempts to show that the pus reaches the coagulum from without, by the capillary action of the coagulum; but this very unnatural hypothesis is quite inadequate to the solution of the question. We know, from many highly important analogies, that in ordinary cases the metamorphosis of the coagulum begins at its central nucleus, and that the purulent matter in the midst of the plug obstructing the vein cannot be regarded as the product of the inflamed coats of the vein.

C. Chronic Phlebitis

Chronic Phlebitis, as already observed at p. 256, is occasionally a consequence of the acute form of the disease; it may, however, likewise occur independently of the latter.

In the latter case it consists in chronic inflammation of the cellular coat, into whose tissue, and the contiguous layers of the circular fibrous coat, it deposits its products.

The cellular substratum of the vein must obviously participate in this process. Its anatomical indications are chronic inflammation of the cellular tissue.

It gives rise to dilatation, varicosity, and thickening, through the hypertrophy and sclerosis of the cellular coat of the vein; and, secondarily, through the new layers of lining membrane that are formed from the impeded blood-current, to the gluing of the vein into its cellular bed, to rigidity of the venous coats, and to gaping of the cut tubes; in short, it makes the veins approximate in character to arteries.

It has a great tendency, on very slight provocation, to pass into acute phlebitis.

Its most obvious causes are persistent distension and dilatation of the veins, in consequence of the impediments presented to the passage of the blood through them, besides which, it very often arises from the inflammation of the contiguous cellular tissue by an extension of the process. In accordance with what has been already stated, this condition is especially frequent in varicose veins, and in the veins of the lower extremities, where it very frequently originates in the subcutaneous tissue, which is then the seat of chronic inflammation, arising from habitual eczema.

Phlebitis very generally follows the course of the blood-current towards the heart, at all events during the early stages of its development; but yet exceptional cases are not unfrequently noticed, in which the inflammation follows a different course, and extends, during its more advanced stages, in an opposite direction.

It still remains for us to notice the phlebitis which attacks some special portions of the venous system.