Setting aside all dilatations of the smaller vessels and capillaries, constituting the so-called aneurysma anastomoticum and telangiectasis, we shall here treat of all that concerns the new growth of bloodvessels.

Upon a somewhat slender foundation of facts with which we have to commence, we must endeavor to build up a superstructure of well-considered hypothesis.

1. The common occurrence of this new growth in inflammatory products is incontestable, more especially in the adventitious membranes, affecting serous tunics. It is at the same time matter of certainty that such new vessels by no means originate through any prolongation of pre-existent vessels in the contiguous textures, but that the new process of development is altogether an independent one, and that only at a later epoch do the new-formed vessels enter into anastomosis with the older ones.

The process of the new growth of bloodvessels in inflammatory products of this kind is as follows:

In the first place, blood is seen to occupy little vacant spaces within the blastema or exudate thrown out in consequence of the inflammatory stasis. In other words, certain, for the most part irregularly spherical, ramified, to the naked eye point-like, arese, unlined with any proper membrane, fill with blood; areae obviously determined by the upspring-ing of blood out of the blastema. Both their remoteness from old vessels, and their ulterior development, controvert the idea of the contained blood consisting of little extravasates. This blood represents an aggregate of blood-corpuscles which the concurring testimony of Vogel and myself has shown to be of various magnitude, for the most part imperfectly round; not precisely disk-like, nor possessed of the intense redness of old blood-corpuscles. They are moreover soft, and adhere both to each other and to the parietes of the containing areae. From these areae there are gradually developed in all directions, sometimes, however, predominantly in a single one, blood-streamlets contained within chinks or canals in the blastema, and having no perceptible confining membrane. In minuteness of calibre, they excel the finest capillaries. Their next step is to become invested with a structureless confining membrane, the internal bloodvessel membrane, to which the outer layers associate themselves by and by. Finally they shoot out from various centres to anastomose with one another, and eventually with the old textural vessels.

In this process two material points remain unaccounted for, namely, first, the primitive development of the blood-corpuscles in those central areae. The question is - their spontaneous and independent origin out of the common blastema being manifest, what portion of the latter is devoted to this purpose, and what chemical changes does the act involve?

Secondly: How do the vessels originate? In reference to the last question it may be asserted:

(a.) If we may judge from past observations, the vessels in these blas-temata do not spring from primary blood-holding cells. The absence at first of any sharply defined contour in the said areae disproves their being primitive cells, or the blood-streamlets emanating from them, prolongations of cells. This leads us to the more probable assumption that:

(b.) The blood forms out of the blastema generally, and where the latter has wrought itself into cells, not within these, but in intercellular spaces between them. Where, however, blood and bloodvessel formation frequently precede cell-development, and more especially where it takes place in blastemata in which cell-development is either wanting altogether, or plays only a very subordinate part (for example, in fibroid blastemata), it can only be alleged that the formation takes place in chinks and chamberlets worked out of the blastema by the blood itself. The structureless membrane which subsequently confines the blood streamlets, is in all likelihood a secondary endogenous formation out of the blood, the remaining layers being built over it, so to speak, externally, out of the blastema.

As regards the relation of new bloodvessel development to the character of the blastema, the following points seem to present themselves for further inquiry.

(a.) In different products of inflammation, there is virtually a very different degree of proneness to the new growth of bloodvessels. In some it is excessive, in certain others, in the progress of development into precisely the same texture (the areolar), it is very faint indeed. Upon the parietal layer of the cerebral arachnoid, adventitious membranes occur, which along with an inconsiderable amount of nuclei, of nucleated cells, and of areolar-tissue fibrils, consist mainly of bloodvessels.

(5.) The new growth of bloodvessels is directly proportionate to the general capacity of the blastema for textural change. Blastemata which linger long in their primitive crude condition, and also which serve for the groundwork of indistinct fibroid textures, exhibit little, if any, new growth of bloodvessels.

The new formed vessels give token of a delicacy of structure, and a vulnerability in full accordance with their recent origin. To this are probably due the hemorrhagic products upon their becoming, when only just formed, the seat of inflammatory stasis. The fact is, moreover, to be inferred from the new-formed vessels originally consisting of the primitive vessel-membrane alone; and not until a later period attaining the perfected organization of old bloodvessels. In new-formed vessels of considerable calibre, we have frequently missed the layer of transverse-oval nuclei.

The vascular apparatus of new growth is marked by, for the most part, long, stretched vessels, by rare dichotomous ramification, with hardly perceptible decrease of calibre, or by a wide-meshed disposition.

A nervous system has not as yet been demonstrated in them.

The new bloodvessels both in the spurious membranes adverted to, and also in other new growths, are, as experience has again and again shown, susceptible of inflammation, and this in very early stages of their development. Here, for reasons both self-evident and already referred to, they are wont to yield essentially hemorrhagic products.

The manner in which their anastomosis with old vessels, or with particular arteries or veins is effected, has not been thoroughly made out by experiment. As regards the former case, it is probable that the anastomosis is brought about by an act of resorption in the wall of the old vessel, at the point where the new vessel rests.

With respect to the second point, Van der Kolk has distinctly shown that in the case of adhesions of the lung to the costal parietes, a connection becomes established, on the one side with the system of the pulmonary artery, on the other side with the aortic circulation. And although this fact may not warrant all Van der Kolk's deductions, it is nevertheless highly important, as offering a connecting link with other observations of his own upon anastomoses, to which we shall hereafter have to revert.

New-formed vessels doubtless undergo obliteration in spurious membranes, just in the same gradual manner as in the cicatrix, and probably for the most part in the progress and sequel of the retrogression, - the wasting - of the new textures themselves.

2. As in inflammatory products, so also in other blastemata, does a new growth of bloodvessels occur. An examination of these proves incontestably that there is a second mode in which a new growth of bloodvessels may take place. We have satisfied ourselves of the development of new vessels out of parent-cells in cancerous structures, composed, amongst other elements, of spherical or acinus-shaped parent-cells. Numerous cyst-like cells, with structureless parietes, contained in place of the brood cells of carcinoma, soft, adherent blood-corpuscles. Many of them bulged out in all directions into coecal sacs, freighted with the same contents, and entering into anastomoses with others. Blastemata, therefore, entering into cell-development, are in reality capable of producing a new development of bloodvessels out of cells.

Certain new growths are remarkable for being rich, others for being, in various degrees, poor in bloodvessels. The former are mostly loose in texture, and consequently capable of considerable intumescence. Their hyperaemiae are for obvious reasons, readily exaggerated into hemorrhage, and their inflammation is especially liable to determine hemorrhagic products. Amongst the malignant new growths, medullary cancer is notorious in this respect. Its highly developed vascular apparatus is doubtless the source of its excessive nutrition, of its rapid and often monstrous growth. It is pronounced by Van der Kolk to be of arterial nature, in other words, to anastomose with arteries only.

Very vascular new growths form the transition-link to nearly pure bloodvessel-formation. For blastemata are not wanting which present almost exclusively the groundwork of new bloodvessel-formation - in other words, of a new growth, consisting almost exclusively of new bloodvessels.

To this class belong the following new growths, concerning the development and import of which much obscurity still prevails.