The blastema for pathological new growths ultimately proceeds from the general fluid of nutrition, the plasma of the blood. Accordingly, its source is that out of which all normal textures are developed. Its bodily detection and demonstration in its simple, primitive form, are, however, mostly a matter of difficulty, except, perhaps, in cases where it is somewhat copiously produced, in the train of peculiar and often rapidly fatal processes, which may be experimentally analyzed grade for grade, - for example, in inflammation and hyperemia. It exudes through the parietes of vessels wherever capillaries exist, or it appears as an endogenous segregation from the blood within the circulating system. In rarer instances, it is deposited by extravasation out of lacerated vessels.

The blastema is originally fluid, and it may either abide in this condition or solidify. The earlier or later solidification, that is, its becoming a fixed elementary body, and the degree of the resulting density and consistence depend mainly upon the presence of coagulable protein, and upon the degree of its coagulability, as also upon the absence of those counter-checks to coagulation, alkalies, acids, and certain salts.

Rapidly solidifying blastemata, especially when products of inflammation, are very commonly termed plastic, - improperly, however, because coagulability of the blastema stands by no means in any direct relation to the faculty of development. ' Many blastemata, distinguished for their coagulability, do not rise above the lowest grade of form-development, and not alone do they stop at the grade marked out by the process of coagulation, but their ulterior tendency is to liquefy. An example is afforded in tubercle.

As a fluid, primitive blastema recently secreted is amorphous. Sooner or later, however, it is marked by the development of form-elements, in the shape of molecular granule, nucleus, cell. Solidified blastema is either at the outset amorphous, or displays, from the moment of coagulation, certain, and, indeed, higher elementary forms, - more especially fibrillation.

The blastemata are colorless, or they assume the tint of the plasma, or they are of a reddish gray, - the fibrinous of various tones of yellow, - the albuminous, whitish, particularly when fat enters simultaneously into their composition, - or they display various shades of red from adhering blood-pigment, or from the presence of blood-globules, etc.

Chemically considered, all blastemata for pathological new growths are protein compounds, for the most part in various degrees of oxidation.

The main conversion which the blastema undergoes is its development into textures. It is capable, however, of abiding in its rude primitive condition - of remaining dormant - or of breaking up, or lastly, even of becoming reabsorbed.

Before we proceed to consider these several attributes of blastemata, it seems desirable for us to render ourselves familiar with the main conditions for its development or non-development.

If, participating in the current opinions as to the conditions necessary for the development of blastema, we admit

(a.) A faculty of development originally and essentially inherent in the blastema, and inseparable from the idea conveyed by the term.

(b.) The necessity of certain outward and general conditions, particularly a mean temperature, the presence of water (moisture) and of oxygen.

(c.) The necessity of extant life in the textures into which the blastema is effused, and a fortiori, in the individual. In necrose textures no development takes place at all.

(d.) The necessity, in order to become developed, that the blastema should abide in close contact with the living textures; for beyond this the influence of the vital power certainly appears to be limited. The development of blastema usually commences close to the living textures, and bulky effusions of blastema remain in a backward state when removed from these textures lingering either in their rude primitive condition, or at the stage of form-development, determined by coagulation, or lastly, breaking up.

(e.) The specific influence exerted by circumjacent textures upon the mode of development, and upon the form of blastema. We know that, in the act of nutrition, of regeneration, even in pathological processes, blastema in areolar tissue becomes developed into areolar tissue; blastema in serous membranes into areolar tissue, nay, even into serous layers and sacs; blastema in bone, into bone; we know that, in tumors, fibroid textures often imitate the texture of the organ; that fibroid tumors of the uterus, for example, represent the elementary forms of organic muscular fibre; - that in bones, cartilaginous new growths are wont to assume the form of enchondroma.

All this generally admitted, the failure of such influence does not, as regards many, and the more momentous cases, appear satisfactorily to explain either the non-development of blastema, its tarrying in its rude primitive condition, its arrest at an inferior stage of embryonic development, its disintegration, or its development to unwonted heterogeneous textures. This becomes the more obvious if, in relation to the aforesaid conditions, we reflect:

(a.) That, as a rule, the absence of moisture is not absolute, and that it is also in other ways conditional.

(b.) That the absence of an adequate, general, and specific influence in the circumjacent textures can never be assumed directly, but only through the one-sided conclusion that, notwithstanding the existence of other requirements, a blastema has failed to become developed, a fact which might admit of a very different interpretation.

Thus, to discuss a matter of the greatest importance in the arena of facts, the sojourn of certain fixed blastemata, - for example, tubercle - in the primitive condition, is not ultimately referable to the absence of moisture; the absence or rather paucity of water depending upon the high degree of coagulability proper to the said blastema. This coagulability must, however, be inherent in the blastema itself. Again, there are blastemata which never get beyond the embryonic grades of development, - for example, the pus-blastema, the blastema of medullary and of colloid cancer. Deficiency of vital power, or of determining influence on the part of surrounding textures cannot, in every instance, furnish grounds for the non-development of blastema. Thus we see very minute portions of blastema, - for instance, of tubercle - in robust individuals, in the closest contact, with, nay, in the centre, of vigorous textures, undeveloped. On the other side, in a very low degree of vital power, where one might rather expect little or no blastema to be produced, we meet with enormous masses of it under various forms of heterologous growths, engaged in the process of development. The phenomenon so commonly regarded as an arrest of textural development, - founded in deficiency of vital energy, of adequate working power, - namely, fibrous callus, in the regeneration of bone, - cicatrix in muscle, etc, - is, we think, interpretable as qualitative alienation, the blastemata not abiding at the embryonic stages of development of the textures to be regenerated, but forming into other textures, perfect after their kind.

Still less is this deficiency calculated to illustrate that qualitative variety in the development of blastemata, exemplified in so many heterologous growths. How should we therefrom apprehend the derivation of a cyst, of an areolar-carcinoma, and the like? How often should we not be driven, instead of deficiency, to assume an equally unintelligible excess of power, where we find, in textures of an inferior grade, new growths developed, the elements of which belong to textures of a higher order.

These remarks of themselves lead to the conclusion:

1. That the abnormal development of the blastemata is founded, not in a deficiency, but in an anomaly, of determining influence.

2. That the different blastemata themselves, at the outset, possess indwelling properties of their own. We can have little hesitation in establishing, as a basis of the doctrine of new formations, a native anomaly in the blastemata, this being practically demonstrable. Such, for example, are the various morbid relations of protein substances, and in particular the anatomically demonstrable anomalies in the constitution of fibrin in the blood itself, with which anomalies the different exudation, (as blastemata) correspond both as to form and chemical composition.

In this manner certain blastemata bear, in their primitive character and composition, the grounds for their non-development, - the seeds of their dissolution, - for example, croupous fibrin, - tubercle, - pus-blastema.

Other blastemata, on the contrary, possess the indwelling faculty of development in so exalted and inextinguishable a degree, as to form, in large serous cavities, into free aggregations of blastema without any abiding contact with textures - free fibroid concretions.

Areolar new growths are so frequent, simply, in our opinion, because their blastemata are so frequent, and their production consequent upon so many different processes of exudation.

The blastema for animal muscular fibre appears, on the contrary, to exude only in the normal process of nutrition, or where this process is exaggerated to hypertrophy.

It is very common for mixed blastemata to exude. Hence the frequent coincidence, in one and the same new formation, of such various elementary forms, and of such different modes of development.