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184 ORIGIN AND DEVELOPMENT OF CANCER, something of the disturbances of nutrition occasioned by unhealthy conditions of the blood quoad its chemical composition; we know something of the origin of rhowmatism, and gout, and syphilis, and of the effects they preduce; but they are very different from the phenomena of new formations. Surely the arising of a fibrous tumonr, an enchondroma, or a cancer, implies a very different kind of action to that which is observed in any blood discaso. We cer- tuinly believe the blood to be affected, probably in its chemical composition, as well as, and most importantly, in its vitel endow- ments, but we do not think it is the only scat of primary alteration. Were it so, how would it be possible to account for the constant preference inanifested by scirrhus, and by other twmours, for par- ticular sites? We conceive then, that in the case of cancer, the blood and the general system, but especially some partienlar part, haying suffered some unknowu deterioration or perversion of their vital power, a formative process is set up in the specially weakened part (perhaps in consequence of a blow or other injury), causing tho development of cell and fibre structure, which soon constitutes a new growth, endowed with powers of assimilation and vegetation to an almost indefinite extent. The tondency to cancorous disease, that is to say, the deterioration of the blood, and of the assimila- tive powers, may exist for a long time before it expresses itself in the tangible reality of a tumour; but when this is formed it becomes an engine for multiplication of similar tumours, and intensification of the cancerous diathesis. It is not possible to trace the process further back than to the tissues themselves. In tho vast majority of instances the growth manifestly originates within or in the interstices of textaral elements; in some few it has been foundin thecoats of the vessels, but in none has it been certainly proved to have originated in the blood, Cancerous growths haye, indeed, been seen within the veins, but this has been the result of perforation of their walls by formations external to them. Development proceeds in rudimentary cancerous tissue just as it would do in healthy; nuclei and fibres seem to arise in the same way; and the view taken of the pathological process must depend upon the light in which the physiological processes of growth and development are regarded.

Theories of the dexelopment of New Growths.—According to one theory the formation of new elements, whether in physiological or pathological circumstances, has been regarded as a production de nove, or as the transformation of an amorphous substance into formed elements, much as a saline solution transforms itself into crystals. ‘This may be called the dlastema theory, or the theory of free cell development. On this theory the formation of a new growth begins with the exudation (from the vessels) of a certain quantity of blastema, which proceeds to develop eell - and fibre-structure. In the case of morbid growths, such as cancer, the special character or morbidity of the growth depends upon the blood and genoral system, but especially on the particular �