Concerning the particular changes which took place in the nature of this obstructed humour, many different opinions prevailed. Some thought it necessary, that the black bile should be charged with an acid, and that this produced ulceration, when “its sharp cutting points had surmounted and destroyed the volatile smegmatic and balsamic salts of the blood.” Others conjectured, that by an “adustion or over-concoction,” it grew sharp and burning: But Wiseman observes, that it is more probable that it becomes somewhat arsenical. It would, however, be useless to enumerate the different changes which this imaginary humour was supposed to undergo. It is sufficient to observe, that these were almost universally believed to depend upon the previous stagnation, in consequence of obstruction; and this leading point has uniformly been insisted on by every succeeding author, whatever might have been his particular notion with regard to the nature of the obstructed fluid, whether bile, blood, or lymph; and even the anatomical structure of the part has been brought in support of the doctrine of obstruction. One of the latest writers[116], though he talks nothing of “coagulating acids[117],” yet insists fully on this mechanical cause as the origin of cancer; “for,” says he, “the circulation in the glands being carried on by a set of vessels much more minute than those with which other parts of the body are supplied, (let this be proved), obstruction will much more readily and easily occur in them than in other parts.”--“When the substance of a gland happens to be the part, a determination is made to this, being neither, as is found by experience, so proper as the cellular substance, or the formation of pus, nor, from its softness[118], so susceptible of inflammation, as a membrane; an indolent hard swelling, called a schirrus, comes, merely by the _obstruction_ and _distension_[119] of its different vessels, very naturally to be produced.” [116] Bell on Ulcers, p. 319. [117] Dioni’s Chir. p. 248. [118] Does inflammation depend upon the hardness or softness of the inflamed part? [119] One should expect, that the distension of the vessels would diminish the cause of obstruction, or remove it altogether. It is rather unlucky, that the advocates for obstruction have made it the cause of simple inflammation, scrophula, cancer, &c.; and therefore all these diseases ought to be nearly, if not entirely, similar in their nature, and to require exactly the same means of cure.