It is, however, only in the first and middle stages that these morbid growths can be easily confounded one with the other. Both appear small at first, but increase with great rapidity ; and both attain a size not often observed in other tumours, the fatty tumour alone ex cepted. The same purple colour, the same meandering of blue veins, and the same in equality of surface are found on both ; and when the osteo-sarcoma is about to ulcerate, it may be observed to be soft in some places and firm in others, like fungus hwmatodes. But here the resemblance ends. Throughout the entire case the osteo-sarcoma is harder, firmer, and more unyielding : it attains to a much greater size previous to ulceration, and when ulcerated it does not shoot out (at least in its more common forms) a soft and spongy and bleeding fungus ; neither does it destroy its victim with such rapidity.
In the Repertoire Generale d'Anatornie et de Physiologie Pathologiques (4 trimestre de 1826), there is an account of a disease of the tibia related by Lallemand and commented on by Breschet, who considered it to be some species of aneurismal tumour, more particu larly as it is stated to have been cured by the application of a ligature on the femoral artery. The precise nature of this tumour, however, is only conjectural, as it was never demonstrated by dissection ; neither is it right in the present state of our knowledge to question the cor rectness of these authors' opinions. Nature sometimes makes extraordinary deviations from the ordinary courses both of disease and re covery, and the circumstance of our inability to explain the processes adopted by her is not sufficient to warrant a denial of their existence. It may, however, be remarked that if the case alluded to was, as is said, an aneurism situ ated within a bony case and cured by the operation already stated, such recovery must have been based on principles totally different from those on which an artery is tied in an ordinary case of aneurism.
In the museum of the school in Park-street, there is a preparation perhaps in some de gree illustrative of this cellulated aneurismal disease. It exhibits a morbid expansion of the walls of a humerus removed from a woman in Stevens's Hospital : the entire shaft of the bone seems to have been engaged, and the transverse diameter of the tumour is about five inches and a half. Within are a number of cells lined by a vascular membrane of an exceedingly dark red colour, the deep tinge of which has scarcely been weakened by the immersion of the preparation in fluid for more than seven years ; and it is known that during life this enormous tumour imparted an in distinct sense of pulsation. lt appears by no means improbable that the commencement of this disease was in the medullary membrane, which gradually became altered and poured out the material, whether blood or otherwise, with which its cells were filled. In proportion as this accumulated, the cells must have en larged and the bone swelled. In many places the external parietes are seen thinned down to the strength of parchment or paper, and had the disease been allowed to progress, they might have been removed by absorption. Had such an event occurred, and the integu ments subsequently given way, it is easy to conceive that a fungus might have sprung from this vascular membmne, which, occasionally pouring forth an abundant and incontrollable flow of blood, would in every particular have so far resembled fungus hwmatodes, that even an experienced practitioner might have found it difficult to distinguish between them.