340 PHILOSOPHICAL TRANSACTIONS. [ANNO 17Q8. 



large size, not less than a swan's quill, were sent to the tumour; which was situ- 

 ated behind the chorion, and lay imbedded in the foetal portion of the placenta. 

 The general form of this tumour was oval; about 44 inches long, and 3 inches 

 broad; the thickness about 3 inches; and it weighed upwards of 7 oz. Its shape 

 resembled that of a human kidney; 1 edge being almost uniformly convex, while 

 the other, where the vessels approached it, was a little hollowed. The general cha- 

 racter of the surface of the tumour was convexity; but in some parts of it there 

 were slight indentations, more particularly in the course of the large vessels. 



The whole of the tumour was inclosed in a firm capsule, in the substance of 

 which the large vessels were contained, nearly in the same manner as they are found 

 in the dura mater. In the interstices of the vessels, the capsule did not appear to 

 be vascular; at least there were no vessels capable of carrying the injected matter. 

 The blood-vessels, branching off from the funis to supply the tumour, partly went 

 over one side, and partly over the other side of the tumour; ramifying as they ran, 

 till, meeting at the convex edge of the tumour, they anastomosed very freely. 

 From the large trunks on the surface, small branches were given off, penetrating 

 into the substance, and supplying the whole tumour with blood. On making a 

 section through the tumour, in the direction of its length, the consistence was 

 found to be uniform, firm, and fleshy, very much resembling, in this respect, the 

 kidney. The cut surface, on examination, had somewhat of a mottled appearance; 

 some parts being highly vascular, while others were white and uninjected. 



If the mere existence of such a tumour is not to be considered as a disease, there 

 was no appearance of any morbid tendency in any part of it. The whole structure 

 seemed to consist of a regularly organized matter throughout, supplied with vessels 

 exclusively belonging to itself, and not passing to it from the surrounding parts, as 

 is generally the case in diseased masses. Those who are inclined to consider every 

 new appearance in the structure of parts as disease, may be disposed to include this 

 under that appellation. But disease consists in such an alteration in the structure, 

 or functions, of a part, as occasions the natural operations of it to be imperfectly 

 performed, or entirely arrested. This tumour appears to have produced no such 

 effect : all the common and known functions of the placenta were performed, not- 

 withstanding the existence of this substance: the child had been as well nourished, 

 and the benefits arising from the application of vital air or oxygen, to its blood, 

 just as well supplied, as if the tumour had not existed. 



It cannot be said of this, as it might of some tumours, that it would in time 

 have shown marks of a morbid tendency, so as to have deranged the common ac- 

 tions of the placenta; because, when gestation terminates, the life, and all the uses 

 of the placenta, are at an end. I am disposed, therefore, to consider this fleshy 

 substance, as a solitary instance of a formative property in the vessels of the pla- 

 centa; which they have not been hitherto generally known to possess.* 



* The placenta sometimes becomes converted into a mass of hydatids, connected to each other by 

 small filaments j but this must be considered as a disease, inasmuch as the natural structure is destroyed, 



