Proceedings of the Manila Medical Society 259 



the smallest discernible area to one which is 2 or 3 centimeters 

 in length. The rarefication presents moderately well-defined 

 borders separating it from the unaffected bone and varies in 

 translucency from the slightest differentiation of unnatural trans- 

 parency to one simulating a perforation. Most of the lesions 

 appear to originate in the interior of "the bone, while a number 

 can be seen as small excavations on its outer surface. When the 

 lesion is on the surface of the bone, the periosteum is usually 

 destroyed, but occasionally the cortex shows thickening and the 

 periosteum is separated from the bone. In two cases of this 

 series there is a general thinning of the cortex of the bone and 

 a loss of the cancellous-tissue appearance. About 2 per cent of 

 the cases show a nodular type of lesion, evidenced by swelling 

 over the surface of the bone, with a localized thickening of the 

 cortex, which sooner or later in the course of the disease shows 

 rarefication in its center. In the chronic lesions marked irregu- 

 larity of the bony outline is evident, and the picture characteristic 

 of the earlier lesions is more or less lost. The bone, as a whole, 

 becomes deformed, and the growth of the bone is interfered 

 with both in length and breadth. This dwarflike picture is most 

 frequently noticed in the cases showing the lesions in the epi- 

 physes. Within the joints the destruction is most frequently 

 seen on the parts of the articular surfaces most exposed to 

 trauma as oval or irregularly shaped excavations, making the 

 outline of the articular surface rough and uneven. It is con- 

 cluded from this series of cases that the joint pains complained 

 of are due, in most part, to the presence of the lesions on the 

 articular surfaces. With the exception of the 2 per cent of 

 cases showing as a swelling over the surface of the bone, the 

 X-ray picture is different from the bone lesion of syphilis, in 

 that the periosteal proliferation and the thickening of the cortex 

 of the bone are absent. Also, in the 2 per cent of cases where 

 thickening of the cortex is present, the thickening remains local- 

 ized, does not tend to extend along the whole length of the bone, 

 and sooner or later shows rarefication in the center of the lesion. 

 The bone lesion of yaws may simulate (1) tuberculous or septic 

 central abscess, (2) gumma, (3) hydatid cyst, (4) benign cyst, 

 (5) fibrous osteitis, (6) en chondroma, (7) endothelioma, (8) 

 secondary carcinoma, (9) myeloma, and (10) sarcoma. The 

 differential diagnosis can be made only by combining the radio- 

 graphic appearances with all clinical data, including the history, 

 physical signs, and evidence of disease or tumor in other parts 

 of the body. The Castellani treatment causes a gradual disap- 



