300 REPORT OF THE HARVARD AFRICAN EXPEDITION 
often leads to a thickening of the intima and narrowing of the lumen and some- 
times to obliteration of the vessels. 
Giant cells are frequently found in the older lesions but are usually not preva- 
lent except when the advanced lesions occur in regions where striped muscle fibers 
are present. In such lesions, Landois ! states, giant cells are always present. 
In the more advanced lesions of syphilis where suppuration and gummatous 
conditions have supervened, the cellular infiltration observed has a greater 
tendency to diffuse spread than to the formation of nodules such as are seen in 
tuberculosis and to a less extent, in framboesia. The gummatous lesions in 
syphilis are especially characterized in addition by a peculiar form of granulation 
tissue, richly cellular. The infiltration, however, may sometimes be zonal in 
character. In the center there may be an area of caseous coagulation necrosis 1n 
which fibrous tissue and the contours of the blood vessels can still be distinguished. 
External to this is frequently an area or zone in which fibroblasts, epitheloid cells, 
round cells and a few giant cells are observed, the whole being enclosed in more 
dense fibrous connective tissue. Finally, at the periphery, there may be a zone of 
newly-formed granulation tissue rich in small round cells, plasma cells and a few 
leucocytes and newly-formed blood vessels. There is a marked tendency to 
fibrous change in such lesions and, where the gummatous formation is extensive, 
they often lie in cicatrizing connective tissue in which the walls of the vessels 
are infiltrated by cells and thickened, and there may be infiltration by round cells 
and plasma cells in the vicinity. 
The examination of caseous gummata for spirochaetes practically always 
results negatively. In contrast to tuberculosis with tubercle formation, the 
syphilitic lesions (as pointed out especially by Baumgarten) retain numerous 
blood vessels and this fact, he believes, as well as the great tendency to fibrous 
changes, is a very important point in differentiating the syphilitic from the 
tubercular lesions. 
In the examination of the primary and secondary granulomatous lesions of 
yaws histologically, the papillae are often elongated and may be frequently seen 
in the base of the ulcer of the yaw, sometimes almost reaching the surface. There 
is usually much hyperplasia and thickening of the epithelium and below this a 
dense infiltration, especially with plasma cells. 
The Spirochaeta pertenuis is found usually only in the epidermis, though 
recently Goodpasture * has demonstrated that it may occur, though rarely, in the 
perivascular connective tissue in certain of the long papillae which extend far up 
into the thickened epidermis. Schébl* has found the spirochaetes during the 
acute stage in the lymphatic glands near the framboetie lesion in experimental 
animals, but says that in contradistinction to syphilis they are never present 
there after the lesion itself has healed. 
A striking feature of the lesions in yaws is the great thickening of the epidermis 
and the degenerations which occur in the epithelial cells. In many instances there 
1 Landois: Beitrige zur Klin. Chirurgie (1909), p. 63. 
2 Goodpasture: Phil. Jour. of Sci. (1923), XXII, 268. 
8 Schobl: Loc. cit. 
