22,3 Goodpasture: The Histology of Healing Yaws 275 



It appears in sections from case 1 that the margins of abscesses 

 are extended by invasion of surrounding tissue by treponemata, 

 and leucocytes accumulate about masses of these organisms lying 

 within and about necrotic epithelial cells. With the destruction 

 of the etiological agent all acute inflammation rapidly subsides. 

 Finally, leucocytes and miliary abscesses and treponemata may 

 be found in basal epithelium in young papules showing no evi- 

 dence of surface infection. 



Treponemata may be found in great numbers within the 

 pockets of hsemorrhagic, serous, and purulent exudate, and they 

 are less numerous in the dilated intercellular spaces of the 

 epidermis and within degenerated epithelial cells. They can 

 also be demonstrated within serous and cellular exudate about 

 terminal vessels of papillae. These organisms are the source of 

 injury. In their presence epithelial cells become swollen or 

 shrunken, their nuclei pallid or hyperchromatic and distorted. 

 Many of them, becoming necrotic, are apparently dissolved as 

 in miliary abscesses. Their injurious action extends to the 

 vascular bed of the papillae and the corium. Capillaries are 

 dilated; their walls are injured, and haemorrhage and cellular 

 exudate ensue. With the accumulation of serum and cells within 

 the epidermis the epithelium is further injured and its normal 

 differentiation is arrested. There is a loss of pigmentation, and 

 cornification is absent. Leucocytes and red blood cells are exuded 

 upon the surface, fibrin is deposited, and serum oozes through 

 the intercellular spaces. Along with this exudation epithelial 

 cells are disrupted and thrown off prematurely. With surface 

 evaporation a superficial scab is formed. In the meantime the 

 epithelium of the basal layer actively multiplies and, as the 

 papillae project upward, the epithelial pegs correspondingly 

 pierce downward. Mitotic figures are numerous in the irregular 

 stratum germinativum, and the margins of this layer are for 

 the most part definitely outlined, though occasionally ruptured 

 by accumulating exudate within, and sometimes apparently by 

 the growth of treponemata and resulting injury about the apical 

 terminations of papillae without. Not infrequently large branch- 

 ing pigment strands are seen in the basal layer ramifying 

 among intercellular spaces, but isolated pigment granules are 

 rare. Differentiation of the hair shaft is arrested, and one 

 finds in the depths of hair follicles abortive shafts and hyaline 

 epithelial pearls. Cells of sebaceous and sweat glands do not 

 appear to be injured, although there is frequently a mononuclear 

 exudate about the latter. Larger branches of nerves and erector 



