22,3 Goodpasture: The Histology of Healing Yaws 267 



corium. The upper portion of hair follicles does not escape 

 invasion. Leucocytes are also scattered in greater or lesser 

 numbers throughout the epidermis in intercellular spaces. 

 These spaces are dilated by the presence of serous exudate. A 

 thin layer of purulent exudate, often communicating with miliary 

 abscesses below, overlies the surface. There is no ulceration 

 through the epidermis, though the abscesses sometimes break 

 through the basal layer. There are various degenerative changes 

 in epithelial cells ; some are pale and shrunken, others vacuolated 

 especially about the nucleus, and many are cast off into abscess 

 cavities where they undergo hyaline necrosis. Normal differ- 

 entiation is arrested, keratinization does not occur, and nuclei 

 are preserved more or less intact out to the surface. There is 

 an absence of general pigmentation in the inflamed area, though 

 in Levaditi preparations large, branching, pigment strands can 

 be found here and there in the stratum germinativum. Mitotic 

 figures in epithelial cells are abundant. 



In the cedematous perivascular connective tissue, which is 

 relatively poor in cells, there are, in addition to the polymorpho- 

 nuclear, a considerable number of the large mononuclear type, 

 which however are rarely engaged in phagocytosis; this is in 

 striking contrast to the condition in yaw 2, following treatment. 

 The large mononuclear cells are fairly numerous also in miliary 

 abscesses. There are a few lymphocytes and there is a moderate 

 increase in fibroblasts, some of which are to be found in mitosis, 

 but no plasma cells appear. 



In the superficial layer of the corium there is a mononuclear 

 infiltration, but this is not nearly so abundant as in case 2. 

 Most of the cells are of the lymphocytic type, though small 

 groups of plasma cells are to be found, and there are many 

 polymorphonuclears. The arrangement is perivascular. The 

 mononuclear-cell exudate does not extend so deeply into the 

 corium as in case 2 but, even so, there are a few plasma cells 

 accumulated about coils of sweat glands. Eosinophiles are not 

 numerous in the lesion, but there are a few irregularly scattered 

 both in the corium and in the epidermis. 



Levaditi preparation. — Sections stained by Levaditi's silver 

 method disclose an enormous number of treponemata, especially 

 in the epidermis. They are present in great abundance in the 

 miliary abscesses and in areas of epidermis densely infiltrated 

 with leucocytes. A few can be found in the epithelium at the 

 margins of abscesses where there is no cellular infiltration. Here 

 the treponemata lie in the dilated intercellular spaces, and even 



