22,3 Goodpasture: The Histology of Healing Yaws 271 



epithelium ruptures through the basal layers and becomes 

 bounded below the connective tissue of corium. The elongated 

 and widened papillae and a thin layer of corium just beneath the 

 basal epithelial cells constitute the least cellular portion of the 

 lesion. Here a loose reticulum of collagen fibrils, the wide inter- 

 stices of which are filled with serous exudate, support enormously 

 dilated blood vessels and gaping lymphatics. There is an active 

 diapedesis of polymorphonuclears going on, and they are the 

 most numerous cells. There are in addition a few plasma cells, 

 fewer lymphocytes, and a number of fibroblasts evidently 

 greater than could be normally present. Many of the smaller 

 blood vessels and lymphatics must also have been produced in 

 the general inflammatory activity. 



Beneath this zone of oedema the denser corium is filled with 

 compact masses of mononuclear cells which fade off into the 

 depths of the corium in the form of small isolated cellular islands. 

 Where infiltration is densest the collagenous connective tissue 

 has been pushed apart and its fibrils separated until only a thin 

 wavy reticulum remains. While blood vessels of various sizes 

 course through these areas, the distribution of cells is so ex- 

 tensive that there can hardly be said to be a perivascular ar- 

 rangement, although deeper in the corium there is distinct 

 perivascular infiltration. The majority are plasma cells with 

 numerous lymphocytes which not infrequently form the nucleus 

 of a group with the periphery bounded by a thick zone of plasma 

 cells. There is also a generous sprinkling of polymorphonu- 

 clears, especially on the more superficial side: In the depths of 

 the corium there is a cellular infiltration not only about blood- 

 vessels but also about coils of 'sweat glands and, to a less extent, 

 about hair follicles. These infiltrations are plasma cells and 

 lymphocytes. There are a few hyaline plasma cells, but no 

 giant cells. Mast cells are not abundant. 



There is a rather peculiar distribution of polymorphonuclear 

 eosinophiles in the lesion. They are not abundant but occur 

 unexpectedly in groups in certain parts of the epidermis. The 

 cellular exudate of a minute abscess may be entirely composed 

 of them, or in wide areas none may be found. In the (edematous 

 zone of the corium their distribution is irregular; only in certain 

 places do they form almost a complete sheath about small blood 

 vessels. 



Levaditi preparation.— Sections 1 millimeter thick were fixed 

 in 10 per cent formalin and stained by Levaditi's silver method. 



