22,3 Goodpasture: The Histology of Healing Yaws 279 



tissue cells become numerous throughout the portions involved 

 by exudate. At the end of this time definite reparative changes 

 have occurred in the epidermis. Leucocytic and fluid exudate 

 has almost completely disappeared and the epithelium has 

 actively reassumed its normal differentiation in direct propor- 

 tion to the degree of hyperplasia. Pigment granules have been 

 reformed in a quantity greater than normal within and about 

 the lower cells of the stratum germinativum. Grossly, the 

 yaw has assumed a dark slate gray color; its surface is dry 

 and covered by a crust of keratinized epithelium. The freshly 

 cut surface presents also a brownish tint in the corium, which 

 is due to the presence of a golden brown granular pigment 

 within cells there. 



With loss of exudate and by rapid keratinization, with prob- 

 ably diminished growth, the epidermis has reassumed a degree 

 of thinness approaching the normal, and the papillae are lower 

 and more compact. Thus, very rapidly the surface becomes 

 level with the surrounding skin, leaving a circumscribed pale 

 or deeply pigmented spot to mark the site. After healing not 

 infrequently hairs within these areas grow rapidly and to a 

 greater length than the normal, indicating persistence of a 

 growth stimulus, manifested also by more or less hyperkera- 

 tosis which continues for a while. In children pigmentation 

 often does not occur so rapidly nor to such an extent as in adults, 

 and the healed skin remains pale or even whitish. 



In the older dry yaws such as those in case 5, relatively 

 little change is to be noted three days after treatment. There 

 are still a few leucocytes, both polymorphonuclear and mono- 

 nuclear (epithelioid type), in small clusters and distributed 

 singly. In the one preparation which we studied there was 

 extremely active mitosis in the stratum germinativum — much 

 more than in the tissue removed before treatment — but this 

 may well be an accidental variation. There was also some de- 

 struction of leucocytes and lymphocytes in the corium. These 

 lesions, however, were already, by spontaneous healing, in the 

 stage of increased pigmentation and hyperkeratosis, and no 

 treponemata were demonstrated in either preparation. 



From the histological structure of these older lesions one 

 gets the impression that treponemata which must be harbored 

 there, though difficult to demonstrate, may be less accessible 

 to the destructive action of intravenous neosalvarsan than those 

 in the more acute lesions. This is indicated by the connective 

 tissue thickening about the blood vessels of the papilla? and the 



