EXPLANATION OF PLATE. 



FIG. 1. Human skin, excised twenty hours after being rubbed lightly with a small 

 brown-tail caterpillar. The nettling hair has penetrated only the super- 

 ficial layers of the epidermis. About it a minute quantity of fluid 

 separates the horny layer; its point is embedded in a mass of deeply 

 staining coagulum in which are necrotic epidermal cells. 



FIG. 2. A section from another portion of the same piece of excised skin. The 

 point of the nettling hair has in this instance passed through the epidermis 

 and penetrated the coriurn. A more or less conical mass of sequestrum 

 marks its course. A small number of leucocytes are present in the tissue 

 about the injury. (Since the point of the nettling hair showed but faintly 

 in this photograph, its outline has been sharpened for purposes of repro- 

 duction.) 



FIG. 3. A section of a caterpillar, showing the nettling hairs as they are developed 

 upon its skin. An area of cuticle is shown, upon which are numerous 

 rounded sockets, each of which bears a number of nettling hairs with 

 their points inserted in the sockets. Below this area is a mass of long 

 fusiform cells, and to the left is a large deeply stained cell marking the 

 insertion of one of the coarse hairs of the caterpillar. 



FIG. 4. A minute cavity formed about a nettling hair which has penetrated the 

 epidermis. Adherent to the nettling hair, the point of which is directed 

 to the right, is a mass of deeply stained coagulum. The fluid in the 

 cavity contains degenerated cells. (Magnification greater than in other 

 figures.) 



FIG. 5. A lesion showing the effect of excoriation of the affected area. A minute 

 portion of the epidermis is necrotic, and is included in a small crust. The 

 nettling hair does not appear, and has probably been rubbed away. There 

 is considerable cellular exudation into the subjacent corium. 



