Application of scanning electron microscopy to the study of skin window preparations.

Skin window preparations are made on the anterior aspect of the forearm, using a method already described in detail (Ghosh et al, 1973). After careful cleaning of the skin with soap and spirit, the epidermis is scraped away over a small area with a sterile scalpel blade until exudation is noted. Loose squames are wiped away and a sterile coverslip is applied. For this purpose a circular coverslip of 13 mm diameter is used. A cardboard square is placed over the coverslip for protection and secured with surgical tape. Serial examination of preparations can be carried out by removing coverslips at appropriate intervals and replacing them with fresh ones. Immediately after removal the coverslip is washed in sterile isotonic saline in a Petri dish for about 10 minutes. The specimen is then fixed by transferring the coverslip to another Petri dish containing fixative. The fixative used is 1-5 % glutaraldehyde in phosphate buffer pH 7*3 freshly made from stock solutions A and B. Solution A consists of 15-6 g per litre of NaH2P04.2H20, and solution B of 35-8 g per litre of Na2HP04.12H20, the solutions being mixed in a proportion of A:B, 23:77. After fixation for 45 minutes the coverslip is transferred to another Petri dish containing sterile, particle-free distilled water and washed for about 10-15 minutes. It is then slowly dried by being left in a wet chamber overnight. Handling of the coverslip in the above procedures is facilitated by placing it immediately after removal in a small metal cap with holes punched in it.