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The inhibitory activity of human semen on the growth of Staphylococcus aureus has been reported previously (Rozansky, Gurevitch, Brzezinsky, and Eckerling, 1949).The Function of Human Semen The investigation has now been extended using 12 addi.ional freshly isolated strains of Staph. aureus.Materials and Methods.-Seventy-five specimens of semen from 53 patients (of the male sterility clinic) between the ages of 23 and 51 years were examined. Six of these were azoospermic, 25 oligospermic (less than 60 million spermatozoa per ml.), and 22 were normospermic. Ten specimens of human blood serum, 10 of cerebrospinal fluids, 10 of fluids from ovarian cysts, eight of amniotic fluids, four of pleural exudate, three of tears, and three of ox semen* were also tested in a similar manner. Materials were only taken from patients who had not received antibiotic treatment. The specimens of human semen were kept at room temperature for four hours before examination, then tested immediately, or after 72 hours at 80 C. or 14 days' refrigeration at 80 C. Twelve specimens were also examined after heating at 900 C. for 30 minutes. In addition to the three strains of Staph. aureus used in the previous study, 12 freshly isolated strains from surgical cases or pyogenic skin infections were tested. All strains were actively haemolytic, coagulase-positive, and mannitol-positive. The method described in the previous study (Rozansky et al., 1949)

1 . Sloughing of homogenous skin grafts and clouding of corneal transplants have been shown to be due to antigen-antibody reaction; antigens A and B have been demonstrated in human epidermis and corneal tissue; and anti-red-cell agglutination has been observed in dogs after homogenous bone transplantation. Human bone was therefore examined in thirty-three experiments to determine the presence or absence of A and B antigens. 2. The bone was separated into hard cortical bone, hard washed cancellous bone and soft-tissue washings of bone. 3. Adsorption experiments showed that A and B antigens are absent from cortical bone. A and B antigens are present in cancellous bone.

Several attempts to demonstrate the presence of A and B antigens in the human epidermis have been undertaken in the past, but with negative results (1, 2). Recently, Coombs, Bedford, and Rouillard (3) proved by the mixed agglutination method the existence of A and B group specific substances in epidermal cells.In continuation of studies on the A and B antigens in the human cornea (4, 5) the presence of these antigens in the human epidermis was investigated.The following is a report of this investigation. MATERIAL AND METHODSThin split thickness skin was obtained by means of an electric dermatome from 19 patients, selected at random, who were admitted to the hospital for various skin grafting procedures. No differentiation was made between secretors and non-secretors. Part of this skin was used for skin grafting, the rest rinsed in physiological saline and despatched to the laboratory, completely immersed in a container full of saline. There the excised skin was cut to standard size, 3 X 3 cm. and washed 3 times in 200 ml. normal saline. The flask containing saline and skin was agitated vigorously on a Kahn shaking machine for 10 minutes. In order to test for complete removal of erythrocytes, the last saline washing was centrifuged in large conical tubes and the minute sediments examined microscopically for red blood cells. If only one erythrocyte was found, three additional washings were carried out. Every sediment was further tested by the Benzidine Reaction (6). This was sometimes found to be positive after the first washing, but always negative after the third. After this treatment the skin was used either fresh or frozen at -200 C in 2 ml. of normal saline. For every experiment 0.5 X 0.5 cm. pieces of skin were cut into very thin slices with the aid of fine scissors and scalpels. These slices were homogenized for 30 minutes in a small pyrex glass tissue grinder with a pyrex glass pestle connected to a variable speed stirring apparatus. Five-tenths ml. of saline was added to the homogenate during homogenization. To prevent excessive heat production the grinder was immersed in 1 This study was aided by a grant from the Hematology Research Foundation, Chicago.an ice bath and the stirring carried out at intervals. The fine white pasty mass obtained served as antigenic material. Preparation of sera. Sera were inactivated at 560 C for 30 minutes, and titrated for anti-A and anti-B isoagglutinins. Only sera with the minimal titer of 1:128 when undiluted were used for absorption experiments. Sera were distributed in small quantities stored at -20°C until used; no serum was frozen and thawed more than once.Isoagglutinin determination. Titrations of isoagglutinins were performed by the double serial dilution method against freshly prepared 2 per cent erythrocyte suspensions. Results were read after allowing the tubes to stand at room temperature for 30 minutes. The titer was expressed as the last dilution at which agglutinates could be detected by the naked eye. The tubes were neither centrifuged nor examined micros...