Abstract
1. Streptolysin production by twenty-seven strains of haemolytic streptococci grown in a special buffered glucose serum-free broth has been compared and a very marked variation noted.2. The anti-streptolysin titres in healthy individuals and in others at the commencement of illness showed a pronounced variation.3. Throat infections with S. haemolyticus usually produced a rise in the level of circulating anti-streptolysin in the patients' blood, and this could be considered diagnostically significant.4. Throat infections with haemolytic streptococci showed rather more rapid production and higher titres of anti-streptolysin than did skin infections such as erysipelas, and both throat and skin infections were greatly superior to uterine infections in this respect.5. Neither the level of circulating anti-streptolysin at the commencement of infection nor the rate and height of response could be shown to have any bearing on the severity of the disease, except that a poor anti-streptolysin response was found in certain cases of relapses and toxic complications of throat infections. This appeared, however, to be merely indicative of a general poor antitoxic response and not to have any meaning by itself, except that in certain arthritic cases where the question of its importance was more open. No correlation whatsoever was noted between anti-streptolysin response and relapses and septic complications in erysipelas.6. In general the anti-streptolysin response in infection appeared to depend more on the individual than on the site or severity of infection.