Complement fixation tests were carried out by Odaira but his results were much less satisfactory than those he obtained by means of agglutination. Rapaport made an extensive study of this test, using the sera of patients in various stages of convalescence. Three hundred and fifteen convalescents showed 54.5 per cent. positive while 300 controls only gave 9.5 per cent. positive results. Most of the positive cases were in patients three to five days after their illness, but the reaction was found in convalescents after from 1 to 45 days. Sera from acutely ill patients at times showed negative or slightly positive reactions but these same sera after keeping for some days and retesting often gave strongly positive results. This would appear to be a promising field for investigation. _Anaphylaxis_ Hypersensitiveness was noted by W. F. Robertson in chronic infections with B. influenzæ. Wollacott in a letter to the British Medical Journal suggested that the severity of the recent outbreak of influenza may possibly be due to the development of a state of anaphylaxis. There would seem to be at least some evidence in favor of such a view in the fact that the severe outbreak was preceded by epidemics of a milder form of influenza and that the influenza bacillus was probably widely spread during this time. Greenwood, as quoted above, noted that primary cases always precede the mass attack. Of course, the term anaphylaxis has been used to explain almost everything. Nevertheless, the theory is interesting. The skin tests which we did for hypersensitiveness were, as I have noted above, negative but there is a possibility that the failure of the reaction may indicate a higher resistance or even an antitoxin, now that the bacillus can be classed as a toxicogenic one. Anti-influenza sera have been produced by a few investigators (Latapie, Wollstein) but have not found any practical application during this pandemic. Vaccination is discussed elsewhere in these studies. _Experiments on the Human_ There has never been in the history of medicine so many experiments on human beings as have been carried out in the attempts to discover the etiological factor in the recent pandemic of influenza. Davis has called attention to a successful human inoculation with pure cultures of B. influenzæ which he performed in 1906. During the present investigation at least 200 men have volunteered as experimental subjects, and the results of many different methods of attempting to transmit the disease, have been disappointing and inconclusive. I will not attempt to review the reports at present available, as a great deal of the work done has not yet appeared in print. The important point is that the results do not affect the various views held as to the causative agent in pandemic influenza nor the massive evidence for transmission of the disease under natural epidemic conditions.