INTRODUCTORY. Is a preliminary communication (an abstract of which appeared in this Journalz), it was shown that there were great differences in the severity of the symptoms exhibited by rabbits " sensitised " by a previous injection of foreign serum on re-injection with the same. Those differences correspoiided with differences in the amount of precipitin produced in response to the first injection. With abundant precipitin the symptoms were severe and the result often fatal ; with precipitin

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... ess marked the symptoms were mild and were followed by perfect recovery. During the anaphylactic illnem it was shown that a diminution of the animal's serum-complement occurs, i.e. a larger dose of the fresh serum is required than before to dissolve the same combination of washed blood corpuscles and hemolytic immune body. The present paper discusses the mechanism of the symptoms in the rabbit. The illness referred to is that following immediately upon intravenous injection; the phenomena obtained by other routes of administration-subcutaneous, intraperitoneal, or intracerebral-are not included, nor are such late eflects as death after twenty-four hours. This immediate illness is remarkably uniform and does not vary with the different proteins, but has been produced in my experiments with substances of such diverse origin as serum (equine, bovine, and human), milk, foreign blood corpuscles (human and bovine), bacteria, and the vegetable protein of the rice Part of a thesis for the degree of M.D. of the University of Edinburgh.