When a foreign protein is reinjected one or more times into an animal, two phenomena can be observed. One of them relates to the changes in the reactivity of the animal and comprises the different aspects of anaphylaxis. The second phenomenon concerns the reinjected protein. The first of the two phenomena has been studied much more extensively and has attracted more attention than the second, although the problem of the latter was formulated and presented in clearcut experiments by Dehne and Hamburger1 as early as 1904.
The various phases of this problem in animals have since then been investigated by a number of authors. In spite of the controversies that are natural and unavoidable in the study of any subject, the results obtained by a large majority of the writers are sufficiently consistent to justify the statement that as far as the experimental animal is concerned the problem may