Serum Sickness in Rabbits. ∗

Abstract

It is well known that serum sickness appears in a very large proportion of individuals injected for the first time with normal horse serum or with various antisera. For the experimental study of this reaction it is of value to be able to reproduce in laboratory animals a condition analogous to serum sickness in man. We believe that the results reported below are the first ones concerning the occurrence of serum sickness in rabbits.

When a single injection of horse serum is given to rabbits in sufficient quantities either intravenously, intramuscularly, subcutan-eously or into the subscapular tissues, there appears, from 3 to 7 days after the injection, a reaction characterized by erythema and edema. This reaction is evident on the rabbit's ears; there is noted a generalized flush which may involve the entire lower three-quarters of the ear, and which may be diffuse, confluent and of even intensity, or diffusely distributed, mottled and with discrete darker patches; the edema appears characteristically in the basal third of the ear but may extend upward to involve the entire lower two-thirds of the ear. The edema is frequently so marked that the pitting subsequent to pressure can be noted visually. The erythema and edema may each occur alone but both are usually present. These reactions can easily be differentiated from those occurring in the normal rabbit's ears; here hemorrhages, petechial or more extensive. and small circumscribed patches of erythema may be noted. Such appearances are very common. At times edematous areas often associated with trauma or hemorrhage occur; in the normal animal these latter reactions are usually noted in the upper half or twothirds of the ear, and such areas were found in only 35 of 147 normal animals which were observed for periods of 2 to 8 weeks.