604 ANAPHYLAXIS IN RELATION TO INFECTION AND IMMUNITY 



before the appearance of symptoms was the time required for the produc- 

 tion of the antibody, which then reacted upon the serum still remaining 

 in the body-cells and fluids, and that the products of this interaction 

 caused the lesions and symptoms of serum sickness. It was then but 

 a short step to apply these principles to other infectious diseases. This 

 "period of incubation" was formerly regarded as representing a stage 

 during which the infecting microorganisms multiply in the body of the in- 

 fected individual, to that point at which they could give rise to symp- 

 toms of disease through the agency of their toxins or through interference 

 with the metabolism of the host in other ways. But, as von Pirquet has 

 pointed out, this theory does not hold in serum sickness, as the serum may 

 be sterile arid no infecting microorganisms are at work. Instead, he and 

 Vaughan would have us believe that during this period antibody forma- 

 tion is taking place, and that an antibody-antigen reaction will occur with 

 the development of pathologic changes and symptoms just as soon as 

 these changes have progressed to a certain point. The period of incuba- 

 tion will vary not only in point of time of reaction, but also qualitatively 

 and quantitatively, and using this as a basis von Pirquet recognizes 

 three main groups, depending upon whether the antibody is present in 

 our body-fluids as the result of a previously acquired infection (acci- 

 dental or by vaccination), or whether it must first be developed. 



Group I : Reaction appears after eight to twelve days, as in measles, 

 smallpox, whooping-cough, chickenpox, and other infectious diseases in 

 which the antibodies must be developed before the symptoms are pro- 

 duced. This interval corresponds quite closely to that observed in 

 serum sickness. If at this time the antigen, i. e., either the albumins 

 of the horse serum, if we are dealing with serum injections, or the bac- 

 teria in case of an infection has disappeared from the body, no symptom 

 will, of course, result; if, however, some of the material is still present, 

 a reaction occurs, during which the protein poison (anaphylatoxin) is 

 produced, and to which, in turn, the symptoms that then develop may 

 logically be attributed. 



Group II: The reaction appears after three to seven days. If, on 

 the other hand, the secondary infection, as. e. g. } pneumonia, erysipelas, 

 etc., is acquired after a lapse of months or several years, or if the second 

 injection of serum is given after this time, i. e., at a time when the anti- 

 bodies called forth by the primary infection or first injection have 

 disappeared, a certain interval of time will elapse before symptoms of 

 sickness develop, as in the case of the first group. This interval, how- 



