KELATION OF ANAPHYLAXIS TO INFECTIOUS DISEASES 567 



that the products of this interaction caused the lesions and symptoms 

 of serum sickness. It was then but a short step to apply these prin- 

 ciples 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 infected individual, to that 

 point at which they could give rise to symptoms 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 and 

 no infecting microorganisms are at work. Instead, he and Vaughan 

 would have us believe that during this period antibody formation 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 incubation 

 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- 

 ever, instead of being from eight to twelve days, is now from three to 

 seven, a fact readily explained on the basis that a cell that has once been 

 stimulated to active antibody formation will subsequently respond to 



