ANAPIIYL.\XIS IN ITS RELATION TO DISEASE 155 



sequcntly respond to the same stimulus with increased activity. 

 This may be diagrammatically represented} as shown in Fig. 3. 



Theoretically we should expect another possibility to exist, viz., 

 the occurrence of an immediate, followed by a hastened reaction, as 

 the result of a second injection. This may actually occur, and is 

 readily explained by the assumption that at the time of the second 

 injection a small amount of antibody was still present, but that 

 this was not sufficient to satisfy the affinities of the total amount 

 of albumin introduced; that a portion of the latter hence calls forth 

 the production of an additional amount of antibody which occurs 

 in a " hastened" manner, and meeting with some of the free antigen 

 gives rise to the hastened reaction, as shown in Fig. 4. 



If now we compare these findings with certain occurrences which 

 may be observed in connection with some of the infectious diseases, 

 it will be seen that the appearance of certain symptoms which we 

 note in some of the latter, may readily be explained upon the same 

 basis as the reactions which follow 7 reinjections of horse serum, as 

 above outlined, so that the inference seems justifiable that the 

 underlying mechanism in the two groups of cases is also essentially 

 the same. 



As is well known a first vaccination with cowpox lymph is followed 

 by a period of seven to eight days, during which there is a slowly 

 developing local reaction without any noticeable systemic symptoms. 

 During the first two days the local response is evidently purely 

 traumatic in character. On the third or fourth day the specific re- 

 action begins in the form of a small papular elevation which, between 

 the fourth and sixth days, is then differentiated into a central 

 papilla and a surrounding areola. Up to the eighth day the latter 

 extends but slightly beyond the papilla, but between this and the 

 eleventh day it rapidly develops so as to form a well-marked inflam- 

 matory zone surrounding the central area, reaching its largest size 

 between the eleventh and the fifteenth day. After this it gradually 

 disappears, while the papilla dries up and exfoliates. Coincidently 

 with the development of the areola, there are frequently also systemic 

 symptoms, of which fever and leukopenia are the most striking. 



If now we compare this picture with that of serum sickness, we 

 find very striking points of similarity which strongly suggest that 

 the underlying mechanism is in all probability the same. Here, as 

 there, we have a period of incubation of virtually the same duration. 



