THE NONSPECIFIC AGENTS 45 



streptococci, as is shown by the fact that when given a streptococcus dose, 

 such as will kill normal animals within twenty-four hours, they show no 

 change in their behavior. They are immune not only toward the strain 

 of streptococcus with which they were primarily infected but also against 

 foreign strains of streptococcus. However, this immunity is not absolute 

 but relative, for it is broken down by a strain of especially high virulence, 

 in which case the infection runs an acutely fatal course, as in the controls. 

 This partial immunity does not lie in the fact that the superinfection does 

 not "take"; on the contrary, the streptococci used for the superinfection 

 appear in the blood and organs, and by the aid of especially "marked" 

 strains could be shown to remain present for some time. The partial im- 

 munity consists, therefore, merely in a depression of the virulence of the 

 infection. This immunity was developed in from six to twenty-four hours 

 after the experimental infection. It does not seem to have anything to 

 do with anaphylaxis, but presents a new kind of immunity. They theorize 

 that the passing of an acute infection into a chronic phase is conditioned 

 by the development of this "depression immunity." The latter is not the 

 result of the chronic infection, but every infection that is not rapidly fatal 

 has its course determined by the depression immunity. Each phase of 

 the infection is the result of the antagonism between the causal germ and 

 the degree of depression immunity at the moment. This assumption throws 

 light on natural immunity and all other forms of immunity which do not 

 fit into the picture of immunity from antibody production. 



Otto Wiegand has recently contributed to the same subject and Berliner 

 and Citron working with chicken cholera in guinea-pigs have confirmed 

 the findings of Morgenroth and his associates. 



