RECRUDESCENCES IN INFECTIONS. 



101 



tuberculosis, or the separation of minute fragments 

 of thrombus infected with streptococci. 



Examples of a more or less regular periodicity 

 are found in the various relapsing fevers, which 

 are caused by spirilla. The first attack of the 

 European relapsing fever lasts for six or seven 

 days. This is followed by a period of apyrexia of 

 five or six days, followed by another febrile period. 

 Recovery is usually established after three or four 

 such attacks. In the relapsing fever of South 

 Africa the first attack has a shorter duration 

 (about three days), and those which succeed may 

 last only one or two days, according to Koch. 

 During the febrile attacks the blood swarms with 

 spirilla, whereas in the intervals it is compara- 

 tively free from organisms. In explanation of this 

 it has been assumed that the febrile attacks are cut 

 short by the development of a certain degree of 

 immunity. This results in a more or less complete 

 sterilization of the blood, although spirilla which 

 remain in the lymphoid organs, particularly the 

 spleen, seem to be protected. At the time of a 

 relapse, either the immunity has decreased suffi- 

 ciently, or the remaining organisms have gained in 

 virulence to such an extent that a general reinva- 

 sion takes place. In the end the immune forces 

 gain the upper hand and the body becomes com- 

 pletely sterilized. 



Some of the chronic infections are subject to 

 irregular recrudescences. Syphilis and trypanoso- 

 miasis of man begin as acute infections. After 

 the acute secondary stage has apparently passed, 

 syphilitics frequently suffer recrudescences, with 

 general manifestations, and it is probable that the 

 number of micro-organisms in the blood increases 



Regular 

 Recurrences. 



Recrudes- 

 cences in 

 Syphilis, etc. 



