RELAPSING FEVER. 643 



The organism has not been grown artificially, 

 but it may be kept alive for a number of days in 

 the blood or serum of patients. As the micro-or- 

 ganisms die, agglomerations are formed and they 

 undergo granular changes. 



The organism is not found in Nature, and, 

 since it occurs only in the blood of the sick, it has 

 long been assumed that infection can be accom- 

 plished only by the inoculation of infected blood. 

 The parasites have been demonstrated repeatedly 

 in bedbugs which are found on the mattresses of 

 the sickbed, and monkeys have been infected by 

 inoculating them with the blood found in the 

 bodies of these insects, and by the bites of the lat- 

 ter (Tictin). It is said that they may remain 

 alive in bedbugs for as long as thirty days. It is 

 not altogether excluded that other vermin also 

 transmit the disease. 



The spirochete does not appear in any of the ex- 

 cretions, unless these happen to be of a bloody 

 character. 



Certain monkeys, those belonging to the slender- 

 nosed family (Catarrhince) , may be infected by 

 injecting the blood of patients, provided the blood 

 used is taken during the paroxysm, i. e., at a time 

 when the microbes are known to be in the blood. 

 Novy has found that the disease can be readily 

 transmitted to white rats and mice; rabbits and 

 guinea-pigs appear to be refractory. In mice, as 

 in monkeys and man, relapses occur regularly. 

 In rats, however, immunity is established after 

 one attack. The incubation period in man usually 

 is from five to seven days, and in monkeys from 

 one and one-half to four days. Cloudy swelling 



