THE DOCTRINE OP CONTAGIUM VIVUM. 32S 



next day they were scanty, and the day after again abundant; 

 they even varied at diiferent hours of the same day ; some- 

 times they vanished altogether for a time, and then reappeared 

 in vast numbers a few hours later. Throughout these varia- 

 tions the temperature remained steadily high, or with only 

 slight or moderate oscillations. 



These discrepancies had been observed by previous in- 

 quirers, and had led some to doubt whether the spirilla had 

 anything to do with the virus of relapsing fever; but a 

 happy idea suggested itself to Heydenreich which seems 

 capable of explaining them. 



He found that when a little blood containing spirilla was 

 abstracted from the patient and kept at the ordinary tem- 

 perature of the room, the organisms lived in it for several 

 days; but if the blood was placed in an incubator and main- 

 tained at the normal temperature of the body, they died in 

 from twelve to twenty hours, and if the temperature was kept 

 up to fever heat (104 deg. F.) their life was still shorter ; 

 they only survived from four to twelve hours. This led him 

 to the conjecture that during the main paroxysm, not one, 

 but several successive generations of spirilla were born and 

 died before their final disappearance at the crisis. He sur- 

 mised that in the usual course, the broods would overlap each 

 other more or less, the new brood making its appearance 

 before the last survivors of the old brood had passed away. 

 This explained the variable number of spirilla found on 

 different days and different hours of the same day. Some- 

 times the old brood would have altogether perished before 

 the new brood reached maturity; this explained the occasional 

 temporary absence of spirilla from the blood; it also ex- 

 plained the remissions or pseudo-crisis sometimes observed 

 in the course of the paroxysms. So precise was the correspon- 

 dence found to be between the appearance of the spirilla and 

 a subsequent rise of temperature, that Heydenreich was able 

 to predict with certainty, during the apyrexial periods, the 

 approaching advent of a transient rise of temperature from 

 the reappearance of spirilla in the blood, although at the 

 time the patient presented no other indication of what was 

 about to happen. 



If these observations are to be relied on, and they appear 

 to have been' made with the most scrupulous care, we are 

 led to the conclusion that the spirilla are the actual virus of 

 relapsing fever. 



The same conclusion is also strongly indicated by the re- 

 sults of inoculation experiments. Relapsing fever is easily 

 communicated to a healthy person by inoculation with th&, 



VOL. XVII.— -NEW SEE. Tf 



