104 



SIXTEENTH REPORT. 



INCUBATION PERIOD AND DURATION OF INFECTION IN RATS 

 AND IN GUINEA PIGS, INOCULATED WITH TRYPANO- 



SOME GAMBIENSE. 



J. FRANKLIN MORGAN. 



This article is a compilation of the records of rats and guinea pigs inocu- 

 lated with Trypanosome Gambiense at the University of Michigan. The 

 record starts from the receiving of two rats from Liverpool, England, during 

 the latter part of June, 1906 and extends over a period of seven years to 

 August, 1913. During this time, 453 animals (331 rats and 122 guinea 

 pigs) were inoculated, not counting the 12 reinoculations — 1 rat and 11 

 guinea pigs. Over one-fourth of the rats were bled for cultural experiments 

 in vitro — while only 6 guinea pigs were used for that purpose. The remainder 

 were stock animals — that is, animals for perpetuating the organism. 



TABLE L 



Incubation period. 



Time of inoculation till the appearance of organism in the blood. 



Rats. 



Guinea Pigs. 



From the above table it will be seen that 121 rats infected from 6-10 days 

 are near their entire average of 8 days and that 50 guinea pigs infected 

 from 17-25 daj's are near their average of 19 days. Nearly one-half of the 

 animals were near their entire average. The longer time required for a 

 guinea pig to become infected is probably due to the larger size of the ani- 

 mal. 



