106 



SIXTEENTH REPORT. 



(b) Inoculated witli Blood from Guinea Pigs. 



Note. — Per field is the average number of organisms seen in a field of a drop of blood with a No. 7 

 objective. 



Abbreviations: — I. C. — incubation period — days. 



D. I. — duration of infection — days. 



A. I. — amount of blood injected. 



P. F.— per field. 



P. I. — place of inoculation. 



S. C. — Sub cutaneously. 



I. P. — Intra peritoncally. 



The place of injection and the amount of blood used plays an important 

 part in the length of the incubation period. The susceptibility of the ani- 

 mal is also an important factor. Three rats, Nos. 33, 34, and 35, were in- 

 jected intraperitoneally at the same time, with the same amount of blood 

 from the same animal. The first one did not show any infection for 18 

 days, while the other two were positive on the sixth. As these animals 

 were bled for cultural purposes, no conclusions can be drawn from the dura- 

 tion of infection. As to the amount of blood, number of organisms present, 

 place of injection, compare Nos. 37 and 38 with Nos. 68, 427, 448 and 449 

 (Table III). With fewer number of organisms and subcutaneous injections, 

 the incubation period is longer. There are some exceptions, but on the 

 whole this has proved true among the guinea pigs. 



There also appears to be a longer incubation period and duration of in- 

 fection of rats inoculated from guinea pigs than of those inoculated from 

 rats. This is not so true among the guinea pigs. 



Rat No. 88a was inoculated twice. No infection showing in 65 days, it 

 was reinoculated with blood from a guinea pig. The first time it was inocu- 

 lated with guinea pig blood, but this was much richer than the second 

 inoculation. It contained 100 organisms per yield instead of 3. The in- 

 cubation period was nearly three times the average and the duration of 

 infection was the longest of any rat, 106 days or nearly six times the average 

 for the duration of infection. Whether the first injection had anything 

 to do with the prolonging the life of the rat, the writer is not prepared to 

 say. 



