454: 



Mr. G. F. Dowdeswell. 



[Jan. 18, 



period of incubation is in nowise proportionate to the quantity used 

 for inoculation, and (2) that in the so-termed second generation of 

 infection, septicheemic blood is already infective in the 100 1 QQO th of a 

 drop. Infection was then transmitted throngh the fonrth, fifth, and 

 sixth generations, by inoculation with similar small quantities and 

 like results, the animals dying respectively within 23, 48, and 20 

 hours. The blood of this latter — the sixth generation — was diluted 

 to different degrees, and ten drops of the solution injected into four 

 other rabbits, which received — Xo. 11. y^rth gtt. ; Xo. 12, y^-o^th; 

 Xo. 13, j Q \ q ; No. 14. 1 000 1 000 th of a drop. These died all in my 

 presence in, respectively 20, 26, 2bh and 20 hours, showing in addition 

 to the first point above-mentioned, that there is no appreciable 

 shortening of the incubation period between the second and the sixth 

 generation. As the blood here proved to be infective in the ten- 

 millionth part of a drop, it was now necessary to determine the limits 

 of infectivity in the first generation. 



Again five drops of putrid bullock's blood, diluted with an equal 

 bulk of saline solution, were injected into a rabbit, Xo. 15, which died 

 within 48 hours ; its blood was diluted as before, and ten drops 

 injected into each of five other rabbits, so that they received — Xo. 16, 

 one-thousandth; Xo. 17, one hundred-thousandth; Xo. 18, one- 

 millionth; Xo. 19. one ten-millionth: and No. 20, one hundred- 

 millionth of a drop. Xo. 16 died in 24 hours, Xos. 17 and 18 died 

 within (that is, were found dead in) 35 hours, and Xo. 19 within 48 

 hours ; Xo. 20 was apparently unaffected ; subsequently, however, it 

 lost flesh, though continuing to feed, without any material rise in 

 temperature or the occurrence of microphytes in the blood, and a 

 small abscess was found at the spot of injection, which suppurated 

 and healed spontaneously in about eighteen or twenty days, and the 

 animal recovered. 



From this series of experiments it appeared that the blood of an 

 animal poisoned by inoculation with putrid matter, in the so-termed 

 first generation, is infective in less than the millionth part of a drop, 

 and the considerations mentioned below showed that it was useless 

 attempting to investigate the limits of infectivity beyond this point ; 

 but in order to ascertain whether there occurred subsequently any 

 appreciable shortening of the incubation period, as was considered to 

 be the case by MM. Coze and Feltz. infection was transmitted in 

 succession up to the tenth generation, in which the blood of a rabbit 

 that had died septiehasinic. was a earn diluted as before, and ten drops, 

 each of the same dilutions as in the last-recorded experiments, injected 

 into four other rabbits, one-thousandth, one-millionth, a ten-millionth, 

 and a hundred- millionth of a drop respectively into rabbits Xos. 21,22, 

 23. and 24. vrhich died, Xo. 21 in twenty- one hours, while the other three 

 survived upwards of twenty-seven, but died during the night within 



