68 G. F. DOWDESWELL. 



are to that of authrax, and the statements here made refer only 

 to these animals. 



After infection with putrescent blood, the animal remains 

 without showing any symptoms of disturbance till within a few- 

 hours of death ; it then becomes dull, remains motionless, closes 

 its eyes, and shortly afterwards dies without further change in 

 about seventy hours, or somewhat more, after infection. From 

 such an animal, if the smallest possible quantity of blood be 

 taken on the point of a lancet or scalpel, and another mouse 

 inoculated therewith in any part of the body, infection occurs 

 with absolute certainty. I have not known one failure in the 

 experiments of several years. Infection established, the disease 

 runs its course in exactly the same way as in the former case, 

 but the period of incubation is materially shorter, only averaging 

 about sixty hours ; after, however, the first case of infection by 

 putrid, as distinguished from septicsemic blood, I have not 

 found that there is any increase of infective virulence, as has been 

 previously asserted. I judge of this by the period of incubation^ 

 which, did any increase of virulence occur, would be shortened, 

 but so far is this from being the case that, in a long series of 

 inoculations of one year's experiments, this period, in the last 

 few of the series, was actually longer than in the first of the 

 same. 



Although no symptoms of disturbance are observable in an 

 infected animal till near its end, that is, till upwards of fifty 

 hours after infection, yet I have found that the blood from the 

 living animal becomes infective within eighteen hours after 

 inoculation, and is then as infallibly and actively virulent as that 

 of an animal in which the disease had run its course to its fatal 

 termination ; nor does any difference in the incubation period of 

 the infection so established occur. 



On the death of an animal from septicsemia, decomposition 

 proceeds with such excessive rapidity, and septic Bacteria appear 

 and multiply so greatly, that no conclusions can safely be drawn 

 from such cases ; even in the course of two or three hours very 

 marked changes occur. I have therefore rejected all such, and 

 for this examination have always killed the animal shortly before 

 death would have occurred, as soon as any affection was evident, 

 and another animal has been at once inoculated with its blood to 

 test the occurrence of infection. 



In old mice, as probably in all other domestic animals, various 

 pathological changes of the different organs very frequently occur ; 

 in these experiments, I therefore generally used young mice. If 

 the organs of one of these are examined after death, the only 



' Dr. Koch has observed the same thing, and discussed the question, 

 op. cit. 



