PART I.] Circumstances under which Bacteria appear in Blood. 157 



The above tables show that of seventy-three specimens of blood derived from forty- 

 seven different animals, fourteen, or somewhat over 19 per cent., contained bacteria in 

 smaller or larger numbers ; that the presence of bacteria was not the result of any special 

 experimental treatment ; and that bacteria may be found in specimens of blood obtained 

 from the bodies of animals killed while in full health, and without having been subject 

 to any operative interference previously. The animals were in every instance dogs, so 

 that the question of idiosyncrasy in hindering or promoting the development of bacteria, 

 can be so far set aside when the results of any one set of cases are compared with those 

 of the others.* Of the fourteen specimens ten were obtained from the bodies of animals 

 at periods varying from b\ to 48 hours after death, and only four from cases in which 

 the animals had been killed immediately before the examination, and in which changes 

 dependent on post-mortem decomposition could not be supposed to have played any 

 important part in the production of peculiarities in the blood. Table X shows the 

 length of time which elapsed in each instance between the death of the animals and 

 the time at which the specimens of blood were obtained, and brings out the fact very 

 distinctly that, in so far as the whole of the present experiments are concerned, it was 

 this that almost invariably determined the existence of bacteria in the blood. In three 

 of the four 'instances in which bacteria were found in the blood immediately after the 

 death of the animal the numbers present were so very small as to fail to constitute a 

 characteristic of the blood or escape the suspicion of accidental introduction. 



In one specimen (No. 3, Table VIII), however, obtained immediately after death, 

 bacteria were present in abundance ; and in another (No. o, Table V), in which their 

 numbers were considerable, death had occurred at such a short time previously (5^ hours) 

 that it may not be deemed warrantable to conclude that all the bodies present had 

 really been developed subsequent to the death of the animal. That it would really be 

 an unwarrantable conclusion is, however, very doubtful, as two of the experiments in 

 healthy dogs show that, with the high temperature of the hot months, a development 

 of bacteria may take place within a very few hours in the blood of animals into the 

 system of which such bodies had been previously artificially introduced. In the 

 case under discussion the body was exposed to the hottest part of the twenty-four hours 

 of a day towards the close of May, Even, however, if it be assumed, that the bacteria 

 were certainly in this case not due to post-morteon processes, their appearance in the 

 blood can be readily explained without supposing that they exerted any essential 

 influence on the death of the animal, for, as death followed within three hours after 

 the injection of several drachms of fluid containing an abundance of bacteria, it may 

 well have happened that all those introduced had not been destroyed ere death occurred, 

 and that, on its occurrence, the medium and temperature being favourable, they rapidly 

 developed and multiplied. 



* In the blood of rabbits, for example, bacteria are said to be much more readily developed than in the 

 blood of other animals. 



