94 Mi-. E. H. Haiildn. [May 22, 



authors, n,nd which I have applied to this research, is to mix a small 

 quantity of a culture with a few cubic centimeters of blood serum. 

 A drop of this serum is immediately taken, and a gelatine plate 

 culture made with it. Again, at intervals varying from a half to 

 twenty-four hours, plate cultures are made containing drops of the 

 serum. The first plate culture serves as control. The number of 

 colonies that appear in it is observed. A progressively decreasing 

 number of colonies will be found in the succeeding plate cultures, 

 owing to the gradual decrease in the number of bacilli that remain in 

 a living condition in the blood serum. A curious point about this 

 property of blood serum is that it vanishes in the act of killing the 

 microbes. That is to say, a given q\iantity of blood serum can 

 only kill a limited number of microbes. If the number of microbes 

 added to the serum is beyond this limit, the survivors find the 

 blood serum to be an excellent food medium, and, after a time, 

 begin to grow and reproduce. This fact, together with the com- 

 paratively low temperature (six hoars' heating to 52 or half an 

 hour's heating to 55) at which the bacteria-killing power 

 vanishes, has led some of the above-quoted authors to ascribe it 

 to a " sort of ferment-like activity." Buchner* found that the 

 bacteria-killing power vanished on dialysing the serum into distilled 

 water, not, however, if it was dialysed into 75 per cent, sodium 

 chloride solution which had been brought to the same degree of 

 alkalinity as the serum. From this and other facts, Buchner is 

 brought to believe that the property in question is connected with 

 the intactness of " Nageli's hypothetical Micella? " present in tlie 

 serum, and is due to a residuum of the " life " possessed by the 

 plasma from which it is derived. Surely, an equally obvious conclu- 

 sion would be tliat it was connected with the presence of some 

 unknown globulin, which, like other globulins, is only soluble in 

 dilute salt solutions, and, therefore, would be precipitated after 

 dialysing into water, and remain in solution on dialysing into phy- 

 siological salt solution. The experiments of Lubarscht have shown 

 that this power practically does not exist in the living blood plasma ; 

 consequently (on the hypothesis that it is due to some specific 

 germicide), it must be due to a substance present in bleod serum 

 absent from the plasma. Further, the above-mentioned observations 

 suggest that it is due to a substance of the nature of a ferment. 



Can it be fibrin ferment ? The facts that a bacteria-killing power 

 is possessed by peptone plasma, but not by magnesium sulphate 

 plasma, are not in complete disaccord with this suggestion. A 



* Loc. tit. 



t " Ueber die bakterienvernichtenden Eigenschaften des Blutes und ihre 

 Beziehungen zur Immunitat," ' Centralblatt fur Bakteriologie und Parasitenkunde,' 

 vol. 6, 1889, p. 528. 



