568 MICRO-ORGANISMS AND DISEASE [chap. 



minutes), while others, e.g., staphylococcus pyogenes aureus 

 and albus, streptococcus erysipelatos, bacillus of fowl cholera 

 and swine fever, and proteus hominis, are only very slightly 

 affected by it; on proteus vulgaris, bacillus fluorescens 

 liquescens, bacillus aquatilis, and bacillus prodigiosus it has 

 no appreciable effect. But also in the cases where the fresh 

 blood exerts its inimical action this only takes place if the 

 relative number of bacteria added is limited, for the killing 

 power of a given quantity of fresh blood is Hmited, so that 

 if the number of bacteria introduced be too large the killing 

 power of the blood does not extend to all bacteria; and 

 having been consumed and exhausted in killing a certain 

 number of them, others escape, and these, then, are capable 

 of rapidly multiplying, as in any other medium. The power 

 of the blood to kill certain bacteria rests with the plasma, 

 and it is the same power that also kills the leucocytes. 

 There is a remarkable parallelism between blood plasma 

 and leucocytes on the one hand and blood plasma and 

 bacteria on the other, for when the blood plasma kills the 

 leucocytes it also kills bacteria, e.g., fresh blood and blood 

 plasma ; but fresh peptonised blood and peptonised plasma, 

 which have not this power on the former, have it not on the 

 latter. When blood is heated to 52° or 58° C. for twenty 

 to thirty minutes (Nutall) it loses the power of kiUing 

 bacteria, which it otherwise killed ; blood mixed with mag- 

 nesium sulphate loses the killing power ; when blood is 

 kept for several hours it also loses this power. Blood to 

 which bacteria had been added and thereby killed coagulates 

 quicker (Grohmann), just as blood which kills the leucocytes 

 coagulates quicker. 



Buchner (Cetitralbl. f. Bakt. und Parasif., vi.) has made 

 very extensive observations on the germicidal power of 

 blood plasma and blood serum ; he points out an important 



