BLOOD SERUM. 109 



in blood serum has been confirmed by the work of Lilienfeld, whose 

 paper was published in 1895, while that of the American investi- 

 gators was published in 1893. 



The germicidal action of the nuclein, obtained as above stated, 

 from blood serum, was abundantly demonstrated by a long series of 

 experiments published in the original contributions on this subject 

 and in part reproduced in the third edition of this book. 



In the third edition of this book there occurred the following 

 paragraph : " The origin of the nuclein now found for the first time 

 in blood serum is an interesting question. Does it come from the dis- 

 integration of the polynuclear cells, or shall we regard certain white 

 blood corpuscles as unicellular organisms whose function it is to 

 secrete this nuclein ? " It will be seen from what is to follow that 

 practically all the investigations, which have been carried on since 

 the above paragraph was written, have had for their object the solu- 

 tion of the questions there proposed. 



Buchner has long used the term alexins to designate the germi- 

 cidal substance or substances that exist in blood serum and whose 

 exact nature has not yet been determined. His most potent argu- 

 ment against alexin being a nuclein lies in the fact that when blood 

 serum is heated to 56° or 58° it loses its bactericidal properties; 

 while it is well known that aqueous solutions of nucleinic acid are 

 not altered by much higher temperatures. A serum whose germi- 

 cidal action has been destroyed by heat is designated as inactive. 

 It is within the range of possibility that there may be a nuclein or a 

 nucleinic acid so labile that it loses its germicidal action at the rela- 

 tively low temperature mentioned above. It is also possible that 

 while an aqueous solution of nucleinic acid may retain its germicidal 

 properties at 100°, when mixed with the constituents of blood 

 serum it may be altered at a much lower temperature. It will be 

 seen from this that the effect of temperature upon the alexins of 

 the blood is a matter of importance inasmuch as it may be suggestive 

 of the composition of these bodies. Bail ' in his studies on the 

 action of leukocidin found that while this toxin dissolves or disinte- 

 grates the leucocytes, it does not destroy the bactericidal substance 

 contained in them and that when this phenomenon occurs the ger- 

 micidal constituent of the white blood corpuscle passes into solution, 

 and that such a solution may be boiled without losing its germicidal 

 properties. He also ascertained that when isolated leucocytes are ex- 

 tracted with alkaline sodium chlorid solution and this extract precipi- 

 tated with acetic acid and then redissolved in an alkaline inactive di- 

 lute blood serum, a germicidal solution is obtained and that this may 

 be heated for one-half hour to 85° without loss of bactericidal prop- 

 erties. Furthermore, he showed that the germicidal properties were 

 due to the substance precipitated with acetic acid inasmuch as he 

 ^Arehiv f. ffygiene, 30 and 32. 



