GERMICIDAL SERA 215 



mycelial structure. The albuminous bodies act on the bacteria only 

 when the former are in an active state. 



Vaughan pointed out an inconsistency between Buchner's experi- 

 mental results and his conclusions. Experimentally he ascertained that 

 peptic digestion of blood serum does not destroy its germicidal proper- 

 ties and yet he concludes that the active principle is serum albumin. 

 Since serum albumin is converted into peptone by peptic digestion and 

 since peptone forms an excellent medium for bacterial growth, Buch- 

 ner's conclusion that serum albumin is the germicidal constituent of 

 blood serum cannot be true. This criticism has held. 



In 1893 Vaughan and McClintock, after reviewing the literature 

 up to that time, reported their work on the germicidal constituents of 

 blood serum as follows: 1. Serum albumin is not the germicidal con- 

 stituent. 2. The germicidal substance must belong to the proteins. 

 Otherwise, it would be difficult to explain the fact that a temperature 

 of 85 C. renders blood serum inactive. 3. The only protein likely to 

 be present in blood and which is not destroyed by peptic digestion is 

 nuclein. 



Having reached these conclusions, the following questions naturally 

 presented: 1. Is there a nuclein in blood serum? 2. Has this nuclein, 

 if there be any, germicidal properties? Their work answered both 

 these questions in the affirmative. The existence of nuclein in blood 

 serum was confirmed by Lilienfeld and by Kossel, and its germicidal 

 action by the latter. Furthermore, it was demonstrated that injec- 

 tions of nucleinic acid, prepared from yeast and spleen cells, increased 

 both the number of leukocytes in the blood and the germicidal action 

 of the serum. However, Buchner very properly declined to accept 

 nucleinic acid as the chief germicidal constituent of serum, since the 

 latter is inactivated at from 56 to 58 C., while aqueous solutions of 

 nucleinic acid are not altered by much higher temperatures. 



It should be stated, parenthetically, that the relation of nucleinic 

 acid to the intracellular ferment of the polynuclear leukocytes has 

 never been satisfactorily worked out. The researches of Schattenfroth 

 and others have shown marked differences between the extracellular 

 and intracellular constituents of the blood. The latter has no hemo- 

 lytic action on the red corpuscles of other species while the former 

 may have. The intracellular germicide is not affected by the salt 



