FURTHER DEVELOPMENT OF KNOWLEDGE 185 



In other experiments in which heating was more prolonged a 

 similar regeneration was observed, though not as pronounced as in 

 the one cited above. The largest amount of restored complement 

 seemed to be present after about 24 hours. After this gradual de- 

 terioration again ensued. It is quite impossible to offer an adequate 

 explanation for this at the present time. Gramenitski 68 acknowl- 

 edges this, but permits himself certain speculations which we repeat 

 in nearly his own language, since there is much in them which seems 

 to us reasonable. The complement, as indeed all other active serum 

 constituents, must be looked upon as colloidal in nature. When heat 

 is applied to such substances alterations occur which gradually lead* 

 to coagulation. As this occurs there is an aggregation of particles 

 and a consequent diminution of surface tension. This last point has 

 been experimentally demonstrated by Traube, 69 who has regularly 

 found a fall of surface tension as serum was heated to 56 C. And 

 of greatest interest in this connection is the further determination by 

 Traube that a gradual restoration of the surface tension takes place 

 as the serum is allowed to stand. It is not inconceivable, therefore, 

 that the inactivation of complement by heat may depend upon an 

 alteration of its colloidal state, i. e., an aggregation of the particles, 

 which, if not carried too far, may be reversible and followed by a 

 gradual dispersion as the serum is kept 24 hours. On the same 

 grounds the gradual deterioration of complement on standing may be 

 compared to the slow settling out of colloidal suspensions which 

 eventually results in spontaneous precipitation, a process which 

 occurs not only in chemically well-defined colloids, but is often ob- 

 served in sera. Bechold has referred to this as "das Altern Kol- 

 loidaler Losungen." 



Of great interest, furthermore, in connection with the physical 

 properties of complement is the discovery made by Jacoby and 

 Schiitze 70 that complement can be inactivated by shaking. This 

 astonishing observation has been confirmed by Zeissler, 71 Noguchi 

 and Bronfenbrenner, 72 Ritz, 73 and others. It appears, according to 

 these observers, that guinea pig serum, when subjected to active 

 shaking, can eventually be robbed thereby of its activating prop- 

 erties. The success of such experiments depends somewhat upon the 

 concentration of the serum, and is best observed in a dilution of 1 

 part, to 10 parts of salt solution. Under such conditions complete 

 inactivation may be observed within 20 to 25 minutes. Between the 

 inactivation of complement by heat and that which results from 



* 8 Gramenitski. Loc. cit., p. 504. 



69 Traube. Zeitschr. f. Imm., Vol. 9, 1911, and Biochem. Zeitschr., 1908. 



70 Jacoby and Schiitze. Zeitschr. f. 1mm., Vol. 4 ? 1910. 



71 Zeissler. Berl. kl. Woch., No. 52, 1909. 



72 Noguchi and Bronfenbrenner. Journ. of Exp. Med., Vol. 13, 1911. 



73 Ritz. Zeitschr. f. Imm., Vol. 15, 1912. 



