434 BACTERIOLOGICAL CHEMISTRY 



a proteolytic effect of complement. It seems much more 

 probable that the lysis is due to an alteration of the 

 physical state of the cell walls, making them permeable 

 to the cell contents. This view is rendered the more likely 

 since " artificial " complements, either colloidal silicic 

 acid or one made by mixing sodium oleate, methyl 

 alcohol and calcium chloride, have the same effect, 

 which would appear to be due to a lowering of the surface 

 tension. 



Complement appears to be quite non-specific ; the 

 complement in the serum of any animal is effective in all 

 reactions, but the activity of complement in the sera of 

 different animals varies appreciably and also varies in 

 any one animal depending on the system tested ; the 

 guinea-pig is a particularly good source of complement 

 for hsemolytic systems. 



Complement is very susceptible to heat, being des- 

 troyed by heating at 56° C. for fifteen minutes, resembling 

 in this respect many enzymes. It is also very susceptible 

 to physical and chemical changes, even mechanical 

 shaking is sufficient to inactivate it. Complement is 

 destroyed by acid and alkali and by ultra-violet light. 

 If the activation has not been carried too far it is partially 

 reversible and standing restores a part of the activity. 

 This suggests that the inactivation is due to a change 

 in the colloidal condition, probably to an increased 

 aggregation of the particles which may spontaneously 

 disperse again. Complement is almost certainly protein 

 in nature since it is attacked by trypsin, which destroys 

 the end-piece (see below) first. It is readily adsorbed by 

 non-specific adsorbants, even by filtration through a 

 Berkefeld candle. 



The Structure of Complement. — The complex nature 

 of complement was first demonstrated in 1907 by Ferrata, 

 who showed that on removing the salts from serum it lost 

 its complementary activity ; the euglobulin was pre- 

 ci Imitated and the albumin remained in solution. Neither 



