n6 PHYSICAL CHEMISTRY IN MEDICINE. 



does not form an amalgam with mercury. A similar 

 behavior can be mimicked in immunity reactions when 

 the haptophore groups are lost while the ergophore 

 groups are retained, or conversely. According to BIL- 

 LITZER'S observations, it is the fact that both metals 

 possess the same electrical charge which prevents the 

 formation of an amalgam. How easily, however, it may 

 be concluded from work with colloidal mixtures that 

 new chemical compounds have been produced is indicated 

 by the interesting fact that no less a man than BERZELIUS 

 did this in a study of colloidal gold and came to similar 

 conclusions, as did EHRLICH in a study of toxin-anti- 

 toxin mixtures. In gold-purple, which has been recog- 

 nized through an excellent investigation of ZSIGMONDY 

 as a mixture of colloidal gold and colloidal stannic acid, 

 the gold shows some variations in reaction. Misled 

 by this fact, BERZELIUS drew the conclusion that gold 

 exists in gold-purple as the oxide. It is a fact of great 

 importance that, in a mixture of two colloids A and B, 

 .the properties of A disappear for many reactions, while for 

 others those of B disappear. According to the beautiful 

 experiments of ZSIGMONDY, in a mixture of orthostannic 

 and metastannic acids certain of the chemical properties 

 of the metastannic acid are concealed by the ortho-com- 

 pound, while toward other reagents the properties of the 

 ortho-compounds fall entirely into the background. Every 

 species of animal represents a different reagent toward 

 the same mixture of toxin and antitoxin, in which at one 

 time the effect of the toxine, at another that of the anti- 

 toxin, may hold the upper hand. Besides the phenom- 

 ena of neutralization, this fact has done most to sup- 

 port the belief in the existence of toxins having different 



