vi PREFACE 



metabolism. Nitrogen absorbed with the oxygen is, in 

 part at least, utilized in replacing the waste in this element, 

 and the carbon brought into the molecule at the same 

 time is in part detached by the free valences in the carbo- 

 hydrate groups, and used to repair loss in this part of the 

 molecular structure. In the living molecule it is probable 

 that nitrogenous metabolism proceeds much more slowly 

 than the carbon and hydrogen metabolism, but both move 

 rhythmically, and the tempo depends upon the swing of 

 the atomic groups that constitute the molecule, and this 

 rate can be changed, hastened or retarded, by alterations, 

 either physical or chemical, in the medium in w r hich life 

 resides. When the molecule is in active life its food is 

 prepared for it by ferments, and it is quite certain that 

 these ferments have their origin in the nitrogenous metab- 

 olism of the living molecule. 



The keystone or archon of the protein molecule is our 

 poison. It is common to all protein molecules. It is the 

 primary group. One protein differs from another in the 

 secondary and tertiary groups. Ordinary proteins are not 

 poisonous, because in them the chemism of the primary 

 group is satisfied by combination with secondary groups. 

 Strip off the secondary groups and the primary becomes 

 poisonous on account of the avidity with which it combines 

 with the secondary groups of other molecules. 



The specificity of proteins resides in the secondary groups 

 of their molecules, and all specific protein reactions are 

 due to these groups. This is true of agglutination, precipi- 

 tin, and lytic reactions. Biological relationship between 

 proteins is dependent upon the chemical structure of their 

 molecules. The poisonous part of a protein is its primary 

 group; the sensitizing part is found among the secondary 



