352 CHEMISTRY OF THE PROTEIDS 



acid is present, and also the order in which they are linked to one 

 another. 



Nobody realises more than does the author the absolute necessity 

 of preparing the different chemical constituents of the body in as pure 

 a form as possible, but do not let us forget that such * purification ' 

 means stripping a compound, by means of recrystallisation and other 

 processes, of certain perfectly normal constituents, which give the 

 specific character to the compound in question. Purification in many 

 cases may be compared to macerating, for example, three heads, 

 covered with white, red, and black hair, till nothing but the skull is 

 left, and then saying these three heads were all alike. Over-purification 

 must lead to the survival of the more resistant radicals at the expense 

 of the more unstable or perishable ones. At present we are ' learning 

 our bones,' but let us also remember the soft parts. 



