The proteins common to all tissues may be termed the constitutive set, those that are expressed in several but not all tissues, the semiconstitutive set, and those restricted to aspecific tissue type, the dif erentiative set. Besides the constitutive set of proteins and the cell-specific secretory proteins (some secretory proteins may be constitu- tive), there remains another set of proteins of undetermined magnitude, but ofconsiderable probable significance.
1
—
—