Biochemistry Definitions and Classifications of Branches

Biochemistry is a hybrid science. It arose from the overlapping of more or less purely chemical issues and more or less biological issues. Consequently it is subject to a great variety of definitions reflecting the scope of the pure sciences and the manner in which they are combined. The manner of combination results either in an emphasis on biology or on chemistry.

"Biochemistry" is a term which stresses chemistry and to most biochemists, at least of two or three decades ago, it meant '"the chemistry of biologically important substances." The emphasis has been shifting to "the chemical aspects of living processes" and, we venture to predict, will lead to the employment of the expression "chemical biology." This is a trend in all scientific development and has led, for example, in the borderland between physics and chemistry, to the emergence of two subjects, "physical chemistry" and "chemical physics." Thus, we can expect another pair, "biological chemistry" (or biochemistry) and "chemical biology," to divide the field now customarily described by the former term. The term "physiological chemistry," designed possibly to call attention to the dynamics of the biological processes has been falling into disuse, because physiology is after all only one branch of biology. If it is retained it may become a branch of "biological chemistry."

It is possible also that "chemical biology" might receive a name like "cheobiology." The trend toward renaming in the direction in which "chemical" serves as the adjective is illustrated by the relatively rise of "chemical embryology". If we are right, this in itself may become a branch of "chemical evolution" which in turn would be a branch of "chemical biology."

Other definitions of biochemistry emphasize, consciously or unconsciously, the philosophy of the definer. The author of the definition, may be an outright materialist, in which case he would stress the physical basis of life, or an idealist of one kind or another who believes in entelechies, life principles and the like. One hates to think of what would become of the subject according to such a definition if there were no special distinctive "biotic energy."

The modern trend is toward what the author has called "dynamic biochemistry" before favoring wholeheartedly "chemical biology." A convenient, but theoretically poorly founded, distinction is that of a "pure" and an "applied" science. The varieties of "applied biochemistry" include what the medical student gets as "pathological chemistry" or what the botanist might take up as "phytochemistry," the zoologist as "zoochemistry."

There are even more complicated hybrids in such subjects as "biogeochemistry" and the loosely defined field of "comparative biochemistry"' which ranges over all living types in an evolutionary manner.

We suggest that order in this creation of sectors of research might be set up by listing the divisions of biology as (1) morphology (2) distribution (3) physiology and (4) aetiology and the customary divisions of chemistry as physical, inorganic, organic, analytical, etc., with subdivisions such as "colloidal" and the like, and then blending them into hybrid sciences. This will account for the appearance of such terms--used in England--as "aetiological chemistry" meaning the division of biochemistry dealing with "cause and effect in the determination of development" and thus naturally including as a part of itself "chemical embryology." In this connection we would prefer "chemical aetiology" or "chemical evolution." New subjects might be, for example, "colloidal chemical physiology" or "chemical genetics" or "chemical immunity." At present these subjects are suggested by expressions like "the biochemistry of genetics. . . . . the biochemistry of the earth," (i.e. of living forms in the earth's development), etc., etc.