PHILOSOPHICAL BIOLOGY 463
Eaeh form, o^ozyhemoglobin, b-oxyhemoglobixiy etc., appears always in its own proper form and axial ratio when the blood of different individuals of the same species is examined. . . . But upon comparing the corresponding substances in different species of a genus, it is generally found that they differ one from the other to a greater or less degree; the differences being such that when com- plete crystallographic data are at hand the species can be difitinguished by these differences in their hemoglobins.
Let lis assume there is ground for qnestioning the fuU trustworthi- ness of this conclusion. Notice the strong presumption of its general reliability produced by its accordance with evidence from a wholly different kind of research on the serum of blood, namely, that on the precipitin reaction; and from still another kind, namely, that on the hemolytic action of one blood upon another. Kor should we fail to recognize the convergence of evidence for chemical specificity of organ- isms drawn from comparative investigation on milk; on the enzymes of digestion; and from such direct analyses of organic structure as those of the sperm of many species and genera of fishes. I mention only one other line of evidence of like purport clearly to be counted as chemical, though not usually so cited; namely, that of the odors and flavors of plants and animals. This is an exceedingly rich field of inquiry, even though diflScult of cultivation by ordinary laboratory methods. The methods to be chiefly relied upon here are those of the senses of smell and taste, and it is interesting to reflect that there is available for utilization not merely these senses in man, but in animals as well. In the olfactory sense of the ant and the scent hunting dog, for example, we have a method of chemical discrimination — of qualita- tive chemical analysis if you please — ^which seems to surpass in delicacy anything laboratory manipulation can hope to attain.
Natural history and biochemistry are being inevitably drawn to- gether by the very nature of their subject matter. Descriptive zoology and botany are becoming chemical in part, and bio-chemistry is becom- ing zoological and botanical in part. Organisms are indeed being reduced to chemistry" in the familiar phrase; but the statement tells only half the story, unless it specifies the f articular chemistry to which they are reduced. Each kind of organism has a chemistry to some extent imique. In one of its aspects biochemistry is becoming a sub- division, or branch, of systematic zoology and botany, just as anatomy has been for a long time. " Almost any group of tissues," said Minot, " would offer a favorable opportunity for the discussion of genetic classi- fication." Seemingly the same may be said of biochemical substances.
Many biologists working in several provinces of the organic realm, particularly in those which, like cytology and biochemistry are concerned with the minute and difficultly observed structure and functions of organ- isms, appear to be laboring under the delusion that they are doing some- thing totally different from description. They seem to think their work
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