tially of those characters physical and mental which the individual inherits from its male parent; as the nucleus of the ovum must be for the female parent. In the series of divisions by which the fertilized ovum separates into the cells which form the tissues of the body, the material or chromatin of the fused nuclei is with the utmost exactness divided equally to each, so that every unit of the system receives its share of this chemical endowment. This much the study of structure has taught us. But to the chemist the ultimate explanation of these processes seems to lie in the nature of the chemical substances composing the chromatin. In the salmon the ova and sperm are easily obtainable, and afford the unfertilized eggs and spermatozoa almost free from admixture with other matter. Accordingly the methods which Miescher employed for the separation of the constituents of these cells were simple, yet yielded the material sought in quantity and purity. The nuclei from the sperm proved to be composed mainly of a peculiar compound or series of compounds of the nature of ethereal salts. The acid radical was nucleic acid—a substance previously discovered by Miescher in the white corpuscles of the blood of mammals; the other component was an organic base which he called protamin. To the question as it presented itself to Miescher's mind, whether protamin may be regarded as the essential element in fertilization, the answer must be in the negative. Miescher found that protamin is not present in the sperm of the frog or the testes of a bull; and subsequent investigators have shown that it is absent even in some fishes. Yet in these cases it is apparently replaced, and the same functions performed by another substance of basic character known as histon. Miescher was led by these facts to the view that there is no one substance which can be regarded as the essential element in fertilization; but that the chemical processes involved are probably a series of reactions.
To attempt even an outline of the investigations and discoveries to which Miescher's study of the chemistry of the cell has led, would necessitate reviewing one of the most fertile fields of biological chemistry, and would involve much that is important in pathology as well. rt is sufficient here to point out that what has been accomplished is in great measure the ripening fruit of the seed planted by Miescher in the quiet of his laboratory a generation past. In the final solution of the profounder biological problems, these investigations on the salmon and the researches to which they have led will probably be found to have contributed in large measure toward that object, which Miescher in one of his letters—almost the last before his death—expressed in the words—"There remains then this great question to be fought out by the biologists of the future—Is it chemical composition or cell structure to which we must look as the ultimate basis of vital phenomena?"
