Nucleic acids : their chemical properties and physiological conduct / by Walter Jones.
- Jones, Walter, 1865-1935
- Date:
- 1920
Licence: In copyright
Credit: Nucleic acids : their chemical properties and physiological conduct / by Walter Jones. Source: Wellcome Collection.
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![characteristic that the two latter parts together make up a mass that is insignificant in comparison with the mass of the head, while the tails are threads of extreme fineness which dissolve easily in acetic acid, leaving the heads as insoluble granular masses. From comparative histological studies of the growing testicle and also from other considerations we are led rather directly to the con- clusion that the spermatozoa head is to be regarded as a metamor- phosed nucleus, so that Miescher was in possession of material in great quantity admirably adapted to a chemical examination of the cell nucleus. He found the spermatozoa heads free from protein, and made up almost exclusively of a single chemical individual—a salt of an organic base rich in nitrogen and of an organic acid containing phos- phorus (Miescher [1874, 1]). The organic base was protamine; the acid, nucleic acid. While Miescher had previously isolated “ nuclein ” from pus cells, its demonstration lacked the clearness which character- izes his discovery of protein-free nucleic acid in the spermatozoa heads, and does not admit of the corollary that nucleic acid is formed in the body from the decomposition products of protein. Miescher’s work has been experimentally tested many times, and has been submitted to the closest critical examination, only to be found without a flaw (Schmiedeberg [1896]: [1900]). He was for- tunate enough or wise enough to take advantage of the rare opportun- ity for scientific investigation which was afforded by the Rhine salmon, and became at a stroke the discoverer of both protamine and nucleic acid. Miescher came close to another discovery of no less importance than the isolation of nucleic acid from cell nuclei. Upon warming a specimen of protamine with nitric acid a yellow spot was formed which changed to bright red when moistened with alkali. Appreciating the significance of the reaction, Miescher [1874, 2] asked Piccard to make an examination of salmon sperm for purine bases. Piccard [1874] made successive extractions of salmon spermatozoa with hydrochloric acid of increasing strength. The first extract contained only pro- tamine; but the final extract, made with boiling acid, produced the well-known gelatinous purine precipitate with silver nitrate in am- monia and was found to contain considerable quantities of guanine and hypoxanthine. Considering the analytical methods at his disposal, Piccard's results are admirable; guanine was correct, and adenine, at that time unknown, was always mistaken for hypoxanthine. But un- fortunately Piccard added that the composition of salmon sperm as given by Miescher must be revised to include guanine and hypoxanthine, which are to be ascribed partly to nuclein and partly to protein. He](https://iiif.wellcomecollection.org/image/b29807499_0015.jp2/full/800%2C/0/default.jpg)
