proton

1. (particle physics) A positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element, composed of two up quarks and a down quark.Examples: "The dance of the electrons about the prota, each electron and each proton consisting of a series of waves occupying the whole of the limited universe and obeying the laws of nature as they pass, is known to all."Synonyms: pparticle

2. (particle physics) A positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element, composed of two up quarks and a down quark.Synonyms: pparticle

3. (obsolete, anatomy) Synonym of primordium.Examples: "It is a well authenticated fact that, in the case of section of a peripheral nerve, the nuclei of the sheath of Schwann pass to the centre of the lumen and form the protoplasmic prota of the segments of the new nerve[…]. From studies of the development of the olfactory organs in reptiles, as reported briefly in earlier numbers of this Journal, the writer has been abundantly convinced of the truth of Beard’s statement that the olfactory prota arise from the skin[…]."; "This paper constituted the proton (the primordium, or ‘Anlage,’ if you prefer) of my own subsequent contributions, and likewise, so far as I knew at the time, of the simplified nomenclature in America."; "a, b. Prota of primitive segments (protovertebræ).[…]These soon become partially constricted off from the fore-brain, their narrow pedicles—the optic stalks—being the prota of the optic nerves. The dorsal wall of the fore-brain continues to grow forward and upward from the rest of the vesicle, and soon forms a fourth ventricle or permanent fore-brain, the proton of the cerebral hemispheres.[…]By the sixth week the otocyst has been converted by a fold into two portions—a dorsal part—the utriculus, from which three projections arise, the prota of the semicircular canals (Fig. 91), and a ventral part, the sacculus, from the anterior end of which the cochlea is developed.[…]These are the Müllerian ducts, the prota of the female internal organs of generation.[…]The cords acquire a lumen and become the prota of the seminiferous tubules."Synonyms: primordiumobsolete