PROTOVERTEBRA
Pro`to*ver"te*bra, n.; pl. Protovertebræ . Etym: [Proto- + vertebra.]
(Anat.)
Defn: One of the primitive masses, or segments, into which the mesoblast of the vertebrate embryo breaks up on either side of the anterior part of the notochord; a mesoblastic, or protovertebral, somite. See Illust. of Ectoderm.
Note: The protovertebræ were long regarded as rudiments of the permanent vertebræ, but they are now known to give rise to the dorsal muscles and other structures as well as the vertebral column. See Myotome.
PROTOVERTEBRAL
Pro`to*ver"te*bral, a. (Anat.)
Defn: Of or pertaining to the protovertebræ.
PROTOXIDE
Pro*tox"ide, n. Etym: [Proto- + oxide: cf. F. protoxide.] (Chem.)
Defn: That one of a series of oxides having the lowest proportion of oxygen. See Proto-, 2 (b). protoxide of nitrogen, laughing gas, now called hyponitrous oxideNO. See under Laughing.
PROTOXIDIZE
Pro*tox"i*dize, v. t. (Chem.)
Defn: To combine with oxygen, as any elementary substance, in such proportion as to form a protoxide.
PROTOZOA
Pro`to*zo"a, n. pl. Etym: [NL., fr. Gr. (Zoöl.)