. Popular science monthly. cut from an apple or orangeJ having a crescentic outline and wedge-^ shaped section. The sharp edge is con-I cave and is directed upward. On oneI side of each of the horns of this cres-I cent a rhombic piece is applied, which,^ widening upward, supports the separate5 arch of the vertebra. These three pieces^ when together leave a central vacancy,H which becomes, when all the vertebrae^ are placed end to end, a canal or This was occupied by what is known asg the chorda dorsalis, which is the cen-E< tral axis of the body of the simplest« vertebrates, and is p
. Popular science monthly. cut from an apple or orangeJ having a crescentic outline and wedge-^ shaped section. The sharp edge is con-I cave and is directed upward. On oneI side of each of the horns of this cres-I cent a rhombic piece is applied, which,^ widening upward, supports the separate5 arch of the vertebra. These three pieces^ when together leave a central vacancy,H which becomes, when all the vertebrae^ are placed end to end, a canal or This was occupied by what is known asg the chorda dorsalis, which is the cen-E< tral axis of the body of the simplest« vertebrates, and is present in the earlyI embryonic stages of all. In the growthg of a reptile or mammal this flexible^ chorda is replaced by the bony verte-§ bral bodies. The osseous material ap-§ pears in the membranous sheath which!<, covers it, and, gradually encroachingg on it, first cuts it into segments and(^ then fills it entirely. In the rhachito-« mous batrachia this process is not com-,1 pleted, as the chorda remains more or.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
