Some stages in the development of the pharynx of the embryo horse

Abstract

NINETEEN FIGURESOur knowledge of the embryological development of the horse is f a r from being complete. Few niammals have had their pharyngeal regions thoroughly investigated, and the horse has been almost completely neglected. Present-day attention on the endocrinal secretions in the human has revived a i d vitalized the interest in the pharyngeal derivatives. Since the liorse is a high-typed ungulate, with many embryological and aiiatoniical structures in cominoii with man, it is hoped that the findings of this investigation may aid in a more accurate interpretation of what is revealed in the human. The literature, even 011 the general embryological development of the horse, contains few contributions. Ewart (%) reviews this literature, mentioiling such contributors as Hausmann, Huxley, Bonnet, and Martin, whose contributions were based largely on the early embryonic membranes, with practically nothing on organologp. Ewart ('15) was able to state the accurate age of a certain horse ernbr>-o as being twenty-one days old. His drawings of appropriately selected cross-sections of this stage and the description of the structures iiivolved uridoubtedIy make a worthy contribution, but he considered the pharynx only incidentally. Robinson and Gibson ( '17) described the recoiistruction model of Ewart's twenty-one-day embryo, and this account serves as a valuable aid in interpretiiig Emart's figures. Sisson ( '21) deals adequately with the gross anatomy of the adult horse, henct: this work is accepted as a standard text in many veterinary medical schools. 233

Morphologic stages of the equine embryo proper on days 17 to 40 after ovulation

“…24 Two equine embryos, one 13 mm (about day 30) and one 18 mm (about day 37) in length, corresponded to porcine embryos of approximately 8 mm (about days 20 to 21) and 20 mm (about days 27 to 28) in length. 25 Compared with ovine embryos, development of equine embryos lagged by about 2 to 4 days during stages 10 to 13 (ages: equine embryo, days 17 to 24; ovine, days 16 to 21). However, during stages 15, 16, and 17, the limbs, which are a critical external feature for Carnegie staging, took even longer to develop in the horse.…”

Comparative embryogenesis in ungulate domesticated species

“…hircus: Hayssen et al, 1993;Tsukaguchi, 1912;C. capreolus: Hayssen et al, 1993;Keibel, 1906;Retzius, 1900;Sakurai, 1906;Equus caballus: Ewart, 1917;Martin 1890: cited in Ewart, 1917Robinson & Gibson 1917, Acker et al, 2001Betteridge et al, 1982;Evans & Sack, 1973;Harrison & Mohn, 1932;Rüsse & Sinowatz, 1991;Schnorr & Kressin, 2006;Vitums, 1969;O. aries: Bryden et al 1972, Butler & Juurlink, 1987Evans & Sack, 1973;Rüsse & Sinowatz, 1991;Schnorr & Kressin, 2006;Rüsse, 1991a, 1991b, P. tajacu: Smith & Sowls, 1975R.…”

“…Our study is based on a compilation of embryological literature ( B. taurus : Evans & Sack, 1973; Krölling, 1924; Michl, 1920; Rüsse & Sinowatz, 1991; Schnorr & Kressin, 2006; C. hircus : Hayssen et al, 1993; Tsukaguchi, 1912; C. capreolus : Hayssen et al, 1993; Keibel, 1906; Retzius, 1900; Sakurai, 1906; Equus caballus : Ewart, 1917; Martin 1890: cited in Ewart, 1917; Robinson & Gibson 1917, Acker et al, 2001; Betteridge et al, 1982; Evans & Sack, 1973; Harrison & Mohn, 1932; Rüsse & Sinowatz, 1991; Schnorr & Kressin, 2006; Vitums, 1969; O. aries : Bryden et al 1972, Butler & Juurlink, 1987; Evans & Sack, 1973; Rüsse & Sinowatz, 1991; Schnorr & Kressin, 2006; Rüsse, 1991a, 1991b, P. tajacu : Smith & Sowls, 1975; R. tarandus : Retzius, 1900; Sus scrofa : Butler & Juurlink, 1987; Evans & Sack, 1973; Keibel, 1897; Rüsse & Sinowatz, 1991; Schnorr & Kressin, 2006) and subsequent analysis. Embryological characters were coded for another paper on the mammalian developmental event evolution (Werneburg et al, 2016).…”