. Journal of anatomy . ginous sphenoidreaches its highest degree of development, the orbital wings are enormouslygreater than the temporal wings, reaching out even beyond the orbitalcavities into the temporal fossae, making for but not reaching thatextraordinary but temporary cartilage—the parietal platte. Both limbsof the orbital wing are now developed, the posterior one being fused withthe corpus sphenoidale, the anterior not so as yet, but in close contact 216 Professor Fawcett witli it, and so practically completing the optic foramen. Anteriorlythis orbital wing is expanded so as to form a
. Journal of anatomy . ginous sphenoidreaches its highest degree of development, the orbital wings are enormouslygreater than the temporal wings, reaching out even beyond the orbitalcavities into the temporal fossae, making for but not reaching thatextraordinary but temporary cartilage—the parietal platte. Both limbsof the orbital wing are now developed, the posterior one being fused withthe corpus sphenoidale, the anterior not so as yet, but in close contact 216 Professor Fawcett witli it, and so practically completing the optic foramen. Anteriorlythis orbital wing is expanded so as to form a great part of the orbital roof,and this expansion becomes connected mesially with the perpendicularplate of the ethmoid—a spheno-ethraoidal fissure separating its innersegment from that of the ala orbitalis proper. This is well seen inHertwigs model of the cranium of an 80 mm. embryo which is beingfigured in most of the text-books of to-day. The alae temporales (greater wings) are absurdly small by comparison M G-. Fl(i. 1-2. with the alse orbitales. As seen from the front thej^ lie almost wholly belowthe level of the orbit, extending not higher than the later formed lowermargin of the orbital plate of the great wing of the bony sphenoid, and areperforated not far from their upper extremities by the second division ofthe fifth nerve. The whole, practically, of the orbital plate and that partof the sphenoid which is found in the temporal fossa, as well as the externalpterygoid plate, are at this time membranous and will later be ossifiedectochondrally, as will, to a large extent, be seen in the photograph of asection of an 80 mm. embrj^o (fig. 14). In the same model (30 mm.) theprocessus alaris sends backwards a pointed process which comes intocontact with the auditory capsule (Jacoby). This condition is even visibleat the 110 mm. stage (fig. 15). Notes on the Development of the Human Sphenoid 217 It may be mentioned here that the foramen ovale and foramen spinosumare gener
Size: 1763px × 1417px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, booksubjectanatomy, bookyear1867
